Predicting Angle Anatomy Using Anterior Segment Optical Coherence Tomography In Implantable Collamer Lens Surgery

The Implantable Collamer Lens (ICL) is a posterior chamber phakic intraocular lens used for refractive errors correction. Indicators of ICL safety are vault size and iridocorneal angle size. Previous studies found an association between increased vault size and angle closure, with an increase in intraocular pressure and endothelial cell loss. No previous studies have investigated the association between preoperative angle anatomy and ICL vault using the Anterion (Heidelberg Engineering, Inc) swept-source optical coherence tomographer (SS-OCT). The purpose of this study was to study the associations between preoperative characteristics of angle anatomy and crystalline lens vault, and the ICL vault and angle parameters after ICL implantation.

Refractive Surgery Unit of the Ophthalmology Department of Unidade Local de Saúde de Santo António (ULSSA), a tertiary hospital in Oporto, Portugal.

Retrospective analysis of eyes previously submitted to ICL implantation between July 2022 and November 2023. Examinations took place prior to surgery and after three to six months with Anterion SS-OCT. Vault size was manually measured. Scleral spur location, anterior lens surface and iris contour segmentation were manually confirmed and edited after automatic processing. Multivariable linear regression analysis was performed to examine the association between crystalline lens vault, ICL size, lens power, white-to-white (WTW) distance, anterior aqueous depth (AQD), central corneal thickness (CCT), pupillary diameter, scleral spur angle at 750 µm (SSA750), and postoperative ICL vault and SSA750.

Thirty-nine eyes of 22 patients were included. Mean age was 31.5±5.9 years old and 70.0% were women. The multivariable linear regression analysis revealed significant associations between preoperative crystalline lens vault and postoperative ICL vault (β=-0.321, p=0.005). After adjusting for the other covariates, a linear regression model including crystalline lens vault (β=-0.584, p = 0.005) and preoperative SSA750 (β=-0.584, p = 0.005) showed the best fit. Preoperative crystalline lens vault also showed to be the best single predictor of the percentage of reduction in SSA750 after surgery (β=-0.321, p=0.005).

Our findings underscore the importance of preoperative crystalline lens vault and angle measurements in predicting postoperative variation in scleral spur angle and ICL vault. Preoperative crystalline lens vault emerged as the strongest predictor of the percentage of reduction in scleral spur angle after surgery. Preoperative crystalline lens vault and SSA750 showed superior predictive accuracy for postoperative ICL vault and, in our model, WTW was not correlated with ICL vault, despite its association with lens size selection. Our results suggest that the measurement of crystalline lens vault and angle by OCT may be more important than WTW in predicting ICL vault and should be included in the preoperative study for the choice of lens size.