Contact lenses are easily spotted by the doctors doing the testing. You're fooling only yourself if you try and get around it.
It is advised that you don't wear contact lenses to the medical but wear your specs instead. I have forgotten why but I wear specs, not contacts so it's never been an issue.
(An aside, I only wear my specs when I need to watch tv, drive and fly. Reading, using the computer and generally wandering about the house I don't wear them.)
For the eye test, you'll have to do the reading with and without your lenses. If your eyesight is corrected to a suitable level then you'll pass that bit. (unlike JAA)
Hearing test. Keep away from loud noises leading up to the test. If you ride a loud motorbike, wear ear plugs (should do it any way). Don't blast your ears with noise for about 24 hours prior to the test. It's not a big deal.
The Australian medical is pretty straight forward. Basicaly, if you're in reasonable condition, can hear, can see, don't have diabetes, you'll pass. Relax.
