Visualization of the optical path of the diffractive multifocal Tecnis ZM001 IOL compared to spherical diffractive and refractive multifocal lenses

Background: A method is developed to demonstrate how implanted diffractive multifocal IOLs process the light they receive from the cornea.

Methods: Monochromatic green light is projected through a model eye with a physiological cornea in front of the IOL. The converging bundle of light leaving the IOL is visualized. Also a US-Airforce target is projected through the model eye. The projected (retinal)image is captured with a CCD camera. The IOL's tested are the TECNIS ZM001 diffractive multifocal lens; a refractive multifocal lens (Array SA40N); a spherical diffractive multifocal lens (CeeOn 811E) and 2 monofocal lenses.

Results: The converging light bundle of a diffractive lens mainly consists of 2 different light bundles, that are refracted/diffracted to 2 focal points independent of pupil size. The light bundle coming from a refractive multifocal lens consists of a number of small bundles coming from different refracting zones, that are refracted to 2 main focal points. At 5mm pupil size the projected US-Airforce target shows the best image quality for the TECNIS ZM001 lens. The quality of both far and near image of this lens is better than the image quality of a monofocal spherical IOL.

Conclusions: The functional difference of diffractive and refractive multifocal lenses is demonstrated in a physiological model eye by visualizing the light bundle after passing the IOL. Also an impression could be given of the difference in quality of the projected retinal images.