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

Zhongjun Tang,1– 4, Zhuotong Wu,2– 4, Ziyi Guo,2– 4 Linda Zheng,5,6 Xingtao Zhou,2– 4 Shengtao Liu2– 4 1Department of Ophthalmology, Minhang Hospital, Fudan University, Shanghai, People’s Republic of China; 2Department of Ophthalmology and Optometry, Eye and ENT Hospital, Fudan University, Shanghai, People’s Republic of China; 3NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, People’s Republic of China; 4Shanghai Research Center of Ophthalmology and Optometry, Shanghai, People’s Republic of China; 5Sydney Eye Hospital, Sydney, NSW, Australia; 6Royal Prince Alfred Hospital, Camperdown, NSW, AustraliaThese authors contributed equally to this workCorrespondence: Shengtao Liu, Department of Ophthalmology and Optometry, Eye and ENT Hospital, Fudan University, Shanghai, People’s Republic of China, Email 282985766@qq.com Xingtao Zhou, Department of Ophthalmology and Optometry, Eye and ENT Hospital, Fudan University, Shanghai, People’s Republic of China, Email doctzhouxingtao@163.comPurpose: 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.Keywords: ICL V4c, decentration, vertical implantation, visual outcomes, angle alpha, wavefront aberrations