Residual astigmatism after toric intraocular lens implantation: Analysis of data from an online toric intraocular lens back-calculator

Abstract

To evaluate some possible causes for residual astigmatism after toric intraocular lens (IOL) implantation based on an analysis of data from an online toric IOL back-calculator. Retrospective data review. An online toric back-calculator was designed to allow users to input preoperative toric planning information along with postoperative IOL orientation and refractive results. These were then used to determine the optimum orientation of the IOL to reduce refractive astigmatism. The collected aggregate data were extracted from this calculator to investigate the associated reasons for residual astigmatic refractive error with toric IOLs. The study analyzed 12 812 records with a mean postoperative refractive astigmatism of 1.89 diopters (D). Refractive astigmatism was significantly higher with higher IOL cylinder power (P<.01) but was not different by IOL manufacturer. Ninety percent of IOLs were not at the ideal orientation, despite 30% being at the preoperative calculated orientation. Misalignment showed a directional bias for some IOLs but not for others. The mean calculated percentage reduction in residual cylinder after reorientation was 50%±31% (SD), with the magnitude of residual astigmatism after IOL reorientation expected to be 0.50 D or less in 37% of eyes (4835/12 812). Expected outcomes were significantly different by IOL type. Analysis of data from the online toric back-calculator provided insights into the nature of residual astigmatism after toric IOL implantation. The reasons for residual astigmatism in this data set varied by IOL type. Proprietary or commercial disclosures are listed after the references.