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The binocular harmonization technology reduces prismatic side effects from each eye which leads to a more balanced experience while reading with progressive lenses. The higher the difference is in lens power in the left and in the right eye the more side effects the wearer will have. The image from the right eye gets deviated in comparison to the left eye.

The binocular harmonization technology takes that information into consideration and changes the progressive corridor lengths for each eye to ensures both eyes have similar reading support when looking down. This technology is available with high-end progressive lenses from Hoya.

Some wearers of progressive lenses really stick to this brand when buying progressive lenses so I wanted to compare the hoya lenses with the Binocular Harmonization Technology with a pair of progressive lenses without the Binocular Harmonization Technology. In this case, I ordered the Eden Zeta lenses from Novacel for comparison.

The Binocular Harmonization Technology can only work when the prescription is different in the left and in the right eye. So I ordered both progressive lenses with a difference of two diopters between the eyes. A bigger difference than that will probably require the wearer to get a slab off to minimize the side effects. Those side effects are:

• Vertigo when wearing progressives
• When you can only read with one eye at a time
• Headaches

Reference:

• progressive-glasses.com/what-is-binocular-harmonization-technology-does-it-work

Prescription eyeglasses have become a major demand by majority of the people these days worldwide, as the usage of digital devices such as computers, LED TV’s and mobile phones, etc. are being vastly used by individuals of every age as well as children. But fortunately, there is an arrival of a latest and a revolutionary technology that can highly assist those, who love to see the world clearly than ever before.

This latest technology in eyeglass industry is known as Free-Form Progressive Lenses," a groundbreaking digital manufacturing procedure, making use of computer-assisted design and developing to produce a futuristic, customized eyeglass lenses according to your provided prescription.

Just imagine that you go for shopping to get a new pair of pants from a branded store, and that is slightly longer or unfitted on you. So what would you ask them? Certainly to get it customized, so it fits perfectly and making you look exceptional. The same thing happened here as you can now get your current lenses customized for particular prescriptions and frames.

Difference Between Standard & Free Form Lenses

Free form lenses are among the prevalent types of advanced lenses, produced by utilizing free form technology, letting users to attain improved optics. Let’s discuss the main comparison of standard & free form lenses:

Standard Lenses:

Standard lenses are mainly the pre-molded lens, having the progressive design formed on its front exterior. In its production, the prescription is created on its back surface and this way the mold is not changed.

These are digitally designed that is made via software measuring a person’s prescription and some additional factors like frame fitting position. What is does is it lets them to be modified according to every person rather than simply using pre-molded lenses.
If you can recall the very first time you came to see any high-definition LED TV, could you imagine how you compared it with the analog TV picture? It definitely would have appears crispier as well as clear, didn’t it! Now think similarly this matter with your prescription glasses and you will perhaps see more satisfactorily with the lenses you are using, but wouldn’t it be beneficial if you could do advancement to high-definition for your eyes?

Advantages of using Free-form Progressive Lenses
Some top-ranking eyeglasses companies such as Goggles4u believes that the free-form progressive lenses technology could be the revolution in vision improvement. Furthermore, it can also recover eyesight precision that custom-made free form lenses deliver. With this type of lenses, you can expect to achieve:

Excellent Low-Light & Night Vision: These free-form lenses have the ability to decrease the glare and radiance effects produced by light causes in the dark, such as those from a car’s headlights.

Reference:

• reddoptical.co.zw/what-we-do
• 2020mag.com/ce/the-optics-of-free-form
• Advantages of Free Form Progressive Lenses (goodrichoptical.com)
• goggles4u.com/clearer-crisper-vision-through-free-form-progressive-lenses

Bifocal glasses are used to correct vision at two distances—a prescription on top for far away and a different prescription on the bottom for near.  Most people think of bifocals as reading glasses for people over forty who lose their ability to focus up close as they age.  But children can also need reading glasses.

 Many children have not developed sufficient control over their focusing systems, the natural lens inside the eye that keeps images clear, especially up close.  Some children lack the ability to sustain sufficient focusing over an extended time period, so after a while print begins to blur.  Others can’t make fast focusing shifts from one distance to another, like from the board to their desks, so any time they look away, everything is blurry.   Some children have a tendency to over focus, and the additional stress causes eyestrain and headaches.  If they over focus too much, the additional tension on the visual system can make the eyes to turn too far inward, causing double vision. Finally, near work at school places much more stress on the visual system than distance viewing, and some young children respond by translating the visual stress into physical and emotional symptoms—back and neck tension, headaches, constriction of their perceptual fields and a reduction in their visual space, a tendency to develop nearsightedness, and avoidance of the reading tasks that are causing the physical and visual discomfort.                   eResearch by Navid Ajamin -- spring 2013

Prescribing reading glasses effectively treats many of these problems. A convex plus lens relaxes the child’s focusing system, relieving much of the visual stress.  In fact, prescribing a low power plus lens is so effective in keeping children’s visual system comfortable during extended close work at school that they are often called “learning lenses.”

  Reading glasses that use a bifocal are a good option for school-aged children who only need the additional correction up close.  The bifocal gives them the lens support they need for deskwork but doesn’t change their distance vision. Sometimes vision therapy is also prescribed when the focusing problem is severe enough that additional interventions are also required.

New advances in lenses allow children flexibility in the type of bifocal they choose. Many children still prefer the flat-top bifocal because the line separating the two powers helps them tell exactly where their distance prescription ends and their near prescription starts.  However, some children or parents don't like the look of the "line", so for them progressive no-line bifocals are a good option.  The lens is made so that the change between prescriptions is so gradual no line appears.  Another very popular option is the "half-moon" bifocal. It has the advantage of a clear delineation between powers liked lined bifocals but when the glasses are on the child's face, the bifocal is invisible like progressive lenses.

When bifocals or reading glasses are prescribed, it is important that children wear them for all close work, especially at school and during homework. Sometimes children will only need the bifocals for a few years as they develop control of their focusing system.  Others may need the additional near-point support for as long as they are in school and spending a lot of time reading.Bifocals are an important tool for optometrists when working with children who spend up to eight hours a day using their eyes for reading and school work. 

Many children have not developed sufficient control over their focusing systems, the natural lens inside the eye that keeps images clear, especially up close.  Some children lack the ability to sustain sufficient focusing over an extended time period, so after a while print begins to blur.  Others can’t make fast focusing shifts from one distance to another, like from the board to their desks, so any time they look away, everything is blurry.   Some children have a tendency to over focus, and the additional stress causes eyestrain and headaches.  If they over focus too much, the additional tension on the visual system can make the eyes to turn too far inward, causing double vision. Finally, near work at school places much more stress on the visual system than distance viewing, and some young children respond by translating the visual stress into physical and emotional symptoms—back and neck tension, headaches, constriction of their perceptual fields and a reduction in their visual space, a tendency to develop nearsightedness, and avoidance of the reading tasks that are causing the physical and visual discomfort.

  Prescribing reading glasses effectively treats many of these problems. A convex plus lens relaxes the child’s focusing system, relieving much of the visual stress.  In fact, prescribing a low power plus lens is so effective in keeping children’s visual system comfortable during extended close work at school that they are often called “learning lenses.”

Reading glasses that use a bifocal are a good option for school-aged children who only need the additional correction up close.  The bifocal gives them the lens support they need for deskwork but doesn’t change their distance vision. Sometimes vision therapy is also prescribed when the focusing problem is severe enough that additional interventions are also required.

New advances in lenses allow children flexibility in the type of bifocal they choose. Many children still prefer the flat-top bifocal because the line separating the two powers helps them tell exactly where their distance prescription ends and their near prescription starts.  However, some children or parents don't like the look of the "line", so for them progressive no-line bifocals are a good option.  The lens is made so that the change between prescriptions is so gradual no line appears.  Another very popular option is the "half-moon" bifocal. It has the advantage of a clear delineation between powers liked lined bifocals but when the glasses are on the child's face, the bifocal is invisible like progressive lenses.

When bifocals or reading glasses are prescribed, it is important that children wear them for all close work, especially at school and during homework. Sometimes children will only need the bifocals for a few years as they develop control of their focusing system.  Others may need the additional near-point support for as long as they are in school and spending a lot of time reading. 

By adding an additional lens power for up close, optometrists are able to adjust children’s focusing system to give them better control and eliminate eyestrain, blurred vision, headaches, and fatigue.  

Reference:

• childrensvision.com   Children's Vision Information Network
• childrensvisionwichita.com/eyecare-services/vision-therapy/bifocals-for-children.html

See Also:

• Bifocals for Children Suny College of Optometry -- University Eye Center

• A prescription for bifocals may help children

• Bifocal spectacles slow progression of nearsightedness in kids

Polarized bifocal sunglasses are a great option if you wear bifocals and you spend time reading outdoors. Many people love to read outdoors and this is wear these glasses come in handy.

Additionally, many professions requiring employees to work outdoors need to wear bifocals in order to read various print or instruction.
Why Would Someone Want These Sunglasses?

Polarized bifocal sunglasses are a newer invention particularly aimed at people that read outdoors or need to see fine print when outside. It protects the eyes and helps the reader see the text more easily.

These are also useful for those that like working outdoors on their laptop. Netbooks are quite popular, but the text is smaller simply because the screen is smaller, so it makes it difficult to read the text without bifocals.

Who Normally Purchases these Glasses?

If you are 40 years old or older, you may have noticed that the fine print on your pill bottles you are no longer able to see. It is a normal part of aging and normally 40 years old seems to be the magic number when people begin having problems seeing small print.

Of course, bifocals can be purchased in many strengths at your local drugstore for very inexpensive, but they have no tint so they would only be helpful when indoors.

Polarized bifocal sunglasses since they are the newest invention on the market, cost a bit more, but they also include 100 percent UV protection.

What this means is you can read outdoors and ensure your eyes are protected from the sun's harmful UV rays.

What are other Reasons that Someone Would Purchase These?

Many truck drivers or those that drive for a living, use bifocal sunglasses because they often have to read maps and see the dash panel, which can prove difficult if you have a hard time seeing smaller print.

Moreover, those that go fishing find these sunglasses very useful because they can see the small hooks in order to bait their fishing lines.

If you have ever been outdoors with a regular pair of sunglasses on and struggled to see fine print, you obviously could benefit from these sunglasses.

What About Magnification?

Sunglasses with specialized bifocal lenses come in the same strengths you normally find at your local drugstore, such as 1.5, 2.0, 2.5, 2.75, and 3.0 magnification. Always make sure you test them well before purchasing them.

It is a good idea to bring in a book or a newspaper with you so that you can test out the different magnifications.

Obviously, you want make sure they are the right strength because purchasing a pair with too high of a magnification can cause you to develop headaches or simply not be able to see any fine print.

Final Thoughts

The polarized bifocal sunglasses option are a great way in which to be outdoors, have UV ray protection, reduces the glare of the sun, and be able to see what you are reading. Try to find the anti-scratch variety because they will last much longer than those that do not have the coating applied.

Reference: sunprotectionandyou.com

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)

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