The primary aim of any corneal surgery is to provide a surface whereby vision correction is made easier.
A medical success is a clear cornea with no signs of rejection and that has healed well, so may differ to your interpretation of a success.
20 years on you can not tell I have had a graft, infact once the redness had gone and because I used to play rugby many assumed I had been hit in the face. I can still see the graft but I need to be very close to the mirror with the light right. Not many people get close enough to look that deeply into my eyes
It is pretty much 50/50 if you end up needing glasses on contacts. I went through glasses, a good period with no vision correction, back to glasses and now on contacts again. What is worth remembering ciontact lens technology is moving on and with a more normal shaped cornea the lenses although still the hard ones are a lot more compfortable.
Think long and hard before going for a graft as once done unlike some other corneal surgery can not be undone afterwards.
Good luck.