ObjectiveTo observe and evaluate the functional-structural correlations of quick contrast sensitivity function (qCSF), quantitative color vision, best-corrected visual acuity (BCVA), and peripapillary retinal nerve fiber layer (pRNFL) thickness among different stages of diabetic retinopathy (DR). MethodsA prospective cross-sectional observational study. From November 2023 to August 2025, 135 eyes of 79 patients with type 2 diabetes diagnosed at the Endocrinology Department of Lanzhou University Second Hospital were enrolled. According to the presence and severity of DR, the eyes were divided into no DR (NDR) group (53 patients, 99 eyes), non-proliferative DR (NPDR) group (18 patients, 27 eyes), and proliferative DR (PDR) group (8 patients, 9 eyes). Forty healthy volunteers (80 eyes) were selected as the control group during the same period. All subjects underwent BCVA, qCSF, color vision, and optical coherence tomography (OCT) examinations. BCVA was measured using the international standard visual acuity chart and converted to logarithm of the minimum angle of resolution (logMAR) for statistical analysis. Contrast sensitivity (CS) was measured at spatial frequencies of 3, 6, 12, and 18 cpd using a CS test instrument; the complete qCSF was plotted using Bayesian adaptive psychophysical algorithms, and the area under the log CS function (AULCSF) was exported. The average, superior, nasal, temporal, and inferior pRNFL thicknesses were measured using OCT. Binary logistic regression analysis was performed to identify risk factors affecting different stages of DR progression; receiver operating characteristic (ROC) curve analysis was used to evaluate diagnostic efficacy. ResultsSignificant differences were found among the control, NDR, NPDR, and PDR groups in logMAR BCVA (H=41.077), AULCSF (F=48.893), CS at different spatial frequencies (F=27.528, 35.194, 49.427, 39.689), color vision (H=41.165), and inferior and temporal pRNFL thicknesses (F=6.518, 3.177; P＜0.005). No significant differences were observed in superior, nasal, or average pRNFL thicknesses (F=1.828, 1.832, 0.934; P＞0.05). Multivariate binary logistic regression analysis showed that AULCSF and CS at 3 and 6 cpd were independent protective factors for DR progression (P＜0.05); color vision was an independent protective factor for DR progression (P＜0.05); BCVA was an independent risk factor for NPDR and PDR (P＜0.05), and pRNFL thickness was an independent protective factor for NPDR and PDR (P＜0.05). ROC curve analysis showed that the AUC values of AULCSF and color vision in distinguishing NDR (AUC=0.701?0.850) and NPDR (AUC=0.642?0.838) were higher than those of BCVA (AUC=0.610?0.726) and pRNFL thickness (AUC=0.501?0.560). ConclusionsDuring the progression of DR, qCSF and quantitative color vision can identify neural functional abnormalities earlier than visual acuity decline and structural damage during DR progression.