The goal of this observational study is to enroll diabetic patients with diabetic retinopathy and those without diabetic retinopathy, follow up and observe the long-term changes in ocular structure and function of the subjects by comparison, analyze their association with multimodal biomarkers, and explore new methods for the early diagnosis and risk prediction of diabetic retinopathy.

Participants will be followed up over a 5-year follow-up period, during which they will undergo ophthalmic examinations, blood tests, and questionnaires.

Inclusion Criteria:

• Participants must understand the clinical trial, voluntarily participate, and sign the informed consent form.

• Aged 18-80 years, with no restriction on gender.

• Healthy control group: No history or diagnosis of diabetes.

• Diabetic group:

  i) Definite diagnosis of diabetes. Both type 1 and type 2 diabetic patients will be included in this study.

ii) Based on dilated fundus examination, subjects are classified into NDR, NPDR, and PDR groups according to the staging of diabetic retinopathy.

• Idiopathic epiretinal membrane (iERM) group is set as the control group for intraocular specimen collection and analysis in PDR patients: Funduscopic examination shows gold foil-like reflection or glass membrane-like substance covering the macular area, causing local retinal folds, with or without tortuosity and deformation of small perimacular blood vessels; OCT examination reveals a hyperreflective band on the retinal surface of the macular area; meeting the indications for pars plana vitrectomy combined with internal limiting membrane-epiretinal membrane peeling: visual acuity < 0.3, or visual acuity > 0.5 but accompanied by progressive vision loss, severe metamorphopsia, diplopia, visual field defect, or other symptoms that significantly affect quality of life, and surgical treatment can be performed if actively requested by the patient; no diagnosis or history of diabetes.

Exclusion Criteria:

• Complicated with other severe ocular diseases (e.g., glaucoma, age-related macular degeneration, uveitis, etc.).
• A history of previous ocular surgery.
• Complicated with severe systemic diseases (e.g., ischemic heart disease, stroke, malignant tumor, and severe liver or kidney diseases) or a history of systemic surgery (e.g., coronary artery bypass grafting, arterial/venous thrombolysis, organ transplantation, etc.).
• Complicated with cognitive impairment (MMSE score < 24), mental illness (e.g., schizophrenia, bipolar disorder), or inability to cooperate with questionnaires and ophthalmic examinations due to language comprehension deficits.

Participants are planned to be enrolled from the outpatient department of Zhongshan Ophthalmic Center, as well as community populations in Guangzhou and surrounding provinces and cities.