This research project is a prospective, randomized controlled trial designed to assess the short-term effects of varied red light therapies on the choroidal and retinal structures in adult myopes. The primary objective is to determine which specific retinal regions or cells are primarily affected by short-term repeated low-level red-light (RLRL) therapy, potentially inducing choroidal thickening. The secondary objective is to assess the safety of different types of red light therapy in adult myopes.

The study will enroll 45 myopic adults aged 18-40 years old as participates. They will be randomly assigned into three RLRL groups: small circle (d=0.30mm), medium circle (d=0.50mm), and annular groups (an inner diameter of 0.50 mm and an outer diameter of 0.70mm) without disclosure of their specific group to maintain study blinding. The groups are differentiated by the size and shape of the light spots formed on the retina but with the same power (0.15 mW with a 4 mm pupil size). The Eyerising Myopia Management Device, modified for this study, will be used to administer RLRL with three different spot patterns, adhering to safety standards to minimize risk and ensure participant safety.

Before the treatment, baseline data will be collected from each participant. Baseline assessments will consist of demographics information, visual acuity checks, axial length measurements, subjective refraction, slit-lamp examinations, adaptive optics imaging, optical coherence tomography and angiography (OCT & OCTA), posterior blood flowgraphy, electroretinography (ERG), and the Flicker-plus test. Then participants will undergo daily treatments for 14 days, using the therapy settings of the group to which they have been assigned. The treatment will last for 3 minutes twice a day, with a minimal interval of 4 hours. During the 14-day study period, participants will undergo daily assessments by a series of ophthalmic examinations.

Outcomes measured will track changes in choroidal thickness, electrical activity of the retina, axial length, and best corrected visual acuity, alongside other image reports such as adaptive optics imaging, posterior blood flowgraphy and OCT & OCTA scans.

This study addresses the gaps in understanding how RLRL therapy affects myopia and aims to identify the retina's high-response areas to red light. By doing so, it hopes to minimize unnecessary exposure and potential damage, enhancing the safety and effectiveness of the therapy.

Inclusion Criteria:

1. Age: 18 to 40 years.
2. Myopic spherical equivalent refraction (SER) between -1.00D to -6.00D in both eyes.
3. Best corrected visual acuity (BCVA): 20/20 or greater.
4. Informed consent for participation.

Exclusion Criteria:

1. Anisometropia greater than 1.50D.
2. Ophthalmic diseases other than refractive errors, including but not limited to strabismus and binocular vision abnormalities in either eye.
3. Systemic diseases (e.g., endocrine, cardiac diseases) and developmental abnormalities.
4. Inability to attend regular follow up assessment.
5. Undergo RLRL therapy in the past 6 months
6. Contraindications to RLRL therapy.