Try not to let the course intimidate you. Your school should give ample practice problems. Work them out on paper, and don't just read through the problems and solutions. If you aren't doing well after the first few assessments, then you could try to ask a professor for additional practice sets. Like the previous poster said, there is a bit of a learning curve, but it's really fairly formulaic.
Treat optometry school like your full time job because it is. It's much more memory based than undergrad, in my opinion. You'll have a lot of information to take in, but if you're consistent with studying every day (or almost), then it's manageable. Yes, it will be stressful, and at times you'll think the course load is impossible, but it's really not. I did pretty well academically when I was in school, but I still found time to do things that I liked by trying to break everything into manageable chunks.