This testing may be recommended by your eye doctor for a variety of reasons. It is a painless test that involves sitting in front of a machine to obtain a non-invasive image or map of the front surface of the eye (cornea). Advanced tomography testing can capture a 3-D image that includes both the front and back surface of the cornea. This can be very important in early diagnosis and treatment of certain eye conditions as well as a screening tool for refractive and cataract surgery. It may also be used as an adjunct tool for specialty contact lens fitting