Background: Contrast requirements in patients suffering from retinitis pigmentosa (RP) exceed those of healthy subjects. So far, studies examining contrast sensitivity have been performed at luminance levels of several 100 cd/m2. However, to simulate as closely as possible outdoor levels of luminance, several 1000 cd/m2 are necessary.
Patients and methods: We used the Vistech contrast sensitivity charts at a standard high luminance of 5500 cd/m2. Contrast sensitivity was evaluated in 20 healthy subjects (visual acuity 1.10 +/- 0.15) and 25 patients with RP (visual acuity 0.50 +/- 0.29) with and without commercially available cut-off spectacle filters (Zeiss F 80, Zeiss F 90 and Rodenstock L 660.
Results: Patients with retinitis pigmentosa showed an increase of contrast sensitivity with all three cut-off filters. This was statistically significant at a spatial frequency of 1.5 cycl/deg (P < 0.027), but not for higher frequencies of 6-18 cycl/deg (P < 0.5). The healthy volunteers did not show any increase in contrast sensitivity values with cut-off filters.
Conclusion: Evaluating contrast sensitivity at high levels of luminance is useful to identify patients who benefit from cut-off filters. All RP patients subjectively preferred to wear cut-off filters. A statistically proven beneficial effect of cut-off glasses could be found for low spatial frequencies. An individual fitting of the various types of cut-off filters is inevitable.