Peripheral vision screening for driving in retinitis pigmentosa patients.
The authors evaluated the test protocols used most frequently to screen the peripheral visual field of driving applicants to determine whether they are suitable for detecting peripheral field loss in patients with retinitis pigmentosa (RP). The peripheral vision tests available on the Keystone View Tester and the Titmus Vision Tester were administered to 23 subjects with RP, 3 subjects with Type 2 Usher's syndrome, and 1 subject who was a partially affected carrier of X-linked recessive RP. The subjects had varying degrees and types of visual field loss. Tests were administered using the standard protocol of the State of Illinois, which is a standard procedure used by state licensing bureaus nationwide. Results demonstrate that the screening protocols use stimulus conditions that are primarily sensitive only to appreciable field losses and examine locations that typically lie within an RP patient's remaining visual field rather than at locations that characteristically are scotomatous. The authors suggest that the current test protocols could determine peripheral field impairment more accurately by assessing additional locations in the visual field, and by introducing a background field and/or by reducing the luminance of the test targets.