If you're up chit and/or physical (and by extension, if you have a waiver...though I'm not sure if they do that still) says you require glasses to fly, you're required to wear them from FAM 1 in Primary on when you're in the aircraft. The fleet is big boy rules, but officially you're required to wear them. You can ask for contacts at some point (I don't know when) and I would guess that's either at the FRS or after.
Personally, I couldn't stand my contacts, so I just keep wearing glasses when I fly and they work fine. I could understand the desire not to where glasses in a jet, but they've worked for me in the 200 knots and under category.