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J. Schwiegerling, J. Choi; Through-Focus Measurement of the Optical Transfer Functions of Diffractive and Zonal Refractive Intraocular Lenses. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5272.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the optical performance of various multifocal intraocular lenses (IOLs) for different object vergences.
We fabricated an artificial eye with clinical levels of spherical and chromatic aberration. The model contains a saline-filled wet cell into which various IOLs can be mounted. A narrow slit was imaged through the eye model and captured with a CCD array. The resultant line spread function was Fourier transformed to calculate the Modulation Transfer Function (MTF). A Badal lens is used to create different object vergences. In this manner, we can examine through-focus optical performance of various IOLs. Three diffractive multifocal IOLs (Alcon ReSTOR aspheric, AMO Tecnis ZM900, Acri.Tec Acri.LISA), as well as the AMO ReZoom zonal refractive multifocal were measured. To simulate different lighting conditions, the study was done with 3 and 6 mm pupil sizes. Object vergences from 0 to -5 diopters were explored in 0.25 diopter steps. The MTF was evaluated at 15 cyc/deg for each of these positions.
For the three diffractive lenses, the performance is similar for the 3 mm pupil. For small pupils, the modulation is nearly evenly split between the distance and near vision, with the Acri.LISA biased slightly to distance vision. The ReZoom lens has higher modulation for distance vision, but negligible performance for near vision the 3mm pupil. For 6 mm pupils, both the ReZoom and ZM900 have equally split performance between distance and near vision. The Acri.LISA performance remains slightly biased to distance vision and the ReSTOR aspheric dramtically enhances distance performance.
The MTFs of these lenes illustrate different design philosophies for multifocal lenses. The ReZoom provides almost no benefit to near vision for bright lighting conditions due to a limited number of refractive rings falling over the pupil. For larger pupil sizes, the performance with the ReZoom is split between distance and near vision. Both the ZM900 and the Acri.LISA are full aperture diffractive lenses meaning the near and distance performance remains constant for different pupil sizes. The ZM900 equally splits the performance between distance and near vision, while the Acri.LISA is slightly biased to distance vision. The ReSTOR aspheric is an apodized diffractive transitioning from a pure diffractive under small pupils to a diffractive/refractive structure for large pupils. The effect of the apodization is to equally split performance between distance and near vision for small pupils and dramatically enhance distance performance for large pupils.
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