Try to re-write the OAT and bring your scores up as much as you can. Maybe focus on studying more for the sections you are weaker on. Have you completed your Bachelor's already, or are you still in school? If you still have some time in your undergrad left, do as much as you can to bring up your GPA.
You have the work experience as an optician on your side! If you have not already, try to shadow/volunteer with a few optometrists as well. Also, try to get some more volunteering to amp up your extra curriculars. If you're looking into optometry-specific volunteer opportunities, look into things like VOSH, Special Olympics vision screenings, etc (of course this all depends on when you're planning to apply). Of course, volunteer for these things because you want to, not because you need to! They are great ways to contribute to the community and get some hands on experience at the same time!