Optometry schools average GPA is usually around 3.3 or 3.4 But, it does vary from school to school. I know from personal experience that UC Berkeley's average GPA is around 3.6. So, if you want more detailed info on averages for all seventeen optometry schools go the ASCO webpage. (american schools and colleges of optometry) I'll post the website later. They can answer lots of your questions too!
The entrance exam for optometry is the OAT (optometry admissions test) It's given twice a year in October and February. If you want to purchase review materials for the test.. check out ecampus.com or barnesandnoble.com and put OAT into their search features. OAT review books are really hard to find at bookstores.
Hope this helps! good luck! and if you have any other questions don't hesitate to ask!