Surgically induced astigmatism after posterior chamber phakic intraocular lens implantation

Aim: To assess astigmatism induced after phakic intraocular lens (Visian ICL, STAAR Surgical) implantation. Methods: Seventy-three eyes of 47 patients undergoing ICL implantation through a horizontal 3.0 mm clear corneal incision were retrospectively examined. The amount of corneal astigmatism before and 3 months after surgery using an automated keratometer (ARK-700A, Nidek) and corneal topography (ATRAS995, Carl Zeiss Meditec) were quantitatively investigated. The surgically induced astigmatism was assessed by vector analysis using the Holladay-Cravy-Koch formula. Results: The corneal astigmatism was significantly increased from 1.10 (0.51) dioptres (D) to 1.44 (0.57) D using the keratometer (Wilcoxon signed-rank test, p<0.001). It was also significantly increased from 1.16 (0.53) D to 1.45 (0.57) D using corneal topography (p<0.001). On the other hand, the manifest astigmatism was significantly decreased from 0.93 (0.60) D to 0.72 (0.58) D (p<0.001). The surgically induced astigmatism was 0.45 (0.26) D at an axis of 93.3 degrees using the keratometer and 0.49 (0.26) D at an axis of 98.0 degrees using corneal topography. Conclusions: ICL implantation induces corneal astigmatism through a with-the-rule astigmatic shift of approximately 0.5 D, which was small but not negligible for candidates for refractive surgery.