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A. C. Kingston, G. E. Altmann, P. Ludington; The Effects of Corneal Aberrations, Tilt and Decentration on Intraocular Lens Performance. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3341.
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© ARVO (1962-2015); The Authors (2016-present)
The aim of this study is to determine how corneal aberrations, and intraocular lens (IOL) tilt and decentration affect retinal image quality. The Tecnis Z9000, B&L LI61U and B&L SofPort AO IOL’s were investigated.
A Monte-Carlo simulation with (1000) trials was done to assess IOL performance in the presence of corneal aberrations, and tilt and decentration of the IOL itself. Each lens was evaluated at a 3.0mm and 5.0mm pupil with photopic and scotopic lighting conditions, respectively. For each Monte-Carlo trial, a 20/20 convolved E was created and the area under the Modulation Transfer Function (MTF) curve was calculated. The convolved E was used to generate a pattern recognition score. The average pattern recognition score and area under the MTF curve were both used to predict the retinal image quality.
When the lenses were evaluated at a 3.0 mm pupil diameter, the amount of spherical aberration inherent in each IOL was small. As a result, the corneal aberrations, along with tilt and decentration of the lens itself, became the dominating factors of optical performance. Even with a reduction in spherical aberration, the SofPort AO yielded a better average pattern recognition score and area under the MTF curve than the Tecnis Z9000 or LI61U lenses. Also, on average the SofPort AO had less variability across the Monte-Carlo eye models, whereas the Tecnis Z9000 had the largest variability at both pupil sizes. For a pupil diameter of 5.0 mm, the average area under the MTF curve for the SofPort and Tecnis IOL’s was approximately equal. However, the differences in pattern recognition scores between all three lens types became more evident. The pattern recogition scores showed that the SofPort AO performed better optically than the two lenses which have inherently larger spherical aberration.
As the pupil size increased the amount of coma and astigmatism produced by the decentered and tilted Tecnis IOL increased. This is due to the fact that the Tecnis IOL is a higher-order asphere. The presence of these two aberrations yielded lower average pattern recognition scores due to the asymmetric blurring of the convolved E’s and also a higher variability in scores across the (1000) trials. Since the SofPort AO lens is an aberration-free IOL it was less affected by the corneal aberrations, and the tilt and decentration of the lens itself.
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