Silent substitution stimulation of S-cone pathway and L- and M-cone pathway in glaucoma

PURPOSE. The study aimed for objective detection of primary open-angle glaucoma with selective color channel stimulation based on the silent substitution technique. In addition, an objective was analysis of the characteristics of individual color channels based on visual evoked potentials. METHODS. Visual evoked potentials were recorded in 141 subjects (39 patients with glaucoma, 71 healthy subjects, and 31 age-matched healthy subjects) with two scalp electrodes after cone-specific flash stimulation. Silent substitution stimulation was presented with a 30-in. liquid crystal display. Separate responses were obtained for short-, medium-, and long-wavelength- sensitive cones. Age-matched subgroups were used to compare patients with glaucoma and healthy subjects. RESULTS. The S-cone responses of age-matched healthy subjects had significantly different slopes for the first positive wave, compared with the responses of patients with moderate glaucoma. This difference was not observed in the L- and M-cone responses. Distinct changes in the S-cone response profiles were observed with increasing severity of glaucoma. Patients with severe glaucomatous damage were recognizable by the altered profiles of their visual evoked potentials. Healthy subjects showed significant differences between color channels. CONCLUSIONS. Glaucoma and its severity were objectively detected by using the silent substitution technique. The stimulation technique and signal analysis enabled assessment of the visual evoked potentials of individual color channels.