Aligning the Axis of Toric Intraocular Lens with the Corneal Steep Meridian by Setting SIA at 0 Diopter: A Prospective Randomized Controlled Trial

Purpose: This study aims to investigate the clinical efficacy of aligning the axis of toric intraocular lens (IOL) with the corneal steep meridian in cataract patients. Methods: This is a prospective randomized controlled trial involving seventy cataract patients who underwent implantation of a Tecnis Toric IOL. Patients were randomly divided into two groups. In the control group, the incision-induced surgically induced astigmatism (SIA) was set at 0.5 D, and the alignment axis was determined using the Tecnis Toric Aspheric IOL Calculator. In the experimental group, incision SIA was set as 0 D and the alignment axis was aligned with the steep meridian of corneal astigmatism. Primary outcome measures, including astigmatism vector analysis, incision SIA and error of refractive astigmatism (ERA) were analyzed. Visual acuity, predicted residual astigmatism (PRA) and residual astigmatism were evaluated at 3 months. Results: Measurements of postoperative uncorrected and corrected distance visual acuity (UDVA and CDVA), degrees of lens dislocation (°), incision-induced SIA, target induced astigmatism vector and actual surgically induced astigmatism showed no differences between the two groups (P > 0.05). The ERA of the experimental group (0.15 ± 0.32 D) was significantly smaller than the control group (0.58 ± 0.48 D) (P < 0.001). Vector analysis of total error vector (EV) was smaller in the experimental group (0.30 ± 0.24 D) than the control group (0.60 ± 046 D) (P = 0.001). The experimental group showed lower postoperative cylinder (0.49 ± 0.23 D) than the control group (0.71 ± 0.49 D) (P = 0.055). Conclusion: This study suggests that aligning the toric IOL axis with the corneal steep meridian showed by setting SIA as 0 D might be an available method to reduce the error of refractive astigmatism.