I think the trap most applicants fall into is using their entire personal statement to prove why or how much they love ophthalmology. Maybe give a brief statement regarding why you got interested, but the personal statement is a chance for the programs to know you as a person. Describe your interests, what you do for fun, your family, pets, interesting trips you've taken, etc. If programs read your personal statement at all, it's to get a feel for whether or not they can work with you for three years.