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Extending depth of focus with a 1 ring diffractive technology


Purpose: To describe a new design to extend depth of focus in the pseudophakic eye and to compare the optical and visual performance provided by this design to that of a monofocal IOL.

Methods: The new design consists of an aspheric anterior optic to compensate corneal spherical aberration and a single diffractive ring on the posterior optic. Optical properties of this design and a monofocal lens that compensates for corneal spherical aberration were evaluated in different pre-clinical settings. Through focus MTF for different spatial frequencies and USAF pictures for a 3mm pupil in white light were measured using an optical bench. In addition, best focus contrast sensitivity (CS) was measured in white light in five subjects using a binocular adaptive optics visual simulator (BAOVS) when the phase profile corresponding to each IOL design was induced bilaterally. CS was measured using the q-CSF procedure with a 4.5mm pupil under mesopic conditions, and evaluated at 1.5, 3, 6 and 12 cpd.

Results: USAF pictures showed that the new lens design extends depth of focus up to -1.5D in the spectacle plane and that it provides a good image quality over a larger range of defocus than the monofocal design. The area under the MTF (MTFa) integrated up to 50cpmm increased by 26% with respect to the monofocal lens at -1.5D and decreased by 18% for distance vision. However, CS for far was not statistically different between both models for any of the spatial frequencies evaluated, except for the highest spatial frequency evaluated (12cpd was 1.18±0.10 vs 1.06±0.04logCS for the monofocal and new design, respectively).

Conclusions: The optical quality and visual performance provided by a new diffractive IOL designed to extend the depth of focus were compared with a monofocal IOL that corrects corneal spherical aberration. Binocular visual simulation and preclinical data showed that the new design improved visual performance at intermediate and provides similar CS to a monofocal IOL at distance.

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