This is as much a PR question as a requirement question.  If your patient has a vision benefit, and you are contracted with the vision plan, it’s best that the patient gets her/his benefit once during each contract period (one year, two year, etc.)  If the patient has a medical diagnosis that requires follow up visits, all the visits that are due to doctor’s orders (e.g. RTO 90 days, repeat VF and IOP, POAG) should be billed to the patient’s medical insurer and the patient will be paying the deductible, copays, etc.  Once during each contract period, though, the patient gets a break and the claim goes to the vision plan with its lower deductibles and copays.

Ideally, all this would be established in office policy first and then in discussions with each patient who has medical diagnoses that require scheduled follow up visits.  If handled correctly, with constant reinforcement with each patient about complying with scheduled appointments, honoring requirements of vision and medical insurers’ agreements, etc., it should reduce the number of disagreements and make it clear to your patients that you are devoted to taking excellent care of them, helping them get the benefits they deserve, and honoring the contracts that you and they have signed with the insurers.