September 1, 2025
By Eman A. Alzghoul, PhD, MScOptom, BscOptom, FIACLE, FBCLA
Photo Credit: Getty Images
Orthokeratology lenses are widely used for myopia control in children, but the underlying mechanisms for myopia control remain unclear.1 While peripheral myopic defocus alone cannot fully explain OrthoK’s effectiveness, emerging evidence suggests that changes in accommodative and binocular function may play a role. Previous studies have documented various functional changes following OrthoK treatment, including exophoric shifts and reduced accommodative lag, with some research indicating that children with lower accommodation amplitude experience better myopia control outcomes.2,3
To address these knowledge gaps, Zhu and his colleagues conducted a prospective, self-controlled study that examined the longitudinal (two-year) relationship between changes in accommodative/binocular vision function and myopia progression in children after they switched from spectacles to OrthoK. Assessments included accommodative amplitude, response, facility, AC/A ratio, ocular alignment, relative accommodation, vergence ranges, reading ability and stereoacuity at baseline and seven follow-up visits.
The study’s strengths lie in its comprehensive multi-parameter evaluation and frequent follow-up schedule, enabling precise tracking of functional changes. Results showed that ocular alignment, accommodative facility and positive relative accommodation stabilized within one month, whereas accommodative amplitude, AC/A ratio, stereoacuity and reading ability stabilized within six months.
Notably, negative relative accommodation increased significantly after two years, indicating possible long-term adaptation. However, no significant associations were found between changes in visual function and myopia progression, suggesting that OrthoK’s myopia control effect may operate independently of accommodative or binocular function changes.
Abstract
The relationship between accommodative and binocular function with myopia progression in myopic children undergoing orthokeratology
Shenlin Zhu, Yutong Song, Bi Yang, Xue Wang, Wei Ma, Guangjing Dong, Longqian Liu.
Purpose:
To determine the relationship between changes in accommodative and binocular function with myopia progression in myopic children over a two-year follow-up period, and to determine when changes in visual functions stabilized after switching from spectacles to orthokeratology (Ortho-K).
Methods:
This prospective, self-controlled study followed thirty-six participants (aged 8–14 years) for two years after they switched from spectacles to Ortho-K. Accommodative and binocular function were assessed prior to and 1, 3, 6, 12, 18 and 24 months after commencing Ortho-K. Measurements included accommodative amplitude, accommodative response, accommodative facility, accommodative convergence/accommodation (AC/A), ocular alignment, positive relative accommodation (PRA), negative relative accommodation (NRA), horizontal vergence range, reading ability and stereoacuity. Myopia progression was quantified by the change in axial length.
Results:
Ocular alignment, monocular and binocular facility, and PRA stabilized after 1 month. The distance blur point in the convergence range, the distance break and recovery point in the divergence range, accommodative amplitude, calculated AC/A, stereoacuity and reading ability stabilized within 6 months. After two years of Ortho-K, NRA significantly increased (p = 0.044), while it showed no significant difference after one-year of lens wear (p = 0.49). The distance break point in the convergence range showed no significant difference (p = 0.20), but significantly decreased after one-year (p = 0.005). There were no significant correlations between the change in axial length with changes in accommodative or binocular function (p > 0.05).
Conclusion:
Accommodative and binocular function changed significantly after switching from spectacles to Ortho-K and most of the parameters stabilized within the first 6 months. There was no association between the change in accommodative or binocular function and myopia progression.
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Eman Alzghoul, PhD, FIACLE, FBCLA, earned her doctorate in Vision Science from the School of Optometry and Vision Science at UNSW Sydney. She is currently an Assistant Professor in the Department of Optometry at Jordan University of Science and Technology (JUST). Her research focuses on myopia control and contact lenses.
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References
- Cho P, Tan Q. Myopia and orthokeratology for myopia control. Clin Exp Optom 2019;102(4):364–77. https://doi.org/10.1111/cxo.12839.
- Felipe-Marquez G, et al. Binocular function changes produced in response to overnight orthokeratology. Clin Experiment Ophthalmol. 2017;255(1):179–88. https://doi. org/10.1007/s00417-016-3554-0.
- Song Y, et al. Accommodation and binocular vision changes after wearing orthokeratology lens in 8- to 14-year-old myopic children. Clinical and Experimental Ophthalmology. 2021;259(7):2035–45. https://doi.org/10.1007/s00417-021-05106-2.
