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Updated: Jul 14, 2026
05:14
Comparison of Agreement and Accuracy using Binocular Wavefront Optometer with Autorefractor and Phoropter
Published on: September 16, 2025
Refractive error and visual acuity changes in orthokeratology patients
Sin Wan Cheung1, Pauline Cho, Wan Sang Chui
1School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China. sopeggy@inet.polyu.edu.hk
Summary
Orthokeratology (ortho-k) visual acuity is comparable to spectacle correction at high contrast but worse at low contrast, especially with residual refractive error. Evaluating monocular visual acuity at various contrast levels is recommended for ortho-k patients.
Area of Science:
- Ophthalmology
- Optometry
- Vision Science
Background:
- Orthokeratology (ortho-k) is a non-surgical method to correct refractive errors.
- Assessing visual acuity (VA) at different contrast levels is crucial for understanding visual function.
Purpose of the Study:
- To evaluate refractive error and visual acuity (VA) in ortho-k subjects.
- To compare post-ortho-k VA with spectacle-corrected VA in a matched control group.
Main Methods:
- 31 ortho-k subjects and 31 spectacle-wearing controls were tested.
- Visual acuity was measured at 90%, 48%, 21%, and 7% contrast levels using the Waterloo Four-Contrast LogMAR VA Chart.
- Refractive error was measured in both eyes of ortho-k subjects.
Main Results:
- Ortho-k achieved significant reduction in refractive error (92% in better eye, 84% in worse eye).
- Post-ortho-k uncorrected VA correlated with residual refractive error at all contrast levels.
- Post-ortho-k VA was comparable to controls at high contrast (90%, 48%) but worse at low contrast (21%, 7%).
Conclusions:
- Residual refractive error significantly impacts post-ortho-k visual outcomes.
- Ortho-k VA is inferior to spectacle correction at low contrast levels.
- Monocular VA assessment at both high and low contrast is recommended for ortho-k patients.
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