Comparison of rotational stability of the implantable collamer lens after using a vertical or horizontal implanting orientation

PURPOSE: To compare rotational stability of the implantable collamer lens (ICL) between horizontal and vertical implantation. SETTING: Zhongshan Ophthalmic Center, Guangzhou, China. DESIGN: Prospective 1:1 matched design. METHODS: 94 cases (185 eyes with a vertical elliptical ciliary sulcus) were included with a 1:1 matched design based on ciliary sulcus morphology, preset deviation angle, and vault. Follow-ups at 4 days, 1 month, 3 months, and 6 months postsurgery measured rotational angles using slitlamp photography. Latent class trajectory modeling was used to investigate the postoperative rotational angle trajectories. RESULTS: 6 months postoperatively, both groups exhibited similar visual acuity and refractive outcomes. The horizontal group had a significantly greater rotation angle than the vertical group (F group = 13.638, P < .001). In addition, a statistically significant difference ( P = .004) in the average trajectories of rotational angles was observed. The vertical group displayed a greater presence in the low-stable trajectory subgroup while demonstrating a reduced presence in the moderate-increase and high-fluctuation trajectory subgroups compared with the horizontal group. The horizontal group had a 3.750 times higher risk of rotation angle ≥3 degrees compared with the vertical group, which represented a statistically significant difference (95% CI, 1.346-10.446). In both groups, a positive correlation between the preset deviation angle and the rotation angle was observed, with correlation coefficients of 0.320 ( P = .030) and 0.371 ( P = .011), respectively. CONCLUSIONS: Vertical ICL implantation showed better rotational stability than horizontal implantation in eyes with a vertical elliptical ciliary sulcus, offering guidance for ICL surgery.