Association between axial length and toric intraocular lens rotation according to an online toric back-calculator

AIM: To assess the relationship between axial length (AL) and intraocular lens (IOL) rotation among eyes receiving a tonic IOL and subsequently entered into an online tonic back-calculator database. METHODS: Retrospective analysis of data collected online via astigmatismfix.com, a freely available online toric back-calculator where surgeons enter pre- and postoperative information to help manage residual postoperative astigmatism. Included records were deemed valid with entry of AL and IOL orientation between January 2017 and March 2019. Rotation was determined by a difference of >= 5 degrees between pre-operative intended IOL orientation and actual post-operative IOL orientation. Frequency and magnitude of rotation are presented with means and associated standard deviation (SD). Linear regression models of this association are presented. RESULTS: Records of 6752 eyes were included in the analysis, of which 74.8% were determined to have a rotated IOL. The magnitude of rotation increased with each millimeter (mm) increase in AL with a mean rotation of 13.3 degrees (SD: 12.8 degrees) for eyes with AL 20-20.9 mm and a maximum mean rotation of 30.6 degrees (SD: 30.3 degrees) among eyes with AL 29-29.9 mm. General linear modeling demonstrated a significant association (P<0.0001) with a parameter estimate of 1.19 (standard error: 0.159) and R-2 of 0.0083. CONCLUSION: Analysis from an online database indicates that tonic IOLs inserted into eyes with longer AL are more likely to rotate and to rotate more degrees from the target axis. The findings from this study are clinically relevant for surgeons implanting toric IOLs.