Optic atrophy can be caused by poisoning -a) Phosphorusb) Ethyl alcoholc) Methyl alcohol d) Lead

**Core Concept**
Optic atrophy refers to the degeneration of the optic nerve, which can result from various causes including toxic exposures. In this context, the question focuses on the specific types of poisoning that can lead to optic atrophy.

**Why the Correct Answer is Right**
Methanol (methyl alcohol) poisoning is a well-known cause of optic atrophy. When methanol is ingested, it is metabolized to formic acid, which is highly toxic to the optic nerve and can cause irreversible damage. This process is mediated through the enzyme formic acid dehydrogenase, which is involved in the metabolism of formic acid. The resulting optic atrophy can lead to permanent vision loss.

**Why Each Wrong Option is Incorrect**
**Option A:** Phosphorus poisoning primarily affects the liver and gastrointestinal tract, rather than the optic nerve.
**Option B:** Ethyl alcohol (ethanol) poisoning can cause a range of symptoms, including visual disturbances, but it is not a primary cause of optic atrophy.
**Option D:** Lead poisoning can cause a range of systemic effects, but it is not typically associated with optic atrophy.

**Clinical Pearl / High-Yield Fact**
Methanol poisoning should be suspected in patients with sudden onset of visual disturbances, particularly if they have ingested a suspected toxic substance. Early treatment with fomepizole or ethanol can help prevent further damage.

**Correct Answer: C. Methyl alcohol**