Master Sgt. Mark Slater, 28th Medical Operations Squadron NCO in charge of optometry, administers a corneal pachymetry test to Airman 1st Class Jordan Fishburn, 28th Logistics Readiness Squadron aircraft parts store technician, during a pre-operation procedure in the optometry clinic at Ellsworth Air Force Base, S.D., Oct. 24, 2014. As part of pre-operation procedures, the test measures the thickness of the cornea and allows surgeons to examine the layout of their patient’s eyes to identify defects. (U.S. Air Force photo by Senior Airman Zachary Hada/Released))