Toric intraocular lens orientation and residual refractive astigmatism: an analysis.

Purpose: To analyze intraocular lens (IOL) orientation data from an online toric back-calculator (astigmatismfix.com) for determining if differences were apparent by lens type.

Methods: A retrospective review of astigmatismfix.com toric back-calculations that included IOL identification and intended orientation axis.

Results: Of 12,812 total validated calculation records, 8,229 included intended orientation and lens identification data. Of the latter, 5,674 calculations (69%) involved lenses oriented 5° or more from their intended position. Using estimated toric lens usage data, the percentage of lenses with orientation ≥5° from intended was 0.89% overall, but the percentage varied significantly between specific toric lens brands (<0.05). The percentage of back-calculations related to lenses that were not oriented as intended was also statistically significantly different by lens brand (<0.05). When IOLs were misoriented, they were significantly more likely to be misoriented in a counterclockwise direction (<0.05). This was found to be due to a bias toward counterclockwise orientation observed with one specific brand, a bias that was not observed with the other three brands analyzed here.

Conclusion: The percentage of eyes with lens orientation ≥5° from intended in the Toric Results Analyzer data set was <1% of toric IOLs in general, with the relative percentage of Tecnis Toric IOLs significantly higher than AcrySof Toric IOLs. Both of these had higher rates than the Staar Toric and Trulign Toric lenses, with the availability of higher Tecnis and AcrySof cylinder powers a likely contributing factor. The AcrySof Toric IOL appears to be less likely than the Tecnis Toric IOL to cause residual astigmatism as a result of misorientation. The Tecnis Toric IOL appears more likely to be misoriented in a counterclockwise direction; no such bias was observed with the AcrySof Toric, the Trulign Toric, or the Staar Toric IOLs.