The term RELATING TO VISION can be summarized by two crossword solutions: OPTIC (5 letters) and OPTICAL (7 letters). OPTIC is an adjective that refers to the eye or vision, while OPTICAL is an adjective that refers to the science of light and vision. Both terms are related to the field of optics, which is the study of the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it.