Diffractive properties of the Diffrax bifocal contact lens.

We have verified that the Pilkington Diffrax lens behaves optically as a diffractive bifocal contact lens. The longitudinal chromatic aberration of the lens is similar to that predicted by theory, both on and off the eye. The over-refraction with the lens on the eye is similar to the distance subjective refraction, which is also as predicted.