I seem to remember that this used to be the case in 1.1.1, but in more recent version, you can't w5 while blind. I'm not sure why this was changed, but this is rather annoying, IMHO, since when you hit a light trap, for example, the normal instinct is to w5 until blindness goes away. I don't really see any downside to allowing it.

Also probably problematic for Zen Monk type games...