Optics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.
Optometry is a health care profession which involves examining the eyes and applicable visual systems for defects or abnormalities as well as the medical diagnosis and management of eye disease. Traditionally, the field of optometry began with the primary focus of correcting refractive error through the use of spectacles. Modern day optometry, however, has evolved through time so that the education curriculum additionally includes intensive medical training in the diagnosis and management of ocular disease in countries where the profession is established and regulated.
Why has not man a microscopic eye? For this plain reason, Man is not a Fly. Say, what the use, were finer optics giv'n, T' inspect a mite, not comprehend the heav'n?
Alexander Pope, An Essay on Man (1733-34), Epistle I, line 193.