Purpose To evaluate the long-term outcomes of anterior segment parameters following implantable collamer lens (ICL V4c) implantation in highly myopic patients. Setting A tertiary specialized eye hospital in Shanghai, China. Design Prospective, non-randomized, consecutive case series. Methods This study included 32 eyes of 20 patients with high myopia who underwent ICL V4c implantation with a 3-year follow-up. Preoperative assessments included standard biometry and anterior segment parameters. Postoperative evaluations were conducted at 1 day, 1 month, 3 months, and 3 years. Parameters assessed included corneal endothelium-anterior capsule distance (ACD-L), corneal endothelium-ICL distance (ACD-ICL), ICL-anterior capsule distance (ICL-L), anterior chamber angle (ACA) parameters, and iris metrics. Results ACD-L decreased significantly postoperatively (P < 0.001) but remained stable thereafter. ACD-ICL increased over time, while ICL-L (vault) decreased significantly (P < 0.001), with the most pronounced changes occurring in the first month. All ACA parameters (ACW, AOD500, ARA500, TISA500, TIA500) decreased significantly compared to preoperative values (all P < 0.001) but showed no significant differences among postoperative follow-up points (P > 0.05). Iris parameters (IA, IV) showed transient changes at 1 day post-surgery but returned to baseline levels thereafter. Conclusions ICL V4c implantation demonstrated safety and efficacy during the valuable 3-year follow-up. While the anterior chamber angle narrowed and vault height decreased initially, the anterior segment structure remained stable over the long term. Crucially, the vault decrease was primarily driven by a posterior shift of the ICL rather than an anterior shift of the crystalline lens, confirming the long-term safety regarding cataract formation.