For Cathay the Hong Kong equal opportunities ordinance prevents an employer from discriminating against a prospective employee on medical grounds (accepted a normal class 1 medical is already held). Also, I understand the Hong Kong CAD have no objection to pilots who have undergone PRK subject to a satisfactory outcome (obvious) and sufficient recovery/assessment time between procedure and approval.
Bottom Line: Be honest and you'll have the same chance as the next guy who has'nt had the procedure