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Tom D Padrick, Nicole Fram, Robin Vann, Michael Breen; Comparison of 4 Methods of Toric IOL Cylinder Power Selection. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1151.
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© ARVO (1962-2015); The Authors (2016-present)
There is a need to improve refractive outcomes in cataract surgery when using toric IOLs. The purpose of this work is to compare the theoretical predicted post-op cylinder to the actual manifest cylinder for 4 different methods used to select the cylinder power of a toric IOL.
This is a retrospective analysis of data from 106 eyes obtained in a prospective randomized study comparing the Alcon on-line toric calculator (2014 version) to the ORA Intraoperative Aberrometry system (ORA System (Alcon, Fort Worth, TX)). All eyes were implanted with the Alcon SN6AT(x) toric IOL suggested by ORA. Preoperative biometry was obtained using the LENSTAR LS900. Pre op cylinder ranged from 0.64D to 4.11D. Post op manifest refraction was obtained between 21 & 35 days by a masked observer. The residual cylinder from the post op refraction was compared to the predicted residual cylinder by each method for the toric cylinder power implanted. In this analysis, only the preop biometry and post op manifest refraction from the Intraoperative Aberrometry arm of the study was used to evaluate and compare cylinder prediction error (CPE) calculated using the Alcon on-line toric calculator, the Holladay toric calculator, the Barrett toric calculator and the ORA Intraoperative Aberrometry system. It was assumed that for each method the IOL axis was perfectly aligned with the cylinder axis predicted by the method. Errors that may have occurred because the method predicted incorrect axes could not be evaluated in a retrospective analysis.
The cylinder prediction error (CPE) is defined as the post op manifest residual cylinder minus the formula predicted residual cylinder for the IOL implanted. We calculated and compared the Mean CPE, Median CPE, %CPE<=0.50D, %CPE<=1.0D and maximum cylinder CPE for each method. The table in Figure 1 list the results of this analysis. The ORA results were statistically better (p<0.05) in all cases except the Median Cyl PE compared to Barrett (p=0.051) and the %<=0.50D compared to Holladay (p=0.39) and Barrett (p=0.17).
The use of ORA intraoperative aberrometry for selection of the toric IOL cylinder power improved the cylinder refractive outcomes for all 5 metrics used in this analysis.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Figure 1. Comparison of cylinder prediction error for 4 methods used to select the cylinder power of a toric IOL.
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