Managing moderate to high astigmatic myopia in kids with spherical vs toric orthokeratology

Paper title: Efficacy and factors influencing toric orthokeratology lenses in managing moderate to high astigmatic myopia

Authors: Hong H (1), Long Y (2), Li L (3), Lu H (1), Lin E (1)

1. Optometry Center, People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
2. Department of Outpatient, People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
3. Department of Hepatobiliary Surgery, People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, China

Date: June 2025

Reference: Hong H, Long Y, Li L, Lu H, Lin E. Efficacy and factors influencing toric orthokeratology lenses in managing moderate to high astigmatic myopia. Optom Vis Sci. 2025 Jun 1;102(6):387-393.

[Link to open access paper]

Orthokeratology (ortho-k) is a widely used contact lens option for myopia control in children and adolescents, but its success depends heavily on lens selection and fit. Spherical ortho-k designs are generally suitable for up to −1.50D of corneal astigmatism, beyond which toric ortho-k designs are typically required to achieve stable centration and visual outcomes

Astigmatic myopia in adolescents presents challenges for both visual correction and myopia control, particularly in cases of moderate to high astigmatism powers, which exceed the capabilities of spherical orthokeratology designs. Toric ortho-k lenses can incorporate either a fully toric design with toric back optic zone radii, to correct a central cornea more astigmatic than the periphery, or a spherical optic zone with toric periphery design for limbus-to-limbus astigmatism. Currently, there is limited research into the efficacy of toric ortho-k for myopia control in clinical practice. This study evaluated the performance of toric ortho-k lenses in children 8 to 17 years with myopia (-1.00 to -6.00D) and moderate to high astigmatic myopia (-1.00 to -3.00DC) and analysed which baseline factors may influence treatment success.

Key points were as follows:

• After 12 months, axial length increased by 0.20mm in the toric lens group vs 0.47mm in the spherical group.
• Final spherical equivalent refraction at 12 months was −0.64D in the toric group vs −1.04D in the spherical group and unaided acuity was better in the toric group by 0.04 logMAR (2 letters).
• Post-treatment cylinder values were similar between groups (1.60D in toric vs 1.50D in spherical).
• Statistical modelling showed strong predictive accuracy for baseline factors such as older age, higher baseline spherical error and longer axial length.

This study provides clinically useful evidence for managing children with moderate to high astigmatic myopia who fall outside the fitting range for spherical ortho-k. Toric ortho-k lenses, designed for apex astigmatism, were more effective than spherical designs in slowing axial elongation and improving spherical refractive error over 12 months, with average axial growth of 0.20 mm in the toric group compared to 0.47 mm in the spherical group. Post-treatment cylinder outcomes were similar between groups, suggesting that toric lenses did not result in over- or under-correction despite the higher baseline astigmatism.

The findings also help identify which patients may respond best. Older children with more significant myopia and longer axial lengths at baseline showed slower axial growth. Statistical modelling supported the reliability of these predictors, indicating that these baseline characteristics could help guide patient selection for toric ortho-k. Overall, on average, children with astigmatism of 1 to 3D achieve better acuity and myopia control outcomes with toric compared to spherical ortho-k, even with only small differences in acuity and refraction outcomes. 

Further research is needed to understand why these specific baseline characteristics of older age, higher baseline myopia and longer axial length are associated with better outcomes. The authors suggest that possible contributing factors may include age-related differences in ocular biomechanics, variations in peripheral refraction profiles, or naturally slower rates of axial elongation in older or more myopic eyes.

The study focused on using full toric designs, but did not stratify outcomes by the magnitude or specific pattern of corneal toricity (e.g. apex vs limbus-to-limbus), or whether different designs, such as toric periphery only, are equally effective. Future research is needed to determine how lens design interacts with corneal toricity to optimise treatment outcomes. 

Additionally, while the statistical model showed strong predictive power, it has yet to be validated in external or prospective populations. While the predictive model showed good performance in this cohort, its clinical usefulness will depend on how well it performs in patients with different corneal profiles, refractive characteristics, and lens design choices. Long-term follow-up would also help determine whether the observed axial length control is sustained beyond 12 months.

Significance: Toric orthokeratology lenses show potential in slowing myopia progression in adolescents with moderate to high astigmatic myopia. These findings support the broader application of toric orthokeratology in managing challenging refractive conditions and mitigating myopia-related complications.

Purpose: This study seeks to probe the efficacy of toric orthokeratology lenses in controlling moderate to high astigmatic myopia in adolescents and to analyze the risk factors influencing treatment outcomes.

Methods: One hundred adolescent patients with moderate to high astigmatic myopia who were treated at our medical facility from January 2022 to January 2023 were randomly selected as the study subjects. All patients were allocated to either the experimental group (n = 50) or the control group (n = 50) using a random number table method. The control group was subjected to treatment with spherical orthokeratology lenses, whereas the experimental group was treated with toric orthokeratology lenses. Changes in uncorrected visual acuity, axial length, cylinder diopters, sphere diopters, and average corneal curvature before treatment and after 12 months of treatment were compared between the two groups. The logistic regression analysis was conducted to identify the factors influencing the efficacy of toric orthokeratology lenses in controlling moderate to high astigmatic myopia in adolescents.

Results: Both cohorts showed substantial improvements in uncorrected visual acuity, axial length, sphere, and average corneal curvature compared with their pre-treatment values, with the experimental cohort showing greater improvements than the control cohort (p=0.01, 0.03, 0.00, 0.00). There were no significant differences in cylinder between the two groups after treatment (p=0.56). Univariate analysis unraveled significant differences in age, baseline sphere, average corneal E value, baseline axial length, and central corneal thickness (p=0.00, 0.03, 0.04, 0.02, 0.05). Receiver operating characteristic curve analysis displayed that the area under the curve for the logistic regression model attained 0.82, with a 95% confidence interval of (0.69, 0.95), sensitivity of 88%, specificity of 72%, and a Youden index of 0.61.

Conclusions: Toric orthokeratology lenses demonstrate potential efficacy for adolescents with moderate to high astigmatic myopia by slowing myopia progression. Patients who are older, severely nearsighted, and have longer baseline axial length experience more significant control over myopia progression.

[Link to open access paper]