[Effect of cut off filters on contrast perception in retinitis pigmentosa]

Cut-off filter glasses can protect retinitis pigmentosa (RP) patients from dangerous short-wave light and UV radiation. Subjective improvements in contrast sensitivity and glare sensitivity are additional beneficial effects of such glasses. Because of the relatively high costs the prescription of cut-off filters is limited. To establish an objective criterion for prescription we performed psychophysical tests of contrast sensitivity in 12 RP patients with and without cut-off filters. We used a computerized test (Neuroscientific, New York, NY) in which six spatially different static sinusoidal grid patterns were presented on a high-resolution monitor (Joyce). Contrast-transfer functions were derived by a two-alternative forced choice method. Only 2 of the 12 tested patients--all of whom reported subjective beneficial effects of the cut-off filters on contrast sensitivity--showed significant improvement in the test. In 5 patients we found non-significant improvement while 5 showed nearly no change. Patients with low contrast sensitivity showed a relatively high benefit from the filters, especially with low spatial frequencies. However, in the majority of RP patients the method used here cannot provide objective criteria for the prescription of cut-off filters.