Abstract
Purpose: :
To evaluate the changes of the photopic negative response (PhNR) of the full-field ERGs in patients with retrobulbar optic neuritis.
Methods: :
Three patients with bilateral retrobulbar optic neuritis were studied. The PhNRs were recorded before, immediately after, and 3 months after beginning steroid pulse therapy. Five patients with unilateral glaucomatous optic atrophy (OA) and five normal subjects were also studied. The PhNR was elicited by full-field white stimuli on a white background of 16 ms duration. The correlations between the PhNR amplitudes and the visual acuity (VA), mean deviation (MD) of the Humphrey field analyzer (30-2), and ganglion cell complex (GCC) thickness measured on the SD- OCT images were calculated for all subjects.
Results: :
At the acute phase, the VA, MD, and GCC thickness varied considerably in the three cases of retrobulbar optic neuritis even between the two eyes. Nevertheless, the PhNRs in both eyes were not significantly different from that of the controls. However, the PhNR in both eyes were reduced by >30% of the original amplitudes two months after beginning the therapy. PhNRs were still recorded even in eyes with severe decreases in the VA, MD, and GCC thickness as opposed to its absence in eyes with OA with severe decreases of the VA, MD, and GCC thickness.
Conclusions: :
The PhNR is not a sensitive indicator of VA for retrobulbar optic neuritis at the acute phase. A decrease in the function of the RGCs is probably not evident until two months after the onset of the retrobulbar optic neuritis. These results suggest that there are probably two types of optic nerve diseases in electrophysiological function, one is sensitive and the other is not sensitive to RGC damages.
Keywords: optic disc • ganglion cells • electrophysiology: clinical