“Legally blind” pertains to being visually impaired by the law when eyeglasses or contact lenses cannot correct your vision beyond particular standards. To be considered legally blind, one must have a 20/200 visual acuity or worse in your better eye with corrective glasses or contact lenses on it.
Legal blindness can affect your ability to obtain a driver’s license or receive benefits from the government as a disabled person.
Measuring Visual Field
Some people can read small letters on the Snellen’s eye chart but are not able to see the person standing beside them. This is because they are considered legally blind with poor peripheral vision. A wide visual field is important for activities such as crossing the street or driving a car.
Visual field tests measure the field of view and examine any blind spots or unusual narrowing of the peripheral vision. Peripheral vision consists of two parameters: lateral (side to side) and vertical (up and down). The optimal lateral field of view is about 180 degrees. This means that distant objects are clearly visible from the right or left side of the observer.
The average vertical field is narrower and should be about 135 degrees.
You are recognized as legally blind if your peripheral vision is 20 degrees or less. This is a condition called tunnel vision.
Legal Blindness Causes
Injuries and many conditions can cause legal blindness or visual disability.
The 4 top causes of legal blindness in the US alone are cataracts, diabetic retinopathy, glaucoma, and age-related macular degeneration.
Neuropathy, optic neuritis, congenital cataracts, infantile glaucoma, and retinopathy of prematurity can also cause legal blindness. Keratoconus, a condition of corneal thinning, can lead to severe vision loss and may make a person considered to be legally blind.
Resources for People Who Are Legally Blind
There are various assistance and special services to aid legally blind people. Benefits from the Social Security Administration and tax deductions are given to the legally blind.
Low-vision specialists are eye doctors who can best help legally blind people with the latest vision aids for better eyesight. Magnifiers, telescopes, and other digital devices can help legally blind people make the best use of any vision they still have.
These devices are effective in helping a person with legal blindness live more independently and partake in activities that normal people take for granted. Guide dogs who are professionally trained are also a great help for a lot of people who are legally blind.