Evaluation of the Long-term Effect of Ethambutol Usage on the Retinal Nerve Fiber Layer Using Spectral-Domain Optical Coherence Tomography

OBJECTIVES: The aim of this study was to use spectral-domain optical coherence tomography (SD-OCT) to evaluate the long-term effect of ethambutol on the optic nerve fiber layer. METHODS: Twenty eyes of 10 patients who had been treated with ethambutol for tuberculosis were retrospectively evaluated. Retinal nerve fiber layer (RNFL) analyses performed initially and about 2 years after the end of treatment were included in the study. Data of visual acuity, fundus examination, other diseases, and drug use history of all of the participants were evaluated. Color vision was tested with the Ishihara Color Test. Superior, inferior, nasal, and temporal quadrant RNFL parameters were evaluated using SD-OCT. RESULTS: The mean age of the 10 patients was 38.77±14.86 years. There were 6 males and 4 females in the group. The mean length of follow-up was 4.44±1.94 months (range: 2-8 months). The mean RNFL result of the analysis performed 2 years after discontinuation of ethambutol treatment was superior RNFL: 122.45±18.64 µ, inferior RNFL: 131.40±13.31 µ, temporal RNFL: 71.60±8.53 µ, and nasal RNFL: 81.70±9.73 µ. There was significant thinning in the temporal quadrant (p<0.05). CONCLUSION: Long-term use of ethambutol caused thinning in the RNFL. SD-OCT is useful in the follow-up of these patients.