One of my less-riveting tasks at MoD in the early 90s was staffing a paper on "Contact Lenses for Aircrew". Not sure whether it related to 'on entry' or a subsequent need. One aspect, IIRC, was that the user had to carry a pair of corrective specs as well, in case a contact lens went walkabout.
This is all very interesting stuff, and I'm very surprised to discover that wearing contact lenses for any aircrew is allowed. As a wearer, I can vouch that if one or both go 'walkabout' (and they do) it isn't always a simple job getting them back again. I dread to imagine trying to do that while hammering along at 50 ft and 400 kt, or even at 30,000 ft with 300 passengers in the back.