Aim: To assess astigmatism induced after phakic intraocular lens (Visian ICLTM, STAAR Surgical) implantation.
Methods: We retrospectively examined seventy-three eyes of 47 patients undergoing ICL implantation through a horizontal 3.0-mm clear corneal incision. We quantitatively investigated the amount of corneal astigmatism before and 3 months after surgery using an automated keratometer (ARK-700A, Nidek) and corneal topography (ATRAS995TM, Carl Zeiss Meditec). 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 diopters (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° using the keratometer and 0.49 ± 0.26 D at an axis of 98.0° 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.