Three-dimensional analysis of averaged electro-retinograms: normal appearance and bioelectric artifacts

In 10 normal subjects, three-dimensional analysis (X-Y plane and time) was carried out of the dominantly photopic and scotopic components of the electroretinograms (ERG) for the purpose of functional imaging of the retina, after having evaluated bioelectric artifacts. The study of the artifacts had revealed that the major causes of distorting the topographical distribution were blinking, myogenic activities, eye movement, eye position and background activities of the electroencephalograms. In normal subjects, the maximal amplitude of the dominantly scotopic components was located around the lower eyelid, while that of the dominantly photopic components was situated around the upper eyelid. The mechanisms of the equivalent dipole axis of the dominantly photopic and scotopic components were different. However, similar changes in the equivalent dipole axes were found during the periods of eccentric eye positions. Similar topographical characteristics were noted in the latency mapping. The isopotential line of the dominantly scotopic components had a steep gradient and were suggestive of a superficial (peripheral retinal) origin, while that of the dominantly photopic components had a gradual gradient and seemed to be of deep (central retinal) origin. ERG topography would make functional imaging of the retina possible and would be of great diagnostic value.