Differential effects of EVO/EVO+ implantable collamer lens on anterior chamber angle morphology: A comparative cohort study.

OBJECTIVE

To compare the effects of two implantable collamer lens models-EVO+ (V5) with an enlarged optic diameter (up to 6.10 mm) and EVO (V4c)-on anterior chamber angle parameters, intraocular pressure (IOP), and pupil diameter following implantation for moderate to high myopia.

METHODS

This retrospective comparative cohort study included 132 patients (263 eyes) who underwent bilateral ICL implantation (V5: 61 patients/121 eyes; V4c: 71 patients/142 eyes). Anterior segment optical coherence tomography (AS-OCT) was used to measure anterior chamber angle (ACA), angle opening distance at 500 μm (AOD500), and trabecular-iris space area at 500 μm (TISA500) preoperatively and at postoperative day 1, week 1, and month 3. IOP was measured via Goldmann applanation tonometry. Multivariable regression with cluster-robust standard errors was used to adjust for age, sex, anterior chamber depth (ACD), white-to-white distance (WTW), vault, and ICL size.

RESULTS

Baseline characteristics were comparable between groups except for slightly larger WTW (11.73 ± 0.34 vs. 11.64 ± 0.37 mm, p = 0.026) and lower vault (731 ± 201 vs. 816 ± 212 µm, p = 0.001) in the V5 group. TISA500 reduction was significantly greater in the V5 group at both day 1 (-0.188 ± 0.107 vs. -0.095 ± 0.137 mm², p < 0.001) and month 3 (p < 0.001), an effect that persisted after multivariable adjustment (β = -0.113, 95% CI [-0.161, -0.065], p < 0.001). No significant between-group differences were observed for ACA or AOD500 at any time point. IOP was higher in the V5 group preoperatively (16.9 ± 2.7 vs. 15.6 ± 2.2 mmHg, p < 0.001) and at 3 months (16.2 ± 2.5 vs. 15.1 ± 2.3 mmHg, p = 0.001), but mean values remained within normal limits, and the incidence of ocular hypertension (>21 mmHg) did not differ between groups. A significant negative correlation between vault and ΔTISA500 was observed only in the V5 group (r = -0.32 to -0.31, p ≤ 0.008). Pupil diameter changes were comparable between groups.

CONCLUSIONS

Both V5 and V4c ICL implantation provided clinically acceptable IOP and anterior chamber angle profiles. However, the V5 model was associated with a significantly greater and independent reduction in TISA500, likely due to its enlarged optic diameter. Clinicians should consider this differential impact, particularly in patients with borderline anterior chamber angles or elevated glaucoma risk. Longitudinal studies are needed to assess the long-term implications of reduced TISA500 in V5 recipients.