Hi, I was in the same situation as you. The high UAI (Usually around 99) really makes it difficult to get into Optometry straight away. However, now the School of Optometry has started a lateral transfer entry scheme for people who don't get the grades. You start off in Bachelor of Science (Vision Science), do UMAT, and get distinctions in some specified subjects and can apply to transfer straight into 2nd year optom. You do the same subjects as 1st year optoms in 1st year science (vision science).
This was how i got into optom this year (i'm in 2nd year now) but we were the first group to go through the lateral transfer (and the first group to do the 5 year degree) so there were only about 15 or so people who wanted to transfer into optom. This year I've heard that there are about 50 people wanting to transfer, but there are only 20-30 extra spots for people wanting to transfer into optom, so it could get very competitive this way.
If you don't make the transfer, you can always finish Bachelor of science (vision science) and try and do optom post grad somewhere.
Look at the School's website for the proper details
www.optom.unsw.edu.au
hope this helps and good luck!