Legal blindness is a specific classification of severe vision loss, distinct from total blindness, that is often misunderstood. This term defines a threshold for vision impairment used by government agencies to determine eligibility for various services and benefits. It represents a defined standard rather than a subjective feeling of reduced sight.
Criteria for Legal Blindness
In the United States, legal blindness is officially defined by two primary criteria related to visual acuity and field of vision. The first is a central visual acuity of 20/200 or less in the better-seeing eye, even with the best possible correction from glasses or contact lenses. Visual acuity measures the sharpness of vision. This means someone with 20/200 vision must be as close as 20 feet to see what a person with normal vision can clearly see from 200 feet away.
The second criterion involves a significant restriction in peripheral vision. An individual qualifies if their visual field is 20 degrees or less in the better-seeing eye. This condition, sometimes called tunnel vision, means the person’s ability to see objects to the sides, above, and below their central point of focus is severely limited. Meeting either of these thresholds establishes legal blindness for federal disability benefits.
Legal Blindness vs. Total Blindness
A common misconception is that legal blindness signifies a complete absence of sight, but this is not the case. Individuals who are legally blind often retain some functional vision, which varies significantly. They may perceive light, shapes, colors, or even large objects, though with considerable blurriness or limited scope.
Total blindness, in contrast, means there is no light perception. This is a complete loss of sight. While severe, total blindness is less common; approximately 85% of people with eye disorders have some remaining sight, with only about 15% experiencing total blindness. Legal blindness is a classification for administrative purposes, acknowledging a level of vision impairment that substantially impacts daily life, rather than describing a person’s complete visual experience.
Determining Legal Blindness
The determination of legal blindness is a precise process conducted by eye care professionals, typically an ophthalmologist or optometrist. This involves a comprehensive eye examination to assess an individual’s visual capabilities. A primary tool for measuring visual acuity is the Snellen eye chart, where a person reads letters of decreasing size from a set distance.
Visual field tests are also performed to measure peripheral vision. These tests assess the total area an individual can see without moving their eyes. It is important that the assessment is made after all possible corrective measures, such as prescription glasses or contact lenses, have been applied. The results from these objective tests allow eye care specialists to document whether an individual meets the criteria for legal blindness.