Spherical Power As An Independent Predictor Of Long-Term (≥12 Months) Postoperative Vault And Vault Area In Icl And Eyecril Phakic Iols

The STAAR Surgical Visian Implantable Collamer Lens (ICL) is widely used with excellent visual outcomes. Postoperative vault—the distance between the anterior crystalline lens surface and the phakic intraocular lens (pIOL)—is a critical safety parameter. The Biotech Healthcare Eyecril pIOL is a hydrophilic acrylic alternative  to ICL. While previous studies have evaluated early postoperative vault behavior (<6 months), limited data exist regarding the independent role of spherical lens power and comparison between lens models.

This study aimed to evaluate independent predictors of long-term vault and vault area at a mean follow-up exceeding 12 months and to explore endothelial cell changes between ICL and Eyecril lenses.

The study was conducted at the Department of Ophthalmology of the Centro Hospitalar e Universitário de São João (CHUSJ), a tertiary academic medical center in Porto, Portugal. All surgical procedures, including the implantation of both STAAR Surgical Visian ICL and Biotech Healthcare Eyecril Phakic IOLs, as well as all specialized preoperative and postoperative multimodal imaging, were performed within this institutional setting.

A retrospective analysis was performed including all consecutive ICL and Eyecril implantations at our center.

Preoperative and postoperative biometric parameters were obtained using ANTERION® optical coherence tomography (OCT), including:

• White-to-white (WTW)
• Anterior chamber depth (ACD)
• Crystalline lens thickness(LT)
• Postoperative vault (Vlt)
• Vault area (Vlt_area)
• Postoperative pupil diameter

Endothelial cell density (ECD) was measured using TOPCON® SP-2000P.

The study included 33 eyes from 17 ICL patients and 3 eyes from 2 Eyecril patients. Vault measurements were recorded at the most recent postoperative examination.

Multivariate linear regression models were constructed to identify independent predictors of long-term vault and vault area.

The mean follow-up was 15.42 ± 7.08 months.

A multivariate linear regression model including spherical power, WTW, ACD and LT was statistically significant (F(4,22)=6.944, p<0.001), explaining 55.8% of the variance in vault (adjusted R²=0.478).
Spherical power was the only independent predictor (B=–27.5 µm/diopter, β=–0.580, p=0.001), while WTW, ACD and LT were not significant.The regression model for vault area was also significant (R² = 0.489, p < 0.001). Pupil diameter was the strongest predictor (β = 0.512, p = 0.002), followed by spherical power (β = –0.319, p = 0.042).

Mean endothelial cell change was: (p=0.003)

• –224 ± 402 cells/mm² in the ICL group
• –994 cells/mm² in the Eyecril group

Interpretation is limited by the small Eyecril sample.

At a mean follow-up exceeding 12 months, spherical power was the only independent predictor of postoperative vault and vault area, explaining a substantial proportion of vault variability independently explaining a sybstantial proportion of vault variability.

These findings suggest that spherical power may play a relevant role in long-term vault behavior, particularly in highly myopic eyes, and could warrant consideration in postoperative monitoring strategies.

The current sample size does not allow reliable comparison of endothelial cell loss between Eyecril and ICL models.

Vault area may represent an additional geometric parameter with potential value in the assessment of postoperative safety.