Proceedings of: Workshop on Improving Building Design for Persons with Low Vision

Official Definitions

Okay, the official definition of low vision usually goes hand-in-hand with blindness, and low vision and blindness are often in the same sentence. And there’s a kind of commonsense definition of blindness. We think we have no useful vision, that you can’t use your vision at all. But then the technical definition of blindness is usually defined in terms of some level of visual impairment and it’s usually even visual acuity or visual fields.

The World Health Organization defines blindness as corrected visual acuity (slide 4). By corrected I mean wearing your glasses, getting the best vision you can. The corrected visual acuity that’s less than or equal to 20/400 in your better-seeing eye – and I’ll explain what these numbers mean – or your maximum diameter of your visual field is under 10 degrees. Then you qualify for the term blindness, according to the World Health Organization criteria.

World Health Organization finds low vision and its corrected visual acuity that’s less than 20/60, but it’s greater than or equal to 20/200. So if you’re in that range, your vision’s impaired, but still is useful to you, then use the term “low vision”. And they also include a visual field definition that if the maximum diameter of the visual field is 10 degrees or greater, but less than 20 degrees, then you earn the term low vision from the World Health Organization.

In the United States, blindness is defined as part of the Social Security Act for purposes of defining disability for disability benefits (slide 5). And blindness is – today is defined as corrected visual acuity in the better-seeing eye that is less than 20/100. It used to be less-than or equal to 20/200. The reason for the change is that we got new eye charts. The eye charts used to be 20/100, 20/200 was the next line. We got new eye charts and added a 20/160 line in between. Subsequently, we had a lot of people who could read 20/160; they lost their blindness-related benefits, because of 20/160.

So people like Dr. Siemsen and Dr. Alibhai had the old Snellen charts in the other room. And if you had to come in for a disability test, they’d take out the old Snellen chart and checked to see if – and finally, commonsense prevailed and said what you really mean is they can’t read the 20/100 line, they can read the 20/200. So the cut really is 20/100. So that’s the new definition of blindness for the disability insurance.

The maximum visual field [diameter of] less than 20 degrees. Remember, that’s the low-vision range for the World Health Organization; it’s blindness for the U.S.

Low vision is not a term that is used in that way; however, it is defined by Medicare. And to be eligible for payment for services that are provided for rehabilitation of your vision – receiving rehabilitation related to your visual impairment, Medicare defines low vision using ICD-9-CM codes – these are diagnostic codes (slide 5). And mild low vision, which they don’t pay for, is in the range of less than 20/40, but greater-than or equal to 20/60. Moderate low vision – they’ll pay for that – is less than 20/60 and greater than 20/200 and/or if your visual acuity is better-than or equal to 20/60, you have blind spots in your central field that interfere with your functioning. So if you can document that, you’re still classified as moderate, even though your acuity might not reach those particular [limits]. And severe low vision is anything less-than or equal to 20/200 – same definition as legal blindness.

The ICD-9-CM codes go onto to break up severe low vision into severe, profound, near-total blindness, total blindness, but in Medicare’s, those don’t make a difference. And so we’ve tended to just stop at the severe to be all inclusive after that.