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This deal may not be for everyone but if you satisfy the research pre-conditions and are willing to travel to UNSW to participate in the research then it is definitely a good freebie.
You can drive there and they have free parking for optometry customers, Entry is on gate 14 and park within the Barker St car park on the ground level.
I am personally participating in the study too and it has been a good experience. Every visit, I was able to get my $20 coles gift card with no dramas.