Assuming that you have had no prior transplant, the first question I would ask is why you have blood vessels growing into your cornea. BV's are an indication of prior or ongoing inflammation so any condition leading to corneal inflammation
needs to resolved otherwise the transpant should not be performed
That said a blood vessel at the transplant / host junction will lead to localized rejection. Efforts should be made to eliminate the blood vessel if possible -- but these are virtually impossible to eliminate completely and are only amenable to treatment if the blood vessels are on the surface. Once vessels get into the graft they will invade it completely.
Sounds like a difficult case which may be better left untreated.