What is Legally Blind?
This is an important question that has consequences affecting how we as a society and the government help people who have difficulties due to visual impairment from myriad causes. Many times I’ve heard patients say that they or someone they know was “legally blind“ without their glasses. This is not the actual definition of legal blindness.
Legally Blind Definition
The definition of legally blind vision is when someone has 20/200 or worse vision on a standard vision chart in their better eye, or when they have less than 20° of peripheral vision on a visual field test. Legal blindness is not a medical definition but a legal definition. It qualifies people who are visually impaired to have benefits from the government to help them function. The benefits can be things like low vision therapy, low vision aids, seeing eye dogs, canes, braille training, etc., to allow them to function well in spite of their visual impairment. It is a huge help to people who may not be able to afford the therapy, training, and devices to allow them to live a full and productive life. It’s a wonderful use of our public funds to help people who may not be able to help themselves as well as they would like.
There are many other difficulties that people who are visually impaired may have. Having a severe visual impairment can slow reading times and makes transportation and mobility more difficult. Many people who are visually impaired may have other associated physical disorders due to the same cause of their legal blindness. Hearing impairment is often associated with genetic or inherited disorders that cause legal blindness or visual impairment. Physical function is often also reduced in people who are considered legally blind.
Therefore someone who says they have “legal blindness” without their glasses really doesn’t know what is considered legally blind. What’s considered legally blind is when you cannot see better than 20/200 on a vision chart even with your glasses or contact lenses. Not all blurry or decreased vision is due to glasses or contact lenses. Not all people who qualify as legally blind have no vision at all. In fact, most people who meet the definition of legally blind have partial vision. The list of causes for legal blindness is extremely long. The top causes in the United States, according to the CDC, in order of frequency are:
- Age-related Macular Degeneration
Age-Related Macular Degeneration
Unfortunately, a common cause of legal blindness in the United States is age related macular degeneration or ARMD. Age-related macular degeneration is typically found in people in the 60s and older, usually Caucasian people with less pigment in their skin and eyes. It’s almost unheard of in African or Asian races. The damage of ARMD is thought to be due to ultraviolet radiation damage over their lifetimes in the central part of the retina called the macula. The ultraviolet radiation is thought to cause a cascade of biochemical effects resulting in deposits of material called drusen that damage the underlying delicate retinal tissue that is responsible for the reaction to and processing of light energy that is focused on it. Without the functioning retina tissue that is damaged by ARMD, light energy and the transmission to the brain in the location of the retina are perceived as a blind spot. As the blind spots coalesce, the perception of faces, words, road signs all diminish. A person with advanced ARMD is unable to drive, read or clearly see faces. The end stage of ARMD does not progress to complete loss of vision, but can severely impact quality of life for those who are unfortunate to have it. Visual aids, magnifying glasses, have historically been all that patients could use to help. Technology in smart phones that can read text and speak directions, magnify anything, Uber for transportation, auto pilot development in cars have helped and will continue to make countless visually impaired individuals’ lives better.
Treatment for ARMD
Treatment for ARMD has improved and although it doesn’t currently reverse the damage, treatment can slow or stop the progression of damage to the macula. It currently consists of injections into the back of the eyes that stops the growth of irregular and leaky blood vessels that lead to scarring in the macula.
Prevention of ARMD
Most preventative recommendations are to minimize exposure to the damaging rays of the sun at an early age. Much like skin cancer, the damage to the delicate retinal tissue is possibly done in our childhoods. Hopefully the next generation will have worn sunglasses more regularly than the baby boomers who have lots of ARMD. Another possibly helpful preventative measure is to take antioxidants such as vitamins A, C, and E, lutein, zeaxanthin, copper (added to prevent copper insufficiency due to zinc), zinc, and manganese.
Other Causes of Legally Blind
There are many other reasons for the legally blind meaning. Most of them are related to some systemic illness. Diabetes is one of the most damage our eyes. However the incidence of legal blindness due to diabetic retinopathy has decreased substantially in recent years. Better nutrition, better treatment and monitoring such as non-invasive no stick glucose monitoring internally as well as insulin pumps that can be placed under the skin and refilled via a reservoir has allowed those afflicted with diabetes to control their blood sugar much more tightly and easily than in previous generations. This constant blood sugar monitoring and stabilization has minimize the damage done to micro vasculature in patients with diabetes.
Glaucoma is another condition that has had both better treatments, better understanding and better monitoring. Well, as a condition we are by the optic nerve is damaged generally due to increased intraocular pressure. This is one of the conditions that can impair the visual field. I remember a patient many years ago that did not know he had glaucoma because he could see 20/15 uncorrected. His field of vision, however, was greatly reduced due to end stage glaucoma. This is a cautionary tale to remind people to get an annual eye exam to screen for glaucoma. It can be a silent cause of vision loss.
The rest of the conditions that can cause someone to meet the legally blind definition are things such as trauma, although fortunately or unfortunately, however you look at it, trauma is most frequently in just one eye. And someone can function completely normally with just one eye. Connect tissue disorders, such as rheumatoid arthritis, lupus, and others, can cause inflammation in the eyes that can lead to cataracts, glaucoma, retinal detachment and other permanent causes of loss of vision. There are other genetic diseases such as Sticklers syndrome and Marfan’s syndrome that can cause internal problems in the eye such as retinal detachment and lens dislocation. The list is long, but fortunately many of these conditions can be treated to allow the patient a long life with functioning vision.
What does Legally Blind Mean?
The legally blind definition arose from the need to quantify a level of visual function below which people would have an extremely difficult time functioning without help and would require training and devices. The help is designed to allow them to function if they have a “legally blind prescription” or are qualified as legally blind meaning they have poor or no vision. This is one instance of government knowing and responding to the need of those who know what it means to be legally blind.
How are Visually Impaired People Helped?
There are many ways people who meet the legally blind vision criteria are helped. There are low-vision specialist optometrists and other vision care professionals who specialize in helping those with low vision. There are myriad devices, such as magnifying glasses arranged in different ways, so that they help with a person’s low vision needs. Sometimes these hang around their neck to allow them to see what is in their hand. Also, technology has been a huge help. Smart phones allow someone to interact verbally with their phone with apps such as Siri and Alexa. These currently allow simple directions such as “find my phone” with an audible tone, “read directions”, and “read the text.” The verbal interaction has added a huge functional component to those who are visually impaired. Future technology will allow auto pilot function on automobiles which would allow someone to be potentially totally independent. These are exciting advances that have helped people immeasurably and will continue to do even more in the future.
It’s never been a good time to be visually impaired, but with new treatments, preventive measures, and technology like smart phones, auto pilot, and Uber, life has become increasing independent for those who are visually impaired. I foresee a future in which artificial eyes may be able to interface with the neural tissue of the eye or brain, similar to a cochlear implant in those with hearing impairment. This may allow increased resolution of the world around them, so that those with visual impairments may be able to function at a near 100% level to those who are not visually impaired. It is a goal of vision professionals to maximize the visual function of all their patients, regardless of the cause of their decreased vision. Fortunately at SharpeVision, we can transform the lives of those who wear glasses to see clearly. Imagine a world without glasses or contact lenses? It would be very difficult for many people who have strong glasses to function without them. Laser vision correction has allowed a generation of people to function with perfectly clear, uncorrected vision without any glasses or contact lenses. It’s amazing and getting better all the time! Schedule your free comprehensive evaluation online, or give us a call, to see if you could see clearly without glasses or contact lenses. I think you can!
Dr. Matthew Sharpe