What is legal blindness?

Ray F. Gariano, MD
Legally blind is defined as having vision in either eye that is no better than 20/200. This level of vision makes some activities -- such as driving a car or reading a newspaper -- impossible without special visual aids. On the other hand, a person who is legally blind may still be able to do things like cook, watch television read large-print books and safely remain mobile inside and outside of the home.

Legal blindness is defined as having less than 20/200 vision while wearing corrective lenses. The following conditions can lead to blindness:

  • Cataracts are a cloudiness in the lens that can block light from reaching the retina. Cataracts become more common as we age, but it is not solely tied to age. Babies can be born with a cataract. Cataracts can require surgery, where the lens is removed and replaced with an intraocular lens.
  • Glaucoma - If certain eye fluids do not drain out correctly, pressure build in the eye. This causes cells and nerve fibers to die. It can be treated with medications and surgery.
  • Diabetic retinopathy - People with diabetes can get blocked blood vessels, leaking blood vessels and certain scarring that can lead to blindness. These conditions can be treated with laser surgery.
  • Macular degeneration - In some people, the macula (responsible for fine detail in the center of vision) deteriorates with age for unknown reasons. This can cause loss of central vision. It can sometimes be helped with laser surgery.
  • Trauma – Any eye trauma, including chemical injuries, can cause damage to the eyes that can prevent adequate vision.
  • Retinitis pigmentosa is an inherited disease that can cause a degeneration of the retina and excess pigment. First, it causes night blindness, then tunnel vision. Often, the condition gradually progresses to total blindness. It has no known treatment.
  • Trachoma is an infection caused by the organism Chlamydia trachomatis. It is a common cause of blindness in many parts of the world but is rare in the United States. It is treated with antibiotics.

Continue Learning about Visual Impairments

Visual Impairments

Optical issues with the eye are quite common, possibly because we started as cavemen who did not have to read tiny letters on a computer screen as you may be doing right now. Conditions that may be corrected with optics include as...

tigmatism, near and far sightedness and some forms of visual field distortion. Some eyes have trouble seeing color the way other's do. This is called color blindness, and is more common in men. As we age there are common diseases and concerns including cataracts and glaucoma. Having diabetes can make you more likely to develop retinopathy, when blood vessels in the retina break and leak into the eye. Some conditions may lead to partial or total blindness. Legal blindness is a legal term more than a medical one, but meeting the standard for legal blindness can qualify you for special help.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.