The purpose of this clinical trial is to evaluate the effect of repeated low-level red-light (RLRL) therapy on the retinal function and structure among myopic teenagers.

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 has been demonstrated. It is crucial to look for effective ways to control myopia in children to reduce risk of myopic pathologies in later life. Repeated low-level red-light (RLRL) therapy is an innovative and non-invasive therapeutic treatment for a variety of eye diseases. A previous randomized clinical trial suggested that RLRL could effectively controlled myopia progression without clinically observable side effects.

The purpose of this study is to evaluate the effect of RLRL on the retinal function and structure among myopic teenagers aged 15-16 years. The RLRL therapy will be carried out at school under supervision of the parents according to a standard protocol for the first month and then will be discontinued for 1 month. Detailed functional and structural examinations, including full field electroretinogram, multifocal electroretinogram, microperimetry, visual acuity, intraocular pressure, optical coherence tomography, optical coherence tomography angiography, cycloplegic spherical equivalent refraction, and biological parameters will be evaluated at 1 month, 2 months after enrollment.

Inclusion Criteria:

1. Age: 15-16 years at enrolment.
2. Myopia: cycloplegic spherical equivalent refractions (SERs) range from -1.00 to -5.00 diopters (D) and astigmatism less than -2.5 D in either eye.
3. Best corrected visual acuity equal to or better than 0.8 in either eye.
4. Normal fundus, or tessellated fundus.
5. Provision of consent and able to participate in all required activities of the study.

Exclusion Criteria:

1. Secondary myopia, such as a history of retinopathy of prematurity or neonatal problems, or syndromic myopia with a known genetic disease or connective tissue disorders, such as Stickler or Marfan syndrome.
2. Strabismus and binocular vision abnormalities in either eye.
3. Refractive media opacity: corneal opacities, cataract, or implanted intraocular lens, etc.
4. Ocular abnormalities that affect retinal function: macular degeneration, diabetic retinopathy, retinal detachment, glaucoma, or ocular hypertension, endophthalmitis, uveitis, optic neuropathy, etc.
5. Previous history of refractive surgery, intraocular surgery, laser therapy, and intravitreal injection, etc.
6. Systemic abnormalities: diabetes, hypertension, etc.
7. Drugs therapies with toxicity effect on the retina: hydroxychloroquine, etc.
8. Prior treatment of myopia control in the past three months, drugs, orthokeratology, progressive addition lenses, bifocal lens, etc.
9. Other contraindications, including but not limited to ocular or other systemic abnormalities, that the physician may consider inappropriate for enrolment.

Data will be shared as open data after proper anonymization.