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Huawei Zhao; The tolerance analyses of cylindrical axial misalignment of a TIOL. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3104.
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© ARVO (1962-2015); The Authors (2016-present)
Toric intraocular lens (TIOL) has been proven safe and effective on correcting the astigmatic effects due to the corneal astigmatism in pseudophakic eyes. However this efficacy can be much degraded due to the post-operative cylindrical axial misalignment (CAM) of the implanted TIOL with the intended orientation. This study is to analyze the tolerance to the CAM based on optical image quality metrics and simulate the potential impact from the CAM for a TIOL with different optical designs.
A pseudophakic average corneal eye (ACE) model (Piers, et al, Opt. Lett. 2004) implanted with a mimicked TIOL was utilized in optical design software ZEMAX® OpticStudio™ 15.5 (ZEMAX LLC, Washington). The eye model has been further coupled with more clinical relevant variables including the corneal astigmatism and the CAM. The TIOL matching the corneal astigmatism has different optical designs coupled with different refractive index and ABBE number or equivalent in refractive, diffractive, or both in a monofocal or multifocal way. Based on the retinal l image quality metrics including modular transfer function (MTF) required for resolve an object with different spatial frequencies, corresponding tolerance levels to the CAM are calculated. The impact of CAM in photopic light is also simulated and calculated by sensitivity test and optical ensemble analyses (Zhao, Opt. Lett. 2009) by applying additional clinically observed statistics of the above variables.
The CAM impacts on the simulated image quality varied with the corneal astigmatism. The higher the corneal astigmatic power was, the more sensitive to the CAM and the more degradation by the CAM of the calculated MTF. For a given CAM and corneal astigmatic power, the more MTF degradation was found for the TIOL with lower material ABBE number. The CAM tolerance varied with the object spatial frequency, IOL material ABBE number or equivalent, and the corneal astigmatism. The smaller CAM tolerance was found with higher the spatial frequency or the corneal astigmatic power. The larger CAM tolerance was found with the higher material ABBE-number or equivalent by the IOL diffractive surface coupling.
The TIOL with different optical material and designs can have different tolerance to the CAM without significant image quality degradation. Choosing the TIOL with larger CAM tolerance can lead to more effectiveness of the corneal astigmatic effect reduction.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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