My advice is that you should apply to Optometry School ASAP, so the summer before you senior year when it opens in July. It's easier to take the OAT that summer as well compared to that fall because you'll have more time to study since you won't have 5 classes during the summer. By the time you apply, you should be done researching the different schools and finalize where you want to go, be done shadowing multiple optometrists, have your LOR's figured out, have a decent amount of extra-curricular/volunteer experience, and best case scenario only have a couple of pre-req's left to finish and have worked in an Optometry practice(s).