Factor Analysis Affecting Undercorrection of Astigmatic Reduction in Toric Intraocular Lens (IOL) Implantation

Abstract

Purpose: : To analyze the factors affecting postoperative undercorrection of astigmatic reduction in Acrysof^® Toric IOL implantation in the cataract patients

Methods: : Medical records were retrospectively reviewed in 21 eyes of 21 patients who underwent phacoemulsification with 2.7 mm of clear corneal incision and implantation of the Acrysof^® Toric IOL (SN60T, Alcon) for less than 2.00 diopters (D) of corneal astigmatism. Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and manifest refraction were measured at 3 months after surgery. Expected residual astigmatism using default value (0.5D) of surgically induced astigmatism(SIA) of Toric Acrysof® calculator and the astigmatic outcome using the surgeon's real SIA (0.0D) were compared with postoperative actual astigmatism, respectively. Astigmatic reduction rate was also compared according to the mismatches of cylindrical powers and axis in preoperative measurements using automated keratometry, IOL master and topography. Postoperative change in the axial alignment was assessed.

Results: : All the 21 eyes showed significant improvement in UCVA and BCVA with significant reduction of astigmatism by 58.2%. Expected residual astigmatism using zero value of SIA was closer to the value of postoperative actual residual astigmatism than that using the default SIA (0.5D). Reduction rate was not significantly different depending on the preoperative mismatches of cylindrical powers or axis. Postoperative alignment changes were not significant over time.

Conclusions: : Toric IOL calculator tends to underestimate residual astigmatism, and the calculation with zero value of SIA appears to overcome the undercorrection of astigmatic reduction.

Keywords: cataract • intraocular lens • astigmatism