Legal Blindness and Visual Acuity

What does 20/20 mean?  Measuring visual acuity

The number to the left of the slash (/) is the testing distance.  Most people are tested at 20 feet, resulting in a reading of 20/X.  The number to the right of the slash (/) indicates the distance at which a person with normal vision can see the testing object.  For example, if a person’s vision was determined to be 20/40, that would indicate that at a testing distance of 20 feet, the patient was able to read what people with normal vision could read at 40 feet.

  • Ideal vision, or acuity, is considered to be 20/20.  Those with 20/20 vision can see an object 20 feet away as they are intended to see it.
  • Low Vision is acuity of 20/70; the lowest visual acuity acceptable to retain a daytime only restricted driver’s license in the state of Illinois.  Prevent Blindness America has state-by-state standards for visual acuity requirements for driving privileges.
  • Legally Blind is acuity of 20/200; a statutory definition created by the Social Security Administration to determine eligibility for disability benefits.  Although there is a significant loss of detail vision, legally blind individuals usually retain some level of functional sight
  • Severe Vision Loss is an acuity between 20/200 to 20/400.
  • Profound Vision Loss is an acuity below 20/400. Generally, a person with this degree of vision loss cannot read a standard eye chart and low vision testing such as counting fingers is used to measure visual acuity.  For example, a notation of “CF 3” on an eye report indicates an ability to count fingers on the examiner’s hand at a distance of three feet.
  • Light Projection is the ability to discriminate light from dark and to determine the light source such as a window or lamp
  • Light Perception is the ability to distinguish light from dark, but the source of the light cannot be determined.
  • No Light Perception is total blindness.