Blindness— A person is considered blind who has no vision, or whose vision with correcting glasses
is so defective as to prevent the performance of ordinary activities for which eyesight
is essential. Central visual acuity of 20/200 or less in better eye with correcting
glasses is considered as economic blindness. A person, however, may be considered
blind if his central visual acuity is more than 20/200 in the better eye with correcting
glasses but a rough test shows him to have a marked field defect. The marked field
defect is one in which the peripheral field has contracted to such an extent that
the widest diameter of the visual field subtends an angular distance no greater than
20 degrees.