Interpupillary distance has been defined by various authors as the distance between the centres of the pupils in millimetres. It is abbreviated as PD, or more correctly, IPD. IPD is the most important interorbital parameter for measuring the distance between the eyeballs. It has been reported to be gender and age specific It also differs between certain racial groups and between near and far viewing.The clinical importance of IPD is to facilitate the correct positioning of ophthalmic lenses before the eyes to eliminate unwanted strain on the eyes due to induced prismatic effects from the lenses.