The purpose of this multicenter randomized clinical trial is to evaluate the adjunctive effect of repeated low-level red-light therapy (RLRL) and orthokeratology (ortho-k) on myopia control in ortho-k non-responders who have undergone ortho-k treatment but were still experiencing fast myopia progression.

Myopia constitutes a major threat to personal health globally for its increased prevalence. Moreover, its dose-related association with irreversible blindness complications such as myopic macular degeneration have been demonstrated. It is crucial to look for effective ways to control myopia in children to reduce risk of myopic pathologies in later life.

Orthokeratology (ortho-k) is the first-line optical method in myopia control, resulting in slowing axial elongation by 43-63%. However, results after ortho-k treatment vary among individuals. Methods with more accurate efficacy and wider application to slowing down myopia progression, especially for myopia with limited ortho-k response, are still urgently required.

Repeated low-level red-light (RLRL) therapy is an innovative and non-invasive therapeutic treatment for a variety of eye diseases. Our previous clinical study suggested RLRL could effectively retard myopia progression without clinically observable side effects.

The purpose of this study is to evaluate the adjunctive effect of RLRL and ortho-k on myopia control in ortho-k non-responders using a multicenter randomized controlled trial design. Ortho-k non-responders are defined as who have continuously undergone ortho-k treatment but were still experiencing fast myopia progression. The subjects will be randomly assigned to either experimental group (RLRL and ortho-k) or control group (ortho-k). Their axial length will be monitored over one year. Changes in axial length in the two groups will be compared.

Inclusion Criteria:

1. Start to receive ortho-k treatment one year ago.
2. Age at enrolment: 8-13 years.
3. Ortho-k non-responders: those who have continuously undergone ortho-k treatment but were still experiencing fast myopia progression (annual axial elongation equal to or more than 0.5 mm) in the past one year in at least one eye.
4. Before wearing ortho-k lenses, spherical equivalent refractions (SERs) ranging from -1.00 to -5.00 Dioptres (D) and astigmatism less than -1.5 D in both eyes, anisometropia less than 1.5 D, and best corrected logMAR visual acuity (VA) equal to or better than 0 in both eyes.
5. Parents' understanding and acceptance of random allocation of grouping

Exclusion Criteria:

1. Strabismus and binocular vision abnormalities.
2. Ocular or systemic abnormalities.
3. Prior treatment of myopia control in the past three months, e.g. drugs, progressive addition lenses, bifocal lenses, etc.
4. Other contraindications.