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S. Ravikumar, A. Bradley, L. N. Thibos; Polychromatic Image Quality in Pseudophakic Model Eyes With Hybrid Diffractive Multi-Focal Intra-Ocular Lenses. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2424.
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Hybrid intra-ocular lenses with refractive and diffractive components have been developed for multi-focal ophthalmic use. Although the lens design generally involves one wavelength (550nm), pseudophakic patients live in a polychromatic environment. The polychromatic performance of these hybrid lenses depends on the interaction of the negative chromatic aberration (CA) of the diffractive component with the positive chromatic aberration of the cornea and the refractive component of the IOL. We have evaluated polychromatic image quality in a virtual pseudophakic eye (based on Indiana Eye) with hybrid diffractive/refractive intra-ocular lens implants.
Pupil plane wavefront maps were developed based upon diffractive lens designs and eye optical characteristics. Polychromatic point-spread functions were calculated by summing monochromatic PSFs at 10 nm intervals across the visible spectrum. Image quality was assessed for a range of pupil sizes and target vergences from +3 to -5 D (working distance range beyond infinity to 20 cm).
The polychromatic IQ metric "Light in the bucket" demonstrates that, with a 3.75 mm pupil diameter, the diffractive lens alone can suffer from a 25% decrease in polychromatic IQ at near focus compared to design wavelength (due to diffractive CA). However in the model pseudophakic eye, polychromatic retinal IQ at near focus is almost identical to monochromatic IQ at the design wavelength because the diffractive lens CA almost cancels the refractive CA of the IOL and cornea. Unlike the near image, polychromatic distance IQ does not benefit from CA canceling effect of the diffractive element. These results are highly dependent upon pupil size, specific lens design and the levels of monochromatic aberrations present in the pseudophakic eye.
Inclusion of a hybrid IOL with approximately +3D of add power essentially achromatizes the near image. Also, polychromatic analysis is essential to obtain the desired near/distance balance in retinal image quality.
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