**Core Concept**
Methanol poisoning is a toxic condition caused by the ingestion of methanol, a potent alcohol that can lead to severe metabolic acidosis, visual disturbances, and even death. The body metabolizes methanol into formic acid, which is responsible for the toxic effects. Effective treatment of methanol poisoning involves the inhibition of the enzyme responsible for converting methanol to formic acid.

**Why the Correct Answer is Right**
Fomepizole is a specific antidote for methanol poisoning that acts by inhibiting the enzyme alcohol dehydrogenase (not aldehyde dehydrogenase), which is responsible for converting methanol to formaldehyde, the precursor to formic acid. By inhibiting this enzyme, fomepizole reduces the formation of formic acid and subsequent metabolic acidosis. This mechanism of action is critical in the treatment of methanol poisoning.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is true. Hemodialysis is an effective treatment for methanol poisoning when the serum methanol concentration is above 50 mg/dl, as it helps to remove methanol from the body and prevent further metabolism to formic acid.
**Option C:** This statement is true. High anion gap metabolic acidosis is a common complication of severe methanol poisoning, resulting from the accumulation of formic acid and other acidic metabolites.
**Option D:** This statement is true. Visual disturbances, including blurred vision, blindness, and even retinal damage, are common complications of methanol poisoning due to the toxic effects of formic acid on the retina.

**Clinical Pearl / High-Yield Fact**
In the treatment of methanol poisoning, it is essential to note that fomepizole should not be used in conjunction with ethanol, as ethanol can also inhibit alcohol dehydrogenase and reduce the effectiveness of fomepizole.

**Correct Answer:**
✓ Correct Answer: B. Fomepizole acts by inhibiting aldehyde dehydrogenase