Longitudinal analysis of retinal nerve fiber layer and ganglion cell-inner plexiform layer thickness in ethambutol-induced optic neuropathy.

PURPOSE: The aim of the study was to evaluate longitudinal analysis of peripapillary retinal nerve fiber layer (RNFL) and perifoveal ganglion cell-inner plexiform layer (GCIPL) thickness in patients being treated with ethambutol (EMB). METHODS: This prospective longitudinal cohort study enrolled 37 patients who were treated with EMB for pulmonary tuberculosis. Best-corrected visual acuity, color vision test, automated perimetry, fundus photography, and RNFL and GCIPL thickness were measured at baseline and at 4 and 6 months after the start of EMB treatment, using Cirrus optical coherence tomography. RESULTS: Among 37 patients, EMB-induced optic neuropathy occurred in one patient (2.7 %). In this patient, thickening of the RFNL and thinning of the GCIPL were noted at the onset of symptoms. After discontinuation of EMB, RNFL and GCIPL thickness progressively normalized. Changes in RNFL and GCIPL thickness were not statistically significant in the 36 patients who did not exhibit EMB-induced optic neuropathy-related symptoms during follow-up (all P values > 0.05). CONCLUSIONS: Thickening of the peripapillary RNFL and thinning of the perifoveal GCIPL is an effective quantitative and early marker for diagnosis of EMB-induced optic neuropathy.