Residual refraction after myopic implantable collamer lens implantation: clinical data vs optical models

To compare the predictive accuracy of four optical modelling scenarios for postoperative refraction after myopic Implantable Collamer Lens (ICL) implantation using patient-specific clinical biometry and to validate the results against clinical postoperative refraction and vault data.

This retrospective study analysed 215 eyes following myopic ICL implantation. Four optical vergence models were implemented using patient-specific preoperative biometry and measured postoperative vault. The scenarios differed in their treatment of corneal and phakic intraocular lens (pIOL) thickness: (A) thick cornea and thick pIOL; (B) thin cornea and thick pIOL; (C) thick cornea and thin pIOL; (D) thin cornea and thin pIOL. Postoperative spherical equivalent refraction was defined by objective autorefraction, with a sensitivity analysis for the subjective refraction in a subset of eyes. Prediction accuracy was assessed using mean error, mean absolute error, refractive accuracy thresholds, and Bland-Altman analysis. Two-dimensional dispersion was evaluated using standard distance deviation and standard deviational ellipses (SDE). Ellipse-aligned variance was compared using Brown-Forsythe tests with Bonferroni correction. The prediction accuracy of all scenarios were contrasted against the standard.

Scenarios assuming a centrally thick pIOL (A and B) systematically overestimated postoperative refraction, with biases exceeding + 1.0 D and wide limits of agreement (> ± 3.0 D). Thin-pIOL models demonstrated substantially improved agreement. Scenario C showed the lowest bias (0.30 ± 0.48 D), narrowest limits of agreement (- 0.62-1.21 D), smallest SDE area, and significantly reduced variance along both ellipse-aligned axes compared with Scenarios A and B (p < 0.001). No significant dispersion difference was observed between Scenarios C and D. Scenario C achieved prediction accuracy that was very close to that of the manufacturer's calculation algorithm.

For myopic ICLs with central thinning and a central aperture, optical models assuming a thin pIOL provide postoperative refractive prediction. Model selection should prioritize optical relevance along the visual axis rather than anatomical complexity.