What is Legal Blindness?

Many of us can remember watching the 1992 Olympics in Albertville. Nancy Kerrigan competed as a figure skater, but her mom was not in the stands. She was beneath the stands with Nancy's father watching on a television set. Brenda Kerrigan is legally blind. She lost all of the vision in her left eye and most of the vision in her right eye in 1972 when she contracted a rare virus. Because she could not see anything at a distance, the only way she could watch her daughter skate was to stand very close to the television. At that time, this situation brought a lot of attention to the condition known as Legal Blindness and Nancy would eventually start the Nancy Kerrigan Foundation which raises money for the visually impaired.

But what is Legal Blindness? The term Legal Blindness was defined to help people receive government assistance from the Social Security Administration and to be used by the Department of Motor Vehicles to measure vision and keep our roads safe. To be considered Legally Blind, you must meet at least one of two criteria regarding visual acuity and/or peripheral vision.

Legal Blindness differs from Total Blindness in that a person who is considered Legally Blind will still have some vision whereas a Totally Blind person will not be able to perceive any form or light.

A person who is Legally Blind has a CORRECTED visual acuity of no more than 20/200 in their best seeing eye, or a field of vision that is 20° or less in their best seeing eye.

Let's break that down.

The standard for visual acuity in the United States is measured by the Snellen test. Normal visual acuity is classified as 20/20. In the Snellen test, you are shown a chart that is 20 feet away consisting of letters which get smaller as they progress down the chart. Each line of letters is assigned a number based on what a "normally sighted" person can see at 20 feet. Some people will see the 20/20 line perfectly. Some people will see lines with even smaller print than the 20/20 line clearly. They are the eagle-eyed folks with 20/15 vision or better. Some will not even be able to make out the big E at the top of the chart at 20 feet. The standard for legal blindness is 20/200. This means the person in question sees at 20 feet what a person with normal visual acuity sees at 200 feet. In other words, their vision is ten times worse than that of a normally sighted person.

But wait. In order to be considered Legally Blind, you must have a CORRECTED visual acuity of no more than 20/200. Corrected visual acuity is your vision with corrective lenses- glasses or contact lenses. Most people who are nearsighted or farsighted or have astigmatism are fully correctable to 20/20. This means that once they put on their glasses or contact lenses, they can read the chart every bit as well as a "normally sighted" person. In order to be considered Legally Blind, your vision must be WORSE than 20/200 in your BEST eye while you are wearing your glasses or contacts. So, how poorly you see without your glasses or contact lenses has nothing to do with it. As long as your vision can be corrected to better than 20/200 in one eye with corrective lenses, you are not considered to be Legally Blind no matter how nearsighted, farsighted, or how much astigmatism you have. Also, if your corrected vision in one eye is less than 20/200 but you can see better than 20/200 with glasses or contact lenses in your other eye, you are not considered to be Legally Blind.

The second criteria for determining Legal Blindness has to do with Peripheral or Side Vision. "Normally Sighted" people have a lateral or side field of vision that is 180º. This means that even while you are looking straight ahead, you can see a person standing at your side. Peripheral vision is important to everything we do. We rely on it when walking around, driving a car, or crossing a busy street. Some people have very good eyesight and can see tiny letters from far away, but they cannot see a person standing beside them due to poor peripheral vision. If a Visual Fields test reveals that your field of vision is severely restricted to 20º or less (also known as tunnel vision), you are legally blind; even if you can see 20/20 on an eyechart.

So, what are the causes of Legal Blindness?
There are four leading causes:

Age Related Macular Degeneration (AMD or ARMD)- a leading cause of vision loss in Americans aged 60 or older, AMD occurs when the central portion of the retina known as the macula deteriorates. The macula is responsible for the sharp central vision required for reading or driving.

Cataracts- a clouding of the lens that causes blurred vision. Although usually age related (over half of all Americans will have a cataract by age 80), some cataracts are the result of genetic disorders and others are caused by diabetes or even trauma to the eye.

Diabetic Retinopathy- a disease found in diabetics caused by changes in the blood vessels of the retinal tissue in the back of the eye. This affects an estimated 4 million American adults over the age of 40.

Glaucoma- a condition in which increased pressure within the eye causes damage to the optic nerve thereby decreasing vision. It is estimated that over 2 million Americans have Glaucoma but only half of those are aware they have it.

What are some resources for those who are Legally Blind?

Legal Blindness is considered a disability, and those who are Legally Blind may receive benefits from the Social Security Administration.

Low Vision aids such as magnifiers, telescopes, and digital devices can help those who are Legally Blind to maximize their remaining vision.

Guide dogs are extremely helpful to those who are Legally Blind.


Can Legal Blindness be prevented?

The most important thing you can do to preserve your vision is to have yearly eye exams. Your Optometrist is not only checking your vision, but also monitoring your intraocular pressure, testing your visual fields, visually inspecting your retinas, and monitoring any risk factors you may have from disease, genetics or lifestyle.

Be sure to eat a healthy and varied diet. Get plenty of green leafy vegetables, and good proteins. Fish is also a valuable source of healthy nutrients for your eyes.

Do not smoke. And if you do smoke, quit immediately! Smoking is one of the leading causes of Macular Degeneration and Cataracts.

Always protect your eyes when outdoors. A good pair of sunglasses or Transitions Light Adaptive Lenses will protect your eyes from the harmful UV rays of the sun.


There are over 1 million Legally Blind Americans. Those who are Legally Blind can still have a very enjoyable life filled with hobbies such as reading, cooking, crafting and more, but Legal Blindness is a very real condition that can greatly affect one's quality of life.

So, now that you know the real facts, the next time someone tells you they are "Legally Blind without their glasses", you can help them to understand the truth.


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