Which of the following is the most characteristic ocular manifestation of methanol poisoning?

Explanation

## Ocular Manifestations of Methanol Poisoning **Key Point:** Methanol poisoning causes a specific pattern of optic nerve damage: - **Acute phase:** Optic neuritis (inflammation of the optic nerve) - **Chronic phase:** Optic atrophy (degeneration of nerve fibers) - **Outcome:** Permanent blindness if untreated or inadequately treated **High-Yield:** The optic nerve is exquisitely sensitive to formic acid (the toxic metabolite of methanol). Formic acid causes: 1. Mitochondrial dysfunction in retinal ganglion cells 2. Selective damage to the optic nerve head 3. Irreversible axonal loss leading to optic atrophy **Clinical Pearl:** Blindness in methanol poisoning is often bilateral and permanent, even after recovery from systemic toxicity. Early recognition and aggressive treatment with ethanol (to inhibit ADH) and hemodialysis (to remove formic acid) are critical to prevent vision loss. **Mnemonic:** **FOAM** — **F**ormic acid damages the **O**ptic nerve → **A**trophy → **M**ethanol blindness. ## Pathophysiology Formic acid preferentially accumulates in the vitreous humor and damages the optic nerve head through: - Inhibition of cytochrome c oxidase in mitochondria - Impaired ATP production in retinal cells - Selective toxicity to the optic nerve (higher metabolic demand) ## Why Other Options Are Wrong | Manifestation | Why Not Characteristic of Methanol | | --- | --- | | Acute angle-closure glaucoma | Not a recognized feature of methanol toxicity; occurs in other conditions (acute angle closure, uveitis) | | Retinal detachment | Not typical of methanol; seen in trauma, high myopia, or diabetic retinopathy | | Cataracts | Not a feature of acute or chronic methanol poisoning |