Abstract
Abstract: :
Purpose: To isolate the cone and rod system contributions to detection thresholds with the use of chromatic dark-adapted kinetic perimetry. Methods: Long and short wavelength stimuli were presented under dark-adapted conditions in a Goldmann perimeter bowl. Visual fields were measured for the II and V target sizes with a long wavelength filter (band pass between 680 nm and 800 nm) and a short wavelength filter (peak transmission at 400 nm with a half height bandwidth between 340 nm and 475 nm). An infrared LED and infrared-sensitive goggles were used for continuous fixation monitoring in the dark. Light intensities through these filters were matched scotopically by producing equal peripheral boundaries on six normals. To validate the application of this procedure, we evaluated one patient with achromatopsia and another patient with congenital stationary night blindness. We then tested three patients with retinitis pigmentosa (RP). Results: The patient with achromatopsia showed superimposed isopters for the two stimuli, which were perceived achromatically, demonstrating, as anticipated, that the peripheral field boundaries were rod mediated. The patient with congenital stationary night blindness showed a larger isopter to the long wavelength stimulus than to the short wavelength stimulus, both perceived chromatically, showing that cones were determining peripheral thresholds for both stimuli. In two patients with RP, we observed a mosaic pattern of cone or rod threshold detection of the chromatic stimuli. The peripheral isopters were rod mediated while the cone system determined the central field isopters. In the third RP patient, cones mediated both the peripheral and the central field isopters. Conclusion: The use of chromatic dark-adapted Goldmann perimetry facilitates the determination of whether visual field isopters are mediated by the rod or cone system in various retinal diseases.
Keywords: visual fields • dark/light adaptation • retinal degenerations: hereditary