If they were afraid you wouldn't pass the physical, I'm sure it would have come up before now...
And I agree with north. As long as they are both prescribed, I would be honest about it, because ultimately the person who tests you is probably no one that you would have to answer to anyways... and your boss is probably not going to read anything on the test other than whether or not you passed. As long as you pass, any other info will probably be forgotten within a week.
Good luck!