Methods for investigating optical characteristics of bifocal diffractive-refractive intraocular lenses

Peculiarities of designing and determining the refraction (lens power) and the diffraction efficiency of bifocal hybrid (diffractive-refractive) intraocular lenses (IOL)—implants—are considered. Methods for designing the refractive IOL for near and far vision are analyzed and compared by means of measuring the focal lengths in the air and medium. It is shown that in investigating the hybrid lenses it is more convenient to estimate the conformity of the profile height with the designed value from the relationship of intensities of the 1st and 2d diffraction orders in the air and of the zero and 1st orders in the medium. Admissible errors of measurements and deviations of the hybrid IOL parameters are determined and used for calculating the refraction and diffraction efficiency.