Legal Blindness, Definition

Definition

The degree of poor visual function that qualifies a person as formally blind. This definition is relevant in case of social security or insurance issues if the patient is severely visually disabled but has a residual visual function. The definition – determined by a visual acuity threshold and other criteria such as visual field defects – is different from country to country.

The U.S. definition states as follows: “An individual shall be considered to be blind for purposes of this title if he has central visual acuity of 20/200 or less in the better eye with the use of a correcting lens. An eye which is accompanied by a limitation in the fields of vision such that the widest diameter of the visual field subtends an angle no greater than 20 degrees shall be considered for purposes of the first sentence of this subsection as having a central visual acuity of 20/200 or less.”

The 20/200 threshold (1.0 logMAR) is also used in Australia, while in the UK 20/400 and Germany 20/1000...