The application of chromatic dark-adapted kinetic perimetry to retinal diseases

Abstract

Purpose To demonstrate the value of a 2-color perimetric procedure for determining cone and rod system contributions to the dark-adapted kinetic visual field (VF). Design Prospective evaluation of perimetric testing procedure. Participants Five patients with retinal diseases and 6 visually normal individuals. Methods Long- and short-wavelength stimuli were presented under dark-adapted conditions in a Goldmann perimeter. Visual fields were measured for the II and V test target sizes with a long-wavelength filter (cut-on at 600 nm) and a short-wavelength filter (cutoff at 510 nm). Light intensities through these filters were matched scotopically for the rod system by producing equal peripheral boundaries on 6 visually normal individuals. To validate the application of this procedure, we tested a patient with congenital achromatopsia and another patient with congenital stationary night blindness (CSNB). We then tested 2 patients with retinitis pigmentosa (RP) and 1 patient with Usher's syndrome to determine the cone and rod contributions to their VF isopters. Main outcome measures Isopters for long- and short-wavelength test stimuli, and the appearance of the test stimuli, whether reported as chromatic or achromatic. Results The patient with congenital achromatopsia showed superimposed isopters for the 2 stimuli, which were reported as achromatic, demonstrating that the peripheral field boundaries were rod mediated. The patient with CSNB showed an isopter in response to the long-wavelength stimulus that was considerably larger than that in response to the short-wavelength stimulus, both stimuli reported as chromatic, showing that the cone system determined peripheral thresholds for both stimuli. In 2 patients with RP, we observed a mixed pattern of cone or rod system detection of the chromatic stimuli. The peripheral isopters were rod mediated, whereas the cone system determined the central field isopters. In an Usher's syndrome patient, cones mediated both the peripheral and the central field isopters. Conclusions A 2-color dark-adapted Goldmann perimetric procedure was able to determine whether the VF isopters were rod or cone mediated in 5 patients with various forms of retinal disease.