Menon V, Jain D, Saxena R et al.
All India Institute for Medical Sciences, New Delhi, India.
Br J Ophthalmol 2009;93:1251–4.
Editor’s note: In this study, among 52 consecutive patients on directly observed treatment for tuberculosis including ethambutol (15–20 mg/kg/day) for 2 months, no visual function defect was detected prior to the initiation of treatment. No patient reported any visual symptoms. Visual acuity (VA), color vision (Ishihara color plates and Oculus Heidelberg anomaloscope, Oculus Inc, Lynnwood, WA, USA), contrast sensitivity (Pelli-Robson chart), Amsler grid testing, and optic discs were normal during treatment and 1 month after discontinuation of ethambutol. Peripheral visual field constriction (Goldmann perimeter) was identified in both eyes of four patients (8%) after 2 months of therapy, without any abnormality of the central visual field. Visual field constriction was still present 1 month following discontinuation of ethambutol in four eyes (three patients). In 15 eyes (14%; 11 patients), the latency of the P100 component of the pattern visual evoked potential (PVEP) increased by
≥10 ms at 2 months of therapy, with persisting abnormality 1 month after discontinuation of therapy in three eyes. PVEP amplitudes were not affected. In three eyes (3%; two patients), there was a >20
µm reduction in temporal quadrant retinal nerve fiber layer (RNFL) thickness on optical coherence tomography (OCT) 1 month after cessation of ethambutol, all also having a persisting increase in PVEP latency and residual visual field defects at that time.