Delayed and reversible ethambutol optic neuropathy.

Purpose: To document an unusual example of ethambutol optic neuropathy developing three years from treatment start date in the absence of renal dysfunction.

Observations: The patient, an 82-year-old, 61-kg male undergoing treatment for , presented with visual acuity that was significantly worse than baseline three years after beginning a treatment regimen which included ethambutol at <15 mg/kg/day. He was also found to have central and paracentral scotomas in both eyes.