Definition of disability

According to Title II, Sec. 216 of the United States Social Security Act, the term disability means either the "inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to result in death or has lasted or can be expected to last for a continuous period of not less than 12 months" or "blindness" as defined as "central visual acuity of 20/200 or less in the better eye with the use of a correcting lens."