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Retinal function and morphology in monkeys with ethambutol-induced optic neuropathy
Junzo Kinoshita1, Noriaki Iwata, Takanori Maejima
1Medicinal Safety Research Laboratories, Daiichi Sankyo Co., Ltd., Shizuoka, Japan. kinoshita.junzo.dy@daiichisankyo.co.jp
Investigative Ophthalmology & Visual Science
|September 8, 2012
Summary
Ethambutol causes optic neuropathy, damaging retinal ganglion cells (RGCs) in monkeys. This study reveals functional and morphological RGC damage, highlighting RGCs as key targets in this condition.
Area of Science:
- Ophthalmology
- Neuroscience
- Toxicology
Background:
- Ethambutol is known to cause optic neuropathy.
- Retinal abnormalities in ethambutol-induced optic neuropathy are not fully understood.
Purpose of the Study:
- To investigate functional and morphological retinal alterations caused by ethambutol in monkeys.
- To understand the impact of ethambutol on retinal function and structure.
Main Methods:
- Cynomolgus monkeys were administered ethambutol orally at escalating doses.
- Full-field electroretinograms (ERGs) were recorded to assess retinal function.
- Histopathological examination of retinae and nervous system tissues was performed.
Main Results:
- Standard ERGs showed no significant changes.
- Selective attenuation of the photopic negative response (PhNR) was observed in two monkeys.
- Histopathology revealed retinal ganglion cell (RGC) necrosis, decreased RGC density, and inflammation in the optic nerve.
Conclusions:
- Ethambutol significantly damages RGCs, both functionally and morphologically.
- The study implies RGCs are predominantly affected in ethambutol-induced optic neuropathy.
- Findings suggest RGCs are a primary target in this adverse ocular event.
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