title: Ethambutol induced toxic optic neuropathy in HIV positive patients.
abstract: OBJECTIVE
  To determine whether HIV and the use of antiretroviral therapy is a risk factor for the development of ethambutol toxic optic neuropathy. To describe the clinical course of ethambutol toxic optic neuropathy in patients with HIV and to identify prognostic factors.
  
  
  METHODS
  The case notes of 14 consecutive patients referred to the neuro-ophthalmology clinic were reviewed. Data regarding HIV status, antiretroviral therapy, visual function, ethambutol therapy dosage, and ethambutol therapy duration were collected and analysed.
  
  
  RESULTS
  Eleven of the 14 patients were HIV positive. Ten of the HIV positive patients were receiving antiretroviral therapy. The mean dose of ethambutol was 17.25mg/kg/day. No statistically significant difference in mean dose, duration of therapy, age or CD4 count was found between those who showed visual improvement and those who did not. Delay in presentation of more than one month post symptom onset was correlated with poor visual outcome (P=0.001).
  
  
  CONCLUSIONS
  HIV and, perhaps more importantly, the potential mitochondrial toxic effects of Nucleoside analogue reverse transcriptase inhibitors (NRTIs) may be a risk factor for the development of toxic optic neuropathy from ethambutol therapy via a multiple hit effect. Delay in presentation results in poor visual outcome. Regular monitoring is recommended for HIV positive patients receiving antiretrovirals and requiring ethambutol therapy in order to avoid permanent visual loss.
authors.affiliation: Division of Ophthalmology, Groote Schuur Hospital, Cape Town 7925, South Africa.
authors.forename: Hamzah
authors.initials: H
authors.lastname: Mustak
authors.forename: Graeme
authors.initials: G
authors.lastname: Rogers
authors.forename: Colin
authors.initials: C
authors.lastname: Cook
keywords: HIV; ethambutol; optic neuropathy; toxic