You'll find that Medicare does not generally cover routine eye exams. There are things that Medicare Part B will cover but you would need to ask about the specific cases. A good place to start getting information is the Medicare Web Site that discusses coverage of eye examinations.
Eye exams | Medicare.gov has some good info but it might give you just enough information to be dangerous to yourself.
It will however give you some basic ideas on topics to explore with a specific eye clinic.
Best of luck in your search.