Correlation between preoperative biometry and posterior chamber phakic Visian Implantable Collamer Lens vaulting

Objective: To evaluate (1) the effect of preoperative biometric factors on vault error and (2) the difference in achieved vault (AV) and expected vault (EV) after Visian Implantable Collamer Lens (ICL) implantation.

Design: Retrospective, comparative, interventional case series.

Participants: A total of 129 eyes of 75 myopic patients treated with ICL.

Methods: On the basis of the hypothesis that ICL vaulting is due mainly to an inequality between ICL size and the horizontal sulcus-to-sulcus distance (STS) or horizontal white-to-white distance (WTW), we assumed that EV would linearly correlate with ICL horizontal compression, as demonstrated in an ex vivo experiment. Expected vault was defined as follows: EV(WTW[or STS]) = (ICL size - WTW[or STS]) × 1100 μm. With the use of preoperative data as independent variables (including age, anterior chamber depth measured from the central corneal endothelium to the anterior lens capsule, STS, WTW, ICL size, ICL size - STS, ICL size - WTW, STS - WTW, ICL diopter, and mean K-reading), a multiple regression analysis was performed to evaluate meaningful factors affecting AV.

Main outcome measures: Preoperative ICL EV and postoperative ICL AV.

Results: Mean AV was 518.6 (standard deviation [SD] 258.4 μm). The EV(WTW) was 626.6 (SD 220.9 μm), and EV was 242.8 (SD 364.2 μm). Higher ICL compression tended to result in a lower AV than EV, whereas lower ICL compression tended to result in a higher AV than EV. The ICL size - STS was more highly correlated with AV than the ICL size - WTW (Pearson correlation coefficient 0.425 vs. 0.247). Stepwise multivariate regression showed that, in order of the strength of the contribution, ICL size - STS, ICL size, age, and K-reading were significant factors associated with AV (adjusted R(2)=0.369), but ICL size - WTW was not. Among the meaningful factors, ICL size - STS, ICL size, and K-reading were positively correlated with AV, whereas age was negatively correlated.

Conclusions: The ICL vaulting based on only the horizontal compression could not be quantitatively predicted. Additional factors, such as vertical compression by the iris, dampening effect of the ciliary sulcus structure, or innate ICL vault, should be considered to avoid unexpected vaulting after ICL implantation.