Complex sentence: In a photograph of a child's face, red-eye in one eye but not the other may actually be leukocoria, which may be caused by the cancer retinoblastoma, and the child's eyes should be examined by a general physician.
Split into simpler sentences: In a photograph of a child's face, if there is red-eye in one eye but not the other, it may be leukocoria, which may be caused by the cancer retinoblastoma. The child's eyes should be examined by a general physician.