Image quality with multifocal intraocular lenses and the effect of pupil size: comparison of refractive and hybrid refractive-diffractive designs.

PURPOSE

To analyze the image quality with a refractive and 2 hybrid refractive-diffractive multifocal intraocular lenses (IOLs) in vitro to determine the IOL modulation transfer function (MTF) following the EN-ISO international standard for distance and near vision and to study the IOLs' behavior with different pupil sizes.

SETTING

Fundación Oftalmológica del Mediterráneo, Valencia, Spain.

METHODS

This study evaluated 4 IOLs: the hybrid refractive-diffractive AcrySof ReSTOR SN60D3 (Alcon) and Tecnis ZM900 (AMO), the refractive ReZoom NXG (AMO), and the monofocal AcrySof SN60WF (Alcon). The MTF was calculated from the cross-line spread function recorded with the OPAL Vector System (Image Science Ltd.) using fast Fourier transform techniques. The artificial eye model simulated in vivo conditions of the anterior chamber and included an artificial cornea and physiological solution, in which the IOLs were positioned. The pupil sizes varied between 2.0 mm and 5.0 mm in steps of 0.5 mm.

RESULTS

For distance vision and small pupils (2.0 to 3.5 mm), the refractive IOL provided better image quality than the 2 hybrid IOLs. When the pupil was larger, the distance vision was similar with all IOLs. The 2 hybrid IOLs gave better image quality than the refractive IOL for near vision with any pupil size. With the refractive IOL and pupils smaller than 3.5 mm, near focusing did not occur, resulting in poor image quality. Of the hybrid IOLs, the AcrySof ReSTOR SN60D3 provided better distance image quality and the Tecnis ZM900 provided better near image quality.

CONCLUSIONS

The refractive IOL gave better image quality than the hybrid IOLs at distance and with small pupils. With pupils larger than 3.5 mm, the quality was similar. Hybrid IOLs gave significantly better image quality for near vision with all pupil sizes. AcrySof ReSTOR SN60D3 IOLs give better distance vision than Tecnis ZM900 IOLs; the latter gave better near vision. The reference monofocal IOL provided better distance images than any multifocal IOL with all pupil sizes.