what to do about eyewear?

[da fungo]

If you do wear the mono-filament type of semi-frameless glasses:
Bring along a bit of waxed dental floss. Should a lens pop out (happens fairly often) you can lay the floss across the filament; gently work the lens back in; and even more gently remove the floss.
It's easier to do than to describe.

[Plodderman]

Use my glasses and have an old pair just for a spare.

[Hikes in Rain]

I can't imagine wearing contacts on the trail, or more specifically, taking them out and putting them back in on a daily basis. I think of contacts as a vanity thing anyway. Don't need that on the trail.

Not much of an option for me. My vision is bad enough that glasses hamper almost as much as help. Consequently, I'm more comfortable without my pants than without my contacts. Besides, it's just a matter of washing your hands. I do it at home, why not on the trail?