Analysis of the optical performance of presbyopia treatments with the defocus transfer function.

PURPOSE: A variety of techniques for treating presbyopia are available. However, these techniques are often disparate in the mechanisms used to cope with the lack of accommodation. Multizone-refractive, diffractive, and apodized intraocular lens technologies are currently being used. This article evaluates the optical performance of these markedly different technologies in a simple and comparable manner.

METHODS

The Defocus Transfer Function is a mathematical technique for illustrating the Optical Transfer Function for all levels of defocus. By calculating the Defocus Transfer Function, the simulated performance of presbyopia correction technologies on distance, intermediate, and near vision can be evaluated simultaneously. Simulations of an opaque annular ring, a zonal refractive lens, a full-aperture diffractive lens, and an apodized diffractive lens are analyzed at pupil sizes of 3, 4, and 6 mm with this technique.

RESULTS

The opaque annulus begins to act like a Fresnel amplitude zone plate for small pupils. The diffractive lens technologies had sharp optical performance at two distinct foci with a shift in performance from balanced to distance-biased for the apodized diffractive lens. The zonal refractive lens exhibited a multifocal effect. However, the optical performance of this technology fell below that of the diffractive lenses.

CONCLUSIONS

The Defocus Transfer Function is a useful tool for analyzing presbyopia treatments. Different strategies for creating simultaneous vision or extended depth of field are easily compared. It may also be possible to reverse this technique to create an ideal pupil function that meets a desired multifocal performance specification.