Acuity
U.S. Air Force Tech. Sgt. Crystal Foster, 23d Medical Group optometry technician, takes the visual acuity of Staff Sgt. Teranyeli Brook, 23d Medical Group NCO in charge of command support staff, Oct 22., 2013 at Moody Air Force Base, Ga. A visual acuity test measures clarity of vision and is used to determine if a patient requires corrective lenses. (U.S. Air Force photo by Airman 1st Class Sandra Marrero/Released)