to evaluate the prediction error (PE) after applying the Abulafia-Koch formula in an online calculator with and without consideration of anterior corneal surgically induced astigmatism (SIA).
SIA models were calculated with a historical database of 204 right eyes (REs) from a single surgeon, either for manual (2.2 mm) or femtosecond (2.5 mm) temporal clear corneal incisions. PE was assessed in 58 REs operated by the same surgeon with a monofocal toric IOL, calculated considering the PCA estimation in an online calculator with the combination of each one of the following SIA calculation approaches: A) considering only significant centroids after stratification, B) all centroids after stratification and C) a single centroid without stratification.
The consideration of all centroids resulted in an underestimation of SIA in cases of preoperative against-the-rule astigmatism (ATR-A), and an overestimation in with-the-rule astigmatism (WTR-A). After stratification, SIA was only significant in preoperative ATR and oblique astigmatism cases for femtosecond incisions. PE considering PCA only was 0.03@160º. The combination with SIA resulted in a WTR-A surprise in preoperative ATR-A and WTR-A, however only being significant for preoperative ATR-A in calculation approaches B (0.29@84º) and C (0.21@80º). SIA addition to PCA estimation only reduced the centroid for oblique preoperative astigmatism.
Surgeons should consider the calculation of the SIA after stratification by astigmatism type when using the same incision location (i.e. temporal). However, SIA derived from the anterior corneal surface should not be combined with PCA estimation for IOL power calculations.