You lucky boy! This straight from the SA CAA website...
4.5 PRACTICAL FLIGHT TESTS
In some cases, it will be necessary to perform a practical medical flight test with an applicant to determine medical fitness and ability to control the aircraft e.g. pilots with monocular vision, disabled pilots, colour vision appeals etc. In these cases, the medical examiner must refer the case to the panel or to the CAA to arrange for a flight test with a CAA flight inspector.
Seems it's just Europe that has its head stuck up its arse. Practical tests are usually just that, practical, hence not a problem for all but the most serious CVDs. Note that the vast, vast majority of CVD sufferers have only a mild problem which will not bother them during a practical test.