If you are on the margins or pass/fail the timing or your medical and the fitness of your eyes just might be the difference. Your optician can assist in teaching you to exercise the eye that is marginally below standard. A colleague of mine (who has since had PRK treatment and has been flying on a class 1 now for over 8 years) had difficulties before treatment but used to take his medical in the afternoon and after exercising the unfit eye for a number of weeks in the lead up to the renewal. It worked and got him through. The CAA may frown upon surgery but a number of other authorities do not, namely CASA (Australia). I believe the CAA does accept the procedure after a number of years of postoperative monitoring and a visit to their ophthalmic specialist.
Good luck!