ABO for optical

Okay, here's my situation. I'm an apprentice optician, I'm over my 2 years as an apprentice. According to state board, you need x amount of hours as an apprentice. I'm over mine. I never went to school, and it's not necessary. I work for family, and I was trained under a licensed optician. Being I never went to school, I never learned a lot of the theories of optics. From what I've heard, most of the stuff isn't used in the real world. I want to go take my test, and I'd honestly like to get out of my store. In order for me to do this, I need to take the ABO test. Can anyone give me some insight on what to look out for a what to study? Also, if anyone has input on good companies to work for, I'd love to know. I'm in Ohio if that helps any. Thanks reddit users!