A comparative study of visual evoked potentials and of retinal nerve fiber layer photography in neuropathies of the optic nerve.

The degree of retinal nerve fiber loss within the papillomacular bundle in optic neuropathies was evaluated from red-free fundus photographs. Visual evoked potentials were obtained from pattern reversal with variable check sizes. A semiquantitative scale was used for the estimation of nerve fiber loss and amplitude reduction of the visual evoked potentials. A significant correlation was found between both. However, a few patients showed rather well-preserved visual evoked potentials with an atrophic nerve fiber layer. Possibly a small number of invisible remaining fibers are able to sustain nearly normal visual evoked potentials. On the other hand, some patients had abnormal visual evoked potentials in the presence of a normal nerve fiber layer. We conclude that evaluation of the nerve fiber layer of the papillomacular bundle without functional testing of the optic nerve is not sufficient to predict degree of foveal integrity.