The vision standards for commissioning are a bit different (more relaxed) than the vision standards for entry into the Naval academy. If you get into the Naval Academy, you are almost assured that you will be commissioned for Unrestricted Line duty if you decide to go Navy, or you will be commissioned for ground duty for the Marine Corps if that is the route you decide to go.
At this point in time this would be the very last thing that I would be concerned about. You can start worrying about this towards the end of your 3rd class year.
