Long-term stability, efficacy and residual astigmatism after AcrySof Toric IOL implantation

Objective  To evaluate the long-term stability, efficacy, characteristics of residual astigmatism after AcrySof Toric intraocular lens (IOL) implantation and the correlation between residual astigmatism and IOL tilt.

Methods  An observational case-series study was conducted. Thirty-three patients (50 eyes) who underwent phacoemulsification combined with AcrySof Toric IOL implantation for cataract and concurrent corneal astigmatism at the Eye Hospital of Wenzhou Medical University, Hangzhou Branch, from June 2012 to December 2020 were enrolled. Parameters including preoperative corneal astigmatism, total ocular astigmatism within 1-3 months postoperatively, and long-term outcomes over 2 years postoperatively such as visual acuity, corneal astigmatism, total ocular astigmatism analyzed, IOL tilt, decentration and axis orientation were collected and analyzed. The postoperative residual astigmatism was calculated, and its correlation with the IOL tilt was analyzed. This study adhered to the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of Eye Hospital of Wenzhou Medical University (No. H2022-022-K-22). Informed consent was waived for this study as it involved only the analysis of pre-existing, de-identified data.

Results  Long-term mean total ocular astigmatism after AcrySof Toric IOL implantation was (0.60±0.46)D, which was significantly lower than the preoperative (1.70±0.92)D, with a statistical difference ( t=12.900, P<0.001). During postoperative 1-3 months and long-term follow-up, the proportions of eyes with total ocular astigmatism ≤0.50 D were 58% (29/50) and 48% (24/50), respectively, while those with ≤0.75 D were 84% (42/50) and 78% (39/50), showing a slight decline in the corrective effect with no statistical difference ( χ ²=1.004, 0.585; P=0.316, 0.444). The centroid of the change in corneal astigmatism from preoperative to long-term postoperative was 0.20 D@27°, with a statistical difference compared with zero vector ( T ²=13.442, P=0.003). In terms of stability, the average misalignment of Toric IOL at long-term follow-up was (3.40±2.88)°, with ≤5° in 82% (41/50) and ≤10° in 96% (48/50) of eyes. The mean tilt of the Toric IOL was (3.46±1.67)°, and the mean decentration was (0.22±0.14)mm. Residual astigmatism at the long-term follow-up after Toric IOL implantation was (0.67±0.45)D with a vector centroid of 0.21 D@159°. A moderate positive correlation was observed between the tilt direction of Toric IOL and the direction of residual astigmatism ( r=0.494, P<0.001).

Conclusions  AcrySof Toric IOL implantation demonstrates good long-term stability and can effectively correct preoperative corneal astigmatism. The change in corneal astigmatism from preoperative measurements to long-term postoperative follow-ups is relatively minor and has a minimal impact on the long-term outcomes. The direction of residual astigmatism is partially correlated with the tilt direction of the IOL.