What are dioptric and non-dioptric lenses?Dioptric lenses are prescription lenses. They have powers (called dioptres or ‘D’), and are used to correct vision fornearsighted and farsighted people.Non-dioptric lenses are for cosmetic use only; they enhance or change the colour of the iris. A prescription isn’tneeded for non-dioptric lenses, but they should still be fitted by an optician to find the correct base curve and to makesure contact lens wearing is suitable for the individual.