The term 'EYE-PART PREFIX' can be solved by the 5-letter word 'IRIDO'. This word is derived from the Greek word 'iridos', which means 'RAINBOW'. It is a prefix used to refer to parts of the eye, such as the iris, which is the colored part of the eye that controls the amount of light entering the pupil. It is also used to refer to the ciliary body, which is the muscular structure that helps to adjust the shape of the lens for focusing.