I've been wearing (soft) contact lenses for 25 years (hard lenses for 4 years before that). Things were always great with them, but over the last few years (I'm 47 now) I've noticed a strange phenomenon:
If I put my contact lenses (Focus Dailies; each pair thrown away at the end of the day) in my eyes fairly soon after I get up in the morning (doesn't matter if I shower first or not i.e., heading off to the gym), the lenses feel fine for 15 or 20 minutes, but then they start to feel uncomfortable: not really sandpapery or like an eyelash under the lens, but it's as if they want to jump off my eyes. This 'settling time' lasts for an additional 10 or 20 minutes, after which the lenses feel fine again for the rest of the day. If I wait an hour after I get up before putting the lenses in, the problem does not appear.
What is causing this? Some kind of reaching-thermal-equilibrium effect? And what (if anything) can be done to prevent it?