Flash visual evoked potentials predict visual outcome in traumatic optic neuropathy.

PURPOSE: To determine the significance of flash visual evoked potentials (FVEP) in the evaluation of patients with traumatic optic neuropathy (TON).

METHODS

Eleven head-injured patients admitted to our center were diagnosed with unilateral TON. For every patient, FVEPs were obtained in both the affected eye and the unaffected eye. The normal eye thus functioned as each subject's internal control. We determined the amplitudes of FVEP waveforms for each eye and calculated an amplitude ratio of the affected/normal side for all individuals. The best-corrected visual acuity was obtained for each eye 2 weeks after acute hospitalization. We then determined the relation between best-corrected visual acuity in TON and the FVEP amplitude ratio.

RESULTS

In 4 patients in whom the amplitude ratio was at least 0.5, visual acuity in the affected eye was 20/30 or better. In 7 patients, the amplitude ratio was less than 0.5, and visual acuity in the eye with TON did not exceed 20/300 (Pearson r = -0.93, p = 0.0001).

CONCLUSIONS

Flash visual evoked potentials are highly predictive of the degree of visual function in unilateral TON. Finding FVEP amplitudes that are at least 50% of the normal eye appears to be critical in anticipating good, long-term visual outcome.