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. eResearch by Navid Ajamin -- spring 2009
What Causes Night Blindness?
A number of eye conditions can cause night blindness, including:
- Nearsightedness or blurred vision when looking at faraway objects.
- Cataracts or clouding of the eye's lens.
- Retinitis pigmentosa, which occurs when dark pigment collects in your retina and creates tunnel vision.
- Vitamin A Deficiency
- Zinc Deficiency
- Dry Eyes
- 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?
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
وبلاگ تخصصی عینک شامل مجموعه مطالب پزشکی است که اطلاعات مفیدی در رابطه با عینک , چشم، لنز، سلامتی چشم و راه های پیشگیری از بیماریهای چشمی، کنترل و درمان آن را در اختیار شما کاربر محترم می گزارد.
