Patients ask all the time if they are legally blind without their glasses. I know what they really want to know is how to measure their vision. By definition, legal blindness is WITH YOUR GLASSES ON…
Legal blindness: The criteria used to determine eligibility for government disability benefits and which do not necessarily indicate a person’s ability to function.
In the US, the criteria for legal blindness are:
- Visual acuity of 20/200 or worse in the better eye with corrective lenses (20/200 means that a person at 20 feet from an eye chart can see what a person with normal vision can see at 200 feet);
- Visual field restriction to 20 degrees diameter or less (tunnel vision) in the better eye.
Note that the definition of legal blindness differs from country to country and that the criteria listed above are for the US.
Ok, so what that means is you can be totally blind in one eye, but if the other eye can see 20/100 or better with your glasses on, you are not considered legally blind. From a practical standpoint, one eye blind and the other best corrected to: 20/20 you are considered normal; 20/50 your ability to drive comes into question; 20/80 you are not legal to drive in most states.
Another key point is the visual field restriction. Visual field measures your side vision. The two most common reasons for this kind of legal blindness are glaucoma and stroke. What it looks like is tunnel vision; you can see great straight ahead, but things sneak up on you from the side. Tunnel vision is very dangerous when driving, walking across the street, etc.
So when you ask me if you are legally blind when you take your glasses off, the answer is no, but you sure see better with them on!
That is all for now.
Dr. Jill Anderson
Dr. Jill Anderson has been practicing optometry since 1995. She had her own practice from 1997 – 2010 and has recently joined us here at Sight & Sun Eyeworks. She received her degree as a Doctor of Optometry from the University of Alabama at Birmingham School of Optometry. She is a highly skilled Contact Lens Specialist.