The term 'PERTAINING TO VISION' can be summarized by the crossword solution 'OPTIC, ' which is a five-letter word. OPTIC refers to the eye and vision, and is derived from the Greek word 'optikos, ' meaning 'of or relating to sight.' It is used to describe anything related to the eye, such as the science of optics, which studies the behavior and properties of light, or an optical device, such as a telescope or microscope.