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H. Zhao, M. A. Mainster; Anterior vs. Posterior Surface Diffractive Optic Element Placement and Optic Material Selection Affect Multifocal Intraocular Lens Performance. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5723.
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The performance of diffractive multifocal IOLs (MFIOLs) depends on the design and location of their diffractive optic elements (DOEs) in addition to the properties of their optic materials and refracting surfaces. We used optical ensemble analysis (OEA) to compare the performance of contemporary anterior or posterior surface MFIOLs.
An integrated Monte Carlo analysis (OEA) was used to determine the overall optical performance of a population of 100 pseudophakes with MFIOLs, computing modulation transfer functions (MTFs) for near and distance vision over clinically-relevant values (normal distribution) of an ensemble of ocular parameters. Additional analyses of MFIOL diffraction and DOE projection were performed to investigate MFIOL dysphotopsias. Optical performance was compared (1) for idealized MFIOLs that differ only in whether equivalent DOEs are located on the anterior or posterior surfaces of high or low chromatic dispersion optic materials and (2) for MFIOLs in current use.
Near and distance visual performance in diffractive MFIOL pseudophakic populations depend on the same parameters proven to be significant for monofocal IOL populations, in addition to DOE design and placement. Aspheric MFIOLs outperform spherical ones. MFIOLs fabricated from higher Abbe number, lower chromatic dispersion, lower refractive index optical materials provide better pseudophakic visual performance than higher refractive index MFIOLs that have greater chromatic aberration. DOE placement and design affects the characteristics of MFIOL dysphotopsias, which are more likely to occur with apodized anterior IOL surface DOEs than non-apodized posterior surface DOEs.
Optical ensemble analysis provides results consistent with published findings in large clinical trials of monofocal pseudophakes. Its results for multifocal pseudophakic populations are also consistent with clinical data, demonstrating both the value of reduced monochromatic and chromatic aberrations and advantages of posterior over anterior IOL surface diffractive optical elements.
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