It was not airline but just a requirement (to be on the safe side) made by the Medical Department of my friends' countries CAA that delivers pilots and CC the "fit to fly" certificate (both pilots and CC need it in some countries). In the first case I mentioned there only was the need of a medical check in order to obtain a derogation; while in the second she was requested to not to fly for a number of months (my friend then was temporarily assigned to the Crewing Dept) before going back to flying. At the time I asked one of my friends, who worked as an ophtalmologist for an airline, why there was the need to spend a few months on the ground. She replied that there was no real concern, but since it was quite a new procedure (talking about 10 years ago) that had not been tested on the long run, the authorities delivering the "fit to fly" certificate preferred to be on the safe side, and allow it a few months to heal just in case.