Shit that’s terrible. Wonder if your eye was still undergoing changes. 21 is relatively young.
My surgeon requested vision history from my referring optometrist. And did his own work up at the office. Took 2-3 months of follow ups and “adjustments” (ie, prescribing eye drops to fix dry eyes) to ensure vision was stable and dry eyes wouldn’t impact outcome.
I think there was some guidance around waiting 2–3 years since your prescription changed, which I met—though that's obviously imperfect.
There was never any clear cause/effect. My best guess is that it was from being super tense during the surgery. I found it extremely uncomfortable and intense to be fully conscious, knowing it would be bad news if I moved my eyes during the procedure. (They're holding a flap of your eyeball open during it, etc—super fun.)
Would have requested a little higher dose of Valium if I could do it over again. :) And maybe crossed a border to a high-volume specialty shop instead of my local ophthalmologist.