Using #wipe is an occupation that removes the offending gunk from your face in one quarter of the time it would take to disappear normally. The tradeoff is that you are busy during this time. Applying a towel will do the same in one move, but #wipe has the advantage of being always available.
Once you have telepathy, it is usually better to simply wait the blinding out and keep fighting, but monks and vegetarians who can't easily get intrinsic telepathy may find it handy more often. Monks are more likely to be blinded, as they can't wear body armor and take longer to reach a decent AC. If you are playing a monk, eating a floating eye for intrinsic telepathy will only temporarily affect your alignment, so you can get away with it as long you're not also pursuing a vegetarian conduct, pacifist conduct, or protection racket.
Attempting to use this command when there is nothing to wipe off will result in the message "Your face is already clean."