Comparison of Methods to Predict Residual Astigmatism After Intraocular Lens Implantation

PURPOSE: To evaluate and compare the accuracy of three toric intraocular lens (IOL) calculators using keratometry measurements derived from the anterior corneal curvature and direct measurements of the posterior corneal curvature. METHODS: Postoperative corneal astigmatism was measured by the IOLMaster (Carl Zeiss Meditec, Jena, Germany) and Pentacam (Oculus Optikgerate, Wetzlar, Germany). The data were processed by the Alcon, Holladay, and Barrett toric IOL calculators. The error in predicted residual astigmatism (PredRA) was calculated by subtracting the PredRA from the postoperative subjective refraction by vector analysis. RESULTS: The centroid errors in PredRA were againstthe-rule (ATR) with the Alcon (0.56 diopters [D]) and Holladay (0.55 D) toric calculators using the IOLMaster (Carl Zeiss Meditec, Jena, Germany) measurements. The centroid errors in PredRA were lower when Pentacam (Oculus Optikgerate, Wetzlar, Germany) measurements were used (0.38 D, ATR). The Barrett toric calculator using the IOLMaster measurements had the lowest centroid errors in PredRA (0.02 D, P <.001) and achieved the most accurate results: 75.8% and 92.9% of eyes were within 0.50 and 0.75 D of the PredRA, respectively. CONCLUSIONS: The prediction of the postoperative astigmatic outcome can be improved by using appropriate methods of adjustment for posterior corneal astigmatism.