Rethinking the optimal methods for vector analysis of astigmatism

<jats:sec> <jats:title>Purpose:</jats:title> <jats:p>To evaluate the accuracy and usefulness of certain methods of analyzing astigmatic vectors.</jats:p> </jats:sec> <jats:sec> <jats:title>Setting:</jats:title> <jats:p>Cullen Eye Institute, Baylor College of Medicine, Houston, Texas.</jats:p> </jats:sec> <jats:sec> <jats:title>Design:</jats:title> <jats:p>Case samples.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods:</jats:title> <jats:p>Using 2 sample cases for analysis of corneal surgically induced astigmatism and an actual toric intraocular lens (IOL) case, univariate analyses from the ASSORT program were compared to double-angle plots of preoperative and postoperative astigmatism and prediction errors.</jats:p> </jats:sec> <jats:sec> <jats:title>Results:</jats:title> <jats:p>Certain univariate figures for analyzing the 2 sample cases were misleading. For the toric IOL case, some of the key outcome vectors were inaccurate.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions:</jats:title> <jats:p>ASSORT's univariate analysis of astigmatic vectors can be unpredictably erroneous and misleading. Recommended vector analyses should include double-angle plots with centroids and confidence ellipses of preoperative and postoperative astigmatism and the prediction errors, along with means and standard deviations of these vector magnitudes.</jats:p> </jats:sec>