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Ethambutol retinal toxicity: an electrophysiologic study.
M Y Yen1, A G Wang, S C Chiang
1Department of Ophthalmology, Taipei Veterans General Hospital, National Yang-Ming University, Taipei, Taiwan.
Journal of the Formosan Medical Association = Taiwan Yi Zhi
|September 2, 2000
Summary
Ethambutol (EMB) may cause retinal pigment epithelium dysfunction in humans, indicated by abnormal electro-oculogram (EOG) findings during therapy. Early detection of supranormal EOG ratios could signal a toxic state.
Area of Science:
- Ophthalmology
- Neuroscience
- Toxicology
Background:
- Ethambutol (EMB) exhibits cone pedicle toxicity in fish retinas.
- Previous animal studies suggest potential retinal toxicity of EMB.
Purpose of the Study:
- To investigate the potential retinal toxicity of ethambutol (EMB) in human subjects.
- To determine if EMB causes retinal damage in humans.
Main Methods:
- Electrophysiologic investigation including electroretinogram (ERG) and electro-oculogram (EOG) was performed.
- Twenty-seven patients with EMB-induced optic neuropathy and 20 controls were assessed.
- Data collected included patient demographics, EMB dosage, treatment duration, and visual function.
Main Results:
- Electroretinograms (ERGs) were normal in most patients (25/27).
- Electro-oculogram (EOG) findings varied: 12/27 had normal results, while 15/27 had abnormal findings.
- Abnormal EOGs included supranormal light/dark (L/D) ratios (>2.33) in 10 eyes and decreased L/D ratios (<1.65) in 13 eyes.
Conclusions:
- Supranormal EOG ratios may indicate an early toxic effect of EMB.
- Ethambutol (EMB) may lead to retinal pigment epithelium (RPE) dysfunction.
- EOG abnormalities could serve as an early indicator of EMB-induced retinal toxicity.