Many people wonder about the meaning of their vision prescription and how it relates to legal definitions of blindness. Minus 6 vision refers to a specific measurement in eye care. Understanding this measurement and legal blindness criteria clarifies common misconceptions and provides a clearer picture of vision.
What “Minus 6” Vision Means
Vision prescriptions are measured in diopters, a unit that indicates the optical power of a lens needed to correct vision. A negative number, such as -6.00 diopters, indicates myopia, commonly known as nearsightedness. This means that light focuses in front of the retina instead of directly on it, causing distant objects to appear blurry.
Someone with a -6.00 diopter prescription experiences significant difficulty seeing objects far away without corrective lenses. Objects beyond a short distance would appear very unclear. While close-up objects might remain clear, this level of myopia is high and typically requires consistent use of corrective lenses for most daily activities.
How Legal Blindness is Defined
Legal blindness is a specific classification used to determine eligibility for various services and benefits, rather than a description of complete vision loss. In the United States, the definition relies on two primary criteria, both based on “best-corrected” vision. This means the measurement is taken while wearing the most effective glasses or contact lenses possible.
One criterion for legal blindness is a best-corrected visual acuity of 20/200 or worse in the better-seeing eye. Visual acuity is measured using a Snellen eye chart, where 20/20 vision represents normal sight. If a person can only read the top letter on the Snellen chart from 20 feet, while someone with normal vision reads it from 200 feet, their visual acuity is 20/200.
The second criterion for legal blindness involves the visual field, the entire area a person can see without moving their eyes. Even if visual acuity is better than 20/200, a person can still be considered legally blind if their visual field is 20 degrees or less in the better-seeing eye. This condition is sometimes referred to as “tunnel vision,” where peripheral vision is severely restricted.
Is Minus 6 Vision Legally Blind?
A -6.00 diopter prescription refers to the amount of correction needed for uncorrected vision, indicating significant nearsightedness. However, legal blindness is defined by best-corrected visual acuity and visual field. This distinction is crucial because individuals with -6.00 vision can often achieve much better than 20/200 visual acuity when wearing appropriate corrective lenses.
Thus, having a -6.00 diopter prescription does not automatically mean a person is legally blind. While their uncorrected vision is very poor, the ability to improve sight significantly with glasses or contact lenses typically places their corrected vision well above the 20/200 legal blindness threshold. Legal blindness is not based on prescription strength itself, but on the visual outcome after maximum correction.
Beyond Visual Acuity
Legal blindness encompasses more than just the sharpness of central vision. The second definition, a visual field of 20 degrees or less, is equally important for diagnosis. This means that even if a person’s central vision is relatively clear, a severely restricted peripheral view can still qualify them as legally blind.
Other severe visual impairments caused by eye diseases or conditions uncorrectable by standard lenses can contribute to a legal blindness diagnosis. These include conditions affecting the retina or optic nerve. A comprehensive eye examination by an eye care professional is essential for an official diagnosis, assessing visual acuity, visual field, and overall eye health.