Inclusion Criteria:

• Aged ≥ 18 years of age, regardless of gender, with or without type 2 diabetes mellitus and its associated ocular complications; clear consciousness, capable of cooperating with iris OCTA examination (able to stabilize the head to guarantee successful acquisition and interpretable images).
• Voluntary participation in this study with signed written informed consent.
• No history of intraocular surgery in the examined eye (including cataract surgery, glaucoma filtering surgery, retinal surgery, etc.).
• General physical conditions: No acute disease episodes within the recent 3 months (such as acute myocardial infarction, stroke, diabetic ketoacidosis); no severe liver or renal dysfunction (ALT and AST ≤ 2 times the upper limit of normal, serum creatinine ≤ 133 μmol/L).

Exclusion Criteria:

• The studied eye suffers from other ocular diseases that may interfere with examination results apart from the disorders specified in Criterion 1 of the inclusion criteria (e.g., uveitis, retinal vein occlusion, high myopia-related fundus lesions, etc.); invasive ocular treatments were administered to the studied eye within the past 6 months (e.g., retinal laser photocoagulation, intravitreal injection, etc.).
• Subjects complicated with type 1 diabetes mellitus, gestational diabetes mellitus or other specific types of diabetes mellitus; those with autoimmune diseases (e.g., rheumatoid arthritis, systemic lupus erythematosus) or hematological diseases (e.g., leukemia, aplastic anemia); individuals who have taken medications affecting ocular microcirculation (e.g., alprostadil, nitrates) within the past 3 months and are unable to discontinue such drugs.
• Subjects with severe head tremors and inability to maintain a fixed posture during examination, resulting in substandard OCTA image quality (interpretable area < 80%); those with mental disorders or cognitive dysfunction who fail to understand and cooperate with the examination procedures.