Today there are several kinds of corneal grafting. The answer depends upon which type you are undergoing. If it is DALK, it is very safe to conceive in about 6 months after surgery. If it is PK than you may have to wait till all the sutures are removed, and that may be about a year. Modern techniques like DESAEK or DMEK, are also very safe, and about 6 months waiting is ok. The technique depends upon the cause of your corneal disease. In your age, it is usually keratoconus or corneal infection or injury. In the former DALK is the best.