Visual evoked potentials in the detection of subclinical optic toxic effects secondary to ethambutol

In 14 patients with tuberculosis treated with ethambutol hydrochloride, pattern-reversal visual evoked potentials (VEPs) were recorded to monocular, whole-field stimulation before the commencement of treatment and one month and three months subsequently. In six subjects, the VEPs showed changes in the latency and amplitude of the P100 component at the one- or three-month interval. In three cases, the VEP changes reversed after cessation of treatment. In five of the six cases, changes were not associated with a change in visual function, as measured by clinical neuro-ophthalmologic examination. Our findings confirm the usefulness of VEPs in the detection of subclinical optic nerve disease and suggest their use in routine monitoring of ocular function in patients treated with ethambutol.