All I can tell you is what I do in the same situation…
A while back, I was playing in a 6/12 limit game with a little old lady who was doing the same thing as the drunk in your game. She would lift her cards completely off the table and up to her face to see them, and on each street she would look again. As we were playing 10 handed Hold 'em at a STUD table (slightly smaller, designed for 8 or 9 players, not 10), there was basically no way I could avoid seeing her hand, short of asking for a seat change.
Obviously changing seats would have been DUMB, because anyone moved to that spot may not have qualms about using the info they'd get; that would put me at a dis-advantage.
I could not ask for a table change, as this was the only 6/12 LHE game going.
What I did was warn her I had seen her cards first once, then TWICE. The 2nd time was in case she had not heard me or did not understand after the first time I had seen her hand. After that, she was on her own, in my opinion, as was I.
My feelings about the matter were that as long as I did nothing to TRY to see her cards (crane my neck, re-position my chair, look over specificlly to try to catch her at it), then any info which happened to come my way as a result of her failing eye sight was ok for me to use.
To be honest, still I think of that situation, and wonder if what I did was "right".
On the one hand, it is pretty STUPID to even think about passing up such a huge advantage that could result in free money, but on the other hand was that money I won worth "taking advantage" of someone who probably could not physically do anything differently?
Maybe I should have shown her how to cup her cards in her hands so she could raise them to her face to see 'em…who knows.
I can live with the decision I did make though.