I was in this exact position last year. I just couldn't choose between Dentistry and Optometry. Ultimately, for the sake of your application, you need to choose one. Your personal statement needs to be very specific. You must go into the details of why you wish to study your course and aspects of the course that interests you. You should consider which one you prefer first, but also which is more realistic to persue in your perspective. Dentistry requires the UCAT test and an adequate score at that. Optometry does not. Either way, don't fall into the trap of simply talking about "healthcare" in your personal statement. It will seem non-genuine and unfocused.