Eyeworld

Laser-assisted cataract surgery: Intraoperative OCT to predict lens position physical manifestation of the estimate of ELP. Instead, we would use only the three-dimensional morphology of the eye in an algorithm. OCT lens position study In a retrospective study of 120 consec- utive eyes, Scheimpflug images were examined an average of 4.5 months after LACS was performed, and the actual TLP was measured (Figure 1). We subsequent- ly also used swept-source OCT postop- erative imaging, which has confirmed and validated the Scheimpflug image results. The technicians performing these Germany) with a 3-variable multivariate formula, the Haigis formula, using ante- rior chamber depth and axial length, and data from the LENSTAR (Haag-Streit USA, Mason, Ohio), including lens thickness, using Olsen's formula. Because intraop- erative aberrometry relies on axial length segmentation for improved accuracy, in practice it is also highly dependent on the measurement of axial length. For this study, we proposed that we might not need axial length measure- ments to predict the postoperative actual measured true lens position (TLP) as a Three-dimensional morphology may offer advantages in predicting effective lens position B eyond improved safety, the main rationale that surgeons use for adopting laser-assisted cataract surgery (LACS) is the promise of improved accuracy. Effective lens position (ELP) is the most significant source of error in current intraocular lens power calculations. Al- though it has been theorized that refin- ing the capsulorhexis will improve ELP estimates, research has not yet clearly demonstrated improved accuracy. There are significant barriers to demonstrating an improvement: We refract subjectively in 0.25-D increments, resulting in an error of approximately 0.4 D; most lenses are only available in 0.5-D increments; there exist potentially significant differences between actual lens power and box labeling; and lens thickness varies between powers for any given model. Searching for solutions We explored whether there might be a better metric for outcomes analysis by taking advantage of intraoperative OCT to achieve improved predictions and demonstrate improved accuracy. To estimate ELP, we currently rely on axial-based measurements. Olsen's 5-variable multivariate formula for estimating ELP is a good example. To compare our OCT morphology-based technique, we looked at data from the IOLMaster (Carl Zeiss Meditec, Jena, by Joseph J. K. Ma, MD, FRCSC Figure 1. Postoperative Scheimpflug imaging (above) and swept-source OCT imaging (below) 2 Dr. Ma is assistant professor at the University of Toronto, Ontario, Canada. "Intraoperative three-dimensional OCT morphology may be superior to current axial-based formulas in predicting postoperative effective lens position. "

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