Most providers bill them right after the photos are taken, however, the description does state "fundus photography with interpretation and report" so until the interpretation and report are completed the service was not performed. What happens if the photos don't come out, and the patient doesn't return to have them retaken?
Since your provider is doing it this way, I think I would leave it. If your provider belongs to any local, state, or national optometry/ophthamology organizations you could also check with them.
Michele