Influence of Astigmatism Magnitude and Axis on the Selection of Non-Toric versus Low-Powered Trifocal Toric Intraocular Lenses in Presbyopic Refractive Lens Exchange.
Abstract
Purpose
To evaluate the influence of preoperative astigmatism magnitude and axis on the selection between non-toric and low-powered trifocal toric intraocular lenses (IOLs) and their comparative refractive outcomes.
Setting
Memira by Bergman Clinics, Norway; HO Londrina - Hospital de Olhos, Brazil.
Design
Multicenter, retrospective, interventional cohort study.
Methods
Consecutive eyes designated for non-toric (T00) or low-powered toric (T20) trifocal IOLs based exclusively on Barrett Toric Calculator recommendations were analyzed. Generalized Estimating Equations (GEE) were utilized to adjust for inter-eye correlation. Outcomes included preoperative corneal astigmatism (magnitude and axis), estimated residual astigmatism, and postoperative manifest astigmatism, evaluated with double-angle and linear distribution plots.
Results
The cohort comprised 1,628 eyes (T00: 786; T20: 842). The calculator's recommendation between T00 and T20 varied continuously based on both preoperative magnitude and axis. Despite the T20 group having significantly higher preoperative corneal astigmatism (P<0.001), postoperative manifest astigmatism was statistically equivalent between groups (T00: 0.26±0.26 D vs. T20: 0.24±0.26 D; P=0.634). No significant differences were observed in visual acuity, manifest refraction spherical equivalent, safety, or efficacy indices (P>0.05). However, the T00 group demonstrated higher estimated than achieved postoperative astigmatism (0.33±0.16 D vs. 0.26±0.26 D), whereas the T20 group showed lower estimated than achieved astigmatism (0.10±0.08 D vs. 0.24±0.26 D).
Conclusion
The decision between a non-toric versus a low-powered toric IOL relies on an individualized interdependence between magnitude and axis rather than a fixed magnitude-based cutoff. This individualized, calculator-driven approach was associated with comparable postoperative astigmatism between groups, regardless of their baseline differences.