Both a retinal scanner and an iris scanner take rapid photos of the eye, but a retinal scanner takes photos of the retina while an iris scanner takes photos of the iris. Both the iris and the retina have unique patterns that are different even in identical twins. While a retinal scan requires a person to put their eye up to an eye piece for about thirty seconds,an iris scan only requires a quick snapshot of the eye and does not require a person to put their eye up to any eyepiece.