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H. Zhao, M. A. Mainster; The Effect of Chromatic Dispersion on Intraocular Lens Performance. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3141.
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© ARVO (1962-2015); The Authors (2016-present)
Clinical performance of intraocular lenses (IOLs) is limited by monochromatic and chromatic aberrations. Chromatic aberration is caused by chromatic dispersion, which can be characterized by its Abbe number. This study examines how an IOL’s chromatic dispersion affects ocular performance at different optical wavelengths and spatial frequencies.
Photopic polychromatic modulation transfer functions (MTFs) were computed for a Tecnis aspheric IOL using the Zemax optical design program and the Holladay-Piers average cornea eye model. Abbe numbers for current IOLs were measured with an Abbe refractometer. MTF sensitivity analysis was performed keeping all eye model parameters invariant except for (1) IOL Abbe number or (2) IOL material. The radius of curvature of the anterior IOL surface was chosen to provide zero spherical aberration of the eye for all materials. Calculations were performed with and without high pass spectral filters.
Total chromatic difference in refraction between 380 and 700 nm decreases with increasing Abbe number, due largely to contributions of wavelengths below 500 nm. Photopic MTFs depend on Abbe number and pupil diameter. Photopic polychromatic MTF performance for a particular Abbe number generally decreases (1) with increasing spatial frequency for the same optical wavelength or (2) with increasing or decreasing difference in optical wavelength from 555 nm for the same spatial frequency. The magnitude of this decrease is greater with lower Abbe number materials. Spectral filters that attenuate short optical wavelengths improve optical performance more with low Abbe number materials. This improvement is too small to be clinically significant.
Chromatic dispersion affects IOL optical performance, particularly at high spatial frequencies. Optic materials with higher Abbe numbers (lower chromatic dispersion) provide better polychromatic MTF performance. Photopic polychromatic MTF performance is best at 555 nm, generally decreasing at higher or lower wavelengths and with increasing spatial frequency. Chromatic dispersion is more significant than spectral filtering in the clinical performance of IOLs.
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