# Corneal morphological changes after discontinuation of long-term orthokeratology and SMILE surgery outcomes: a retrospective comparative study

## TL;DR

This study compares eye changes in former orthokeratology users and controls after SMILE surgery, finding similar visual outcomes despite corneal changes.

## Contribution

The study provides new insights into the long-term corneal effects of orthokeratology and their impact on SMILE surgery outcomes.

## Key findings

- Former OK users showed increased corneal astigmatism and spherical aberration after lens discontinuation.
- Posterior corneal curvature steepened significantly in OK users, with younger age at OK initiation linked to greater steepening.
- SMILE surgery outcomes were comparable between former OK users and controls in terms of visual acuity and corneal shape.

## Abstract

Orthokeratology (OK) has been widely adopted as a non-surgical intervention to slow myopia progression in children and adolescents. In China, where myopia prevalence is exceptionally high, OK lenses are commonly prescribed to school-aged children as an early intervention strategy. As these individuals reach adulthood, many pursue permanent refractive correction—such as small-incision lenticule extraction (SMILE)—to meet unaided visual acuity standards required for university entrance, military service, or certain occupations. However, the long-term morphological effects of OK wear and their potential impact on SMILE outcomes remain inadequately understood. This study aimed to evaluate ocular biometric and corneal morphological changes following long-term OK lens discontinuation and to compare the visual and surgical outcomes of SMILE between former OK users and spectacle-wearing controls.

This retrospective comparative study included 44 myopic eyes—22 from patients with a history of OK lens wear (average duration: 64.8 ± 22.6 months; discontinuation ≥ 3 months) and 22 from age- and refractive error–matched controls. Examinations were conducted pre-OK (baseline), pre-SMILE, and at 1 month, 6 months, and final follow-up. Parameters included uncorrected and corrected distance visual acuity (UDVA, CDVA), corneal topography, pachymetry, volume, curvature, and higher-order aberrations. Astigmatic outcomes were evaluated using Alpins vector analysis.

After OK discontinuation, the OK group exhibited increased corneal astigmatism (P = 0.030), spherical aberration (P = 0.036), and total aberrations (P = 0.034), as well as decreased vertical coma (P = 0.004), central corneal thickness (P < 0.001), and corneal volume (P = 0.001). Posterior corneal curvature steepened significantly (P < 0.001), while anterior curvature remained stable. Further correlation analysis showed that a younger age at initial OK lens wear was significantly associated with greater posterior steepening after discontinuation at the 3 mm, 5 mm, and 7 mm zones (all P < 0.050). There was also a borderline negative correlation between the duration of OK lens wear and changes in posterior steep K value, suggesting longer wear may result in more pronounced steepening. At 6 months and final follow-up, both groups demonstrated comparable UDVA, CDVA, corneal shape, and higher-order aberrations (all P > 0.050). Vector analysis revealed no significant group differences in astigmatic correction.

SMILE remains a viable option for former OK users; the observed reduction in CCT after lens discontinuation has minimal impact on refractive surgery selection.