Rotational Stability and Vault Outcomes of the EVO ICL Using Oblique Implanting Orientation Compared to Horizontal/Vertical Implanting Orientation

Purpose: To evaluate the outcomes of Implantable Collamer Lens (EVO ICL; STAAR Surgical) implantation using customized oblique implanting orientation, focusing on rotational stability, vault predictability, and refractive efficacy compared to horizontal and vertical implanting orientations. Methods: In this prospective case series, 219 eyes of 110 patients underwent customized EVO ICL implantation guided by ultrasound biomicroscopy (UBM) measurements of sulcus-tosulcus (STS) diameters, ciliary sulcus morphology (MCS), and routine measurement of anterior segment including anterior chamber depth (ACD). Eyes were stratified into horizontal (n = 95), vertical (n = 41), and oblique (n = 83) groups based on implanting orientation. Postoperative assessments at 1 day, 1 week, 1 month, 3 months, and 1 year included refractive outcomes, vault measurements, and rotational degree analysis using slit-lamp photography and Mediview software. Results: At 1 year, all groups maintained ideal vault ranging from 118 to 1,053 µm, with 93.8% of eyes achieving 250 to 1,000 µm. The oblique group exhibited comparable vault (562.0 ± 189.2 µm) to the horizontal (571.2 ± 206.9 µm) and vertical (533.1 ± 185.4 µm) groups, with no significant intergroup differences ( P = .64). Rotational stability showed no statistical differences among groups (oblique: 3.56 ± 2.78°, horizontal: 3.42 ± 2.49°, vertical: 3.24 ± 2.74°; P = .86). The most significant ICL rotation occurred within the initial postoperative week in all groups, with subsequent stabilization observed thereafter. Haptic positioning behind the ciliary processes correlated with reduced rotation ( r = −0.37, P = .004) in the oblique group. Refractive outcomes were consistent across groups, with uncorrected distance visual acuity in 96.7% of eyes achieving preoperative corrected distance visual acuity and 85.5% of eyes having astigmatism of −0.50 diopters or less. Conclusions: UBM-guided customized oblique implantation of an ICL achieved safety, efficacy, and vault predictability comparable to traditional implanting orientations, with good rotational stability, offering an alternative design to achieve optimal vault. Long-term rotational stability requires further observation.