Influencing Factors of Positional Stability of Implantable Collamer Lenses in Terms of Rotation, Decentration, and Tilt in Patients With Myopia

Purpose: To quantitatively assess the positional stability, including rotation, decentration, and tilt, of Implantable Collamer Lenses (ICLs) and analyze the influencing ocular parameters. Methods: Ninety-two eyes were enrolled in this prospective study. Preoperative ocular parameters were measured and the ICL positional stability was evaluated, including rotation, decentration, and tilt during a 6-month follow-up using the OPD-Scan III (Nidek) and Casia2 (Tomey). Correlations between ocular parameters, vault, and ICL positional stability were explored. Results: The mean ICL vault, rotation, decentration, and tilt at 6 months postoperatively were 633.28 ± 211.96 µm, 4.37 ± 3.04°, 0.31 ± 0.16 mm, and 2.67 ± 0.89°, respectively. For rotation, ICL fixation angle (β = 0.894, P = .01) and ciliary sulcus angle (β = 0.043, P = .033) were significant. For decentration, axial length (β = 0.023, P = .027), sulcus-to-sulcus distance (β = −0.109, P = .004), and iris concavity (β = 0.481, P < .001) were independent factors. For tilt, univariate linear regression analyses indicated significant correlations with iris-to-ciliary process distance (β = 0.001, P = .002). RCS analysis revealed a non-linear relationship between vault and ICL rotation and tilt: rotation was greater at vaults <400 and >800 µm, whereas tilt was greater at vaults <400 µm. Low vault (<400 µm) was also a correlated factor for ICL tilt. Conclusions: ICL positional stability was within an acceptable range. ICL fixation angle and the structures of the iris and ciliary body influenced the rotation, decentration, and tilt of the ICL. Abnormal vault values were also correlated with ICL rotation and tilt.