Purpose 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. Design Retrospective data review. Methods 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. Results 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. Conclusions 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. Financial Disclosure Proprietary or commercial disclosures are listed after the references.
Bibliographical noteFunding Information:
Data analysis and the preparation of this manuscript were supported with an investigator-initiated research grant to Ocular Surgical Data, LLC, from Alcon Laboratories, Inc., Fort Worth, Texas USA (IIT: 23134697).