Tech. Sgt. Mark Slater, 28th Medical Operations Squadron optometry NCO in charge, administers a corneal topography exam on Airman 1st Class Charles Wood, 28th MDOS patient travel administrator, during a health evaluation at Ellsworth Air Force Base, S.D., March 15, 2013. Corneal topography is used to identify early stages of some corneal diseases by analyzing the elevation and curvature of the surface of the cornea. (U.S. Air Force photo by Airman 1st Class Zachary Hada/Released)