Anterior Chamber Angle Changes and Its Associated Factor After Posterior Chamber Phakic Intraocular Lens Implantation...

The purpose of this study was to investigate anterior chamber angle (ACA) changes after implantable collamer lens (ICL) placement in eyes with shallow anterior chamber depth (ACD) and the effect of vault size on ACA changes.

In this prospective cohort study of 120 patients (120 eyes) undergoing ICL implantation, participants were stratified into shallow (ACD ≤3.0 mm, n = 60) and normal ACD groups (ACD >3.0 mm, n = 60). Trabecular-iris angle 500 (TIA500), angle opening distance 500 (AOD500), trabecular-iris space area (TISA500), angle opening distance circumference area 500 (AODA500), trabecular-iris circumference volume 500 (TICV500), and anterior chamber volume (ACV) measured by swept source optical coherence tomography (SS-OCT) preoperatively and at 3 months postoperatively were compared within and between groups and according to vault size.

Relative to the preoperative values, the TIA500, AOD500, and TISA500 values decreased significantly in both groups (all P < 0.01). Similarly, the AODA500, TICV500, and ACV values decreased by 52.1%, 48.2%, and 38.9%, respectively, in the shallow ACD group (all P < 0.001), and by 59.2%, 56.6%, and 37.4%, respectively, in the normal ACD group (all P < 0.001). However, the reduction in all ACA parameters in the shallow ACD group in each meridian was significantly lower than that in the normal ACD group, both for low (all P ≤ 0.005) and high vaults (all P ≤ 0.004). Correlation analyses indicated that vault size was positively correlated with the decrease in ACA parameters in both groups (all P < 0.05).

Anterior segment structure was more crowded in patients with a shallow ACD. This necessitates strict ICL size limits (≤12.2 mm for ACD <2.8 mm) and prioritizes long-term SS-OCT surveillance of the superior-nasal quadrant, particularly in high-vault cases.

For patients with a shallow anterior chamber implanted ICL, placement in the superior-nasal quadrant should be considered.