Abnormal Multifocal Electroretinogram (mfERG) in Ethambutol Toxicity

OBJECTIVE: To report the abnormal multifocal electroretinogram (mfERG) findings in two cases of presumed ethambutol toxicity. DESIGN: Retrospective observational case series. PARTICIPANTS: Two patients with ethambutol toxicity and visual loss. TESTING: Multifocal electroretinography. MAIN OUTCOME MEASURE: Waveform measurements on multifocal electroretinography. RESULTS: Two patients with bilateral visual loss due to ethambutol toxicity underwent mfERG testing that disclosed both diffuse and central field loss compatible with retinal dysfunction as a contributing mechanism to the visual field loss. CONCLUSION: Ethambutol toxicity affects not only the optic nerve but probably other retinal elements based upon abnormal mfERG findings.