Legally Blind: What it Means and How it Happens

Vision loss is a serious matter but it does come in varying degrees of severity. Some people with high prescriptions occasionally joke that they are “blind as a bat” without their glasses, but of course this is quite different from someone whose visual impairment is so extreme that it cannot be corrected with eyeglasses, contact lenses or even surgery.

Who is “legally blind”?

If you have ever heard this term, you may have conjured up a vision of an older person with a cane, stumbling through life in complete darkness. But legally blind does not necessarily mean totally blind, and the designation is not in fact a precise indication of an individual’s level of vision.

According to the Centers for Disease Control and Prevention (CDC), a person is considered to be legally blind if their vision cannot be corrected to better than 20/200 or if their field of vision is 20 degrees in diameter or less, in their better eye. The term has statutory as well as medical connotations however, since visual impairment this severe can affect a person’s ability to work and earn a living. The U.S. government actually developed the definition of “legally blind” to help determine an individual’s eligibility for government assistance and disability benefits, and this visual disorder is officially defined in the Social Security Act. The CDC estimates that the federal government spends upwards of $4 billion a year to help Americans with vision loss.

Vision Loss Worldwide

The World Health Organization (WHO) estimates that there are 39 million people worldwide who are fully blind, and 246 million who are considered to have low vision. Approximately 90 percent of these people live in developing countries, so whether they are “legally blind” is not relevant, as there are usually no disability programs or government assistance available to them. According to the WHO, many of the causes of worldwide blindness are actually avoidable and curable, but they persist in developing populations due to insufficient resources and medical care.

Causes of Blindness

In industrialized nations like the U.S., one of the primary conditions that could lead to severe vision loss, and even a qualification of legal blindness, is diabetes. According to the American Diabetes Association, individuals with diabetes have a higher risk of eye complications (such as diabetic retinopathy and cataracts) than people without the disease. The other main causes of eventual blindness in developed countries is glaucoma (damage to the optic nerve from pressure buildup in the eye) and age-related macular degeneration (AMD).

In comparison, the primary cause of vision loss in developing countries is cataracts, despite the fact that they can be treated successfully with surgery to restore vision in affected individuals. According to the WHO, onchocerciasis or “river blindness” is another major cause of severe vision loss worldwide and is contracted from parasite-carrying blackflies that proliferate in riverside areas. This disease is also easily treatable with medication.


Vision impairment of any kind can limit an individual’s ability to carry out daily tasks and activities, and when the vision loss is severe – as it is for those who are considered legally blind – it can greatly impact their quality of life. However, U.S. citizens are fortunate to have different resources available to help them keep living as independently as possible, from assistive technologies to service animals to government programs. If your own vision impairment can be overcome with corrective eyewear or surgery, consider yourself lucky and remember that regular eye exams can spot vision problems early!

For questions or comments, contact Woodhams Eye Clinic.

Image source: Flickr

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