Senior Airman Randolph Callender, 36th Medical Operations Squadron optometry technician, left, uses a pupilometer to measure the distance between the pupils of Tech. Sgt. Jeremy Foster, 36th MDOS optometry technician, Jan. 27, 2016, at Andersen Air Force Base, Guam. The pupilometer is used in place of a millimeter ruler for fitting eyeglasses. (U.S. Air Force Photo/Airman 1st Class Jacob Skovo)