The pattern ERG in man following surgical resection of the optic nerve

Pattern electroretinogram (PERG) results recorded in different laboratories from patients with unilateral traumatic transections of the optic nerve have led investigators to opposite conclusions about the sources of this response. There was no absolute demonstration of complete transection in any of these studies. In the present study, PERGs and flash ERGs were recorded from a patient who, 30 months earlier, had undergone surgical resection of the right optic nerve to remove a glioma. The histological section of the biopsied nerve confirmed complete optic nerve transection. Ophthalmoscopically and angiographically, the right eye was normal except for marked optic atrophy. PERGs were produced by 10 Hz reversal of high contrast checks with check widths from 13 deg 30 min to 12 min arc. Field size was 27 deg X 21 deg and space-averaged screen luminance was 110 cd/m2. Smaller checks (3 deg 23 min to 12 min) produced responses in both eyes, but the responses in the right eye were much smaller than those in the left eye. Large checks and diffuse flashes produced approximately equal responses in the two eyes. The implicit times of the PERGs produced by stimulation of the right eye with smaller checks were shorter than those of the left eye. The authors conclude that, in humans, there is a contribution to the high contrast pattern reversal ERG from cells which are not dependent upon the integrity of the ganglion cell layer. These cells and cells dependent upon ganglion cells may both contribute to the high contrast PERG in the normal human eye.