Government agencies and health insurers use the term legally blind to refer to someone who is not completely blind, but meets their criteria as a person disabled by their visual impairment. (Learn More)

To be considered legally blind, a person must either have worse than 20/200 vision in their best eye or a visual field of 20 degrees or less in their best eye for 12 or more months. (Learn More)

The requirement for 20/200 vision in their best eye relates to visual acuity — the clarity or sharpness of central vision. (Learn More)

The requirement for a visual field of 20 degrees or less in their best eye relates to field of view and peripheral vision — side vision, or what is seen on the side when looking straight ahead. (Learn More)

The Social Security Administration offers disability benefits to the legally blind through two programs that allow the legally blind to work or run their own business as long as the earnings are below $2,040 a month. (Learn More)

legal blindness

The term legally blind refers to a definition of blindness that government agencies, like the Social Security Administration and the Department of Motor Vehicles, and health insurance agencies use to determine if someone is disabled or eligible for certain benefits as a legally blind person.

Unlike those with complete or total blindness, those who are legally blind have some vision. More than 3 million adults in the U.S. over the age of 40 have legal blindness or low vision.

The most common causes of legal blindness and low vision are age-related conditions like macular degeneration, cataracts, diabetic retinopathy, and glaucoma.

What Is the Definition of Legally Blind?

According to the U.S. Social Security administration, in order to be considered legally blind, an individual must have at least one of the following two conditions:

  • Vision that can’t be corrected to better than 20/200 in the “better” eye
  • Visual field is 20 degrees or less in the “better eye” for a period that has lasted, or is expected to last, for at least 12 months

Visual Acuity

The requirement of “vision that can’t be corrected to better than 20/200 in better eye” relates to visual acuity, which is the clarity or sharpness of central vision.

Most people are familiar with the term 20/20 vision. This is because in the U.S., eyesight clarity is measured and expressed using the Snellen visual acuity measurement system.

In this system, individuals are tested through identifying smaller letters on an eye chart. The results are expressed as a fraction in relation to a standardized 20-foot viewing distance.

The term 20/20 is meant to describe normal visual acuity, measured at a distance of 20 feet. Someone with 20/20 vision can see clearly at 20 feet what they should be able to see at this distance.

Someone who doesn’t have normal visual acuity will not be able to see what they should be able to clearly see at a distance. Someone with 20/100 vision, for example, will have to be as close as 20 feet to see what someone with normal visual acuity could see at 100 feet.

Having 20/20 vision doesn’t mean having perfect vision. It just means having normal visual acuity. In fact, someone with 20/15 vision has better vision than someone with 20/20, as they are able to see something at 20 feet that the other person would have to be at 15 feet to see.

Also, there are more factors in visual ability than just visual acuity. For example, some people can see normally at a distance but have trouble focusing on an object up close. Peripheral vision, depth perception, and focusing ability are all important factors in visual ability. This is why visual acuity is not the only requirement for being considered legally blind.

Visual Field

Visual field tests are very different from visual acuity tests. While visual acuity tests determine the clarity and sharpness of central vision, visual field tests determine if an individual has a normal field of view, or peripheral vision.

Peripheral vision (side vision) is very important in daily everyday tasks, especially driving and some work-related tasks.

People with normal peripheral vision have a lateral field of view that creates an almost 180-degree angle (people or objects directly to the right or left in the distance are still visible) and vertical field of view of about 135 degrees.

When an individual’s peripheral vision is tested, their normal field of view is determined. A visual field test will determine someone’s normal field of view without squinting. Abnormal blind spots will also be identified.

A person whose peripheral vision is limited to 20 degrees or worse would be classified as legally blind, even if they have excellent visual acuity. This very limited field of view may be called tunnel vision.

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Social Security Benefits for Blindness and Impaired Vision

The Social Security Administration gives disability benefits to the blind through two programs: the Social Security Disability Insurance program and the Supplemental Security Income (SSI) program. The medical rules for defining legal blindness are the same for both programs, although other rules are different.

To receive Social Security Disability Insurance, an individual must have worked long enough in a job in which social security taxes were paid. In some instances, an individual who hasn’t worked may be able to receive Social Security disability benefits if their spouse or parent has paid social security taxes in a job.

To receive payments through the SSI program, an individual doesn’t need to have worked or payed Social Security taxes, but their income must be below certain dollar limits, which vary by state.

Work incentive rules make it possible to work while receiving Social Security benefits, as long as earnings are not above the limit for blind workers. The limit is $2,040 a month in 2019. Blind self-employed individuals can also earn up to $2,040 a month.

Those who do not meet the criteria for legal blindness, but who have low vision or are visually impaired, may also be eligible to receive Social Security disability benefits if their visual problems alone, or in combination with other health problems, prevent them from working.

References

Benefits Planner: Disability – How You Qualify. (2019). Social Security Administration (SSA).

If You’re Blind or Have Low Vision – How We Can Help. (January 2019). Social Security Administration (SSA).

Visual Acuity: What Is 20/20 Vision? American Optometric Association.

What Does Legally Blind Mean? (February 2018) All About Vision.

Common Eye Disorders. (September 2015) Centers for Disease Control and Prevention (CDC).

Criteria for Being Legally Blind. (December 2, 2018). Verywell Health.