[Improving contrast sensitivity by cut-off filters in high adaptation luminance levels in retinitis pigmentosa].

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.