Optometry office
U.S. Air Force Maj. Justin Holbrook, 31st Aerospace Medicine Squadron optometrist, switches between various lenses during a test chart evaluation, March 16, 2015, at Aviano Air Base, Italy. The test chart evaluates each individual eye to determine their prescription, and then assesses both eyes together. The test uses the Snellen chart, which displays a series of letters to the patient differing in size. (U.S. Air Force photo by Airman 1st Class Deana Heitzman/Released)