CR-39 refers to the material that is used to make the majority prescription lenses. It is an optical grade plastic polymer recognised for its light weight, chemical resistance properties and 'tint-ability'. In comparable prescriptions it is approximately half the weight of glass lenses, while being slightly thicker. Its impact resistance is greater than glass but does not rise to the level of polycarbonate and it should not be considered for applications where impacts are prevalent. On this basis, it is not recommended for active sports and motorcycling. It is more scratch resistant than polycarbonate, but will scratch if not properly taken care of.

Polycarbonate is an impact resistant material. It is becoming used more widely in recent times - especially for motorcycling and action sports. It is also used frequently for the glazing of rimless frames because of these properties. Although polycarbonate is impact resistant, it should not be considered indestructible. Polycarbonate is the strongest material available and will have the tendency to break into larger pieces, instead of the CR39's smaller pieces, and is, consequently, less hazardous. Polycarbonate is thinner than standard CR39.

Polycarbonate lenses are ten times more impact resistant than other plastics making them highly suitable for action sports or folk that are a little (shall we say) heavy-handed! They offer UV protection and stop 99.9% of rays from the sun, fluorescent lights and computer screens. Our polycarbonate lenses are supplied with a scratch resistant coating and are thinner than standard lens and therefore more comfortable to wear.

Comparison of Lens Materials & Material Characteristics

Polycarbonate

- Strongest material for impact resistance
- Lightweight
- Can be coated for scratch resistance
- Most have built-in UV radiation protection

Plastic (CR39)

- About one-half the weight of glass
- Resistant to solvents and pitting
- More choices for coatings and tinting

Reference:

• wikihow.com
• lensology.co.uk
• ezinearticles.com

Eyewear Fit Guide

Here are four tips that you should know to shop the perfect eyeglasses 

 1. Color - "The color of your eyeglasses frames should be in contrast to the natural color tone of your face and hair. For highlighting and outlining your eyes, black frames are great and look classic too."

 2. Proportion - "Eyeglasses frames should be in proportion with your face. Unlike in case of sunglasses, where you pick bigger frames for a better coverage, eyeglasses if chosen too big according to your face may not look that good."

 3. Contrast - "The shape of your spectacle frame should be in contrast to your face shape. That means, If you have soft and round features, go for angular frames and if you have square or boxy features, go for curved shapes to balance the sharpness."

 4. Face Shape - "Choosing the right frame shape for your face is a complicated task but if you keep in mind the following tips, you will never get confused."

 Choosing the right frame shape for your face is a complicated task but if you keep in mind the following tips, you will never get confused.[1]                        eResearch by Navid Ajamin -- winter 2008

Contents:

- Face Shapes
- Nose Size

Face Shapes

With hundreds of frames in all shapes, sizes and colors to choose from, picking the most flattering eyewear for your face can be confusing. Follow this simple guide and we will help you narrow it down.

Before you start shopping, reference a straight-on picture of yourself and trace the shape of your face. Then decide if the lines you've traced look like an oval, circle (round), square or rectangle (oblong). Once you've discovered the shape of your face, the rest is easy! By wearing a contrasting frame shape, you will complement the shape of your face.

Oval Face Shape
Well, aren't you lucky! Since the shape of your face is of balanced proportions, you can pull off just about any frame. Don't limit yourself to the same frame shape you've been wearing since high school. Try something trendier like wraparounds or shields.

Frame Suggestions: Any frame shape, or get adventurous and try Oversized (Women Specific), Rockstar (Women Specific) and FUNKtion (Women Specific).

Round Face Shape
If you've got a round face, the right frame can make your face appear longer and thinner. Play down the roundness with a soft, angular or rectangle style. You'll be surprised at the difference a frame makes!

Frame Suggestions: Wider frames with angular/rectangular (Women Specific) or square (Women Specific) shapes.

Square Face Shape

You've got a strong jaw line, broad forehead and wide cheekbones. It's the face shape of supermodels and Hollywood hotties which can be best flattered with soft curves.

Frame Suggestions: Oval (Women Specific), Round (Women Specific), and Cat Eyes.

Oblong Face Shape

Why the long face? We've got frames that will both widen and shorten your face shape! To create this illusion, choose a frame that does not extend beyond the widest part of your face (short horizontal and long, vertical lines). Round or square shapes will look great on you.

Frame Suggestions: Round (Women Specific), Square (Women Specific).

Nose Size

The cheapest nose job in town. How to make your nose look its best.

Large Nose

A large nose will shrink when adorned with large, oversize frames. Avoid small frames that accentuate your nose. And since oversized (Women Specific) frames are so "in" right now, it will be easy to find the perfect pair!

Long Nose

Try out a pair of frames that have high sidebars, drawing attention upward toward the temples and away from the nose.
Tip: A double bridge or low bridges help a nose appear shorter.

Small Nose

A high bridge in a light color will lengthen your nose and also give a nose that is small in proportion to the rest of the face, a bigger presence. Don't be scared to try oversized (Women Specific) frames - think celebrities with tiny, cute noses hiding behind oversized glasses! [2]

image: zyloware.com

Reference: 1.coolwinks.com/blog/4-ways-to-choose-the-right-eyeglasses-frame-for-your-face/ 2.zappos.com

See Also: Face Shape Guide for Glasses and Eyewear

CR-39, or allyl diglycol carbonate (ADC), is a plastic polymer commonly used in the manufacture of eyeglass lenses. It should not be confused with polycarbonate, a homopolymer made from bis-phenol A, a tough polymer widely used for glazing. CR-39 is a trade marked product of PPG Industries, originally developed by Columbia Chemical Co Inc which evolved through acquisition into the Chemical Division of PPG Industries. An alternative use includes a purified version that is used to measure neutron radiation, a type of ionizing radiation, in neutron dosimetry.

The CR stands for Columbia Resin. During WWII uncured CR-39 Resin was used to coat aircraft fuel tanks. The CR-39 would "self heal" the tanks when struck by flak. The trade name for the original and most popular plastic material used for eyeglass lenses. The abbreviation stands for “Columbia Resin #39,” because it was the 39th formula of a thermosetting plastic developed by the Columbia Resins project of PPG Industries back in 1940. The first commercial use of CR-39 monomer was to help create lighter, more durable fuel tanks for the B-17 bomber aircraft in World War II. After the War, the Armorlite Lens Company in California is credited with manufacturing the first CR-39 eyeglass lenses in 1947. CR-39 plastic has an index of refraction of 1.498 and an Abbe number of 58.

Applications

CR-39 is transparent in visible spectrum and is almost completely opaque in the ultraviolet range. It has high abrasion resistance, in fact the highest abrasion/scratch resistance of any uncoated optical plastic. CR-39 is about half the weight of glass with an index of refraction only slightly lower than that of crown glass, and its high Abbe number yields low chromatic aberration, altogether making it an advantageous material for eyeglasses and sunglasses. A wide range of colors can be achieved by dyeing of the surface or the bulk of the material. CR-39 is also resistant to most of solvents and other chemicals, to gamma radiation, to aging, and to material fatigue. It can withstand the small hot sparks from welding, something glass cannot do. It can be used continuously in temperatures up to 100 °C and up to one hour in 130 °C.

In the radiation detection application, raw CR-39 material is exposed to proton recoils caused by incident neutrons. The proton recoils cause ion tracks, which are enlarged by an etching process in a caustic solution of sodium hydroxide. The enlarged ion tracks are counted under a microscope (commonly 200x), and the number of ion tracks is proportional to the amount of incident neutron radiation.

What is the difference between resin lenses and glass lenses？

In terms of characteristics:
The hardness of glass lens is very strong, and it can be heated to more than 300 degrees when scrubbing, while for resin lens, it can only be heated to about 80 degrees, so glass lens has strong heat resistance performance. However, the glass lens is easy to break and the weight is relatively heavy, while the resin lens is different. However, because the resin lens does not have super heat resistance, the lens is relatively soft and is easily scratched by foreign objects.

Functionally:
Resin lenses have the function of 100% UV protection from the sun, preventing the eyes from being damaged by various harmful rays, while glass lenses do not have the function of UV protection, and the optical transmittance of resin lenses is more than 2% higher than that of glass lenses. However, for patients with high myopia, resin lenses are thicker, so they will not be so beautiful to wear.
Although today's resin lenses have been greatly improved, they are much thicker than glass lenses. Therefore, in terms of high temperature resistance, glass lenses have a significantly better lifespan.
What is the difference between resin lenses and glass lenses? Both resin lenses and glass lenses have their own advantages, but I personally think that resin lenses are lighter in weight and less stress on the bridge of the nose than glass lenses. And the impact resistance is also relatively good, when it is impacted by the outside world, it will not be easily broken, which can protect the health and safety of eyes and vision to the greatest extent. Therefore, resin lenses are more suitable for children and myopia patients with relatively large diopter than glass lens optical lenses.

Common sense of lens material: -- eResearch by Navid Ajamin -- winter 2010
1. Material: PMMA: Acrylic (commonly known as plexiglass), which is cheap and heavy, and the phase clarity of the object is average. The lens is easily broken by external force.
PC: commonly known as space film Advantages: light lens (specific gravity is 1.20g/cm³), high strength, high impact resistance, not easy to split, better clarity than PMMA but inferior to CR-39, generally used for sports glasses and protective glasses; when the thickness of the material reaches When it is 2.5cm, it can be used as bulletproof glass; PC sheet can absorb (or block) almost all ultraviolet rays harmful to human eyes, which is especially suitable for drivers and computer operators.
Disadvantages: 1. It is easy to be scratched and the wear resistance reaches B. All PC sheets must be hard-coated to improve the surface hardness of the focusing lens.
2. The lens has a large chromatic aberration
PL (CABTAC): Commonly known as Poly Lay film, it is a mainstream product in the future market. It is light and effective against harmful light and reflected light. It can see objects with high definition and realism. The original film will not be broken but easily scratched. It is generally used for outdoor fishing. , and students wear all fishing goggles and student goggles in class.
CR-39: commonly known as high-grade resin sheet, it is a high-definition lens, expensive and light (specific gravity is 1.32g/cm³)
Advantages: strong impact resistance, high temperature resistance, 10 times higher than glass, so the lens is not easy to break, and the break is not sharp after breaking; the lens is light in weight; the absorption function of ultraviolet rays is better than that of ordinary optical glass sheets
Disadvantages: The sheet is easy to be scratched, and the requirements for the assembled frame aspherical mirror are high. The resin sheet should preferably be coated with an anti-reflection film to improve the light transmittance of the lens.
Older reading glasses should also be replaced regularly. Presbyopia is caused by the aging of the lens. With the increase of human age, the degree of aging of the lens will increase, and the required correction of the lens power must increase accordingly to meet the needs of the elderly in daily life.
There is no unified regulation on the specific replacement time. When the elderly wear glasses to read newspapers and feel tired and their eyes are sore and uncomfortable, they should be replaced.

There are many lens materials on the market today. Resin lenses are light and easy to carry, but they are easily scratched, so pay special attention to lens care. Glass lenses are cheap, but fragile, and if they are broken, they may cause extremely serious damage to the eyeballs, so they are not suitable for teenagers who exercise a lot.

Polycarbonate (PC)

• Organic material with very high breaking strength
• Inherently soft allowing it to absorb impacts, ideal for safety eyewear
• Mechanical strength class "F" (45 m/sec)
• About 20-25% thinner than plastic or glass lenses
• Requires scratch-resistant coating for durability
• Only limited resistance to chemicals and therefore not suited in combination with frameless safety spectacles

CR39 (Plastic)

• Lightweight organic material
• Very good optical performance even for high prescriptions
• Suitable for working with chemicals and paints / varnishes
• Mechanical strength class "S" (falling ball test)
• Good scratch resistance due to hard layer (optional)
• The middle of the lens should always be thicker in order to meet the requirements for tensile strength

Reference:

• en.wikipedia.org/wiki/CR-39
• uvex-safety.co.uk/en/cr39-versus-polycarbonate-lenses
• edlensxs.com/blogs/industry-news/what-is-the-difference-between-resin-lenses-and-glass-lenses

See Also:

• ophthalmic Lens material and design
• eyewear - Comparing Polycarbonate Lenses With Standard CR39 Lenses

Polarized sunglasses are sunglasses that help diminish the glare of the sun. Polarized sunglasses provide incredibly clear, glare-free vision. These glasses were first worn by pilots to help them see when the sun was shining in different spots during the day. These days, many people wear polarized sunglasses when driving, golfing, and fishing. They look the same of other types of sunglasses, but deflect the sunlight in such a way so that it is not distracting when they are focusing on other things.

This causes the dramatic reduction in glare and increases visibility.

For those who drive a great deal during the day, these sunglasses will help keep the sun from becoming too distracting and help prevent squinting.

eople seem to get less tired, suffer less fatigue, and have fewer headaches on long trips.

Polarized sunglasses can make driving a boat or a car safer and improve outdoor sports performances.

When fishing, wearing polarized sunglasses will allow people to see into the water more clearly and accurately. When the sun is out, it can reflect off the water and cause the visibility to go down. When fishing, many people need to see into the water. Polarized sunglasses take a lot of the glare off the water allowing people to see what is below. This is helpful when boating also. In order to protect the boat from jagged rocks just below the surface, people can navigate the boat around these objects because they saw them ahead of time. These sunglasses can cave people from a wide variety of accidents both in the water and on the road.

Polarized sunglasses are not too expensive and come in a wide variety of styles and colors. They can be found wherever sunglasses are sold. At first, many of these sunglasses came with yellow tinted lenses, but these days the lenses are clear which many people are happy about. For those who enjoy outdoor activities like hiking, hunting, and sports, a pair of these sunglasses will help them get the most out of their day. Buying a pair of these sunglasses will help a person enjoy being out in the sun and not having to worry about missing out on any part of it.

Polarized sunglasses are so lightweight; you'll almost forget you're wearing them. They also provide excellent coverage and protection from wind, glare, and dust. Though they cost a little more initially, the increase in vision is dramatic. They are well worth the investment, especially if they prevent just one accident. eResearch by navid ajamin -- summer 2008

When Should You Wear Polarized Sunglasses?

Glare can be dangerous, especially when driving because it distorts the true color of objects and makes objects harder to see. Glare has been linked to many pedestrian deaths and traffic accidents.

Polarized sunglasses can be especially helpful in situations like:

• Driving: This is especially true on extremely hot days when the combination of hot air near the surface of a road and less hot air above it causes a mirroring effect.
• Playing outdoor sports: Polarized sunglasses help athletes see with greater clarity so that they can safely maneuver while competing in full daylight.
• Water activities: This includes speedboating, sailing, fishing, and other water sports when glare can come from all directions as sunlight bounces off waves or moving water.

How Polarized Lenses Enhance Color and Clarity?

The polarization of the lenses helps to reduce glare, which in turn enhances color and clarity. The chemical treatment used in polarized lenses blocks out certain wavelengths of light, leaving other wavelengths unchanged. This reduces the light entering your eyes and makes colors appear more vivid and clear.

The color of the lens can also affect color perception and clarity. Different colors are better for different conditions, so it’s important to pick the right lenses for your needs.

Benefits of Improved Color Perception and Clarity

Some of the benefits of improved color perception and clarity provided by polarized lenses include:

Enhanced detail

You’ll be able to see details more clearly and accurately, making activities like photography or painting easier.

Vivid colors

Colors will appear sharper and more vibrant due to the reduced glare. This can make outdoor activities such as hiking or bird watching much more enjoyable.

Improved depth perception

Polarized lenses help create a three-dimensional effect, allowing you to perceive depth and distance better. This can be especially helpful for activities like golfing or skiing, where accuracy is important.

Protection from Harmful UV Rays

Polarized lenses also protect from harmful UV rays. These lenses are designed to block out UVA and UVB radiation, which can harm your eyes over time. This is especially important in skiing or hiking, where the sun’s rays can be strong.

How Polarized Lenses Block Harmful UV Rays?

Polarized lenses are treated with a special chemical that helps block UVA and UVB radiation. This treatment allows the lenses to filter out certain wavelengths of light while still allowing other wavelengths through. This reduces the amount of harmful rays entering your eyes and keeps them safe from long-term damage.

Benefits of Blocking Harmful UV Rays

The benefits of blocking harmful UV rays are numerous,

including:

Protection from long-term damage

The reduced amount of UV radiation entering your eyes helps to protect them from long-term damage. This can help you maintain a healthy vision for years to come.

Reduced eye strain and fatigue

Blocking UV radiation can also help to reduce eye strain and fatigue, which is especially beneficial during activities like skiing or golfing.

Long-term health benefits

In addition to providing eye protection, blocking out UV radiation can also help to reduce the risk of skin cancer and other diseases.

Polarised Sunglasses vs Normal Sunglasses:

Normal sunglasses offer basic protection against bright light & UV rays but only polarised lenses block blinding glare and can also enhance visual acuity, colour contrast and visual comfort, blocking 100% of harmful UVA/B light.

Different Types Of Polarised Lenses:

Lenses can be polarised to different degrees and in different ways. Most inexpensive polarised sunglasses have a thin film applied on one side of the lens. Many higher quality lenses have film laminated between two layers of lens material, preventing it from being scratched or rubbed off. In addition, the more dense the film is, the more polarisation it provides.

In most cases, polarised sunglasses don't look any different from regular sunglasses. While denser films tend to be darker, the colour of a lens does not determine how much polarization it provides.

A very dark pair of sunglasses with a light film will not block more glare than a lighter shade of glasses with a denser film. The colour of the lens is also variable; although they cannot be made clear, polarised lenses can be made in grey, brown, green, or other colours.

The Benefits of Polarized Lenses for Children

These lenses help reduce glare from reflective surfaces, improving visual clarity and reducing eye strain. This enhanced vision can improve safety in sports by allowing children to see more clearly and react more quickly to their surroundings.

How to Protect Your Child's Vision Outdoors

As parents, you want the best for your child, including their vision. Here are some tips to help keep their eyes safe during outdoor activities and sports this summer:

• Wear Protective Eyewear: Ensure children wear protective eyewear with UV protection, such as sunglasses with polarized lenses or sports goggles, to shield their eyes from harmful UV rays and potential injuries.
• Use Hats and Visors: Encourage children to wear hats or visors to reduce UV exposure and protect their eyes from direct sunlight.
• Choose the Right Gear: Invest in sport-specific protective eyewear that meets safety standards to protect against impact and debris for specific sports.
• Educate About Safety: Teach children the importance of eye safety, including avoiding direct sunlight exposure and the risks of rubbing their eyes with dirty hands, which can lead to infections.
• Regular Eye Exams: Maintain regular eye check-ups to monitor their eye health and update prescription lenses as needed, ensuring optimal vision.

Reference:

• streetdirectory.com
• verywellhealth.com/polarized-sunglasses-3422163
• popularmechanics.com/science/a28191/polarized-sunglasses-bells-theorem
• danielwalters.com/blog/benefits-of-polarized-lenses-why-theyre-worth-investing-in
• bethesdavisioncare.com/why-polarized-lenses-are-a-game-changer-in-kids-sports

Progressive Lens (No-Line Bifocal) vs. Line Bifocal Advantages

• No sudden "image jump" from distance to near.

• An infinite number of focal points to view objects at different distances.

• No visible line where the bifocal power begins.

• More natural vision for near viewing.

• A variety of lens designs to fit virtually any application.

Progressive lenses, or "no-line" bifocals, are increasing in popularity because of the advantages they offer to wearers of regular "lined" bifocals, along with the many lens designs now available. In addition, the advancements in progressive lens technology have helped reduce their cost over time.

From a safety standpoint, the main reason we recommend that a company cover the cost of progressive lenses for their employees is that many people already wear them in their "street" glasses, and adjusting back to a line bifocal for their daily safety wear can be very difficult, and possibly dangerous. As an individual adjusts back to a line bifocal, their ability to see near objects clearly may be inhibited. This can create a safety hazard, and may also interfere with the quality of their work.

Most companies have found that the additional cost of providing progressive lenses to their employees is outweighed by the many advantages, including increased safety and employee satisfaction.

While progressive lenses are preferred by most people, some are unable to adapt to wearing these lenses comfortably. This is mainly due to slight distortions at the peripheral areas of the bifocal, caused by the "blending" of the bifocal. For most people, this is not a concern, but for those that cannot adjust to this, a regular line bifocal may be the best option.

A variety of progressive lens products are available, including options to fit your budget. Your Optician or Sales Representative can help you make the right choice based on your needs.

Source: U.S. Safety (Prescription Safety Eyewear Program)

Follow these steps for choosing the right pair of sunglasses:

• Insist on 100% UV protection.
• Make sure the sunglasses fit properly. It's not a winter coat they'll grow into.
• Be patient - children need to get used to wearing sunglasses.
• Make sure your child likes the sunglasses and that they are comfortable, or they won't wear them.
• Consider impact-resistant lenses, which protect your child's eyes from injury.
• Make sure the frame has features, like spring hinges, that will stand up to the most active child.
• When children are very young, look for sunglasses with straps or ear pieces that wrap around the ear.
• Kids with prescription eyewear should have prescription sunglasses or sunclips for their regular glasses.
• Older kids who wear contact lenses should have non-prescription sunwear for when they're outdoors.

Reference: medicinenet.com

As summer approaches, new research from optometrists in Australia shows that motorists with a colour vision defect (colour blindness) need to choose the tints of their sunglasses with care. The wrong choice could result in either misreading traffic lights or in significant delay in reading them, with obvious potentially dangerous consequences.

The study shows that some sunglass tints, currently permitted for wear by drivers and riders, cause a measurable decrease in the ability of colour defective observers to detect and recognize traffic signals. This is prima facie evidence of an increased risk in the use of these lenses.

Colour defective drivers are already known to have problems detecting and recognizing road traffic signals relative to people with normal colour vision, in particular longer reaction times and incorrect recognition of signals. Colour defective drivers were found to have significantly worse performance when wearing sunglasses than colour normals. Combinations of signals and sunglasses of similar colours are of particular concern. Drivers wearing lenses with green or green/yellow tints are liable to have problems identifying amber and green traffic lights; those wearing red/brown tints may have trouble with amber and red lights.

Sunglasses come in a wide range of colourations; for this study, clear, grey, green, yellow-green, yellow-brown, red-brown were examined. The yellow/green, the red/brown and the yellow/brown tints pass the current European standards for sunglasses, despite being implicated in decreased performance for people with a colour vision defect in this study.

Prevalence of colour vision deficiency varies according to ethnic origin, with the majority caused by a genetic defect, on the X chromosome, which results in males being far more likely to suffer than females. The most common form of colour deficiency is red/green colour blindness, although blue/yellow is also well-known. Some studies put the prevalence of red/green colour blindness as high as 10% (US white males). Given that young males are already identified as relatively high risk drivers, this research identifies a serious area of concern for road users and the authorities responsible for driver safety. eResearch by Navid Ajamin -- summer 2009

Statistics from Brake, the road safety charity in the UK, show that one in eight driving licence holders is under the age of 25 - yet more than a quarter of drivers killed are from this age group. It also shows that young male drivers have much higher accident rates than young females and that males aged 17-20 are seven times more at risk than all male drivers.

The European Council of Optometry and Optics recommends that motorists have regular eye examinations and ask their optometrist for professional advice about sunglasses.

Reference: American Academy of Optometry

Progressive lenses, also called progressive addition lenses (PAL), progressive power lenses, graduated lenses, no-line bifocals, and varifocal lenses, are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. They are characterised by a gradient of increasing lens power, added to the wearer's correction for the other refractive errors. The gradient starts at a minimum, or no addition power, at the top of the lens and reaches a maximum addition power, magnification, at the bottom of the lens. The length of the progressive power gradient on the lens surface is usually between 15 and 20 mm with a final addition power between 1.00 to 2.50 dioptres for most wearers. The addition value prescribed depends on the level of presbyopia of the patient and is closely related to age.

Advantages and use

The wearer can adjust the additional lens power required for clear vision at different viewing distances by tilting his or her head to sight through the appropriate part of the vertical progression;

• The lens location of the correct addition power for the viewing distance usually only requires small adjustments to head position, since near vision tasks such as reading are usually low in the visual field and distant objects higher in the visual field.

  • Progressive addition lenses avoid the discontinuities (image-jumps) in the visual field created by bifocal and trifocal lenses and are more cosmetically attractive. Since bifocal and related designs are associated with 'old age', proponents have suggested the lack of segments on the lens surface of a progressive lens appears more 'youthful' since lenses associated with younger wearers single vision lenses tend to be free of segments or lines on the surface.

Disadvantages

Distortion: Progressive lenses suffer the disadvantage of the power progression creating regions of aberration away from the optic axis, yielding poor visual resolution (blur), which varies in relation to the quality of the lens. As the lenses combine a range of powers in a single surface there are also geometric distortions to the visual field, which increase with the addition power. Some wearers find the visual discomfort caused by these distortions outweigh the benefits of wearing PALs, this is known as progressive non-tolerance. However, manufacturers claim acceptance rates of 90%–98%. Clinicians generally agree that in order to avoid adaptation problems it is best to start wearing progressive lenses early in the development of presbyopia (around 40 years of age for most people) while the prescribed addition powers are low. The wearer can then adapt to the increases in a series of steps in addition power over a number of years as their presbyopia progresses. Others argue that this stance is a way to sell more lenses.

Peripheral Vision Distortion: Because of the compromise in vertical range of undistorted vision, there is an inherent impact on peripheral vision with progressive lenses which is more obvious than that which is found in single vision lenses. This can affect the intermediate portion of the vision more so than the distance, and wearers who use computers regularly and for prolonged periods of time may benefit from an occupational progressive lens, commonly referred to as an office or extended reading lens.

Fitting: Progressive lenses require careful placement relative to the wearer's pupil centre for a distance-viewing reference position. Incorrect specification of the fitting location can cause problems for the wearer including (depending on the design of the lens) narrow fields of view, clear vision in one eye only, on-axis blur, and the need to alter the natural head position in order to see clearly. eResearch by Navid Ajamin -- summer 2009

Cost: Progressive lenses are generally dispensed at a higher price than bifocal and single-vision reading spectacles due to the increased manufacture and professional service costs.

When selecting a progressive lens design, an eyecare practitioner will usually ask some lifestyle questions, which coupled with prescription restrictions or recommendations and cost can effectively establish suitability for various models of progressive lens. Different lenses have different glazing restrictions, lens material availabilities, maximum and minimum fitting heights, prescription ranges and as such the variation in quality between higher and lower end varifocal lenses is considerable.

How Do Progressive Lenses Work?

For any optical device or instrument to be able to focus at multiple focal distances (i.e., near, intermediate, and distance), an element of the overall optical apparatus must move. In cameras, the barrel of the lens moves to adjust the lens closer or further away from the sensor or film to achieve a focused image. With progressive lenses, it is the eye that moves to achieve in-focus images at various distances. Looking out on the horizontal plane provides clear distance (e.g., driving) vision; looking a few degrees downward provides clear intermediate (e.g., computer) vision; and looking downward even further along the plane of the cheeks provides clear near (e.g., reading) vision. The dependency on vertical eye movement, along with head positioning, to make progressive lenses perform properly often requires individuals to adapt to their new optical environment. With daily wear, the average person typically requires 1-2 weeks to adapt to new progressive lenses.

Reference:

• wikipedia.org/wiki/Progressive_lenses
• eye-deology.com/eyewear/progressive-lenses

See Also:

• Progressive addition lenses
• SIDE EFFECTS OF PROGRESSIVE LENSES

Night blindness is a type of vision impairment also known as nyctalopia. People with night blindness experience poor vision at night or in dimly lit environments.Historically, nyctalopia, also known as moonblink, was a temporary night blindness believed to be caused by sleeping in moonlight in the tropics.Although the term “night blindness” implies that you can’t see at night, this isn’t the case. You may just have more difficulty seeing or driving in darkness.

Night blindness is a heterogeneous group of ophthalmological disorders that results in a diminished ability to see under scotopic (dim light) conditions.

There are both acquired and congenital forms of night blindness.

• Acquired forms of night blindness include an insufficiency of vitamin A and paraneoplastic syndromes (melanoma-associated retinopathy and cancer-associated retinopathy).
• Congenital forms include both stationary (in which the severity remains relatively constant throughout life) and progressive (in which severity increases over time) forms of night blindness.
• Stationary forms can result from genetic mutations in rod photoreceptors or rod bipolar cells.
• Progressive forms include retinitis pigmentosa, choroideremia, and gyrate atrophy.

Some types of night blindness are treatable while other types aren’t. See your doctor to determine the underlying cause of your vision impairment. Once you know the cause of the problem, you can take steps to correct your vision.

nyctalopia is a type of vision impairment. People with night blindness experience poor vision at night or in dimly lit environments. It is not a disease in itself, but rather a symptom of an underlying problem, usually a retina problem.

Your vision relies on light coming through your eye, hitting the retina at the back of the eye, being transmitted through the optical nerve, and processed by the brain.

At night, your pupils will get larger to allow more light in. The rod cells on your retina will collect more light, as they are more photosensitive than the cone cells. Your optic nerve will take this mostly black-and-white image to your brain, where it is interpreted into your surroundings.

What Causes Night Blindness?
A number of eye conditions can cause night blindness, including:

1. Nearsightedness or blurred vision when looking at faraway objects.
2. Cataracts or clouding of the eye's lens.
3. Retinitis pigmentosa, which occurs when dark pigment collects in your retina and creates tunnel vision.
4. Vitamin A Deficiency
5. Zinc Deficiency
6. Dry Eyes
7. Diabetes

Are the Symptoms of Night Blindness?

To identify night blindness, the American Academy of Ophthalmology suggests that people consider the following questions:

• Is moving around the house in dim light a challenge?
• Is driving at night increasingly difficult?
• Is it tricky to recognize faces in dim light?
• Does it take an abnormally long time to adjust to a light room after being in the dark?
• Does it take a long time to see in a darkened room after being in the light?

Other symptoms may also occur with night blindness. The nature of these symptoms will depend on the underlying cause but may include:

• headaches
• eye pain
• nausea
• vomiting
• blurry, or cloudy vision
• sensitivity to light
• difficulty seeing into the distance

The sole symptom of night blindness is difficulty seeing in the dark. You're more likely to experience night blindness when your eyes transition from a bright environment to an area of low light, such as when you leave a sunny sidewalk to enter a dimly lit restaurant. You're likely to experience poor vision when driving due to the intermittent brightness of headlights and streetlights on the road.

How can I Prevent Night Blindness? eResearch by Navid Ajamin -- spring 2009

You can't prevent night blindness that's the result of birth defects or genetic conditions, such as Usher syndrome. You can, however, properly monitor your blood sugar level and eat a balanced diet to make night blindness less likely.

For many people around the world, night vision can be a problem. There are many root causes of night blindness, but the common symptom is the inability to see well or clearly at night.

Different causes of this condition will require different approaches to treatment. Getting regular eye exams to diagnose some issues before night blindness occurs can help to reduce your risk.

People with poor night vision typically are not able to see well in the dark. They are, however, able to see perfectly well during the day, even though transitions from bright environments to dim ones, such as when entering a darkened hall from the sunny outdoors, may be challenging.

One key to seeing at night is a healthy amount of rhodopsin, which is an eye pigment in the retina responsible for night vision. It is used specifically by the photoreceptor cone cells to perceive light, while the rods, on the other hand, are highly sensitive to darkness. Rhodopsin enables us to quickly adapt our vision from a dark room to a light room.

Vitamin A is an essential component of rhodopsin, so a deficiency in vitamin A can result in poor night vision. Though vitamin A deficiency is rare in industrial nations, there are other reasons vitamin A intake may be compromised, including:

• Iron deficiency can affect vitamin A uptake.
• Small-bowel bypass surgery may reduce vitamin A absorption.
• Excess alcohol consumption impairs absorption.
• Medications can affect fat absorption (Xenical) or cholesterol (statins).
• Low fat diets may be low in vitamin A.
• Zinc deficiency is associated with decreased release of vitamin A from the liver.
• Other conditions such as fibrosis, pancreatic insufficiency, and inflammatory bowel disease affect how vitamin A is utilized in the body.

For people whose night vision begins worsening due to other related eye conditions, the vision loss can occur very slowly over time. It can also occur quickly, depending on how acute the eye condition is, such as with untreated retinal bleeding. Cataracts, for example, tend to develop slowly, but for a smaller percentage of the population, they can evolve rapidly.

Symptoms vary (based on the individual) and can include any or all of the following:

• Weak vision in dim light
• Difficulty seeing during night driving
• Slow vision adaption between bright and dim light conditions (such as taking a longer time than other people to adjust to indoor lighting when coming from the bright outdoors)
• Fifty to seventy percent of people with night blindness also have nystagmus and strabismus, as well as low vision and myopia.

Only your doctor can provide an adequate diagnosis of any signs or symptoms, and whether they are night blindness symptoms, or symptoms of another disorder. The determination of the cause of night blindness should be fairly easy with a full, dilated exam and targeted tests, such as an optical coherence tomography scan (commonly known an OCT scan). This is particularly important so that the eye doctor has a history of test results with the patient.

If the night blindness is genetic, your doctor may administer a test called an electroretinogram, which determines the function of the retina and therefore its proper classification.

Reference:

• healthline.com/health/vision-night-blindness
• en.wikipedia.org/wiki/Nyctalopia
• nvisioncenters.com/education/night-blindness
• researchgate.net/publication/284826657_Night_Blindness
• lybrate.com/topic/night-blindness-causes-and-symptoms
• naturaleyecare.com/eye-conditions/night-blindness
• medicalnewstoday.com/articles/324004.php#what-are-the-symptoms

See also: Identifying a gene for canine night blindness

چشمان برخي كودكان ، با آنكه سالم به نظر مي رسند اما از سلامتي و ديد كافي برخوردار نيستند .
رشد و تكامل مركز بينايي در مغز از دوران جنيني تا حدود ده سالگي ادامه دارد ، اما حداكثر سرعت رشد آن تا سه سالگي است .

Classification and Types

• Stimulus deprivation or amblyopia of disuse
• Amblyopia secondary to nystagmus
• Anisometropic amblyopia
• Isoametropic amblyopia
• Strabismic amblyopia
• Meridional amblyopia
• Idiopathic amblyopia
• Organice amblyopia

نتيجه تكامل دستگاه بينايي ، در اين دوران ، ديد واضح و كامل است . در اين مدت ، بخصوص در سه سال اول زندگي ، هر عاملي كه باعث اشكال ديد ، در يك يا هر دو چشم كودك شود ، رشد و تكامل دستگاه بينايي را متوقف مي سازد و در نتيجه باعث كاهش ميزان بينايي طفل مي شود . معني اين سخن آن است كه امكان دارد چشمي را كه از نظر ظاهر كاملا طيعي است از بينايي كامل و طبيعي برخوردار نباشد.
در صورتي كه اشكال ديد كودك ، قبل از پنج سالگي درمان شود ، حتي اگر چشم در اين مدت تنبل شده باشد با درمان ، بينايي كامل بدست مي آيد .
پس از پنج سالگي ، هر چه درمان چشم تنبل بيشتر به عقب بيافتد ، احتمال به دست آوردن بينايي كامل كمتر مي شود . به طوري كه پس از هفت تا ده سالگي ، درمان هيچ تاثيري در بينايي نخواهد داشت.
آمبليوپي نوعي كاهش بينايي است كه در ان نمي توان در چشم و يا در راههاي عصبي بينايي هيچ گونه عيب ارگانيك (ساختماني)واضحي براي آن يافت و در واقع از مواردي است كه نه مريض چيزي مي بيند ونه دكتر در چشم مريض چيزي مي بيند از نقطه نظر باليني زماني تشخيص آمبليوپي مسجل مي گردد كه حتي با بهترين تصحيح انكساري نيز نتوان ديد بيمار را افزايش داد و در روي تابلوي اسنلن حداقل دو رديف اختلاف ديد وجود داشته باشد در اينجا مي توانيم بگوييم چشمي كه ديد كمتري دارد دچار آمبليوپي است با شرط اينكه در ته چشم نيز نتوان هيچ گونه ضايعه ارگانيكي كه مسئول كاهش بينايي باشد يافت نمود.

How Does Amblyopia Occur?
While it is essentially the inability of the eye to focus clearly, the causes are much more detailed and widespread. According to the National Eye Institute, it is caused by a number of conditions, including:

• Strabismus:  The misalignment of the eyes. Strabismic amblyopia is the most frequent cause. In this situation, lazy eye occurs as a result of the brain bypassing the visual information being received from the eye that is misaligned.
• Cataract: The clouding of the front part of the eye. This form of lazy eye is known as deprivation amblyopia and results from light being unable to enter and focus in the eye.
• Blurry vision: Refractive error caused by the eye’s inability to focus light on the retina, often referred to as being nearsighted, farsighted, or astigmatism. This form of lazy eye is known as refractive amblyopia and occurs when the brain disregards the information being received from the eye that has the refractive error; over time, the condition develops as a result of underutilization of the weaker eye.[2]

عوامل ايجاد كننده تنبلي چشم
اشكالات مادرزادي در ساختمان چشم ، مانند آب مرواريد و پايين افتادگي پلك باعث ميشود كه چشم نتواند تصوير واضحي از اشياء دريافت كند و بتدريج دچار تنبلي شود . در مورد كاتاراكت بهترين درمان عمل جراحي است كه اگر پس از تولد تا سه ماهگي هرچه سريعتر صورت بگيرد ، نتيجه بهتري خواهد داشت . اما پس از سه ماهگي نتيجه چندان رضايت بخش نخواهد بود.
در نزديك بيني ، دور بيني و آستيگماتيسم ، اگر ديد هر دو چشم بسيار كم باشد ، هر دو چشم و آگر تفاوت دي آنها زياد باشد ، چشم ضعيف تر نمي تواند تصوير واضحي از اشياء دريافت كند و دچار تنبلي مي شود .
لوچي يا انحراف چشم نيز مي تواند باعث دو بيني شده در نتيجه تصوير واضحي روي شبكيه تشكيل نشود . بدين ترتيب مغز بتدريج براي حذف دو بيني ، تصوير چشم منحرف را حذف كرده و تنبلي چشم ايجاد خواهد شد.

پيشگيري و درمان
تنها راه پيشگيري از تنبل چشم تشخيص بموقع عوامل ايجاد كننده آن است و چون بسياري از اين عوامل براي خانواده ها ناشناخته است ، چشم همه كودكان بايد حداقل سه بار قبل از دبستان در زمانهاي مختلف معاينه شود :

 سه ماهگي -  دو تا سه سالگي - پنج تا شش سالگي

همچنين اگر كودكي انحراف چشم دارد ، والدين بايد به محض تشخيص ، او را نزد متخصص برده و تحت درمان قرار دهند.
درمان تنبلي چشم ، معمولا با بستن چشم سالم است ، تا چشم تنبل به كار بيافتد و تنبلي آن برطرف شود . مدت بستن چشم را متخصص تعيين مي كند و در فواصل مشخص نيز بايد بوسيله متخصص معاينه شود .
گاهي اوقات براي درمان عينك و در برخي موراد جراحي توصيه مي شود . اگر تنبلي چشم بر اثر بيماريهاي مادرزادي مانند آب مرواريد ، پايين افتادگي پلك يا ديگر عيوب ساختماني باشد بايد قبل از سه ماهگي درمان شود و اگر به علتهاي ديگر باشد ، درمان قطعي تا قبل از پنج سالگي امكانپذير است و بعد از آن درمان معمولا نتيجه خوبي ندارد .
گاهي اوقات مدت درمات چندسال است . در اين صورت والدين طفل بايد استقامت ، پشتكار و حوصله لازم را داشته باشند و از رفت و آمد نزد متخصص و ساير مشكلات جنبي آن خسته نشوند.
اگر متخصص توصيه كرد چشم كودك را ببنديد ، طبق دستور او عمل كنيد و چشم كودك را كمتر يا بيشتر از زمان تعيين شده نبنديد .
در صورت تشخيص تنبلي چشم ، حتما تا پايان ده سالگي پيگير وضعيت بينايي و تغييرات عيوب انكساري كودك باشيد.[1]

Reference: 1.parsiteb.com 2.eyeque.com/knowledge-center/facts-about-amblyopia-lazy-eye/

What are mirrored sunglasses good for?

Mirrored lenses also provide UV protection, making them ideal for high-intensity outdoor activities like motorcycling and cycling where sunglasses serve as protective gear. Mirrored lenses also reduce harsh glare from water which make them a great choice for fishing and boating too.

What Are the Pros and Cons of Mirrored Sunglasses?

Mirrored sunglasses come with their pros and cons. It is because this eyewear serves a specific purpose. Thus, it provides advantages and some downfalls in some situations. If you want a pair of sunglasses that can hide your eyes, this type is for you. But first, let me give you a quick idea of its pros and cons.

One benefit of mirrored sunglasses is versatility. It can bring different looks and styles to your face. Regardless of the weather and season, you can be fashionable and protected from the sun. But it can be more expensive. It doesn’t work well under low light conditions too.

Mirrored sunglasses have been gaining popularity. You can look fabulous while having 100% protection against UV rays. But before you spend any bucks, here’s a quick guide of its pros and cons. Let’s find out if mirrored sunglasses are for you.

What Are Mirrored Sunglasses?

Mirrored sunglasses are those that have shiny surfaces on their lenses, we also called them Revo sunglasses or Revo coating sunglasses. It is like a mirror that lets you hide your eyes because others can’t see where or what you’re looking at. But, only people who are looking at you can see the mirrored effect.

How does it happen?

Mirrored sunglasses have reflective coating used on the outer surface of the lenses. This coating comes in different colors like silver, gold, and blue. It may look dark from the outside, but this eyewear lets you see clearer objects when you wear it.

You can get protection from excess light and glare from various surfaces. It includes water, pavements, and ice. Mirrored sunglasses also have thin and metal material for durability.

Speaking of glare, is it the same with polarized sunglasses?

Polarized and mirrored sunglasses are not alike, although they share one common feature. Both can offer anti-glare protection. Polarized sunglasses can block harmful ultraviolet rays through their vertical filters.

Meanwhile, mirrored sunglasses can lower the sun’s glare only through its reflective coating. Thus, there are times when it is not as effective as polarized sunglasses.

Mirrored sunglasses are perfect examples of one-way mirrors. It is a reciprocal mirror that is reflective on one side and transparent on the other. So, the user can view from the reflected lenses, but not vice versa.

Advantages and Disadvantages Of Mirrored Sunglasses

Like many things, mirrored sunglasses also have their benefits and drawbacks. Later in this article, I will give you a more profound explanation. For now, here’s a summary of its advantages and disadvantages.

• Can block glare
• Prone to scratches
• UV rays protection
• Not suitable for LCD
• Brighter vision
• Dark in low light conditions
• Stylish to wear
• Quite expensive
• Good for hiding eyes
• Good for sports
• Durable and versatile

Pros and Cons of Mirrored Sunglasses

Let’s take a deeper look at the pros and cons of mirrored sunglasses. I’ll explain what makes this eyewear excellent, and the compromises to consider. Aside from the obvious shiny lenses, find out if these sunglasses are for you.

Pros: Reduced Glare

Like polarized eyewear, mirrored sunglasses can also reduce glare. It is not through vertical filters, but it’s by the reflective coating used on its lenses. You can also have 100% visibility, but only in bright light conditions. Thus, you can use it while driving, ice skating, and other water sports.

Pros: UV Light Protection

UV protection is the primary function of mirrored sunglasses. It prevents too much light from entering your eyes. So, you won’t need to close or cover your eyes to block the sunlight. Your eyes will feel more comfortable because of less tension.

Pros: Brighter Vision

Mirrored sunglasses offer brighter vision even under extreme light. The layering and coating work together to reflect the light instead of absorbing it. It is the reason why more users are choosing mirrored sunglasses. But, expect that it is not as bright in low light conditions.

Pros: Fashionable

With many styles and options, mirrored sunglasses offer undeniable fashion senses. You can choose from many colors to rock your shades.

Pros: Good For Hiding The Eyes

Mirrored sunglasses will hide your eyes from the outside. If you want to get unnoticed by what you’re looking at, these lenses will do great for you. Other reasons could be hiding puffy eyes and dark circles under the eyes. You don’t have to worry because people can only see their reflections.

Pros: Good For Sports

Are you into any outdoor sports or activities that involve ice or water? Then, mirrored sunglasses can also be your eye protection. Its ability to block UV rays and glare will let you see. This way, you can avoid injuries and falls.

Pros: Durable And Versatile

Mirrored sunglasses come with many layers of advanced coatings. So, you can rely on its durability. Plus, you can wear it for different purposes.

Cons: Extra Care Is Essential

Since it is from glass materials, you need to be extra careful with the sunglasses. Don’t get me wrong. This is durable eyewear, but particular caution is essential. Look out for any scratches. Make sure that you also clean it’s frames and lenses often to maintain its good condition.

You can wash it with some lens cleaning wipes or through dish soap and warm water. But, you can also look for mirrored sunglasses with a scratch-resistant coating to be sure.

Cons: Not Suitable For LCDs

You will notice that the images on LCD screens will look distorted and dark. Try reading a text or looking at an image on your mobile device. It becomes almost impossible to see. Thus, if you’re a pilot or your work requires reading LCDs, these lenses are not for you.

Cons: Becomes Dark Under Low Light Conditions

Mirrored sunglasses don’t absorb enough light. Thus, it will not brighten your vision during low light conditions. If you’re driving and you have to pass through a tunnel, make sure to remove it for a while. It may compromise your vision, which may lead to accidents.

Cons: More Expensive

You may end up spending more money than regular tinted lenses. But, with its advantages, you’re paying for quality and extra features. Mirrored sunglasses are worthy of your every penny, especially in the long run.

Conclusion

Now that you’ve learned the pros and cons of mirrored sunglasses, is it for you? Who would say no to a pair of eyewear that can provide complete UV protection? Plus, you can get a stylish finish? It may be costlier compared to regular tinted glasses. Still, you’ll benefit a lot with those extra features. Give these sunglasses a chance. They also deserve a space in your drawer.

Studies show that exposure to ultraviolet light can contribute to a number of ocular complications, including: photokeratitis, or "snow blindness"; cataracts; pterygium (a benign, abnormal growth on the eye's surface, which may require surgery if sight is threatened); and macular degeneration.     _{eResearch by Navid Ajamin -- summer 2008}

Image: warehouse.com ; cerjousa.com ; indianaeyeclinic.com ; mybesteyeglasses.com ; julbousa.com

Reference: www.kidsource.com

Tips for Maintaining Your New Glasses

Avoid Chemical Contact

Your glasses can be very fragile depending on how they were made. Some lenses have films on them to provide UV protection, scratch or shatter resistance, or even to enhance your prescription. These films are the most fragile part of your glasses, and they can easily be destroyed by contact with certain abrasive chemicals.

While it's obvious that you shouldn't scrub your glasses with, say, bathroom cleaner, it's much less obvious that everyday things we put on our skin, like lotions and sunscreen, can be nearly as bad for our sensitive glasses as the bathroom cleaner we all know we should never use.

These products can contain mild abrasives that do not harm (and sometimes can even help!) our skin but may harm the film on our glasses, especially with exposure over time.

Wash Your Hands

The only way to be certain that you are avoiding any chemical contact with your glasses is to wash your hands before handling them. Lotions and sunscreens are just two of the many things we can have on our hands; often our hands have all sorts of random things on them that we don't notice or can't see.

A simple hand washing before you handle your glasses can help to keep the abrasives from getting onto your lenses and can help keep everything clean.

Rinse Your Lenses

While you're at the sink, run your glasses under a gentle stream of warm water. This will help to carefully remove any loose dirt or other debris that could scratch the lenses when you wipe your lenses.

If you were to omit this step, you might end up scratching your lenses with invisible debris. While the damage might not be visible immediately, it will degrade your lenses more quickly.

Use a Lens Cloth

Once your hands are clean and you've run your glasses under warm water, you can wipe the lenses off to remove any leftover oils and grime. Back away from that T-shirt and put down the paper towels! You should only use a cloth specially designed for lenses. Your local Eyeglass World will sell these as either lens cloths or microfiber cloths. Using a material that was not intended to clean glasses can and will do more damage than the little bits of dirt you're trying to remove.

Use a Cleaning Solution

Usually, a simple rinse and wipe is enough to get your frames back to top condition. However, there are always cases where we end up with grime that just won't come off easily.

In these cases, you should only use a cleaning solution that you get from your optometrist. These cleaners are specially formulated to be very gentle on your glasses, whereas cleaners that might work on other forms of glass could be harsh and cause damage.

Store Them Correctly

Remember, when you've cleaned your eyeglasses, you need to be sure to store them properly to avoid having them collect more dirt, causing you to have to repeat the process more often than necessary.

Use the case your eyewear came in to store them. Hard cases generally provide more protection than soft cases. Even though they tend to be bulkier - they're the safer choice.

Reference:

eyeglassworld.com/eye-vision-patient-education/eyeglasses-education/how-to-maintain-your-glasses

Video Eyewear is a very young field. It was born out of a merging of the old HMD industry, and the need for far smaller, more lightweight devices for augmented reality applications.

Video eyewear basically consists of a display system as light as a pair of sunglasses - maybe five to ten ounces total - that slips over the eyes, delivering sterioscopic displays of a film, or virtual environment to the viewer, along with synchronous sound playback to the ears. eResearch by Navid Ajamin -- spring 2007

To maintain contact with the outside world and prevent total immersion, video eyewear equipment usually maintains a distance from the eyes of two or three centimeters - just enough so the wearer can see over the top of the display if they have to.

The eye can be compared to a camera.

The cornea is the transparent, curved front layer of the eye, where light is first focused before it passes through the pupil.

The pupil, behind the cornea, is a hole in the colored membrane called the iris. Tiny muscles in the iris change the size of the pupil – like the aperture apparatus of a camera – to control the amount of light getting into the back of the eye.

There is a small, powerful lens behind the pupil which changes shape, based on the pull of muscles in the eye, in order to further focus the light on the retina, which is a light-sensitive membrane lining the inside back of the eye.(Incidentally, cataracts are a deterioration of the human lens, and cataract surgery removes this lens and replaces it with a clear, artificial one.)

Like film in an older camera or sensors in a digital camera, the retina is a light-sensitive surface where light energy from the outside world is displayed and initiates a reaction that leads to the formation of an image. In a camera, film must be exposed to chemicals in order to permanently fix the image for future print processing. In the retina, millions of microscopic photoreceptor cells, known as rods and cones, are activated by light and, through a biochemical process, turn light into electric impulses. These impulses travel the optic nerve (a cable built of thousands of nerve fibers) to the visual processing center of the brain, where they are interpreted as vision.

The biochemical process of transforming light into electricity that occurs in the retina (known as phototransduction) makes it the most metabolically active tissue in the body. Just as the chemicals used to process film — or to print from film onto materials such as paper — have to be regularly removed and refreshed in order to maintain the purity of the image-making process, the protein-fat biological waste generated by photoreceptors has to be constantly removed, and fresh nutrients have to be resupplied to the rods and cones. This cleanup and nutrient supply process is carried out by the retinal pigment epithelium (RPE), a single layer of tightly joined cells that lies behind the photoreceptors and in front of Bruchs membrane, and the capillary-rich choroid. Specialized white blood cells, called macrophages, aid in the cleanup.

While scientists are still learning about the variety of factors that can disrupt this cleanup-and-refresh process, the common byproduct of disruption is a druse — a clump of proteins and fats that can grow and connect to other drusen. When drusen become so large that they cannot be cleared away by macrophages, they can push the RPE and photoreceptors away from the back of the eye, creating distortion in the images formed in the brain.

Reference:

• macular.org/about-macular-degeneration/what-is-macular-degeneration/disease-overview/how-the-eye-works-as-a-camera
• collegedunia.com

Many people enjoy participating in sports and like to make sure that they have the appropriate equipment required to optomise their enjoyment and performance.

One essential aspect of performing any sport is your vision. It is important to protect and enhance your eyesight to get the most out of your sport.

Sports Eyewear Solutions offers a range of high quality, technically advanced eyewear for all of your sporting needs, designed by the leading sports brand adidas.

Every sport has different conditions and requirements, it only makes sense that your eyewear is designed for that specific sport.

Fashion V Sports sunglasses. People often choose sunglasses because they are fashionable and then use these same sunglasses for use during sport. Unfortunately fashion sunglasses are not designed to be worn for sporting purposes and therefore lack many features and benefits that make sports sunglasses more comfortable and practical. Why not give yourself a sporting edge and choose the correct eyewear dsigned for the sport you love - just like the professional athletes do? eResearch by Navid Ajamin -- summer 2008

Reference: www.sportseyewear.com.au Related To: Exercise and children

Visual Display Unit (VDU)

Short for visual display unit, VDU is an older British term used to describe any device used with computers to display images. For example, a flat panel display and a projector are both examples of VDUs. However, VDU is most commonly used to describe the CRT monitor, a now archaic standard that has been replaced by flat panel displays.

VDU's and Your Eyes. Although there is no reliable evidence to suggest that even long-term intensive use of VDUs is damaging to the eyes, it is true that VDU users tend to complain of eye strain more than non-users.

Symptoms can range from tired eyes to blurred vision. If VDU operators do experience any of the following symptoms they could have computer vision syndrome. If they find it difficult to focus on distant objects after using a computer, have headaches, eyestrain or dry eyes they need to take extra care when using a VDU.

More people are now using computers for work causing a marked increase in the number of people complaining of eye strain. According to the Health and Safety Executive (HSE) extensive research has found no evidence that visual display units (VDU‟s) can cause disease or permanent damage to eyes. However extended or prolonged periods of VDU work can lead to tired eyes and discomfort. As the eyes now perform more demanding tasks, it may make VDU workers more aware of an eyesight problem. It may also make those with pre-existing vision defects more aware of them if these are not corrected. Computer vision syndrome is also a common eye condition amongst VDU users.

With the rising number of people using computers at work and at home there has also been an increase in the number of people complaining of eye strain. Although scientific research has not proved a link between using computers and permanent eye damage using VDUs for a long period of time can cause some minor eye problems.

Computer vision syndrome is a common eye condition amongst VDU users. Symptoms can range from tired eyes to blurred vision. If you do experience any of the following symptoms you could have computer vision syndrome. If you find it difficult to focus on distant objects after using a computer, you have headaches, eyestrain or dry eyes you need to take extra care when using a VDU to avoid getting computer vision syndrome. It is also best to visit your optician for an eye test to rule out anything more serious.

Several symptoms can indicate digital eye strain, including:

• Sore, tired, burning or itching eyes
• Watery or dry eyes
• Blurred or double vision
• Headache
• Sore neck, shoulders or back
• Increased sensitivity to light
• Difficulty concentrating
• Feeling that you cannot keep your eyes open

Common causes of eyestrain include:

• Looking at digital device screens
• Reading without pausing to rest your eyes
• Driving long distances and doing other activities involving extended focus
• Being exposed to bright light or glare
• Straining to see in very dim light
• Having an underlying eye problem, such as dry eyes or uncorrected vision (refractive error)
• Being stressed or fatigued
• Being exposed to dry moving air from a fan, heating or air-conditioning system

There a number of things you can do to look after your eyesight when using VDUs. Follow the following advice to ensure good eye health:

Computer use strains eyes more than reading print material because people tend to:

• Blink less while using computers (blinking is key to moistening the eyes)
• View digital screens at less than ideal distances or angles
• Use devices that have glare or reflection
• Use devices with poor contrast between the text and the background

Some other factors that can make the condition worse include:

• Glare on your screen
• Poor posture
• Setup of your computer workstation
• Circulating air, such as from air conditioning or a nearby fan

Tips for preventing eye strain

• Using eye drops. A person blinks less than usual when using digital screens, and this can dry out the eyes. Drops or artificial tears can be purchased at most pharmacies, as well as online. Specialty eye drops are available for people who wear contact lenses. Preservative-free eye drops are best.
• Change computer settings. Making text twice as large as usual can reduce eye strain. Reading black text against a white background is easiest on the eyes.
• Reduce screen glare. Protective anti-glare screens can be applied to computers and eyeglasses, to prevent eye problems. Also, flat screens tend to have less glare than curved ones.
• Adjust the screen's contrast. Change settings so that the screen is bright enough to read the text without straining. The right contrast may change, depending on the presence of sunlight.
• Get regular eye checkups. Poor eyesight is a major cause of strain. Regularly attending checkups will ensure that a person has an updated prescription when needed.

Visual

A. Adjust screen angle to suit sitting height. Slightly downward viewing angle i.e. 20-40o from horizontal
B. Adjust display height to minimise head/neck movement.
C. Adjust screen to avoid/minimise reflections and glare.
D. Adjust screen brightness and contrast
E. Vary viewing distance over working day.

Additionally:

• Where document holders used, place at same height, plane and viewing distance as screen to minimise head/neck/eye movement.

• Adjust blinds to minimise glare.

Posture eResearch by Navid Ajamin –- Spring 2008

1. Adjust backrest to support lower back
- Do not slouch
- Sit right back in chair to gain proper support
2. Adjust seat height so have room between legs and table.
3. Knees level with hips
4. Elbows close to sides
3. Adjust height so forearms horizontal
4. Wrist slightly flexed
5. Keep a clear area in front of keyboard to rest wrists when not typing consider using a wrist rest
6. Use foot rest, if required
7. Keep mouse and keyboard within easy reach, avoid over stretching to use mouse

Organisational

• Keep area under desk clear. Remove obstacles.

• Move PC tower unit if this is restricting leg movement.

• Keep desk as clear as possible,but …
  … with supplies close at hand.

• Keep space into/out of workstation clear and free of obstructions.

• Take short breaks every now and again.

• Break-up VDU work with non VDU work

• “Stretch your legs”.

• Rest arms and shoulders periodically.

• Avoid high activity wrist movements during work breaks.

Reference:

unison.org.uk eyehelp.co.uk mayoclinic.org medicalnewstoday.com eyecaretrust.org.uk

Vision therapy is has been shown over decades to successfully play a role in the management of several conditions, including;

• Lazy eye
• Eye turns (strabismus)
• Convergence Insufficiency
• Dyslexia
• ADHD
• Learning difficulties

Who benefits from vision therapy?

Many people can benefit from vision therapy. Some of the most common groups of people who may benefit from vision therapy include:

• Children with visual problems such as amblyopia (lazy eye), strabismus (crossed eyes), and visual perception disorders like dyslexia.
• Adults with visual problems such as binocular vision disorders (double vision, convergence insufficiency), acquired brain injuries, and visual problems caused by trauma.
• Athletes of all ages who want to improve their visual skills, such as hand-eye coordination, reaction time, and visual tracking, in order to enhance their sports performance.
• People who have suffered from a stroke or have been diagnosed with neurological conditions such as multiple sclerosis, traumatic brain injury, or cerebral palsy.
• Individuals who experience visual symptoms such as headaches or eye strain caused by visual problems, or those who have been diagnosed with a specific visual disorder such as myopia, hyperopia, or astigmatism.
• People who have had cataracts or other eye surgery and need to rehabilitate their vision.
• Individuals who have reading difficulties, difficulty with eye-hand coordination, or those who are experiencing difficulties in school or at work due to visual problems.

It’s worth noting that vision therapy is not a one-size-fits-all solution and not everyone will benefit from it. An eye examination and consultation with a vision therapist are necessary to determine if vision therapy is appropriate and beneficial.

Also Read: What is Vision Therapy? How is it helpful in treating Vision Problems?

What are the principles of vision therapy?

Vision therapy works by targeting specific areas of the visual system, including the eyes, the brain, and the nerves that connect them. The therapy includes a variety of exercises and activities that focus on improving visual skills such as eye coordination, focusing, and tracking.

What is vision therapy?

Vision therapy is a program that aims to improve a person’s visual abilities. It uses a variety of ways – such as eye exercises, testing, occlusion (patching) lenses and prisms – to treat a range of visual problems.

Vision therapy may be used to treat problems such as:

• amblyopia (lazy eye)
• eye alignment and coordination problems (including turned eyes or squints)

Each program is designed to suit the specific needs of the individual.

How vision works

Vision is the process of deriving meaning from what is seen. It is more than simply the ability to distinguish fine details (visual acuity). Vision also involves:

• accommodation (focusing)
• convergence (eye aiming)
• binocularity (eye coordination)
• fixation and eye movement abilities
• eye-hand coordination
• visual form perception.

Vision continues to develop after birth and is influenced by the visual environment and someone's experience.

Vision problems can exist even if you have healthy eyes and can see clearly. Difficulties may occur in your eye muscle control and coordination.

If you have vision problems, you may experience visual discomfort when performing visually demanding activities.

How does vision therapy treat eye problems?

According to the Australian Bureau of Statistics

, approximately half the Australian population has some vision problem that requires treatment.

While most people have refractive errors (such as short-sightedness, long-sightedness, astigmatism and presbyopia), in some, their eye problems can be improved by vision therapy.

Although vision therapy is available to people of all ages, it is more effective in children and young adults.

Vision therapy for children and young people

One common problem in children is they may have difficulty coordinating their eyes. To see something clearly, both eyes must be aimed correctly and focused at the right distance.

Any problems with aiming or focusing the eyes can cause a variety of symptoms, including:

• intermittent double vision
• blurred vision
• headaches
• eyestrain.

Children with these problems often do not complain about them, but may simply avoid tasks (such as reading), which are difficult or cause discomfort.

An optometrist may suggest a program of vision therapy to improve eye coordination and focusing.

What does a vision therapy program involve?

A vision therapy program (also known as visual training) is designed by an optometrist to meet individual needs. So, your program may differ from someone else’s.

Vision therapy is typically used to improve the coordination and control of eye movements and a program may include:

• diagnostic tests
• training procedures
• exercises
• use of lenses and prisms – these may be integral to the successful treatment of your vision problem.

The frequency of optometrist visits, amount of home training and duration of the therapy will depend on the nature and severity of your eye problem.

Sometimes you will work with the optometrist in their office and then other times, you may have work to do at home (such as activities and exercises).

Regular practice is important to achieve the best results. Therapy will teach you how to have better eye control to improve your understanding of what you are seeing and reading. You may find that therapy gives you greater confidence and improves your performance in daily activities – such as at school, university, or work.

Reference:

• optometrists.org/vision-therapy/vision-therapy-for-children/what-is-the-youngest-age-to-start-vision-therapy
• betterhealth.vic.gov.au/health/conditionsandtreatments/vision-therapy
• bynocs.com/top-10-ways-vision-therapy-can-benefit-your-visual-health

See Also:

• What Are Visual Skills?
• What is a Behavioral Optometrist?
• Vision Therapists at 4D Vision Gym

9 Ways to Reduce the Symptoms of Computer Eyestrain

Eyestrain is the number one complaint in office jobs, but there are many things workers and employers can do to reduce these symptoms. The best solution is number 1 below—see an eye doctor using the PRIO Vision Tester, and get a pair of eyeglasses specifically to wear when you use the computer.

The potential impact of computer use on children’s vision involves the following factors:

• Children often have a limited degree of self-awareness. Many children keep performing an enjoyable task with great concentration until near exhaustion (e.g., playing video games for hours with little, if any, breaks). Prolonged activity without a significant break can cause eye focusing (accommodative) problems and eye irritation.

Accommodative problems may occur as a result of the eyes’ focusing system “locking in” to a particular target and viewing distance. In some cases, this may cause the eyes to be unable to smoothly and easily focus on a particular object, even long after the original work is completed.

Eye irritation may occur because of poor tearflow over the eye due to reduced blinking. Blinking is often inhibited by concentration and staring at a computer or video screen. Compounding this, computers usually are located higher in the field of view than traditional paperwork. This results in the upper eyelids being retracted to a greater extent. Therefore, the eye tends to experience more than the normal amount of tear evaporation resulting in dryness and irritation.

• Children are very adaptable. Although there are many positive aspects to their adaptability, children frequently ignore problems that would be addressed by adults. A child who is viewing a computer screen with a large amount of glare often will not think about changing the computer arrangement or the surroundings to achieve more comfortable viewing. This can result in excessive eye strain. Also, children often accept blurred vision caused by nearsightedness (myopia), farsightedness (hyperopia), or astigmatism because they think everyone sees the way they do. Uncorrected farsightedness can cause eye strain, even when clear vision can be maintained.

• Children are not the same size as adults. Since children are smaller, computers don’t fit them well. Most computer workstations are arranged for adult use. Therefore, a child using a computer on a typical office desk often must look up further than an adult. Since the most efficient viewing angle is slightly downward about 15 degrees, problems using the eyes together can occur. In addition, children may have difficulty reaching the keyboard or placing their feet on the floor, causing arm, neck or back discomfort.

• Children often use computers in a home or classroom with less than optimum lighting. The lighting level for the proper use of a computer is about half as bright as that normally found in a classroom. Increased light levels can contribute to excessive glare and problems associated with adjustments of the eye to different levels of light.

Here are nine additional tips for ways to reduce eyestrain.

1. GET AN EYE EXAM!

This is the most important thing you can do to prevent or treat computer vision problems.

According to the National Institute of Occupational Safety and Health (NIOSH), computer users should have an eye exam before they start working on a computer and once per year thereafter.

2. USE PROPER LIGHTING

In your office you are likely to find several things that can cause eyestrain, including glare on walls and finished surfaces, reflections on the computer screen itself, excessively bright light coming in from outside, and excessively bright light inside

Eliminate exterior light and reflections by closing drapes or blinds.

When using computers, lighting should be about half that used in most offices. Reduce lighting by using fewer light bulbs or florescent tubes, or use lower intensity bulbs and tubes.

3. TAKE FREQUENT BREAKS

Full time computer users should take a 10-minute break every hour to reduce eyestrain problems according to experts. Part-time users should take frequent breaks, after sitting in front of their display for more than a hour.

4. REFOCUS YOUR EYES

Look away from your computer screen every 10-15 minutes and focus for 5-10 seconds on a distant object outside or down the hallway. This prevents the fixed gaze common among computer users. It also lets you blink, which wets your eyes.

5. BLINK MORE OFTEN

When staring at a computer, people blink less frequently—about 5 times less than normal, according to studies. Tears coating the eye evaporate more rapidly during long non-blinking phases and cause dry eyes. Office buildings may have excessively dry environments that also reduce tearing. For significant problems, ask your eye doctor about artificial tears or eye drops that you can use during the day.

6. MODIFY YOUR WORKSTATION

If you need to look back and forth between the printed or written page and the computer, this can cause eyestrain. Place written pages on a copy stand adjacent to the monitor. Properly light the copy stand. Adjust your workstation and chair to the correct height. Purchase ergonomic furniture to assure proper screen locations and posture.

7. MATCH THE COMPUTER SCREEN TO THE BRIGHTNESS OF THE ENVIRONMENT

Closely match the brightness of the environment with that of the computer screen. The contrast between the background and on-screen characters should be high.

8. MINIMIZE GLARE

Use window shades, blinds or drapes to block out excessive sunlight, or install an anti-glare screen, to minimize reflections on the screen itself. Reduce the internal ambient light if necessary. For conditions where outside light cannot be reduced, use a computer hood to cut glare and reflection. Have an Anti-Reflective coating applied to your glasses. This will prevent glare and reflections on the back side of your lenses form reaching your eyes.

9. EXERCISE EVEN WHEN SITTING

Anyone in a sedentary job, especially those using computers, should also stand up, move about, or exercise frequently. NIOSH recommends several sitting, stretching, and joint rotating exercises for computer users.

As parents or carers, it is essential to recognise the signs of Digital Eye Strain in children.

Some common symptoms include:

• Eye discomfort: Complaints of tired, itchy, or burning eyes.
• Squinting or blinking: Frequent squinting or blinking to refocus their vision.
• Headaches: Recurring headaches, especially after screen time.
• Dry eyes: Experiencing dryness or grittiness in the eyes.
• Double vision: Temporary vision issues like double vision or blurred vision.

Reference:

• yesite.co.za/2004/04/15/impact-of-computer-use-on-childrens-vision
• visiondirect.com.au/optical-centre/eye-care/digital-eye-strain
• gormleyopticians.com/protecting-childrens-eyes-digital-strain
• prio.com/consumers/9ways.cfm

20/20 VISION

What does 20/20 vision mean?

20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.

Does 20/20 mean perfect vision?

No. 20/20 vision only indicates the sharpness or clarity of vision at a distance. There are other important vision skills, among them peripheral awareness or side vision, eye coordination, depth perception, focusing ability and color vision that contribute to your overall vision ability.

Is 15/15 vision better than 20/20?

No. 15/15 means normal sharpness of vision at 15 feet just as 20/20 indicates normal acuity at 20 feet. Most optometrists in Canada use 20 feet as the standard to express sharpness of vision.

Why do some people have less than 20/20 vision?

Visual acuity is affected by many factors. Less than optimum clarity may result from vision conditions like nearsightedness, farsightedness, or astigmatism, or from eye diseases.

Will clarity of vision vary with distance?

Some people can see well at a distance, but are unable to bring nearer objects into focus. This condition can be caused by farsightedness or presbyopia (a loss of focusing ability). Others can see items that are close, but cannot see those far away. This condition may be caused by nearsightedness.

If my vision is less than optimum, what can I do?

A comprehensive eye examination by a Doctor of Optometry should identify those causes, if any, that are affecting your ability to see well. In most cases, your optometrist can prescribe glasses, contact lenses or a vision therapy program that will help improve your vision. If the reduced vision is due to an eye disease, the use of ocular medication or other treatment may be needed. [1]

Eye Information : A-Z of Terms Explained [7]

Words your optometrist/optician might use...

The terms here are the most commonly used by your optician, most will only be of use in special cases or with people with 'complex' prescriptions. However, if you would like to know a little more about your eyes and the words used to describe their health please read on!

• ABERRATION: Any defect or a distortion in any optical system.
• ACCOMMODATION: The process by which the eye increases its power to focus on a specific object.
• ACUITY (V.A. or visual acuity): Describes the clarity of vision.
• AFOCAL: A lens or optical system with zero power.
• AMBLYOPIA: (Also known as having a lazy eye) often occurs when the eye does not develop fully during early childhood and is not usually correctable via opticial means.
• AMETROPIA: A defective refractive ability of the eye e.g short-sightedness or long-sightedness.
• ANISOMETROPIA: Unequal refractice power in each eye, typically greater then 1.00D.
• ANTIMETROPIA: A condition in which one eye is myopic and the other is hypermetropic.
• APHAKIA: The ocular condition in which the lens of the eye is absent, or has been surgically removed.
• AQUEOUS HUMOUR: Fluid that fills and separates the anterior (front) and posterior (back) of the human eye. It is a transparent gelatinous fluid.
• ASPHERICAL: Not spherical, aspherical lenses have a curved surface.
• ASTIGMATISM: When the cornea at the front of the eye is unevenly curved, often resulting in a rugby ball shaped eye, causing blurred vision.
• BIFOCAL: A lens with two focal lengths, usually for distance/near vision.
• BINOCULAR: Relating to both eyes.
• BIOMICROSCOPE: An instrument designed for detailed examination of the eye, used particularly in contact lens practice. (Often referred to as a slit-lamp).
• BLEPHARITIS: A chronic inflammation of the eyelid margins.
• CANTHUS: Either corner of the eye where the eyelids meet.
• CATARACT: Is when the clear lens inside your eye becomes cloudy or misty.
• CONCAVE: A surface shaped like the inside of a sphere.
• CONVERGENCE: Movement of the eyes turning inwards, i.e. towards each other.
• CONVEX: Is when a lens is shaped outward.
• CORNEA: The transparent anterior portion of the eye.
• CRYSTALLINE LENS: The lens of the eye, which focusses light on to the retina.
• DECENTRATION: The displacement, horizontal and/or vertical, of the centration point of a spectacle lens from the standard optical centre position.
• DIOPTRE: The unit of measurement of refractive power of a lens.
• DIPLOPIA: (Double vision) A condition where objects are seen 'double'.
• DISC (OPTIC): The region of the retina, where the optic nerve joins the eyeball.
• DISTORTION: Defect of an optical system resulting in an alteration of an objects original shape.
• DIVERGENCE: Movement of the eyes, turning away from each other.
• EMMETROPIA: An eye which gives perfect vision so that no glasses are required. Occurs when light from an object at infinity is sharply focussed on the retina.
• FIXATION: Maintenance of visual gaze on a single location. The object is sharply formed on the retina.
• FOCIMETER:An instrument that measures the power of a spectacle lens, or contact lens.
• FUNDUS: The back of the eye. The fundus is viewed using an instrument called an ophthalmoscope.
• GLAUCOMA: An eye disease characterised by increased intra-ocular fluid pressure which causes a restriction in field of vision.
• GRAFT: Surgical procedure to replace damaged structures (e.g.cornea) with donor tissue.
• HYDROGEL: A type of plastics material that contains water, commonly used in the manufacture of soft contact lenses.
• HYPERMETROPIA (HYPEROPIA): Often referred to long-sightedness. When people are long sighted, they can see distance objects well but have difficulty focussing on objects that are close. This vision problem occurs when light rays entering the eye focuses behind the retina, rather than directly on it.
• INJECTION (e.g. conjunctival ): Redness of the eye caused by the dilation (expanding) of superficial blood vessels in the sclera (white of the eye).
• INTER-PUPILLARY DISTANCE: The horizontal distance measured between the pupil centres. Usually abbreviated to PD. Essential when making up spectacles.
• IRIS: The coloured part of the eye surrounding the pupil.
• IRITIS: A condition causing inflammation of the iris.
• KERATITIS: An inflammation of the cornea.
• KERATOMETER: An instrument used to measure the curvature of the front surface of the cornea. Often used in contact lens fitting.
• LACRIMAL: Relating to the tears.
• MEIBOMIAN GLANDS: Small glands in the eyelids known as meibomian glands are responsible for secreting oil that covers and protects the surface of the eye.
• MIOSIS: Contraction of the pupil. (A drug that causes this is a miotic)
• MONOCLE: A single lens, with or without a frame, worn by holding between the brow and the cheek.
• MONOCULAR: Relating to one eye (or lens).
• MULTIFOCAL: A lens with multiple powers eg a trifocal or varifocal lens.
• MYDRIASIS: Dilation (enlarging) of the pupil. (A drug that causes this is a mydriatic)
• MYOPIA: Often referred to short-sightedness. When people are short sighted, they can see near objects well but have difficulty focussing on objects that are far away. This vision problem occurs when light rays entering the eye focuses infront the retina, rather than directly on it.
• NEAR VISION: The ability to read/carry out close work, usually at a distance of 33 - 40 cm.
• NEUTRALIZATION: The process of determining the power of an unknown lens, using trial lenses of known power.
• OCCLUDER: A device placed in front of an eye to effectively block vision.
• OPACITY: Condition of a tissue or structure that is not transparent.
• OPHTHALMOSCOPE: A hand held instrument for viewing the eye in particular the retina.
• OPTICAL CENTRE: The point on a lens through which a ray of light will pass undeviated.
• ORBIT: The bony socket of the skull where the eye is situated.
• ORTHOPTICS: Is the diagnosis and non-medical management of abnormalities of binocular vision. This includes strabismus (squint), amblyopia (lazy eye).
• PERMEABILITY: The ability of a material to allow the passage of a gas or fluid.
• PHOTOCHROMIC: A lens made of a material that changes colour as a result of exposure to UV light and heat. For more information on photochromatic lenses please click here.
• PRESBYOPIA: When the lens inside the eye loses some of its flexibility so that it becomes difficult to focus on close objects. Usually occurs with age.
• PRISM: Is used in spectacles to correct a muscle imbalance.
• PROSTHESIS: An artificial eye, or implant.
• PUPIL: The opening within the centre of the iris. Thsi determines the amount of light which enters the eye.
• PUPILLARY DISTANCE: This is the distance between the centre of the the pupils in each eye (measured in millimeters). Important in positioning the lenses of the glasses correctly in relation to the pupils so as to obtain the optimum vision.
• REFLEX: Reaction of certain parts of the eye to a stimulus, e.g. the pupil reflex being the reaction of the pupil to a light stimulus.
• RETINA: The light sensitive layer of cells lining the back of the eye. Often liked to the film of a camera.
• RETINOSCOPE: Hand held instrument used to obtain an objective assessment of a patient's refractive condition (their prescription)
• SALINE: A sterile solution of sodium chloride (salt) in water. Often used to rinse contact lenses
• SCLERA: The white of the eye. A tough opaque fibrous tissue which serves as the eyes protective coat.
• SCOTOMA: An area of partial or complete loss of vision surrounded by a normal field of vision.
• SLIT - LAMP (SLIT-LAMP BIOMICROSCOPE): An instrument used to examine the eye under high magnification. Also used in contact lens practice.
• STRABISMUS: A misalignment of the eyes so that the eyes are not directed towards the same point, when the patient is fixating. As images are formed at different points this often results in 'double vision'.
• SURFACING: The process of generating, smoothing and polishing a spectacle lens surface to a given curvature.
• TONOMETER: An instrument used for measuring the fluid pressure inside the eyeball (the intra ocular pressure (IOP)
• TRIAL CASE: A case containing both spherical and cylindrical lenses which are either positive or negative in power. Used in testing eye sight.
• TRIAL FRAME: An adjustable spectacle frame which can hold several lenses and is used in testing eye sight.
• UNAIDED VISION: Vision without any form of correction i.e spectacles or contact lenses.
• UNIOCULAR: Another expression for monocular, i.e. referring to one eye.
• VERTEX DISTANCE:The distance (in mm) from the surface of the cornea, to the posterior surface of the spectacle lens or trial lens.
• VISUAL ACUITY: The ability of the eye for seeing distinctly the details of an object at a specific distance.
• VITREOUS HUMOUR: The clear gelly that fills the space between the lens and the retina of the eyeball.

eResearch by Navid Ajamin -- winter 2004

Description Term [6] Abbreviation

Reference:

1. foryoureyesonly.ca
2. en.wikipedia.org/wiki/Eyeglass_prescription
3. en.wikipedia.org/wiki/Trifocal_lenses
4. careers.nhs.scot/careers/explore-our-careers/optometry/dispensing-optician
5. wikipedia.org/wiki/Corneal_pachymetry
6. en.wikipedia.org/wiki/List_of_optometric_abbreviations
7. hdavisopticians.co.uk/eye-information-a-z-of-terms-explained
8. specsavers.co.uk/eye-test/what-is-an-optometrist
9. abdo.org.uk/for-the-public/what-is-a-dispensing-optician

Anti-Reflection Coatings

AR coatings are similar to the coatings found on microscopes and camera lenses. They consist of several layers of metal oxides applied to the front and back lens surfaces. Because of the layering effect, AR coatings sometimes have a hint of green or purple color, depending on the individual manufacturer's formula.

The most important benefits of anti-reflective (AR) coating may be the unseen advantage--relief from fatigue and eyestrain caused by glare. AR does have a big cosmetic advantage, but removing the distracting reflections and ghost images that contribute to eyestrain clearly is a bigger benefit. This increases comfort. Being more comfortable in anything we do is a benefit, especially wearing glasses. People always remark how uncomfortable glasses are. Well now you can offer a real solution to that problem. AR Coating!!

Nighttime driving is also enhanced with AR coatings by eliminating the reflections from street lights, headlights from on-coming vehicles, and taillights. By applying an AR coating more light can pass through the lens providing greater image contrast and clearer vision.

Beyond these benefits and features, other ideal candidates are:

1. High Index Wearers-AR helps reduce the concentric rings these strong prescriptions produce.

2. Low Vision Patients-The increase of light transmission from AR coatings can benefit low vision patients.

3. Light-sensitive patients

4. Sunglass wearers

5. First time wearers of glasses

6. Professionals

7. VDT users can benefit from AR's ability to reduce glare.

You get more out of life when you can enjoy it longer. Vision problems such as glare, reflections, ghost images and the fatigue they create reduces your enjoyment. AR coatings improve vision, reduce fatigue, and help you to enjoy every minute of life at work or at play.

AR coatings enhance appearance. It makes lenses look thinner by reducing distracting reflections. Also the wearers eyes are more visible and this improves eye contact for better communication.

Now, we have mention the cosmetic and comfort features but there are more than that. AR lenses when worn in daylight and indoors, most people find it provides noticeable better visual performance, making objects appear crisper and brighter. When reading a newspaper, magazine, or even a computer screen with AR coated lenses images and letters will appear sharper and crisper. [1]

Anti-reflective eye glasses are designed to reduce glare on the lenses. This serves the dual purpose of improving the wearer’s vision and enhancing the appearance of the glasses themselves, particularly in photographs taken with a flash. eResearch by Navid Ajamin -- spring 2008

Composition

1. Anti-reflective coating consists of a series of layers of metal oxides. In the 1980s and 1990s, when anti-reflective lenses were relatively new, the coating was only a single layer that could easily become scratched or smudged.

Today, multiple layers enhance the properties of the anti-reflective coating, including oil-resistant, water-resistant, static-resistant and protective scratch-resistant layers.

Process

2. The process used to apply anti-reflective coating varies depending on the manufacturer. In some cases the coating is sprayed on in liquid form, then exposed to high heat so that the liquid solution hardens and adheres to the lens.

Another process coats each lens with a liquid and places it inside a vacuum chamber, where the vacuum process hardens the coating. In yet another process the anti-reflective coating is built into the material and distributed throughout.Care

3. Anti-reflective lenses require a little more care than regular lenses. They should not be cleaned with harsh chemicals, which can damage the anti-reflective coating. Additionally, they should be cleaned or rubbed only with a wet cloth, as a dry cloth can scratch the lens.[2]

Benefits of anti-reflective coating

Anti-reflective coating (also called “AR coating” or “anti-glare coating”) improves vision, reduces digital eye strain and makes your eyeglasses look more attractive. These benefits are due to the ability of AR coating to virtually eliminate reflections from the front and back surfaces of your eyeglass lenses.

With reflections gone, more light passes through your lenses to optimize visual acuity with fewer distractions (especially at night), and the lenses look nearly invisible — which enhances your appearance by drawing more attention to your eyes and helping you make better eye contact with others.

AR coating is especially beneficial when used on high-index lenses, which reflect more light than regular plastic lenses. Generally, the higher the index of refraction of the lens material, the more light that will be reflected from the surface of the lenses.

For example, regular plastic lenses reflect roughly 8% of light hitting the lenses, so only 92% of available light enters the eye for vision.

Photolithography

Antireflective coatings (ARC) are often used in microelectronic photolithography to help reduce image distortions associated with reflections off the surface of the substrate. Different types of antireflective coatings are applied either before (Bottom ARC, or BARC) or after the photoresist, and help reduce standing waves, thin-film interference, and specular reflections.

High index plastic lenses can reflect up to 50% more light than regular plastic lenses, so even less light is available to the eye for vision. This can be particularly troublesome in low-light conditions, such as when driving at night.

Today’s modern anti-reflective coatings can virtually eliminate the reflection of light from eyeglass lenses, allowing 99.5% of available light to pass through the lenses and enter the eye for good vision.

By eliminating reflections, AR coating also makes your eyeglass lenses look nearly invisible so people can see your eyes and facial expressions more clearly. Anti-reflective glasses also are more attractive, so you can look your best in all lighting conditions.

The visual benefits of lenses with anti-reflective coating include sharper vision with less glare when driving at night and greater comfort during prolonged computer use (compared with wearing eyeglass lenses without AR coating).

When applied to photochromic lenses, AR coating enhances the clarity and comfort of these premium lenses in all light conditions without reducing their sun-reactive performance.

Anti-reflective coating also is a good idea for sunglasses. It eliminates glare from sunlight reflecting into your eyes from the back surface of tinted lenses when the sun is behind you. (Generally, AR coating is applied only to the back surface of sunglass lenses because there are no cosmetic or visual benefits to eliminating reflections from the front surface of dark-tinted lenses.)

Most premium AR lenses include a surface treatment that seals the anti-reflective layers and makes the lenses easier to clean. These hydrophobic surface treatments also repel water, preventing the formation of water spots on your lenses.

Some anti-reflective lenses have surface treatments that are both hydrophobic and oleophobic (also called lipophobic), which means they repel both water and oil. These combination treatments typically contain fluorinated materials that give the lenses properties that are very similar to those of nonstick cookware.

Is anti-reflective the same as anti-glare?

Anti-reflective vs Anti Glare

In short: anti glare coatings will protect against external light sources entering the glasses, while anti-reflective coatings will protect against both internal and external light.

Anti Glare

To get into the physics of it, anti glare solutions equip glasses with diffusive properties which diffuse light that would usually be reflected off of the surface of your lens. This means that instead of producing specular reflection, it creates a diffuse reflection. Instead of the light ray reflecting directly off the lens, it is broken up into many weaker rays, meaning the reflection is far weaker or, often, unnoticeable. This means that anti glare coatings significantly reduce the amount of light that is reflected off the surface of the lens.

Anti-Reflective

On the other hand, anti-reflective lenses go a step further. These solutions use diffusive properties to diffuse both external and internal light. While “internal light” might sound strange, it refers to the small number of transitional light waves which are let loose as the light goes from one medium (in this case, air) into another (the lens). If unchecked, these small light rays can reflect within the lens itself, causing strange visual artefacts that lead to eye strain and discomfort. While these internal reflections may still be present in glasses with anti glare coatings, anti-reflective lenses go the extra mile to ensure the best user experience possible.

Anti-reflective coatings are often used in camera lenses, giving lens elements distinctive colors. Such colors indicate the wavelength of visible light least affected by the antireflective properties of the coating. A variety of colors can be produced whose precise hue depends entirely on the thickness of the coating.

Reference:

1. robertsonoptical.com
2. milenyumtasarim.com
3. en.wikipedia.org/wiki/Anti-reflective_coating
4. allaboutvision.com/lenses/anti-reflective.htm
5. rx-able.com/blogs/blogs/is-anti-reflective-the-same-as-anti-glare

See also:

• Disadvantages of Anti-Glare Coating

• My glasses have an anti-reflective coating. How does that work?

Computer vision syndrome (CVS) is a condition resulting from focusing the eyes on a computer or other display device for protracted, uninterrupted periods of time and the eye muscles being unable to recover from the strain due to a lack of adequate sleep.

Computer Vision Syndrome, also referred to as Digital Eye Strain, describes a group of eye and vision-related problems that result from prolonged computer, tablet, e-reader and cell phone use. Many individuals experience eye discomfort and vision problems when viewing digital screens for extended periods.

Many of the symptoms of CVS can be broadly classified as "asthenopia". Most of these symptoms are also associated with other forms of near work. Neck and/or backaches are listed as a symptom of CVS since the eyes lead the body. Computer workers will often assume awkward postures in order to position their eyes so that they can perform their work - resulting in these musculoskeletal symptoms.

This can be the result of a poorly designed work station, assuming awkward postures due to using spectacles which are improperly designed for the task or due to making accommodations for a particular eye/vision disorder.

Asthenopia is more commonly known as eyestrain or ocular fatigue. It’s a common condition that occurs when your eyes become tired from intense use.

Staring at a computer screen for long periods or straining to see in dim light are common causes.Most of the time, asthenopia isn’t serious and goes away once you rest your eyes. Sometimes, asthenopia is related to an underlying vision problem, such as astigmatism or farsightedness (hyperopia).

Causes of asthenopia

Prolonged use of computers and digital devices has become such a common cause of asthenopia that it has been dubbed “computer vision syndrome” or “digital eyestrain.”

Along with staring at screens for extended periods, other causes of asthenopia include:

• reading for long periods
• staring to see in dim or dark surroundings
• driving long distances
• exposure to bright light or glare
• activities involving intense focus
• being stressed or fatigued
• exposure to dry moving air, such as a fan, air conditioning, or heater
• underlying eye conditions, such as dry eye or uncorrected vision

Computer Vision Syndrome (CVS) Symptoms

In most cases of CVS, the clinician is able to establish a visual diagnosis for the symptoms being experienced.

There are numerous accommodative disorders (e.g., decreased amplitude or infacility of accommodation) and binocular vision dysfunctions (e.g., phoria, strabismus) that can clearly cause the symptoms.

Uncorrected or improperly corrected presbyopia (improper add/or spectacle design) can also result in symptoms. Hyperopia can result in visual symptoms - especially in near workers. Uncorrected astigmatism can also cause symptoms because of the acuity demands of the task.

In some cases myopia can cause a blurred view of the computer screen and/or awkward posture. There is also some evidence to indicate that near work causes the development of myopia in some individuals. A dry eye condition is one which can be exacerbated by computer work due to staring, elevated gaze angle, decreased blinking, and a low humidity environment.

The symptoms of CVS can vary from person to person but commonly include:

1. Eye Strain: (Non-Specific Ocular Discomfort) Aching, burning, or heavy feeling in the eyes.
2. Headaches: Frequent headaches, often starting at the forehead and temples.
3. Blurred Vision: Difficulty focusing on the screen or other objects, both near and far.
4. Dry Eyes: Reduced blinking while using screens can lead to dry, irritated eyes.
5. Irritated Eyes
6. Double Vision: (Diplopia) Seeing two images of the same object on the screen.
7. Neck and Shoulder Pain: Poor posture while using digital devices can cause neck and shoulder discomfort.
8. Difficulty Concentrating: Reduced concentration and increased irritability.
9. Fatigues

Each of the CVS diagnoses presented can be treated - usually with a good prognosis for eliminating or reducing the presenting symptoms.

Computer Vision Syndrome (CVS) Visual Diagnoses

• Binocular Vision Dysfunctions
• Accommodative Disorders
• Refractive Errors
• Astigmatism
• Presbyopia
• Hyperopia
• Dry Eyes
• Myopia

CVS symptoms occur as a result of visual interaction with a task (the computer display) which stresses the visual system. The occurrence of symptoms depends upon the magnitude of any existing visual disorder as well as the demand level of the task. The task demand level can be dependent upon many variables. There are particular environmental factors associated with work at a computer which make it more visually demanding than other near point tasks.

Environmental Factors of Computer Workstations

• Contrast and resolution of the display
• Room lighting
• Viewing distances and angles
• Sustained viewing
• Adjustability of workstation

Appropriate diagnosis and treatment of existing vision problems and control or elimination of environmental factors can effectively reduce the symptoms associated with computer vision syndrome. eResearch by Navid Ajamin -- Spring 2008

What Else Contributes to Computer Vision Syndrome & Digital Eye Strain?

Not surprisingly, the biggest contributing factor to CVS is how much time one spends viewing screen-based devices (including your phone, tablet, e-readers, and other electronic devices). In our constantly connected, hyper-digital society, it is likely that many of us are accumulating at least seven hours of screen time per day. For someone with a computer-based job, that number is likely even higher.

In addition to screen use, other factors such as allergies, preexisting eye or vision problems, and a poor work environment can also lead to the development of CVS. Components of a poor work environment may include:

• Room lighting that is too strong or too dim
• Device screen that is too bright or too dim
• Glare on the device screen
• On-screen text that is too small
• Poor screen placement (too far, close, low, or high)
• Lack of ergonomic desk, seating, keyboard, or mouse
• Poor posture while using any screen (not just a computer screen)

Steps You Can Take to Protect Your Children from CVS

There are many things you can do to reduce your child’s risk of developing CVS. These include:

• Teaching your child about the risks of spending too much time staring at a screen.
• Limiting screen time to one or two hours a day.
• Making your child’s work station more ergonomic — make sure the lighting is adequate (too much light can create glare); chairs should be positioned at a comfortable distance; and the screen should be in the correct position as well — slightly below your child’s eye line and about 18 to 28 inches away.
• Scheduling regular eye exams for your child.
• Getting your kids in the habit of following the 20-20-20 rule: Take 20 seconds to look at something 20 feet away every 20 minutes.
• Wearing computer glasses to help your child’s eyes more easily focus on the computer screen.
• Anti-glare screens or anti-glare coatings on eyeglasses can help reduce glare and eye strain.
• Watching your children for signs of CVS — red eyes, blurred vision, eye rubbing, or stiff neck.

If these symptoms persist, take your child in for an eye exam.

Reference:

• continentalhospitals.com/blog/tips-for-preventing-computer-vision-syndrome-in-children-and-adults
• rochesteroptical.com/optometrist-rochester/what-is-computer-vision-syndrome
• berkeleyeye.com/blog/children-and-computer-vision-syndrome
• healthline.com/health/asthenopia#causes
• eyestraingone.com
• insightseyecare.net
• en.wikipedia.org
• aoa.org

See also: 6 Ways to Effectively Manage Computer Vision Syndrome

​What is an optician?

Opticians, also called dispensing opticians, fill eyewear prescriptions written by an optometrist or ophthalmologist.

The optician will recommend specific eyewear, take measurements, fit and adjust glasses, and teach customers to properly wear and care for their glasses or contact lenses. To be successful as an optician, you should have strong customer service, interpersonal, and communication skills.
Their training includes dispensing eyewear, selecting frames, taking facial measurements and choosing the best lens style for the patient.

ophthalmology. noun. oph·​thal·​mol·​o·​gy -ˈmäl-ə-jē plural ophthalmologies. :

a branch of medical science dealing with the structure, functions, and diseases of the eye.

What are the differences between an ophthalmologist, optometrist and optician?

An ophthalmologist is a medical doctor licensed to practice medicine and perform eye surgery.
Ophthalmologists treat and diagnose eye diseases, prescribe medication, and also fit patients with glasses and contact lenses.

An optometrist is not a medical doctor, but has a post-bachelor's degree in optometry and is licensed to practice optometry. Optometrists perform eye exams and prescribe glasses and contact lenses.

Opticians have the lowest level of training and work with optometrists and ophthalmologists by filling their prescriptions and dispensing eyewear.

Optician Job Description Template

We are looking for a social, friendly optician to work with our customers to find the most suitable eyewear for their needs. The optician will recommend specific eyewear, take measurements, fit and adjust glasses, and teach customers to properly wear and care for their glasses or contact lenses.

To be successful as an optician, you should have strong customer service, interpersonal, and communication skills. You should be able to recommend specialized eyewear such as for sports and occupational use, as well as informing on and recommending tints and anti-reflective coatings.

Optician Responsibilities:

1. Obtaining patient prescriptions from optometrists and ophthalmologists.
2. Taking customer information and measurements of the ocular area.
3. Recommending frames or contact lenses that suit the customer's style, face, and specifications.
4. Adjusting and fitting frames according to the prescriptions and customer's specifications, as well as to suit the customer's face.
5. Preparing work orders for the optical technicians to use to manufacture the lenses.
6. Using specialized equipment, such as calipers, lensometers, and lens gauges.
7. Keeping inventory on frames and contact lenses to ensure product variety and customer satisfaction.
8. Repairing broken frames.
9. Educating customers on how to wear and maintain glasses and contact lenses.
10. Performing administrative duties, such as managing prescriptions, customer records, and insurance.

Optician Requirements:

- An associate's degree or certification in opticianry.
- On-the-job training and experience in clinical work.
- A state license or certification to practice as an optician.
- The ability to operate specialized equipment.
- Excellent customer service and sales ability.

For general eye care, either an optometrist or ophthalmologist is a good option. Both of these types of eye doctors can: Give you a comprehensive dilated eye exam. Write a prescription for glasses or contacts

Reference:

• optinat.com/english.html
• betterteam.com/optician-job-description

Tips for keeping your eyes safe

• Wear safety glasses when mowing the lawn, grinding, hammering, sawing or working with power tools. Occlusive goggles are better than safety glasses at protecting the eye from metal fragments. “I think eye protection is way under-utilized and it’s very easy to do,” said Mason City ophthalmologist Dr. Randall Brenton.

• Wear protective sports glasses for activities such as racquetball or paintball that can possibly injure the eyes.

• Wear eyeglasses with impact-resistant lenses. This is especially important when playing sports or even bike riding.

• Wear sunglasses any time you are in bright sunlight, summer or winter, to protect your eyes from ultraviolet radiation. Sunglasses, sunscreen and hats also protect the lower eyelid from developing skin cancer, Brenton said.

• Sunglasses should block 100 percent of ultraviolet (UV) light. Brown or gray lenses are preferable to blue lenses in blocking out blue light, the most harmful form of radiation, said Mason City optometrist Dr. Jared Kellar. Consider full-wrap shields. Try out a few different sunglasses to find the ones in which you feel most comfortable.
• Eyeglasses can also have UV protection and still remain clear, said Brenton. Ask for it specifically when ordering your eyeglasses.
• If vegetative material gets into your eyes, have it treated immediately. This material can carry fungus, which the eye isn’t good at combating, Kellar said.
• Also seek treatment if you get metal in the eyes, Kellar said. Metal rusts and can be dangerous to the eyes.

Reference: http://www.globegazette.com

Choosing the Right Frame

One way to choose the right eyeglass frames is by face shape. Understanding face shape basics will help you understand which frame is best suited for your face. This guide will help you in identifying your face shape.

General Guidelines:

• The eyes should appear centered in the frame.

• Frames should be in proportion to the face size.

• Frames should contrast the face shape.

Learning how to select frames for your prescription glasses might seem like a daunting task, but it doesn’t have to be. There are a few easy ways to determine which frames would best flatter your face and show off your style and personality.

1. Identify your face shape
2. Choose colors that complement your skin tone
3. Consider your way of living.
4. Flaunt your personality

یکی دوتا نکته برای انتخاب عینک آفتابی:

مهمترین نکته اینه که عینک آفتابی باید حتماً پرتوهای فرابنفش رو بلوک کنه. میزان بلوک فرابنفش (UV block rating)، معمولاً با درصد یا یه عدد نشون داده میشه که سقف این عدد 400 هست. درواقع یعنی لنزی که UV400 باشه ، میتونه 100% پرتوهای فرابنفش رو بلوک کنه.

سازندگان ، موظف هستن که این عدد یا درصد رو روی عینک بنویسن. اما شما چندان به این نوشته ها اعتماد نکنید. فروشگاههای معتبر ، معمولاً یه دستگاهی دارن که میزان جذب فرابنفش رو با اون تست میکنن. از فروشنده بخواهید که عینک رو جلوی خودتون با اون دستگاه تست کنه ، و مطمئن بشید که همه جای شیشه عینک ( مرکز و اطراف شیشه ) به صورت یکنواخت فرابنفش رو بلوک میکنه.

عینک آفتابی به این دلیل که نور مرئی رو بلوک میکنه ، باعث میشه که مردمک قدری گشادتر بشه ، و اگه فرابنفش رو بلوک نکنه ، خصوصاً اگه رنگش خیلی تیره باشه ، مردمک بیشتر باز میشه و آسیب های غیر قابل بازگشتی به چشمتون میرسونه.

دومین نکته درمورد عینک آفتابی خوب برای رانندگی ، پولاریزه بودن هست. جهت صفحات پولاریزه در این عینک ها افقی تنظیم شده ، بنابراین فوتون هایی رو که مماس بر صفحه های عمودی به سمت چشم میان ، بلوک میکنه. بنابراین میتونه بازتاب مستقیم نور خورشید از سطوح ( زمین ، سنگفرش ، آسفالت ، سطح آب ، سقف و بدنه و شیشه اتوموبیل و …) رو بلوک کنه. این خاصیت باعث جلوگیری از خیرگی (Glare) میشه. شعار تبلیغاتی عینک های پولاریزه اینه !See behind the glare یعنی پشت خیرگی رو ببینید!

مزیت پولاریزه بودن عینک رو در هنگام رانندگی ، پیاده روی در جاهایی که سنگفرش براق دارن و همینطور موقع ماهیگیری میتونید متوجه بشید. مثلاً موقع رانندگی ، یکی از چیزهای مزاحم در دید سرنشین ، بازتاب نور خورشید توسط اشیاء روی داشبورد هست که میفته روی سطح داخلی شیشه جلو و منعکس میشه به چشم فرد. درواقع راننده ، تصویر همه این اشیاء رو توی شیشه جلو میبینه و اگه چیزی مثل کاغذ سفید باشه ، ممکنه حتی تصویر این کاغذ ، غالب بشه بر دیدن اشیای پشت شیشه. اگه رنگ داشبورد اتوموبیل هم روشن باشه ، که دیگه حسابی کلافه کننده میشه. یا گاهی درحین رانندگی ، بازتاب نور خورشید از روی شیشه اتوموبیل جلویی ، ممکنه برای فرد اذیت کننده باشه. همه این بازتاب ها توسط فوتونهایی به چشم میرسه ، که مماس بر صفحات عمودی حرکت میکنن. ( یه صفحه عمودی که خورشید ، جسم مورد نظر و چشم روی اون صفحه قرار دارن). بنابراین یه صفحه پولاریزه که جهت پولاریزه ش در سطح افق باشه ، میتونه همه این فوتونها رو بلوک کنه و از شر این بازتاب های آزار دهنده خلاصتون کنه.

همینطور موقع ماهیگیری ، تصویر آسمون که از سطح آب به چشم شما منعکس شده ، باعث میشه که داخل آب رو نبینید. با استفاده از عینک پولاریزه میتونید بازتاب تصویر آسمون رو حذف کنید و ماهیهای داخل آب رو ببینید.

جالبه بدونید عینک های پولاریزه ای هست که شیشه های کاملاً بیرنگ یا حداکثر کهربایی دارن ، و برای مقاصد خاصی مثلاً ماهیگیری ساخته شده. فقط برای حذف بازتاب های مزاحم !

Reference: lotus.sampad.info/?p=80

Astigmatism means that a dot is not imaged on the retina as a dot, but as a line.

You can use this test to see whether you have astigmatism or not.

You can take the test with or without spectacles. Fixate all four circles one after the other and look at the lines. Do you see constant, clear black lines?

First check each eye on its own and then both eyes together.If the lines appear distorted or blurred in one or more directions, this could be an indication of astigmatism. In this case, you should consult an eye care professional.

If you also see the differences while you are wearing your glasses, you should have your prescription checked because uncorrected astigmatism will reduce your visual acuity.

Astigmatism is an imperfection in the curvature of the eye. When the cornea (the clear front cover of the eye) or the lens inside the eye is curved instead of being even and smooth in all directions, astigmatism occurs. This curvature distorts light rays as they enter the eye and causes blurred vision. Both distance vision and near vision are affected.

Astigmatism is not an eye disease; it’s simply a problem with how the eye focuses or “refracts” light onto the retina. It is called a “refractive error,” and may occur at the same time as other refractive errors, such as nearsightedness (myopia) and farsightedness (hyperopia).

The most common symptom of astigmatism is blurred vision. Some people describe it as double vision but in only one eye. Some people with astigmatism develop eyestrain, squinting and headaches from working to focus on near or distant objects.

Astigmatism is usually a stable condition. Astigmatism can be corrected with glasses, contact lenses.

Sometimes astigmatism can be caused by other medical conditions, particularly problems of inflammation of the eyelids.

Distorted or blurred vision is a common issue that many people deal with at some stage of their life. It could be short-lived, or it could be a sign of something more serious. In some cases, the gradual deterioration of vision, that includes distorted vision could be a case of age-rated change, but in order to receive the correct treatment, we will consider the most common reasons you could be suffering from distorted vision.

Astigmatism that gets steadily worse over time may in fact be a condition called keratoconus.

Keratoconus (KC) is a disorder of the eye which results in progressive thinning of the cornea. This may result in blurry vision, double vision, nearsightedness, astigmatism, and light sensitivity. Usually both eyes are affected. In more severe cases a scarring or a circle may be seen within the cornea.

In keratoconus the cornea gets progressively thinner in one area and begins to bulge. These conditions may require more frequent doctor visits and treatment.

Astigmatism is a common vision problem caused by an error in the shape of the cornea. With astigmatism, the lens of the eye or the cornea, which is the front surface of the eye, has an irregular curve. This can change the way light passes, or refracts, to your retina.

This causes blurry, fuzzy, or distorted vision.

Research supported by the National Institutes of Health indicates that about 23% of very young children (from 6 months to 1 year old) have it, but many children grow out of it. By the time they reach school age (5 or 6 years old), only about 9% have astigmatism. The study also showed that it is slightly more common in Asian and Hispanic children. eResearch by Navid Ajamin -- spring 2008

Signs that your child may have astigmatism include:

• Blurred or distorted vision
• Frequent complaints of headaches
• Squinting or constantly closing eyes
• Tilting the head or turning to see better
• Closing one eye to read, watch TV, or see better
• Complaints of eye strain, especially after reading
• Shielding eyes or other signs of sensitivity to light

Astigmatism in children is usually present at birth, but may develop after an eye injury or eye surgery.

Imagine the cornea (front surface of the eye) as a perfectly symmetrical sphere, similar to a soccer ball. There is no astigmatism present when the curvature in one direction (red line in picture) and that of another curve 90 degrees away (blue line in picture) are the exact same. However, if the curvature in one direction is “steeper” or different from the other, then astigmatism is present. Rather than the eye being a perfect sphere, there is irregular curvature on the front surface, making the eye appear more elongated in one direction, like a football. The lens inside the eye can also contribute to astigmatism if there is a cataract or an irregular shape.

Astigmatism is a lifelong condition unless it is treated. It may worsen slowly over time; more typically, it remains stable throughout life.

The 3 Primary Astigmatism Classifications By properly identifying the astigmatism, a more thorough treatment plan can be put in place, and the doctor can more specifically tailor the needs of each patient’s condition.

Here are the three primary types of astigmatism:

• Myopic astigmatism — If you have this type, it means that either one or both of your principal meridians are nearsighted. If only one of your meridians is nearsighted, it means you have simple myopic astigmatism. If both are nearsighted, with one being more pronounced than the other, it means you have compound myopic astigmatism.
• Hyperopic astigmatism — This type means that one or both of your principal meridians are farsighted. Like myopic astigmatism, if only one of your meridians is farsighted, you have simple hyperopic astigmatism. If both are affected, with one being more severe than the other, then you have compound hyperopic astigmatism.
• Mixed astigmatism — As its name implies, this means that one of the meridians is nearsighted, while the other is farsighted.

What is the difference between against-the-rule and with-the-rule astigmatism?

Astigmatism is when your eye’s cornea or lens is irregularly shaped. Normally, the cornea and lens are curved equally in all directions.

Types of astigmatism (A, against the rule; B, with the rule)

If we view the eye as a sphere, “against-the-rule” is astigmatism where the steepest curve lies near the 180-degree meridian (imaginary line connecting east and west points of the cornea), and “with-the-rule” astigmatism (line connecting north and south points) is near the 90-degree meridian. With-the-rule is by far the most common type of astigmatism.

Clinical types of astigmatism:

A, compound myopic

B, simple myopic

C, mixed

D, simple hyperopic

E, compound hyperopic

Reference:

• rodenstock.com
• aao.org/eye-health
• articles.mercola.com
• researchgate.net/figure
• healthline.com/health/astigmatism
• edical-dictionary.thefreedictionary.com
• health.harvard.edu/a_to_z/astigmatism-a-to-z
• bookaneyetest.co.uk/post/vision-appears-distorted
• webervisioncare.com/taking-the-stigma-out-of-astigmatism
• eyeconsultantsofpa.com/resources/astigmatism-children.html

Oblong, Square, Round, Oval, Diamond-Shaped, Heart-Shaped or Triangular Faces

The Benefits of Polarized Sunglasses

Polarized sunglasses have long been used by boaters and fishermen for their amazing ability to reduce the sun’s glare reflected off the water’s surface. The benefits of these lenses are quickly catching on as more and more people are using them for all their outdoor sunglass needs.

When light is reflected off a smooth surface, such as water or a road, the light is usually polarized in a horizontal manner.

Polarized sunglasses combat this glare by blocking light with their vertically polarized filters. This filter reducing the amount of light reflected into the eye and improves visibility and clarity of objects.

Polarizing lenses have atoms in them that are lined up like little picket fences. Light waves can only go through if their waves are vibrating parallel to the pickets.

Ordinary light has vibrations in every possible plane. It is unpolarized. After going through the polarizing lens, the vibrations are only parallel to the atomic picket fences. This light is said to be plane polarized.

If two polarizers are perpendicular, then the light cannot get through them both. These are called crossed polarizers.

Polarized sunglasses are perfect for most outdoor activity such as skiing, golfing, biking or even jogging. Anytime that you need to block glare a pair of polarized lenses can improve your outdoor sight. You can also get polarized lenses in various tints that will further improve your visibility depending on the lighting conditions.

Advantages of Polarized Lenses

Features

• Filters glare

• Enhances contrast

• Reduces squinting

• Constant density tints

• Backside AR compatibility

• Tintable and coatable

• Lightweight

• Thin

Benefits

• Reduces eyestrain, greater comfort

• Improves visual acuity, provides safety

• Eyes feel rested

• Realistic perception

• Reduces reflections and enhances visual clarity

• Certain lens materials can be darkened and provides limitless colour options

• Comfortable Attractive-looking sunwear

1: Two polarized sunglass lenses with polarizations parallel to each other. Polarized light comes through.

2: Two polarized sunglass lenses with one of the lenses rotated to a 90° angle relative to the situation in picture 1. Almost no light comes through due to all of it being blocked. This is described by Malus' law.

3: One non-polarized sunglass lens. Non-polarized light comes through.

4: One non-polarized and one polarized sunglass lens rotated to a 90° angle relative to their normal orientation in the sunglass frames. Polarized light comes through.

Sunglasses (or at least one of the lenses) are not polarized if the near complete blockage of light seen in picture 2 is not observed when one of the lenses is removed and rotated in front of the other lens.

Sunglasses known to be polarized can also be used to test other sunglasses in a similar manner by rotating them in front of the sunglasses being tested.

List of the Disadvantages of Polarized Lenses

1. Polarized lenses make it difficult to view LCD screens.
When you are wearing glasses that have polarized lenses, then the chemical agents added to the product to create the filtering mechanism reduce the amount of light your eyes process from an LCD screen. Although you can still see them when you have a direct line-of-sight, moving to different angles can make the screen disappear completely. It may also impact the amount of color that some people can perceive when looking at information or watching a show.

2. Polarized lenses can alter how you perceive the world.
Heavy machine users are often restricted in their use of polarized lenses because of the way the filtering process alters your vision. This equipment often operates with an LCD screen to inform the operator of current conditions, which the lenses would interfere with during operations. This disadvantage is in place for airline pilots as well since the modern cockpit comes equipped with LCD screens as well. Anyone that must use their phone for work consistently, have access to GPS equipment, or similar needs with their employment may find that this option is not suitable for their needs. eResearch by Navid Ajamin -- spring 2008

3. Polarized lenses can make it challenging to distinguish between white colors.
Downhill skiing enthusiasts sometimes try to avoid using polarized lenses with their googles or sunglasses because of the way the technology filters out the horizontal light waves. Because you have different variations of while on the typical mountain thanks to the snow, hills, and ice, it can be challenging for some people to differentiate between these outdoor elements. Since it only takes one mistake for a catastrophe to occur in this sport, this disadvantage usually keeps skiers away from the product.

4. Polarized lenses need to have built-in UV protection.
Sunny days are always nice to experience, but the prolonged exposure to unfiltered sunlight can cause numerous health issues. The UV radiation can increase the risk of developing cataracts later in life, lead to damage to the retina, and even cause macular degeneration to begin. These injuries are cumulative over the lifetime of an individual, so polarized lenses must have UV protection if they are going to be an effective product. Since some products do not have this feature, you must look for stickers on your product which contain the following information.

• Verification that the lenses block 99% to 100% of UVA and UVB rays.
• The lenses are said to meet ANSI UVA/UVB blocking requirements for Z80.3.
• It states that the lenses provide UV400 protection when worn correctly.

5. Polarized lenses can cause you to see window grids.

When you wear polarized lenses with your sunglasses, then you can sometimes see a grid pattern appear on the windows of automobiles. Some houses can have this issue with their reflective surfaces as well. What you are seeing in these stripes or grids in the glass is an issue that occurs during the tempering process. These intentional stresses make the glass a stronger product, allowing it to have a predictable outcome if you happen to be in an accident. The pattern that you see is a reflection of the arrangement that the flames or heating elements cause during this process.

If you find that these grid patterns become too distracting while driving, then you can take the polarized lenses off. Then you are left with the problem of glare once again, so it becomes a lose/lose situation for some drivers.

6. Polarized lenses cost more than standard products.
If you want to take advantage of what polarized lenses can offer, then you can head to your local Walmart to purchase a pair of sunglasses for $15 (or less) with this technology. Most lenses that contain polarization filters will cost up to 30% more than if you bought a standard lens instead. Some people see this as an investment in their future, but it could also be an issue that takes the product out of the range of affordability.

You will also find that some of the cheaper lenses that are available today meet the industry standards for complete protection, while the premium products do not. That is why it is essential to review every product specification before finalizing your purchase.

7. Polarized lenses can have durability issues.
Instead of applying the chemical process to the plastic lens itself, cheaper sunglasses and goggles often apply a film over a basic lens to create the polarization effect. When you wear glasses with this design, then you will experience issues with flaking, peeling, and bubbling over time with the product. Users who are near the coast or live in high precipitation geographic areas typically see this problem the most often. High levels of sunlight exposure can cause the chemical film to begin fading too, which can minimize the protection you would receive when wearing your glasses.

8. Polarized lenses can be ineffective under specific circumstances.
Because the design of polarized lenses works to filter horizontal light waves, your positioning can reduce the effectiveness of this technology. You will encounter this issue most often during sunrise and sunset. When the sun is directly overhead, there can be some problems with this lens option as well. Some users may see artificial light differently as well, like when you attend a sporting event during the evening with the lights coming on. You can even miss obstacles in the road if the color of the object is similar to what is available in the surrounding environment.

9. Polarized lenses might provide too much filtering for some people.
Whether you are unable to wear polarized lenses because of your work or the way that it changes your vision makes you uncomfortable, there are some alternatives to consider that can still provide help your vision. Glasses with an anti-reflective coating can help you to see through the glare without the same vision alteration experience of polarization. Mirrored sunglasses decrease the amount of light that enters your eyes, which can reduce the impact that horizontal light waves have on your vision. Certain photochromic lenses will automatically darken when they receive light exposure as well.

A Final Thought on the Pros and Cons of Polarized Lenses

It is important to remember that UV-protected lenses and polarized lenses are not the same thing. If you do not see UVA or UVB protection labels on the sunglasses or goggles you wish to purchase, then they will not provide the service that you may want. Many of the polarized sunglasses on the market include a UV protection coating, but it may also peel off as the product ages or receives exposure to extreme conditions.

These lenses are a good option to consider for anyone who spends a lot of time outside. It reduces the bright reflections, eliminates unwanted glare, and can improve your vision under challenging circumstances. Don’t just consider your outward appearance when selecting the best lenses for your eyes because you need full coverage to 100% protect your vision. Some products do not offer that service.

The pros and cons of polarized lenses are typically more about one’s personal preferences. Some people prefer to wear them for the added clarity they receive when outside. Others feel like the filters are distracting when they are taking care of their business each day. If you work with LCD screens regularly, then this item might not even be an option to consider. The good news is that if you are interested in using this lens option for your sunglasses or goggles, then they are priced competitively with non-polarized items.

Polarized vs. non-polarized sunglasses

Why polarized sunglasses? For certain activities, including daytime driving, water sports and winter sports, you may benefit from wearing polarized sunglasses — especially if light is bouncing off surfaces and into your eyes. Both polarized or non-polarized lens types can help you see more comfortably in bright light, but you’ll want to consider polarized lenses for activities and situations that require a reduction in glare.

Daytime driving

Polarized sunglasses can really come in handy when you’re driving on sunny days. Their anti-reflective coating helps mitigate light bouncing off reflective surfaces in your field of vision — these surfaces include windshields, roads, snow and even the hood of your own car. This makes for a safer driving experience free from distractions or even the temporary blindness that can be caused by particularly intense glare.

However, if you find yourself more frequently driving in overcast conditions, non-polarized sunglasses might be for you. They tend to allow for better vision in low-contrast conditions. Just as you should wear sunscreen to protect your skin from harmful UV rays even on cloudy days, you should also wear UV-protection sunglasses when it’s cloudy as long as you can safely see.

For driving on snowy or icy days, it can actually be safer to wear non-polarized sunglasses. In these cases, you want to be able to see the reflected light that alerts you to ice on the road.

Nighttime driving

If you have trouble seeing the road due to the glare of street lights and headlights, you may be wondering if polarized glasses can help you with nighttime driving. The answer is no: You should never wear sunglasses in low-light or dark conditions. While they might be able to address the issue of reflection from headlights and street lights, they’ll ultimately cause more issues by making it too dark to see anything else.

There are anti-reflective night driving glasses made specifically for seeing better in low-light conditions. However, like polarized sunglasses, these can actually inhibit your vision rather than providing more clarity as intended. If you wear prescription glasses, opt for clear lenses with an anti-reflective coating to make sure the glasses themselves aren’t causing glare issues from headlights and streetlights.

Outdoor activities

Polarized lenses can be useful for outdoor activities, particularly when outside light is intensified by glare — when you’re on the road, for instance, or on a body of water. However, there are also outdoor activities for which polarized glasses are not recommended.

Instances where polarized sunglasses can be helpful include:

• Fishing: When you’re on or near a body of water, polarized lenses can help you see more clearly by cutting down on the glare from the water’s reflection. This also means you’re better able to see past the surface of the water, which provides a huge advantage for fishers.

• Water sports: If you’re sailing, kayaking or canoeing — or doing any number of other water sports — polarized lenses can ease the strain on your eyes from the water’s glare. Plus, they’ll help you see more underwater wildlife.

• Hiking: Polarized lenses are ideal for scenic views, as they help enhance colors so you can see vibrant landscapes more clearly.

Polarized sunglasses may not be the best choice for other outdoor activities, such as:

• Winter sports: While you may think polarized goggles or glasses would be helpful while skiing or snowboarding, not being able to see the glare from snow and ice during these activities can actually be detrimental. That’s because this reflection alerts you to dangerous icy patches, which allows you to avoid them.

• Bicycling and running: Using polarized sunglasses comes down to personal preference. Some cyclists and runners wear polarized shades to filter both ambient and reflected light, while others feel safer maintaining the ability to see reflected light.

Reference:

• sunglasses.lifetips.com
• spectacleworld.co.za
• connectusfund.org
• commons.wikimedia.org/wiki
• aao.org/eye-health/glasses-contacts/polarized-lenses
• allaboutvision.com/eyewear/sunglasses/what-are-polarized-sunglasses
• smartbuyglasses.com/optical-center/what-you-need-to-know-about-driving-with-polarized-sunglasses
• brightside.me/articles/7-reasons-thatll-convince-you-to-choose-polarized-over-regular-sunglasses-808091

A thorough eye exam can test all of the eight vision skills needed to read. If your child is having trouble in school, it could be eyesight-related. Learn more about vision changes in school-age children. Good vision is vital to reading well. And although vision may not be the only cause of reading difficulties, it is one cause that is sometimes overlooked.

Needed to read eight vision skills
Reading requires the integration of eight different vision skills. The typical school eye chart test checks only one. Quick eye examinations may cover only one or two. Since a comprehensive eye examination will cover the eight vision skills, it is a must for anyone who is having trouble reading .

The eight skills include:

1. Visual acuity,or the ability to see objects clearly at a distance. Visual acuity is sometimes measured in a school vision screening. Normal visual acuity is referred to as 20/20 vision (or 6/6 vision in the metric system) — a measure of what can normally be seen at a distance of 20 feet, or 6 meters. If a problem is discovered in the screening, a thorough optometric examination should follow.
2. Visual fixation,or the ability to aim the eyes accurately. One type of fixation, called direct fixation, has to do with the ability to focus on a stationary object or to read a line of print. The other type, called pursuit fixation, is the ability to follow a moving object with the eyes.
3. Accommodation,or the ability to adjust the focus of the eyes as the distance between the individual and the object being observed changes. Children frequently use this skill in the classroom as they shift focus between books and blackboards.
4. Binocular fusion,or the brain's ability to gather information received from each eye separately and form a single, unified image. Eyes must be precisely aligned physically or double vision may result. If it does, the brain often subconsciously suppresses or inhibits the vision in one eye to avoid confusion. That eye may then develop poorer visual acuity (amblyopia or lazy eye).
5. Stereopsis,a function of proper binocular fusion enhancing the perception of depth, or the relative distances of objects from the observer.
6. Convergence,or the ability to turn the two eyes toward each other to look at a close object. Any close work, such as desk work, requires this vision skill.
7. Field of vision,or the area over which vision is possible. It is important to be aware of objects on the periphery (left and right sides and up and down) as well as in the center of the field of vision.
8. Perception,the total process of receiving and recognizing visual stimuli. Form perception is the ability to organize and recognize visual images as specific shapes. A reader remembers the shapes of words, which are defined and recalled as reading skills are developed.

Most people don’t realize that you need 17 visual skills
to succeed in reading, learning, sports, and in life!

1. Eye Movement Control
The ability to move both eyes together to point at an intended target or follow along a path, like a line of text

2. Simultaneous Focus at Far
Forming a clear image of something in the distance

3. Sustaining Focus at Far
Keeping an image of something in the distance clear

4. Simultaneous Focus at Near
Forming a clear image of something close to the eyes

5. Sustaining Focus at Near
Keeping a clear image of something close to the eyes

6. Simultaneous Alignment at Far
Lining up both eyes at the same point the distance

7. Sustaining Alignment at Far
Holding both eyes lined up at the same point in the distance

8. Simultaneous Alignment at Near
Lining up both eyes at the same point up close

9. Sustaining Alignment at Near
Holding both eyes lined up at the same point up close

10. Central Vision (Visual Acuity)
This is where "20/20" vision comes in!

11. Peripheral Vision
Being able to see what's on either side of you while your eyes are pointed forward

12. Depth Awareness
Being able to tell that things are further away or closer up than each other (also know as depth perception)

13. Color Perception
Being able to tell different colors apart (if you are not color-blind)

14. Gross Visual-Motor
Moving yourself through space without bumping into things by using information from your vision

15. Fine Visual-Motor
Writing, sewing, texting, and doing other small and close-up activities with accuracy by using information from your vision

16. Visual Perception
Being aware of your environment and what is going on around you in your visual field (the area you can see)

17. Visual Integration
Bringing together your vision and your other senses to accomplish complex tasks, like reading while walking a balance beam

Important Vision Skills for Sports

Dynamic Visual Acuity

If you are playing a sport like racquetball, tennis, soccer or hockey, you need to be able to clearly see objects while you and/or the objects are moving fast. Without good dynamic visual acuity, you will have a difficult time in sports like these.

Visual Concentration

When you commit an error on an easy ground ball or miss a short putt, you might be distracted by things that are happening around you. Our eyes normally react to anything that happens in our field of vision-spectators, other participants or even rustling leaves on an overhanging branch. Visual concentration is the ability to screen out these distractions and stay focused on the object or the target.

Eye Tracking

When you are playing any sport with a ball or a fast-moving opponent, you need to be able to follow objects without much head motion. Eye tracking helps you maintain better balance and quickly react to the situation.

Eye-Hand-Body Coordination

Eye-hand-body coordination is how your hands, feet and body and other muscles respond to the information gathered through your eyes. It is an important part of most sports because it affects both timing and body control.

Visual Memory

When you are pushing a fast break up the basketball court, leading a rush up the ice in hockey or catching the big wave amid a crowd of surfers, you need to process and remember a fast-moving, complex picture of people and things. This is called visual memory. The athlete with good visual memory always seems to be in the right place at the right time.

Visualization

Picture yourself hitting a perfect drive ... long and right down the middle of the fairway. Believe it or not, picturing yourself doing it can actually help you do it. Through visualization, you see yourself performing well in your "mind's eye" while your eyes are concentrating on something else, usually the ball. Using scanning techniques, researchers have found that the same areas of the brain that light up during performance also are at work when you visualize the performance.

Peripheral Vision

When a soccer player sees her teammate out of the corner of her eye, she is using her peripheral vision. Much of what happens in sports does not happen directly in front of you. Therefore, increasing your ability to see action to the side without having to turn your head is important.

Visual Reaction Time

The pitcher releases the ball and you swing ... a little late and you hit a weak foul down the line, or worse, you miss the ball completely. Or maybe you can't quite return that tennis serve. You need to improve your visual reaction time, or the speed with which your brain interprets and reacts to your opponent's action.

Depth Perception

In racket sports, depth perception enables you to quickly and accurately judge the distance between yourself, the ball, your opponents, teammates, boundary lines and other objects. If you consistently over- or underestimate the distance to your target, poor depth perception may be the reason.

Is your child myopic (or nearsighted)?

Which type of myopia does your child have?

Myopia is a condition in which one can see clearly up close but unable to see clearly far away. In a myopic person, the eye is longer than it should be and so light coming into the eye from far away is focused in front of the retina rather than right on it, producing a blurred image. If the myopia starts in a child at a young age, chances are that it will worsen rapidly as the child grows.

There is actually more than one type of myopia, depending on its cause:

• Infantile myopia: the child is born with high myopia, often associated with abnormal pregnancy or poor nutrition during gestation.
• Stress­-induced myopia: the child begins reading at a very young age and tends to be very detail­-oriented. This is myopia caused by excessive near ­work at an age when the child ought to be spending time playing outdoors.
• Myopia induced by binocular dysfunction: the child’s binocular system did not develop properly, therefore reading creates excess stress on the focusing system which in turn, induces elongation of the eye resulting in worsening eyesight.

Here are some of the many visual skills that are improved through Sports Vision Training.

1. Visual Acuity at All Distances (Adaptable Clear Vision)
   Do the two eyes maintain clear vision at varying distances at all times? Clear vision at all distances is important to sports success.
2. Eye Focusing Skills - Shifting and Sustaining Sharp Vision: Do the two eyes shift and sustain focusing power quickly and easily? Accurate eye focusing skills are a big boon for an athlete in any game with moving objects and/or players, especially in a

   

   fast-paced game. Sports Vision Training can enhance focusing power, agility, and speed.
3. Eye Tracking, Eye Teaming, and Eye Movement Skills: Do the two eyes aim, move, and work as an effective coordinated team? Fast, fluid, binocular vision with coordinated eye movements and smooth eye tracking skills are essential to success in sports. Sports Vision Training conditions all of these visual skills simultaneously.
4. Depth Perception: Good binocular depth perception enables accurate assessment of relative distances, such as where the athlete's body is in relation to other objects or people. Sports Vision Training can increase and stabilize binocular depth perception.
5. Peripheral Vision and Awareness: Widening your peripheral field of vision and peripheral awareness allows a better perception of action, motion, space, and objects to the sides of your eyes and body without having to move your eyes in that direction. In other words, you can perceive what is happening around you without having to move your eyes away from a single focal point or visual target.Good or heightened peripheral vision and awareness add greatly to sports performance, such as in team sports. In addition, good peripheral vision contributes greatly to a well functioning vestibular system (good balance).

Of these three types of myopia, myopia induced by binocular dysfunction is the easiest to treat with vision therapy. When a child’s eyes do not work together properly as a team, he may respond by having a performance issue in reading, or he may learn to work his focusing system extra hard in an attempt to overcome the binocular dysfunction. In such cases, treating the underlying binocular dysfunction is key to eliminating the excess strain which induced the worsening myopia to begin with.

Because the binocular dysfunction varies from person to person, we do not prescribe the same vision therapy exercises for myopia control to all patients. There are many programs for natural vision improvement out there, but we don't typically recommend them because they are not customized to address each individual patient's binocular problems.

For stress­-induced myopia, vision therapy may be helpful but it requires constant vigilance and continual therapy. Patients will need to learn drills to reduce the stress on their eyes, learn proper posture and improve visual hygiene. In addition, plus lenses may be prescribed to further decrease the stress on their eyes when reading. For such patients, orthokeratology, an overnight contact lens which reshapes the eye while sleeping, tends to work better in arresting the worsening of their eyesight.

There are several key visual skills that are enhanced through sports vision programs for athletes that aim to achieve their optimal sports performance, these include:
Dynamic visual acuity: this refers to the patient’s ability to see objects clearly while in motion. This is exceptionally important as hand-eye coordination and reflex reactions are essential for success in most sporting activities.
Contrast sensitivity: good contrast sensitivity is needed to determine the difference between an object and its surroundings. Contrast sensitivity is particularly important in situations where there may be low light, fog or glare that could diminish the natural contrast between objects and backgrounds.
Eye tracking: this refers to the ability to follow a fast-moving object, such as a ball or puck.
Switching eye focus: athletes need to be able to change their focus quickly and accurately from one distance to another.
Binocular vision skills: also known as eye teaming skills, these skills determine how well your eyes work with one another to produce a single, clear image.

Processing speed: visual processing speed is defined as the amount of time it takes to make a correct judgement about a visual stimulus – for example, how fast a ball is travelling towards them.
Peripheral awareness: athletes also need to be able to be aware of what is happening at the edges of their vision while also concentrating on a fixed object in front of them.

Sports vision testing can enable your eye doctor to spot any weaknesses that you may have in any of these key visual skills. By identifying them, it is possible for you to undergo treatment to overcome theses issues and meet your specific goals that will ultimately enhance your overall athletic performance. This is known as sports vision training.

Reference:

• hope.vision/child
• novartisophthalmics.com
• covd.org/page/visual_skills
• maranaeyecare.com/sports-vision.html
• sjvisiontherapy.com/specialties/myopia
• drslotnick.com/vision-services/optometric-vision-therapy
• visiondevelopmentinstitute.com/sports-vision-training-specialist
• drbasueyehospital.com/snellen-chart-the-eye-test-chart-for-accurate-vision-measurement
• enchroma.com/blogs/beyond-color/why-sports-are-better-with-enchroma-color-blind-glasses
• aoa.org/patients-and-public/caring-for-your-vision/sports-and-vision/important-vision-skills-for-sports

به نام خالق زیبایی ها

• نسخه های پزشکی دیگران را کپی نکنید. Translation: Navid Ajamin -- winter 2004
• در حد امکان روزانه از سبزیجات تازه٬ گوجه فرنگی٬ هویج و یک لیوان شیر استفاده کنید.
• چشمان خود را در برابر تشعشعات ماورای بنفش٬ گرد و غبار٬ باد و نور زیاد حفظ کنید.
• چشمان خود را در ساعتهای کاری زیاد استراحت بدهید.
• چشمان خود را با ملایمت و مقدار کافی آب روزانه بشوئید.
• همیشه در محیط نوری مناسب و با قرار گرفتن صحیح بدنتان مطالعه کنید.
• بدنتان را در موقعیتی صحیح و با استراحت در فاصله های کاری حفظ کنید.
• درهنگام مطالعه اگر مشکلی دارید و یا عیوب انکساری دارید از عینک استفاده کنید.
• از قطره های چشمی تنها از آنچه برایتان تجویز شده استفاده کنید.
• هنگام کار با کامپیوتر فاصله ایی صحیح از کامپیوتر و لوازمات کامپیوتری داشته باشید.

Healthy vision starts with you! Use these 10 tips to take care of your eyes.

1.Eat right to protect your sight.

Keep your eyes healthy by eating a well-balanced diet. Load up on different types of fruits and veggies, especially leafy greens like spinach, kale, and collard greens. Fish like salmon, tuna, and halibut have been shown to help your eyes, too.

2.Get moving.

Did you know that kids who exercise often have a healthier body weight than kids who don’t? Being overweight or obese can put you at higher risk for diabetes and other conditions that can lead to vision problems.

3.Speak up if your vision changes.

Is your vision blurry? Do you squint a lot? Ever have trouble seeing things at school? Tell a parent or teacher if your eyes are bothering you or if you notice any changes in your vision.

4.Wear your glasses.

Your glasses help you see better, especially when they’re clean and free of smudges. Talk to an adult about how to clean your glasses and how to store them when you’re not wearing them.

5.Keep the germs away.

Always wash your hands before putting them close to your eyes, especially if you’re putting in or taking out contact lenses.

6.Gear up.

Playing your favorite sport? Using chemicals during science class? Mowing the lawn? Wear the right protection to keep your eyes safe. Many eye injuries can be prevented with better safety habits, such as using protective eyewear.

7.Wear your shades.

The sun’s rays can hurt your eyes. Choose sunglasses that block 99% or 100% of both UVA and UVB radiation from the sun. And remember, you should never look directly at the sun.

8.Give your eyes a break.

Do you spend a lot of time looking at a computer, phone, or TV screen? Staring at any one thing for too long can tire your eyes. Give your eyes a rest with the 20-20-20 rule: Every 20 minutes, look about 20 feet away for 20 seconds.

9.Say no to smoking.

Did you know that smoking is as bad for your eyes as it is the rest of your body? Smoking can put you at risk for some pretty serious eye issues, which can lead to blindness.

10.Talk about it.

Does anyone in your family have issues with their eyes? Not sure? Ask! Talking about eye health with your family can help all of you stay healthy.

Reference: https://www.nei.nih.gov/learn-about-eye-health/nei-for-kids/healthy-vision-tips

Video: eyecare tips See also: Simple Tips for Healthy Eyes