Ethambutol-associated optic neuropathy.
BACKGROUND
Ethambutol is used in the treatment of tuberculosis, which is still prevalent in Southeast Asia, and can be associated with permanent visual loss. We report 3 cases which presented with bitemporal hemianopia.


METHODS
Three patients with ethambutol-associated toxic optic neuropathy are described. All 3 patients had loss of central visual acuity, colour vision (Ishihara) and visual field. The visual field loss had a bitemporal flavour, suggesting involvement of the optic chiasm.


METHODS
Despite stopping ethambutol on diagnosis, visual function continued to deteriorate for a few months. Subsequent improvement was mild in 2 cases. In the third case, visual acuity and colour vision normalised but the optic discs were pale.


RESULTS
All 3 patients had some permanent loss of visual function.


CONCLUSIONS
Ethambutol usage is associated with permanent visual loss and should be avoided if possible or used with caution and proper ophthalmological follow-up. The author postulates that in cases of ethambutol associated chiasmopathy, ethambutol may initially affect the optic nerves and subsequently progress to involve the optic chiasm.
Lim
Su-Ann
SA
Department of Ophthalmology, Tan Tock Seng Hospital, Singapore. su_ann_lim@ttsh.com.sg
D000368:Aged; D000995:Antitubercular Agents / Q000009:adverse effects*; D004977:Ethambutol / Q000009:adverse effects*; D005260:Female; D006423:Hemianopsia / Q000139:chemically induced*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009901:Optic Nerve Diseases / Q000139:chemically induced*; D014376:Tuberculosis / Q000188:drug therapy
D000995:Antitubercular Agents; D004977:Ethambutol