Oct. 29, 2014

Yes, I'm Blind

Yes, I'm Blind

Unless you know me or know of me it’s very likely that, after interacting with me, you would not pick up on the fact that I really can’t see very well, at all. I’m one of millions of people that have a visual impairment. The premise of this article is to describe legal blindness in general, a little about me and my visual ability and why I consider myself Ambiguously Blind.

“Visual impairment” is a broad category that describes vision loss that is not correctable with conventional eye glasses or contact lenses. A visual impairment affects a person’s ability to perform the usual activities of daily life such as reading a book, crossing a street, or operating a motor vehicle.

Included in the category of visual impairment is blindness. Total blindness is rather easy to define. A blind person has zero vision, or cannot see anything. For me this conjures an image of a person wearing dark sunglasses and walking with the assistance of a white cane or guide dog. To make things more challenging to understand about me; I am “legally blind.” I do not use the assistance of a white cane or guide dog for mobility. The clinical definition of my visual acuity is 20/400 and is not correctable with conventional eyeglasses or contact lenses. To put that into perspective, “normal” visual acuity is defined as 20/20. In Texas, where I live, a person is considered legally blind with a visual acuity of 20/200 or beyond. Because my vision is not correctable I do not have the privilege of holding a driver’s license, so I’m not able to operate a motor vehicle. To better understand “legal blindness” you need to understand visual acuity and how it is measured.

Visual acuity refers to the clarity with which a person sees an object, and to the sharpness of a person’s ability to see the detail of that object. In the United States, the standard for acuity is measured at 20 feet. “Normal” visual acuity is defined as 20/20 or the ratio of 1:1. This means that a person can read at 20 feet that which most people should be able to read at 20 feet. Visual acuity can range from 20/5 to 20/400 and beyond.

For example, let’s look at visual acuity of 20/80. The first number, 20, is the numerator and constant in the equation. It is equal to the distance, in feet, of the eye of the person being examined from the object of focus. In an eye care professional’s office the object of focus would likely be based on a Snellen eye chart which is named after the Dutch ophthalmologist, Hermann Snellen, who developed the chart in the 1860s. Because of space limitations most eye care professionals use a mirror or projector to give the illusion that the eye chart is 20 feet from the person being examined. The standard eye chart displays 11 rows of capital letters that typically begin with a large E then get progressively smaller in size with each subsequent row of letters.

The second number, 80, is the denominator in the equation and is a relative reference point for the distance, in feet, that a person with normal vision would stand from the eye chart to equal the acuity of a person with 20/80 acuity. In other words, a person with 20/20 vision would be able to read the same from 80 feet as the person with 20/80 vision would read from 20 feet. The higher the second number the poorer the visual acuity. Visual acuity of 20/40 is better than 20/80 or 20/100, etc. Conversely, the lower the second number the better the acuity. For example, visual acuity of 20/10 is better than 20/20 or 20/40, etc. This means that a person with 20/20 vision would be able to read the same from 10 feet as a person with 20/10 vision would read from 20 feet.

Then you have me. My visual acuity is approximately 20/400 in my left eye and zero, or completely blind, in my right eye. This means that I’m 200 feet beyond the 20/200 mark of legal blindness in Texas. I am able to see at 20 feet what someone with normal vision can see from 400 feet which is a ratio of 1:20. To try to explain that ratio in more practical terms I will give two examples.

If I’m standing two feet from a television my ability to see the details of the screen would equal that of a person with normal vision that is standing 40 feet from the same television. If I back up to 15 feet from the television a person with normal vision would equal my vision by standing a football field (300 feet) away.