# Comparative analysis of 70 SMILE and 70 toric ICL eyes for myopic oblique astigmatism: a matched cohort study from an initial pool of 11,929 eyes

## TL;DR

This study compares two eye surgeries for correcting myopic oblique astigmatism and finds that toric ICL offers slightly better precision than SMILE.

## Contribution

A matched cohort study comparing SMILE and toric ICL outcomes for myopic oblique astigmatism using vector analysis and refractive metrics.

## Key findings

- Toric ICL showed slightly better refractive predictability and axis alignment compared to SMILE.
- Both procedures achieved high efficacy and safety indices, with over 80% of eyes within 0.50 D of target.
- Linear regression showed stronger correlation between target and achieved astigmatism in the ICL group.

## Abstract

To compare visual, refractive, and vector-based astigmatic outcomes between Small Incision Lenticule Extraction (SMILE) and toric Implantable Collamer Lens (ICL) implantation in patients with myopic oblique astigmatism.

In this retrospective, matched cohort study, 140 eyes (70 SMILE, 70 toric ICL) with oblique astigmatism were treated at a single center. Groups were matched preoperatively for refractive cylinder and spherical equivalent within ± 0.50 D. Postoperative outcomes at six weeks were assessed, including uncorrected and corrected distance visual acuity (UDVA, CDVA), spherical equivalent (SEQ), astigmatism correction using vector analysis (Alpins method), and safety and efficacy indices. A post hoc power analysis was performed for the astigmatic correction index.

The efficacy index was 0.97 ± 0.17 in the ICL group and 0.94 ± 0.15 in the SMILE group. The safety index was 1.02 ± 0.11 (ICL) versus 1.01 ± 0.09 (SMILE). UDVA equal to or better than preoperative CDVA was achieved in 83% of ICL eyes and 79% of SMILE eyes. SEQ within ± 0.50 D was observed in 85.7% (ICL) versus 81.4% (SMILE). The astigmatic correction index was 0.97 for ICL and 1.04 for SMILE. Linear regression showed stronger correlation between target and achieved astigmatism in the ICL group (slope = 1.04, R2 = 0.77) compared to SMILE (slope = 0.76, R2 = 0.67). Power analysis confirmed 80.5% power to detect clinically meaningful differences.

Both SMILE and toric ICL are effective and safe for correcting myopic oblique astigmatism. However, toric ICL demonstrated slightly greater precision in axis alignment and refractive predictability, supporting its use in cases of high oblique astigmatism where rotational accuracy is critical.