What it Means to be Legally Blind
Like almost everything “legal,” there is a specific definition and purpose for the term “legal blindness.” The definition was developed for purposes of government assistance and to determine when a person would be eligible to receive Social Security disability and other benefits from the government. It is also used to determine if a person is no longer able to hold a current and valid driver’s license.
We all know that 20/20 vision is ideal. Whether it’s reached through nature or with the aid of glasses or contacts, that’s what is wanted. The 20/20 stands for being able to see something at 20 feet that others with good vision can also see at 20 feet.
Legal blindness is when the very best vision a person has, even assisted with glasses or contacts, is 20/200 or worse. So that means the person with that vision can clearly see something at 20 feet that a normal-sighted person sees clearly at 200 feet in their central field of vision. That is one form of legal blindness. The other relates to peripheral vision. Most people have about 140 degrees of peripheral vision without turning their heads in either direction. A person would also be considered to be legally blind if they only have 20 degrees of peripheral vision with their head staying still.
Main reasons for Legal Blindness
The National Eye Institute lists four main reasons for legal blindness in the U.S.
Cataracts. More than half of Americans will have or have had one or more cataracts by the age of 80. Cataracts cause blurry vision that can lead to blindness if left untreated. They are caused by several things including, age, trauma, diabetes, and genetic disorders. Fortunately, cataracts can most often be removed and the person will no longer be legally blind.
Age-related macular degeneration (AMD). This is the leading reason for vision loss in those in the U.S. over the age of 60. The central field of vision begins to degenerate, making fine details harder to see and causing problems with reading and driving.
Glaucoma. Glaucoma is often caused by elevated pressure inside the eye which gradually harms the optic nerve, making it more difficult for the brain to receive the messages needed to translate light into an image. Of the 2 million or so Americans estimated to have glaucoma, only about half of them have had it diagnosed. Glaucoma is usually a slowly progressing disease so it is difficult to detect from visual acuity tests. It is easily caught with full eye exams done at least every two years after the age of 40, and every year after the age of 60.
Diabetic retinopathy. As many as 4 million Americans over 40 may be affected by this disease. Obviously, it’s easier to know to check for deterioration when a patient knows they have diabetes, but type II diabetes is not always diagnosed quickly.
For all of these complaints, the earlier they are detected and treated, the less likely legal blindness will become a problem. Get regular eye exams and make sure that they are complete ones checking for glaucoma, damage due to diabetes, cataracts, and macular degeneration.
Dr. Travis Zigler