This cross-sectional study was performed at the Zhongshan Ophthalmic Centre (ZOC), Sun Yat-sen University, Guangzhou, China. The study protocol was approved by the Institute Ethics Committee of ZOC. The study was performed according to the tenets of the Helsinki Declaration. All participants gave written informed consent before entering the study. Guangzhou is the largest city in Southern China and all patients with DM are required to register in the community health system. Patients with DM from communities near the ZOC were recruited for this study. The inclusion criteria for our study participants were as follows: (1) type 2 DM and aged 30 to 80 years, (2) no history of ocular treatment (ocular treatment naïve), (3) visual acuity of 0.1 or more and able to complete an eye examination, (4) spherical degree of >–6 diopters (D), astigmatism of <1.5 D, and axial length (AL) of <26 mm. Participants were excluded in the presence of any of the following conditions: (1) history of serious systemic diseases other than diabetes, such as uncontrolled hypertension, serious cardiovascular and cerebrovascular diseases, malignant tumor, or nephritis; (2) history of systemic surgery, thrombolysis therapy, or renal dialysis; (3) glaucoma, vitreous-macular diseases (vitreous hemorrhage and retinal detachment), or amblyopia; (5) history of retina laser or intraocular injection, glaucoma surgery, cataract surgery, or corneal refractive surgery; and (6) poor quality of fundus or OCT images resulting from abnormal refractive media (such as moderate to severe cataract, corneal ulcer, or severe pterygium, signal strength index (SSI) for OCT imaging ≤50), poor fixation or other causes.