Flash electroretinogram abnormalities in patients with clinically definite multiple sclerosis.

We studied the flash electroretinograms (ERGs) of 105 patients with multiple sclerosis who were divided into four groups. The first group had no history or clinical evidence of optic nerve dysfunction, the second and third groups had either left or right optic nerve disease respectively, and the fourth group had historical or clinical evidence of bilateral optic nerve disease. Statistical analysis of the data using analysis of variance (ANOVA) showed that the group of patients with no history or clinical evidence of optic nerve disease had no significant difference from the control group for their peak b-wave implicit times but the other three groups were significantly delayed on the affected side(s). Using the Mann-Whitney U-test we found all four patient groups had significantly greater absolute interocular latency differences from the control group. The electroretinal contribution to flash VEP delay was also investigated. In those patients with unilateral or bilateral optic nerve disease we found that in 14-31% of those patients with flash VEP delay there was also abnormal prolongation of the ERG b-wave. These results confirm a high incidence of retinal dysfunction in multiple sclerosis patients and may suggest that transynaptic degeneration of retinal structures occurs in optic nerve demyelination. The significant absolute interocular latency difference in particular may provide another electrophysiological parameter to establish a diagnosis of multiple sclerosis in suspect cases.