Dr. James G. Chelnis contributed an article to the American Academy of Ophthalmology listing 9 very useful resources for OKAP and board exam review. His article can be found here (this may be member-only content).
I don't have any critiques of the resources he lists; from what I can tell, there is no specific order to his recommendations. If you used all 9 resources, I suspect you would do very well.
Out of that list, I personally used the following resources when I studied for the OKAP and board exams: