The choroidal thickness was found to be thinner in diabetic eyes without retinopathy compared to healthy eyes, thus choroidal thickness might be an important parameter for the development of diabetic retinopathy in diabetic eyes without retinopathy. Repeated low-level red-light (RLRL) therapy is an emerging innovative and non-invasive treatment for a variety of eye diseases. Notably, RLRL was found to be effective in thickening choroidal thickness in a 1-year randomized controlled trial, indicating its potential in modulating blood flow in the fundus. This study aims to answer whether RLRL therapy can thicken choroidal thickness in adults with diabetes mellitus or diabetic retinopathy.

The goal of this study is to investigate the effect of repeated low-level red-light (RLRL) therapy on the choroidal and retinal structures in diabetes mellitus and diabetic retinopathy. This study will be conducted with a prospective randomized cross-over design with a total follow-up of 3 months. The control group will use the sham device but with only 5% of the original device's power. Comprehensive ophthalmic examinations, including visual acuity, intraocular pressure, optical coherence tomography, optical coherence tomography angiography, slit lamp will be assesses at baseline and within the follow up

Inclusion Criteria:

1. Aged 35-55 years
2. Diagnosis of type 2 diabetes mellitus
3. No DR or only mild non-proliferative DR (NPDR) assessed by baseline clinical ocular signs and 7-field fundus color photography

Exclusion Criteria:

1. Spherical equivalent (SE) ≤ -6.0 diopter or axial length ≥26 mm
2. Patients with complications such as DME and retinal detachment
3. History of ocular surgical operations
4. Severe systemic diseases
5. Those who could not cooperate with the examination for any reason
6. Cognitive impairment or mental illness
7. Patients with other ocular diseases

Not Provided