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What Does It Mean To Be Legally blind?

By Essilor News

We've all heard the term "legally blind," but what does it really mean? How is it different from complete blindness, and who is considered legally blind?

What does it mean to be legally blind?
The definition of legal blindness was developed as a guideline to help people receive government assistance, such as Social Security disability benefits. The Department of Motor Vehicles also uses the definition to measure vision and keep our roads safe from drivers who have difficulty seeing.

Someone who is legally blind has a corrected vision of 20/200 in their best seeing eye. 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, then you are not considered legally blind.

Most government agencies and health care institutions agree that legal blindness is defined as a visual acuity (central vision) of 20/200 or worse in the best seeing eye or a visual field (peripheral vision) that is limited to only 20 degrees. Visual acuity of 20/200 means that what the legally blind person can see at 20 feet, the average person can see clearly at 200 feet. As for visual field, the average person can see 140 degrees without turning his head.

What are the leading causes of blindness?
According to the National Eye Institute, there are four leading causes of blindness in the United States.

  1. Age-related macular degeneration (AMD) - a leading cause of vision loss in Americans 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 and driving.
  2. Cataracts - by the age of 80, more than half of all Americans have had a cataract, which is a clouding of the lens that blurs vision. Cataracts can result from genetic disorders or even diabetes and trauma to the eye.
  3. Diabetic retinopathy - a diabetic eye disease affecting an estimated 4 million American adults over the age of 40. It is caused by changes in the blood vessels of the retina tissue in the back of the eye.
  4. Glaucoma - a condition of increased pressure within the eyeball that can damage the optic nerve and decrease vision. It is estimated that more than 2 million Americans have glaucoma, but only half of those know they have it.