Abstract
Purpose :
To compare PreOperative IOL Master(IOLm) and Corneal Topography(CT) Ks and PostOperative(PO) results. We also seek to understand some of the factors resulting in outcomes not predicted preoperatively, at the time of toric IOL selection.
Methods :
Retrospective review of 50 Toric IOL eyes, comparing IOLm vs CT values. All patients underwent cataract extraction with LenSx laser assisted surgery and received a 20 degree laser astigmatism correction, performed at the steepest meridian.
PO goal was defined as: +/- 0.50D and < 10 degrees of axis. Failure was defined as: cylinder >0.50D, and/or off axis >10 degrees. Failure were also categorized as Under-Correction (UC) or Over-Correction(OC). Factors assessed included: type of Astigmatism(Ast) corrected, High Ast >2.5D, intraoperative aberrometry (ORA) measured with LenSx and Posterior Ast(PA) measured with Pentacam.
Results :
When comparing IOLm vs CT: cylinder differed by > 0.50D in 36% of cases, and axis differed by > 10 degrees in 32% of cases. 58% of cases reached PO goal of cylinder < 0.50D and axis < 10 degrees. 16% of the cases where found to be UC, with 88% having preoperative ATR Ast. 26% of the cases where OC, with 86% having preoperative WTR Ast. High Ast accounted for 25% of UC, and 29% of OC. ORA underestimated 25% of the UC cases, and ORA suggested and insufficient decrease in 14% of OC. PA accounted for 88% of UC, and 86% of OC, resulting in the most influential factor for improving IOL selection.
Conclusions :
IOLm uses partial coherence interferometry, where as CT uses placido-based technology, both measurement devices do not factor in PA. Pentacam uses scheimpflug technology and has been found to accurately assess anterior and posterior corneal Ast. This study shows that the influence of PA, most commonly resulted in less than optimal toric IOL selection. Our results also demontrate UC of ATR Ast, along with OC of WTR Ast. Our data supports the concept of factoring PA into toric IOL selection. These findings have been described in the literature and have become well accepted. Koch et al., proposed a nomogram, and suggested that 0.5 D should be subtracted in WTR Ast and 0.3 D should be added for ATR Ast. More studies are needed to solidify these ideas, and compare the accuracy of measuring PA with different devices.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.