An eye exam may save your life. We can find everything from brain tumors to breast and lung cancers that have spread to the eye, says Joseph Pizzimenti, an optometrist and associate professor at Nova Southeastern University College of Optometry Eye Care Institute in Fort Lauderdale, Florida. Certain types of bleeding in the retina can signal leukemia. Eye doctors can diagnose brain tumors based on changes in a patient’s field of vision. Malignant melanoma can strike in back of the eye, and patients often don’t know it is there unless the cancer is in the very center of their field of vision, Pizzimenti says.