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Jonathan He, Rajaraman Suryakumar; Simulating Defocus Curve for Monofocal Intraocular Lenses (IOL) with Different Spherical Aberrations. Journal of Vision 2016;16(4):16-17. doi: 10.1167/16.4.7.
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Purpose: To evaluate how spherical aberration affects defocus curve and depth of focus in pseudophakic eyes with monofocal IOLs implanted.
Methods: One-hundred virtual eyes were generated based on a two-surface model eye including corneal and IOL surface profiles. Ocular biometry including corneal aberrations and power anterior chamber depth and pupil size was adopted from literature data for the purpose of combining the two surfaces. Light-in-the-bucket (LIB) metric was computed from point spread function of individual virtual eye. Three monofocal IOLs with spherical aberrations of +0.17μm (ACL#1), +0.08μm (ACL#2) and −0.20μm (ACL#3) were evaluated using the two-surface model and LIB metric at defocus ±2.0D. After correlating simulated LIB metric to clinical visual acuity of ACL#1, a calibration function was generated and applied to ACL#2 and ACL#3.
Results: Monocular visual acuity and LIB metric was best correlated using an exponential function: VA = 0.48*e^(−0.17*lnLIB)−0.60. By applying the calibration function, monocular defocus curves for all the three lenses can be simulated. Prediction error for ACL#2 between simulated and clinical visual acuity within defocus of ±2.0D was all smaller than 0.10 logMAR. Simulated intermediate logMAR visual acuity at −1.5D was 0.32 (ACL#1), 0.33 (ACL#2) and 0.38 (ACL#3). Depth of focus defined using 0.2 logMAR as cut-off was 1.05D (ACL#1), 0.98D (ACL#2) and 0.96D (ACL#3), all of which differences are less than 0.25D.
Conclusions: The two-surface model eye and LIB metric are useful in predicting clinical defocus curve. Simulated results suggest by adding positive spherical aberration in IOLs will hardly extend depth of focus to a clinically significant level.
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