Testing the vision
ANDERSEN AIR FORCE BASE, Guam - Tech. Sgt. Joshua Karash, 36th Medical Operations Squadron optometry technician, uses the phoropter to measure the refractive error to determine the patient’s prescription needed July 18. By changing these lenses, the technician is able to find the necessary prescription to correct a person's refractive error. (U.S. Air Force photo by Senior Airman Carlin Leslie/Released)