Rotational stability and visual outcomes of toric implantable collamer lenses in eyes with horizontal and non-horizontal implanting orientation: an observational study

Abstract

To evaluate the short-term rotational stability and visual outcomes of the toric intraocular collamer lens (TICL) with horizontal and non-horizontal implantation orientation based on the Callisto eye system. This observational study analyzed 77 eyes from 51 patients with horizontal (n = 41) and non-horizontal (n = 36) TICL implantation. Examinations were performed preoperatively and at 1 week, 1 month, and 3 months. Outcomes included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, and TICL axis position; rotational stability was quantified from dilated slit-lamp photographs. The primary endpoint was mean absolute rotation at 3 months. At 3 months, absolute rotation was 3.71 ± 2.72° (horizontal) and 3.15 ± 2.85° (non-horizontal), with no between-group difference (P = 0.385). Rotation ≤ 5° occurred in 73.17% (horizontal) and 88.89% (non-horizontal); ≤ 10° in 100% and 97.22%, respectively. Visual outcomes were excellent and comparable: at 3 months, UDVA 20/20 or better in 100% of eyes in both groups; efficacy index 1.19 ± 0.21 (horizontal) vs 1.17 ± 0.15 (non-horizontal); safety index 1.25 ± 0.21 vs 1.22 ± 0.19. Achieved refraction closely matched target (attempted-vs-achieved slope y = 1.02x + 0.01). Residual cylinder at 3 months was −0.42 ± 0.28 dioptres (D) (horizontal; within ±0.50 D in 87.8%, within ±1.00 D in 97.56%) and −0.33 ± 0.32 D (non-horizontal; within ±0.50 D in 94.44%, within ±1.00 D in 100%); difference non-significant (P = 0.156). Non-horizontal EVO-TICL implantation yields rotational stability, safety and efficacy comparable to horizontal placement over 3 months, with small mean rotations and tight refractive predictability. These findings support non-horizontal orientation as a viable alternative when anatomy or vault optimization warrants it.