The term “legal blindness” is an administrative classification, not a medical diagnosis of total sightlessness. Established primarily by government agencies, it determines eligibility for specific benefits and services. This classification describes a severe visual impairment that meets a set of defined criteria, based on the remaining functional sight. The common question of whether one can be legally blind in only one eye stems from a misunderstanding of how this governmental standard evaluates vision.
The Medical Criteria for Legal Blindness
Legal blindness is defined by two primary measurements of sight, standardized by federal law for determining disability eligibility. The first criterion involves central visual acuity, or the sharpness of vision. A person meets this standard if their best-corrected central vision is 20/200 or less in the better-seeing eye. Best-corrected means the measurement is taken while wearing the most effective corrective lenses, such as glasses or contacts.
The Snellen scale is the traditional measurement tool, where 20/200 means the individual must stand 20 feet away to see what a person with normal vision sees clearly from 200 feet. The second standard relates to the visual field, or peripheral vision. An individual also qualifies if their visual field is so limited that the widest diameter subtends an angle of no greater than 20 degrees, a condition often referred to as tunnel vision.
How the Standard Applies to Monocular Vision
The determination of legal blindness is always based on the visual performance of the “better eye” after the best possible correction. If one eye is completely non-functional or totally blind, but the other eye retains a corrected visual acuity better than 20/200, the individual will not be classified as legally blind.
For example, a person with 20/20 vision in their right eye and total blindness in their left eye is not legally blind because the right eye’s performance exceeds the 20/200 threshold. The administrative classification measures the overall capacity to function in society, which is largely preserved when one eye remains healthy. While the loss of one eye is a significant medical impairment causing a loss of depth perception, it is medically classified as monocular vision impairment, not statutory blindness.
Practical Implications of Legal Blindness Classification
Achieving the classification of legal blindness grants access to specific government programs and benefits. The designation makes an individual eligible for federal support, such as Social Security Disability Insurance (SSDI) and Supplemental Security Income (SSI). These programs provide financial assistance to those unable to work due to their condition. The Social Security Administration (SSA) applies special rules for those classified as legally blind, which can involve higher monthly earnings limits before benefits are reduced, offering greater work incentives.
The classification also grants access to various state and federal resources specifically for the visually impaired, including vocational training, rehabilitation services, and tax benefits. Furthermore, being legally blind imposes specific restrictions, most notably on driving, as the level of visual acuity required for a driver’s license is significantly better than the 20/200 standard.