Yes, it is possible. Report them before undertaking the medical examination.
I know it is possible to detect it by examining the eye with corneal topography. As far as I am concerned, they don't always perform corneal topography though I would be totally honest.
If you had myopia the number of dioptres you needed is not a problem anymore as there are no pre-operative limits for myopia according to EASA Part-MED.
This should apply to astigmatism too.
I can't say anything about other refractive errors.