Factors Affecting Visual Recovery in Patients with Ethambutol-Induced Optic Neuropathy

PURPOSE: To study visual recovery and identify the factors that may affect it in patients with ethambutol-induced optic neuropathy (EON). PATIENTS AND METHODS: Medical charts of patients who developed optic neuropathy after ethambutol (EMB) treatment for tuberculosis infection were retrospectively reviewed. Demographic details and clinical data were examined to assess visual recovery after discontinuation of ethambutol treatment. The univariate and multivariate relationships between various factors and visual recovery were evaluated using regression analysis. RESULTS: Of 5394 patients diagnosed with tuberculosis infection and treated with EMB, 23 patients (0.43%) were diagnosed with EON. Logistic regression analysis found that female sex was the categorical factor significantly associated with good visual recovery with an odds ratio of 12.0 (95% confidence interval 1.56, 92.29; p = 0.02), while linear regression analysis identified good initial visual acuity as the numerical factor significantly related with it (p < 0.001). After adjustment with multivariate analysis, initial visual acuity was found to be the only significant factor associated with visual recovery. All patients with initial visual acuity of better than 20/200 at first visit achieved good visual recovery. CONCLUSION: The incidence of EON in patients treated with EMB was 0.43% in this hospital-based study. Good visual recovery was noted in 39.13% of these patients, and initial visual acuity was the factor that affected visual recovery. It is recommended that patients on EMB have regular screening by an ophthalmologist for early detection of the disease, and if it is discovered, that the use of the drug be immediately discontinued in order to prevent potentially devastating visual loss.