Evaluation of anatomical and visual function for early detection of ethambutol toxicity among tuberculosis patients

AIM: To evaluate if early ethambutol toxicity can be detected by comparing pre - and post - treatment anatomical and visual function using retinal nerve fiber thickness, pattern visual evoked potentials and conventional optic nerve function tests. METHODS:This was a prospective study involving 72 eyes of 36 patients treated with ethambutol according to directly observed treatment short-course(DOTS) strategy in Hospital Universiti Sains Malaysia, Kelantan, Malaysia. The visual acuity and optic nerve function tests were performed by a single investigator. Likewise, Humphrey automated perimetry, optical coherence tomography ( OCT ) measurement of the retinal nerve fibre layer (RNFL) and pattern visual evoked potential (PVEP) were performed by a single technician. The examinations were performed before initiating ethambutol treatment and 3mo after that. RESULTS: There was no change in visual acuity, colour vision, light brightness, red saturation and fundus findings pre and post ethambutol. However, there was a statistically significant deterioration in the mean deviation of the visual field post treatment (P = 0. 010). There were also significant changes on OCT and PVEP, with increased RNFL thickness in all quadrants ( P < 0. 05 ) and PVEP delayed P100 peak latency and amplitude (P