Local ERG for clinical examination of eye diseases.

We used a suction electrode with a frosted front window to record a full-field (general) ERG, and a suction electrode with a short-focus lens and a red-green light diode to record a local ERG. As the suction electrode moved with the eye, the stimulus struck the macula in all positions of gaze. Our data showed that only mildly intense stimuli with an angular size of 10 to 15 degrees induced a retinal response, with a macular contribution of 70%. Patients with various dystrophic changes of the retina, such as Stargardt's dystrophy, vitelliform dystrophy of the Best type, X-linked juvenile retinoschisis, and age-related macular dystrophy of different stages, were examined. In patients with retinitis pigmentosa, the cones were involved in the pathologic process to varying degrees; the behavior of the local ERGs helped determine the final visual acuity. We also observed a reduction in the local ERG in patients with Stargardt's dystrophy that disappeared as the disease progressed. In age-related macular dystrophy, a disturbance of the electrogenesis mainly occurred in the central retina in advanced stages of the disease.