Last updated on June 6th, 2017 at 05:46 pm
Have you ever questioned what it means to be “legally blind”? Some people use the term to explain their vision without eyeglasses or contact lenses if their uncorrected refractive error makes them feel visually handicapped (not able to drive a car, for instance). Others presume it indicates the exact same thing as total loss of sight (complete lack of type and light perception). In fact, the terms “legal blindness” and “legally blind” imply neither of these things.
Definition Of Legal Blindness
Legal blindness is a level of visual disability that has actually been defined by law either to limit enabled activities (such as driving) for safety factors or to figure out eligibility for government-funded special needs advantages through instructional, service, or monetary assistance.
To be considered legally blind, your visual skill needs to be 20/200 or worse in your much better eye while you are wearing restorative lenses.
The U.S. Social Security Administration (SSA) specifies legal blindness as follows:
- Reduced central visual skill of 20/200 or less in your much better eye with use of the best spectacles lens to correct your eyesight; or…
- Limitation of your field of view such that the widest diameter of the visual field in your much better eye subtends an angle no greater than 20 degrees.
(If you have a visual problems however are not “legally blind” according to the SSA definition above, you still may be qualified for Social Security benefits on the basis of disability. See the SSA site for additional details.)
How Many People Are Legally Blind?
According to a 2009 report by the National Federation of the Blind, 1.3 million individuals in the United States were legally blind at the time of the report.
In a 2004 study carried out by the Eye Diseases Prevalence Research Group, nearly one million (937,000) people over age 40 in the United States were legally blind, and another 2.4 million Americans had low vision (fixed visual skill even worse than 20/40 in their much better eye). The study authors approximated the variety of legally blind Americans would increase by 70 percent to 1.6 million by 2020, with a comparable rise in the number of people with low vision, due mostly to the aging of the United States population.
Legally Blind Due To Reduced Visual Acuity
What does being legally blind due to “decreased central visual skill of 20/200 or less” imply?
In the United States, clarity of vision generally is expressed by a measurement system called Snellen visual skill. In this system, you identify smaller sized and smaller letters on an eye chart, and the outcomes are expressed as a portion standardized for a seeing distance of 20 feet.
If you have 20/20 Snellen visual acuity, this indicates the smallest letters you can determine from a distance of 20 feet (the first number in the fraction) are the same size as the tiniest letters a person with historically defined “normal vision” can see at a range of 20 feet (the second number in the fraction).
But if you have 20/200 visual acuity, the smallest letters you can recognize from a distance of 20 feet are the size of the smallest letters an individual with traditionally specified “normal vision” can see from a much higher range — 200 feet, in this case.
So your main vision — the part of your eyesight you use to see and determine things you are looking directly at — is much even worse (10 times worse, in truth) than that of an usually spotted person.
Crucial: In order for you to be thought about legally blind, your visual acuity must be 20/200 or even worse in your better eye while you are wearing corrective lenses. So how inadequately you see without your eyeglasses or contact lenses when you get out of bed in the early morning has absolutely nothing to do with it.
Likewise, if your best corrected vision in one eye is even worse than 20/200, however you can see much better than 20/200 with corrective lenses with your other eye, you are not considered legally blind.
Legally Blind Due To Visual Field Restriction
Visual skill tests determine the clarity of your main vision. Nevertheless, some individuals can see small letters on an eye chart, but cannot see the person standing right beside them due to bad peripheral vision.
The importance of a broad visual field is especially apparent when you consider how much you count on peripheral vision for specific activities, such as driving a car or crossing a busy street.
Visual field tests are totally different from tests of main visual acuity. Whatever device your eye doctor uses to test your peripheral vision, the goal is to identify if you have a normal field of view without unusual narrowing of your peripheral vision or the existence of unusual blind spots.
People with normal peripheral vision have an optimum lateral field of view that creates an angle of almost 180 degrees. To puts it simply, distant things that are located directly to the right or left of the observer are still visible. The normal vertical field of vision of humans is not as expansive — it creates an angle of about 135 degrees. (Objects directly above us and at our feet are not all at once noticeable.)
If visual field screening reveals your peripheral vision is significantly restricted to only 20 degrees (developing a very restricted field of view typically called tunnel vision), you are thought about legally blind — even if you can see the 20/20 line on an eye chart.
Causes Of Legal Blindness
There are many reasons you might be born with a visual disability or become legally blind during your lifetime.
Optic neuritis and neuropathy also can cause legal loss of sight, as can a variety of hereditary conditions, such as genetic cataracts, infantile glaucoma, and retinopathy of prematurity.
Whatever the cause, legal loss of sight makes an individual eligible for unique services and support.
The Social Security Administration provides advantages for the legally blind, and there are federal and state tax deductions as well. There also is a range of non-governmental resources targeted at making it easier to lead a normal life in spite of severe vision impairment.
If you are legally blind or you are a guardian or care company for someone who is, make certain to seek the services of an optometrist who specializes in low vision.
Low vision experts normally recognize with the most recent vision aids such as magnifiers, telescopes and digital devices that can help legally blind people use their remaining vision as effectively as possible. Such devices frequently make it possible for an individual with legal loss of sight live more separately and take pleasure in activities that normally spotted individuals regularly take for approved.
Professionally trained guide dogs likewise are an excellent help for many individuals who are legally blind.