Air Force Staff Sgt. Christina Forest uses lenses of various strengths. Air Force Staff Sgt. Christina Forest uses lenses of various strengths to determine a patient's eyesight prescription for new glasses in the town of El Tortuguero, El Salvador, on March 1, 2005. Forest is deployed to El Salvador from the 89th Medical Group, Andrews Air Force Base, Md., for a medical readiness training exercise. SHARE: Download: Full Size (0.07 MB) Credit: VIRIN: 112497-E-UUV03-959.jpg Photo Gallery