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Huawei Zhao, Martin A. Mainster; Ghost Images And Retinal Image Quality In Pseudophakic Eyes. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6184.
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IOL optical design and optic material determine the quality of primary pseudophakic images as well as the axial location and intensity of ghost images from cornea, IOL and retinal reflections. We analyzed the different possible ghost images in pseudophakic eyes and their potential effects on primary retinal image quality.
Automated Monte Carlo optical analysis was used to analyze primary pseudophakic optical images and the ten possible secondary ghost images formed from reflective pathways in pseudophakic eyes. Optical transfer and point spread functions were calculated using the refractive indices of common optic materials and standard retinal reflectance data. Ghost image size, form, intensity, and location (with corresponding defocus power) were determined for monochromatic and polychromatic light in pseudophakic eyes with different dioptric power IOLs. Alternative criteria were studied for determining whether ghost images are potentially visible and/or degrade primary image quality.
Ghost images in the pseudophakic eye are generated by combinations of reflections off cornea, IOL and retinal surfaces. Ocular media reflections are largely wavelength independent in visible spectrum, but fundus reflectance increases with wavelength, accounting in part for the largely wavelength-independence of intraocular straylight. One optically-significant ghost image arises from fundus reflectance which in turn is retroreflected back to the retina from the anterior surface of the IOL. Pseudophakic visual quality degradation and dysphotopsia from ghost images depends on their axial location, size (and therefore apparent luminance) and form.
Most pseudophakic ghost images are dim, far from the retina and visually insignificant. Higher refractive index optic materials increase IOL reflectance, producing brighter ghost images that potentially reduce pseudophakic visual image quality, particularly in eyes with low dioptric power IOLs.
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