<prompt> The following Rosenbaum chart is used to test for visual acuity at a distance of6 meters3 meters36 cm6 cm  <response>: C 36 cm VISUAL ACUITY: Snellen chart is used to test acuity at a distance of 6 m 20 ft. For convenience, a scale version of the Snellen chart called the Rosenbaum card is held at 36 cm 14 in. from the patient. The Rosenbaum card is a miniature, scale version of the Snellen chart for testing visual acuity at near. When the visual acuity is recorded, the Snellen distance equivalent should bear a notation indicating that vision was tested at near, not at 6 m 20 ft, or else the Jaeger number system should be used to report the acuity. All subjects should be able to read the 66 m 2020 ft line with each eye using their refractive correction, if any. Patients who need reading glasses because of presbyopia must wear them for accurate testing with the Rosenbaum card. If 66 2020 acuity is not present in each eye, the deficiency in vision must be explained. If it is worse than 6240 20800, acuity should be recorded in terms of counting fingers, hand motions, light perception, or no light perception. Legal blindness is defined by the Internal Revenue Service as a best corrected acuity of 660 20200 or less in the better eye or a binocular visual field subtending 20deg or less. For driving the laws vary by state, but most states require a corrected acuity of 612 2040 in at least one eye for unrestricted privileges. Patients with a homonymous hemianopia should not drive. 