All difficult to get in to. Here's the defiinitive guide to the respective careers:
Medicine: Maximum career credibility, just like Casualty, fantastic arrogance and salary once you reach consultant, may marry a nurse
Dentistry: Back ache, working in disguisting cramped mouths, arsey dental assistants, sued at every heel and turn
Optometry: Low stress, some clinical credibility, reasonable pay, might get a bit tedious saying clearer with one or clearer with 2 plus you could still end up in jail for missing something
Go for medicine