Size exchange and vault response in posterior chamber phakic intraocular lens implantation: 12 years at a high-volume center

PURPOSE: To evaluate vault change after implantable collamer lens (ICL) exchange and identify outcome predictors, emphasizing age effects. SETTING: High-volume refractive surgery center, South Korea. DESIGN: Single-center retrospective cohort. METHODS: Records of ICL implantations (2013 to 2024) were reviewed. Eyes requiring exchange were classified upsizing, same-size, or downsizing. Primary outcome: 6-month vault change; secondary: endothelial cell density (ECD). Indications for exchange and age-vault relationships were assessed. RESULTS: Of 22 739 eyes, 110 (0.48%) underwent exchange: upsizing 70, same-size 27, downsizing 13. Indications differed by group: downsizing for high vault (13/13, 100%); upsizing for low vault (24/70, 34.3%) or toric rotation (44/70, 62.9%); same-size for residual refraction (17/27, 63.0%) or toric status change (10/27, 37.0%). Upsizing increased vault from 311.6 ± 223.0 μm to 481.0 ± 278.6 μm (Δ +169.4 μm; P < .001), with smaller gains at age 35 years or older. Downsizing reduced vault from 1284.2 ± 240.7 μm to 539.1 ± 176.1 μm (Δ -745.1 μm; P < .001), restoring 12 of 13 eyes (92.3%) to a prespecified safe range. Same-size exchange produced a small decrease (Δ -62.8 μm; P = .043). Across upsizing and downsizing, older age is linked to vault reduction, yielding smaller gains after upsizing (P = .013) and larger decreases after downsizing (P = .017). ECD showed small but significant declines across all groups (P < .050). CONCLUSIONS: Vault change after ICL exchange was strategy-dependent: downsizing reliably reduced excessive vault, same-size exchange produced minimal change, and upsizing yielded smaller gains that diminished with increasing age. ICL exchange requires careful planning that accounts for exchange strategy, preoperative vault, and patient age.