Comparative Study of ICL V4c Decentration in Vertical vs Horizontal Implantation: Association with Angle Alpha and Validation of Equivalent Visual Quality

Purpose: To compare the decentration of the Implantable Collamer Lens (ICL) V4c and its impact on visual quality between vertical and horizontal implantation techniques. Methods: 50 patients (80 eyes) were assigned to horizontal (40 eyes) or vertical (40 eyes) implantation groups. Preoperative and 6-month postoperative evaluations included uncorrected (UDVA) and corrected distance visual acuity (CDVA), refractive status, corneal topography, and wavefront aberration analysis. Decentration was measured using the OPD-Scan III aberrometer, compared between implantation methods, and analyzed for associations with preoperative angles α and κ. Results: At 6 months, 100% of horizontal and 97.5% of vertical implantation eyes achieved UDVA ≥ 20/20, with all eyes maintaining or improving CDVA. Mean decentration was similar between groups (horizontal: 0.42 ± 0.18 mm; vertical: 0.42 ± 0.19 mm; p = 0.915), with temporal displacement predominating. Angle α significantly correlated with decentration in both groups (p = 0.016; p = 0.017), while angle κ showed no association (p > 0.05). The change of higher-order aberrations did not differ between groups (p > 0.05), and decentration magnitude did not clinically affect optical quality (p > 0.05 for all aberration parameters). Conclusion: Vertical and horizontal ICL V4c implantation demonstrated comparable centration and visual outcomes. Decentration was significantly associated with preoperative angle α, underscoring the clinical importance of angle α assessment for optimal ICL positioning.