Agree with Meldy and Little Sis, there's something very wrong if your contact lenses fall out.
Aside from that, I've done this a couple of ways. In my early days of tri, I used to swim 'blind' and then pick up my glasses which I left somewhere by the side of the pool as I got out. Races are used to people asking if they can do this. I would then switch to sunglasses with the inserts for the bike and run if it was sunny enough, or just ride/run in my specs.
These days I do it the other way around. I have contact lenses and I ignore the 'do not swim in contact lenses' advice for race day only. I make sure I am completely confident of the seal of my goggles and then I can wear whatever glasses I chose on the bike.
I only swim in lenses on race day, I don't train in them. I train 'blind' as I'm happy enough with the blurry vision I do have. I have heard good things about those Aqua Sphere prescription inserts from others though.
Opticians will advise you against swimming in lenses, there are some nasty bugs you can get from doing this and I've seen a woman at my tri club get such an eye infection that meant she couldn't wear her lenses for several weeks. I told the optician that I race so infrequently I was prepared to take the risk for race day and the optician was ok with me weighing up the risks and making my choice.
Edited: 04/09/2012 at 16:38