Tim--
I know exactly what you mean. I've got on the order of -10.5 with moderate astigmatism... used to use soft contacts, but just got off-the-shelf -10.5 lenses that work great underwater. (The astigmatism doesn't appear to be a problem for me underwater... how is it for you?)
I just got back from a two-week vacation at the Red Sea in Egypt (Makadi Bay, south of Hurghada). Did quite a few shore dives, and I know what you mean... the reefs there came right up to the shore, and you just had to be able to see where you're walking... and keeping the mask on was hot, uncomfortable, and the correction wasn't quite right in air. That might be the depth vision problem that you referred to.
What I did was I had gotten a Marsoops leash... a kind of neoprene Croakie-type thing. Cool thing is, you can turn it inside out and it becomes a soft neoprene pouch for your glasses. I'd just wear my glasses until waist depth, put on fins, and "deploy" the Marsoops just before putting my mask on. The glasses with the Marsoops around them just went into a BC pocket; there's a clip that attached to a BC D-ring so I wouldn't lose the amazingly expensive glasses underwater.
And I'd have the glasses right there again when getting out.
I was afraid at first that this wasn't a rigid case; but never had any problem even with inflated BC.
Side benefit to the Marsoops thing is it works like a slightly bulky Croakie to keep my glasses on during boat trips (I'm paranoid about losing my glasses overboard!!!), and it also floats with glasses!
--Marek
kidspot:
I wear -8.5 corrective lenses, while I really need a custom job (for astigmatism) they are wonderful in the water compared to what I used to use (nothing - just big blurs under the water) the problem is that on land I have NO depth perception with them and stumble and trip over the rocks all the way back to my glasses. Of course I could take my mask off, but then I can't see the rocks at all and still trip over them - lol.
Tim