U.S. Air Force Capt. (Dr.) William Catt, 99th Aerospace Medicine chief of aerospace optometry, dials in a phoroptor at the Optometry Clinic in the Michael O'Callaghan Federal Medical Center June 7, 2013, at Nellis Air Force Base, Nev. The phoroptor is commonly used by eye care professionals during eye examinations to determine their eyeglass prescription. (U.S. Air Force photo by Senior Airman Daniel Hughes)
Senior Airman Daniel Hughes
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