Alternating Flippers are used to increase the speed and reduce the latency of the speed of response for patients that have difficulty shifting focus. Alternating Accommodative Flipper (aka Rock Flipper) vision therapy can be conducted in and out or at home for focusing disorders. The primary focusing dysfunction this procedure treats is accommodative infacility (a problem shifting focus from near to far and back again).
Alternating Flippers have a plus lens at the power specified on one side and occluding lens on the other side. Flip the instrument over and you get the same power but minus lens and occluding lens on the alternate side.