Faculty Bibliography

Using clinical and electrophysiologic measures, we evaluated the visual pathway of patients who had multiple sclerosis, 20/20 Snellen acuity, and no history of optic neuritis. Delayed latencies were found in the transient visual evoked potentials (VEPs) of 38% of the patients, and interocular latency differences were abnormal in 67%. Contrast VEPs were abnormal in 46%. Psychophysical determinations of contrast sensitivity were abnormal in 78%. Only 17% of the patients had dyschromatopsia, 36% had afferent pupillary abnormalities, and 59% had optic nerve pallor or nerve fiber layer loss. Psychophysical contrast evaluations and VEP studies were superior to other clinical evaluations in demonstrating visual dysfunction in these patients

Twelve subjects, nine with tobacco-alcohol amblyopia and three with nutritional amblyopia, were studied with pattern and flash visual-evoked potentials. We found abnormal steady-state responses in all 12 patients, including those with minor visual abnormalities, when the contrast of the stimulus was decreased. The latency of the first major positive wave (P100) of the flash- or pattern-evoked potential was not delayed in 11 of the 12 patients. The normal P100 latencies differed from the prolonged latencies found in other patients with loss of central nervous system myelin caused by vitamin B12 deficiency or multiple sclerosis

Contrast thresholds were determined for patients with compressive lesions of the chiasm or optic nerve but whose visual acuity was 20/20 on the Snellen scale. A generalized loss of contrast sensitivity for spatial frequencies ranging from 0.2 to 6.4 cycles per degree was found even in patients with normal color vision and full visual fields. After surgery was performed, improvements in the fields and color vision were seen in those patients who also showed a significant increase in their postoperative contrast sensitivity scores. Contrast sensitivity is shown to be a useful procedure for evaluating very mild visual complaints as well as for establishing early diagnosis and evaluation of surgical therapy in patients with compressive lesions of the anterior visual pathway