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Huawei Zhao, Marrie Van der Mooren, Patricia A Piers; Optical ensemble analysis of a toric IOL using two different methods of optical modeling in realistic pseudophakic eyes. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2718.
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© ARVO (1962-2015); The Authors (2016-present)
The efficacy of a toric intraocular lens (TIOL) in pseudophakic astigmatic eyes can be degraded due to the post-operative cylindrical axial misalignment (CAM) of the implanted TIOL from the intended orientation. This paper evaluates the effect on visual outcomes predicted using two different methods of optical modeling.
Two methods of modeling the effects of CAM were compared. The method1 follows the optical ensemble analysis methodology (Zhao, Opt. Lett. 2009) and the method2 is the physiological average corneal eye model (Piers, Opt. Lett. 2004) both implanted with a common aspheric TIOL. Clinically relevant distributions of CAM and corneal astigmatism (in both methods) and high order aberration (HOA up to 4th order, Wang, JCRS 2003) (in method1) were further included by Monte Carlo sampling. These models are used to artificially assemble 2 groups of 100 realistic pseudophakic astigmatic eyes in ZEMAX (v15.5, ZEMAX LLC, Washington). For simplicity, all TIOLs are 20D+4D cylinder, matching the astigmatic cornea of about 2.9D cylinders. The MTF and visual Strehl ratio (VSR) values at best focus in white light were calculated. Pupil size of 3.5 and 5.0 mm in diameter was set for photopic and mesopic light respectively. MiniTab (v16.5, MiniTab) was used for group statistical analyses. A p value of 0.05 was set for statistical significance.
The mean ocular spherical aberration was not significantly different in both groups (p>0.05) while the mean trefoil and coma aberrations were significantly different (p<0.05). With the CAM of 3.5±2.4 o (average ± 1 standard deviation), the refractive cylinder was 0.57±0.12D and 0.64±0.15D for groups 1&2 respectively (p>0.05). For both pupil sizes the significant higher mean MTF value was found in favor of group1 (p<0.05) at 30 cycles per degree. For 3.5mm pupil size, the significant higher mean VSR value was found in favor of group2 (p<0.05). For 5.0mm pupil size, the mean VSR in both groups were essentially zero.
The image quality of the TIOL with different CAM depends not only on residual refractive cylinder but also on the distribution of ocular HOAs. The use of more physiologically eye models shows that the centered optical performance is important in determining how much rotation can be present before the visual acuity provided by the Toric IOL is significantly reduced.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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