Abstract
Electrical responses to light stimuli of 1° angular subtense were recorded from the eye (electroretinogram, ERG) and from the occiput (visual evoked response, VER) in normal subjects and in patients with visual field defects. Suitable combinations of stimulus and background intensities were able to produce focal retinal stimulation, evidenced by absence of response to blind spot stimulation and by presence of a clear response with foveal stimulation. At a constant level of background light the range of stimulus intensity necessary to effect focal stimulation was much more critical in ERG (1 log unit) than in VER (4 log units). With these parameters, the distribution of VER amplitude on the horizontal meridian of the visual field showed augmentation at the macular area of the retina in the photopic and scotopic state. When the stimulus was moved from the center to the periphery along the horizontal meridian, the b-wave of the ERG diminished in most cases more greatly than the a-wave, and was reduced to a prolonged negative wave at the periphery. Under these conditions, combined recording of ERG and VER was found to be significant in fudging whether field defects resulted from local disorders of the retina or from lesions higher in the visual sijstem.