Per your prior posts, you have stated you're a high school student. I would say that for college, medical school, and any medical specialty, the better you perform in your coursework, the better your chances of achieving your desired goal. Was every ophthalmologist at the top of his/her medical school class? Of course not. Are there some who were in the top 10% of their respective classes who did not match into ophthalmology (if it was their chosen specialty)? Probably, but I would wager not many. Excel in your studies, and you should be able to have your choice of career pursuits. Struggle in your studies, and you will likewise struggle to achieve your goals. It's that simple.