Incidence and prognostic factor of ethambutol-related optic neuropathy: 10-year experience in southern Taiwan

To investigate the incidence and prognostic factors of ethambutol-related optic neuropathy (EON) in one medical center of southern Taiwan, a retrospective chart review study with 4803 newly diagnosed tuberculosis cases from January 2002 to July 2011 at one medical center hospital in southern Taiwan were reviewed. Of these patients, 1004 had ophthalmic records. Sixty-two cases (1.29%) experienced visual impairment and were diagnosed as EON with mean visual acuity of 0.86 ± 0.69 by logMAR. Sixteen of the 62 patients had a follow-up time > 6 months. Of these, eight patients (50%) showed visual improvement (an increase in visual acuity of ≥ 2 Snellen lines) after ethambutol was discontinued. Another eight patients (50%) showed no visual improvement. We analyzed multiple factors between the patients with and without visual improvement by logistic regression, including body weight, daily dose of ethambutol, duration of ethambutol use, cumulative dose of ethambutol, renal function, underlying disease of diabetes mellitus, hypertension, and initial visual acuity showed no statistically significant difference. In conclusion, the incidence of EON was 1.29%. Half of the patients showed visual improvement after discontinuation of ethambutol, and no obvious prognostic factors were found to facilitate the vision recovery. Ethambutol should be discontinued as soon as EON is suspected.