Methyl alcohol poisoning III. Ocular toxicity

Area of Science:

• Ophthalmology
• Toxicology
• Neuroscience

Background:

• Methyl alcohol (methanol) is a known toxic substance with severe systemic effects.
• Ocular toxicity, particularly optic nerve damage, is a critical concern in methanol poisoning.
• Understanding the mechanism of methanol-induced optic neuropathy is essential for effective treatment.

Purpose of the Study:

• To investigate the ocular toxicity of methyl alcohol in a non-human primate model.
• To characterize the fundus changes associated with methyl alcohol ingestion.
• To elucidate the potential mechanism behind methyl alcohol-induced optic disc edema.

Main Methods:

• Six rhesus monkeys ingested methyl alcohol.
• Ophthalmoscopy and fundus photography were used to monitor ocular changes.
• Fluorescein fundus angiography was performed to assess retinal and choroidal circulation.

Main Results:

• All monkeys developed optic disc edema and associated fundus changes within 43-171 hours.
• Fluorescein angiography confirmed optic disc edema but showed normal retinal and choroidal circulation.
• The observed optic disc edema was clinically indistinguishable from that caused by increased intracranial pressure, though no such increase was detected.

Conclusions:

• Methyl alcohol ingestion causes significant optic disc edema in rhesus monkeys.
• The ocular findings in methanol poisoning resemble those of raised intracranial pressure but are not caused by it.
• Axoplasmic flow stasis is postulated as the underlying mechanism for optic disc edema in methyl alcohol poisoning.