Re: Why does methanol cause blindness??

Ethanol and methanol are both alcohols, but the difference lies in the 
metabolic pathways they go through.
Methanol is widely used among the chemical industry, as a solvant or a 
compound in chemical processes. Its ingestion occurs during suicide 
attempts (voluntary ingestion in adults) or during accidental ingestion in 
toddlers (on a general standpoint, never never pour the content of a 
domestic or industrial product such as bleach, chloridric acid and so on in 
a bottle or a can of, say, Coke, spring water, etc).
When ingested, methanol undergoes dehydrogenation in the liver (the enzyme 
in charge of that is alcohol dehydrogenase) and formaldehyde is produced as 
a result of dehydrogenation of methanol. Formaldehyde and related 
compounds such as formic acid have a huge ocular toxicity, your vision 
becomes blurred, you undergo central scotoma (you lose your central vision 
while you keep your lateral vision), and eventually you go blind.
On the other hand, when you drink ethanol (without a m-) which is the 
standard compound of beer, wine, whisky, alcool deshydrogenase transforms 
ethanol in acetaldehyde which has no toxicity by itself (but drinking 
ethanol is hazardous to your health by other ways, such as hepatic 
cirhosis).
Treatment of methanol ingestion relies on ethanol ingestion or injection 
(you try to override alcohol deshydrogenase activity by making it work on 
ethanol) and 4 methyl pyrazole. But prevention is the cornerstone of 
blindness prevention.

Hope it helps.

Luc

Luc A Ronchi, MD
Ped Anesthesia