Legal Definitions

Various countries have defined statutory limits for poor visual acuity that qualifies as a disability. For example, in Australia, the Social Security Act defines blindness as:

A person meets the criteria for permanent blindness under section 95 of the Social Security Act if the corrected visual acuity is less than 6/60 on the Snellen Scale in both eyes or there is a combination of visual defects resulting in the same degree of permanent visual loss.
—Table 13, Schedule 1B, Social Security Act 1991

In the USA, the relevant federal statute defines blindness as follows:

[T]he term "blindness" means central visual acuity of 20/200 or less in the better eye with the use of a correcting lens. An eye that 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 in this paragraph as having a central visual acuity of 20/200 or less.

[8]

A person's visual acuity is registered documenting the following: whether the test was for distant or near vision, the eye(s) evaluated and whether corrective lenses (i.e. glasses or contact lenses) were used:

• Distance from the chart
• D (distant) for the evaluation done at 20 feet (6.1 m).
• N (near) for the evaluation done at 15.7 inches (40 cm).
• Eye evaluated
• OD (Latin oculus dexter) for the right eye.
• OS (Latin oculus sinister) for the left eye.
• OU (Latin oculi uterque) for both eyes.
• Usage of spectacles during the test
• cc (Latin cum correctore) with correctors.
• sc: (Latin sine correctore) without correctors.
• Pinhole occluder
• The abbreviation PH is followed by the visual acuity as measured with a pinhole occluder, which temporarily corrects for refractive errors such as myopia or astigmatism.