Have you ever thought about the term Legally Blind? Although it may seem faintly strange to tag a health condition as 'legal', you must have heard or read about it somewhere. What does it mean to be legally blind? Who is considered to be legally blind? How is it different from complete blindness?
According to the Centers for Disease Control and Prevention, more than 3.3 million people over age 40 are legally blind or have low vision. It is interesting to note that according to American Foundation for the Blind, a person who is legally blind has some usable vision unlike a completely blind person. Complete blindness implies the inability to see anything including the perception of light while partial blindness indicates limited vision.
Legal Blindness Definition
Legal Blindness is not a medical term but a guideline. It is defined by law establishments as a level of visual impairment that limits the activities performed by individuals without assistance. This definition limits activities such as driving for safety reasons, helps determine the eligibility to receive government assistance or monetary benefits.
To be considered legally blind, one of the two criteria has to be met:
1. Reduced central visual acuity of 20/200 or worse in the eye you can see out of the best. Visual acuity refers to how close a person needs to be to an object that's 20 feet away in order to see it in detail. To give you perspective, a legally blind person with 20/200 vision would need to be 20 feet from an object in order to see it as well as someone with 20/20 vision could see it from 200 feet away.
2. Limitation of your field of view. This means the visual field is no more than 20 degrees. For example, if a person has a visual field of only 20 degrees, he can see things that are right in front of him without moving his eyes from side to side but he can't see anything on either side.
You might feel like you're legally blind if you can't see beyond a foot in front of you without wearing glasses, but as long as your vision can be corrected to 20/20 with a visual aid, such as glasses or contact lens, you are not considered legally blind. Blindness in one eye is never defined as legal blindness if the other eye is normal or near-normal.
Causes of Legal Blindness
According to National Eye Institute, there are four leading causes of legal blindness. They are age-related macular degeneration (AMD or ARMD), diabetic retinopathy, cataracts and glaucoma.
1. Age-related macular degeneration (AMD) - A leading cause of vision loss among people aged 60 and older. AMD occurs when the central portion of the retina (known as the macula) deteriorates. The macula is responsible for the sharp, central vision needed for activities like reading, recognizing faces, watch television and driving.
2. Diabetic retinopathy - Damage to the retina of the eye due to diabetes. It is caused by changes in the blood vessels of the retina tissue in the back of the eye. Diabetic retinopathy often can be prevented with early detection, proper management of your diabetes and routine eye exams performed by your optometrist or ophthalmologist.
3. Cataracts - It is the most common cause of vision loss, which is a clouding of eye's natural lens that blurs vision. Cataracts can result from genetic disorders or even diabetes and trauma to the eye.
4. Glaucoma - A condition of increased pressure within the eyeball that can damage the optic nerve and decrease vision. Typically this condition causes no pain and produce no symptoms until noticeable vision loss occurs.
Optic neuritis and neuropathy also can cause legal blindness, as can a number of congenital conditions, such as congenital cataracts, infantile glaucoma, and retinopathy of prematurity. Keratoconus, a gradual thinning of the cornea, also can cause severe vision loss to the point of legal blindness.
While losing the ability to see seems scary, it certainly does not limit your ability to live.