Legal blindness is a specific classification of vision impairment, distinct from the complete absence of sight. It determines eligibility for support services, disability benefits, and tax exemptions. This level of vision loss significantly affects an individual’s ability to perform daily tasks, identifying those who can benefit from specialized aid and resources.
Understanding Visual Acuity and Legal Blindness
Visual acuity measures the sharpness or clarity of vision, indicating how well a person can see details. This is commonly assessed using a Snellen eye chart, where a person reads letters from 20 feet away. Normal vision is 20/20, meaning one sees at 20 feet what a person with unimpaired vision sees at 20 feet.
For legal blindness in the United States, the primary criterion related to visual acuity is 20/200 or less in the better eye. This measurement is based on “best-corrected” vision, meaning the person is wearing their most effective corrective lenses, such as glasses or contact lenses. This means a person sees at 20 feet what someone with normal vision sees at 200 feet. This limitation impacts their ability to perform daily tasks requiring clear central vision.
The Role of Visual Field in Legal Blindness
Beyond visual acuity, the visual field also plays a significant role in defining legal blindness. The visual field refers to the entire area an individual can see without moving their eyes, including central and peripheral vision. A normal visual field typically spans about 160-170 degrees horizontally.
Legal blindness can also be classified if a person has a constricted visual field. This condition is often described as “tunnel vision,” where peripheral sight is severely limited. A visual field of 20 degrees or less in the better eye, even with corrective lenses, can qualify an individual as legally blind. This means the person can only see a very narrow area directly in front of them, making it challenging to navigate their surroundings.
Legal Blindness Versus Total Blindness
A common misconception is that legal blindness means total darkness or no ability to see anything. However, legal blindness does not equate to total blindness. Most legally blind individuals retain some usable vision, ranging from light perception to distinguishing shapes or large objects. Approximately 85% of people with visual impairments have some remaining sight.
Total blindness, in contrast, signifies the complete absence of light perception. Only a small percentage, around 15%, of people with visual impairments experience total blindness. The distinction is important, as many legally blind individuals can still benefit from low vision aids and rehabilitation services that enhance their remaining vision.