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C. D. Pinto; Effects of On-eye Correction of Spherical Aberration Versus Soft Contact Lens Decentration: A Simulation Study. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1572.
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© ARVO (1962-2015); The Authors (2016-present)
To theoretically evaluate and compare the performance of soft contact lenses for different on-eye decentration states, at several spherical aberration levels, representative of a wide patient population.
Starting from the baseline (decentered ) Liou-Brennan (1997) eye model (OD), a -3.00 Diopter eye was prepared using Zemax® ray tracing software, at a 6.00mm pupil size. This eye was then fitted with soft contact lenses in a fashion as to correct ametropia and leave a controlled level of overall Spherical Aberration (Z400) on the whole system, between -0.2um and +0.2um. Those fitted systems then had their contact lens corrections equally decentered on a grid of 2100um x 2100um from the geometrical center of the eye in the fashion described by Greivenkamp and Schwiegerling (1995).Resulting eye models were then analyzed for Tangential and Sagittal MTF, Horizontal (Z310) and Vertical (Z311) Coma, Spherical Aberration (Z400) and for the Salvador Image Quality metric (SIQ), first introduced at ARVO 2008. Variables of interest were then 2-D plotted versus decentration values and analyzed spatially for trends.
Horizontal Coma (Z310) has been demonstrated to be the worst aberration culprit to image quality degradation, according to our models. Moreover, systems with overall positive spherical aberration (> +0.1um) have shown the highest degree of sensitivity to decentration and highest likelihood of poor image quality in most grid positions for the soft contact lens. Best results were shown to be at small negative spherical aberration level (~ -0.05um), where 87.6% of the patients would be likely to achieve an SIQ quality factor of 0.6 or higher, on a scale of zero (0) to one (1).
In addition to correcting refraction errors (Defocus), Spherical Aberration correction may enhance visual quality for most of the ametropic population. This data suggests further study should be pursued to evaluate the application in a customized visual correction solution.
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