SIA has their own set of medical requirements which are confidential. Even if you qualify for Class 1 does not mean SIA will take you. Happened so many times where candidates are rejected after their medical. And yes, once you are rejected after the medical, it's based on SIA's own medical requirements. Any medical questions should be checked with CAAS. None of us are really doctors (some exceptions) and only specialised aviation doctors can give you the actual answer.