Contrast and luminance as parameters defining the output of the VERIS topographical ERG.

The Visual Evoked Response Imaging System (VERIS I) topographical electroretinogram system (EDI Associates, San Francisco, CA) allows measurement of the response of large numbers of retinal areas simultaneously. This paper examines ERG responses derived with the VERIS system to changes in target contrast and to local reductions in luminance. There is a linear reduction of response with reductions of target contrast. Neutral density filters were placed over part of the display, to mimic the localised reductions in response which occur in glaucoma, age-related maculopathy or diabetic retinopathy. There is a definite reduction in response seen with a 0.4 ND filter, indicating that the system should have similar sensitivity in detection of retinal lesions to the commonly used visual field analysis systems.