Historically, diabetic retinopathy has been recognized as a vascular disease. Recent clinical evidence suggests the initiation of diabetic retinopathy with neuropathy rather than microangiopathy. However, the molecular mechanism that drives diabetic retinopathy-associated neuropathy remains mostly unexplored. Here, we reported progressive diabetic retinopathy defects in blood glucose levels, shortening of cone segments and uncoupled appearance of retinal vascular abnormalities from pdx1 +/− mutants zebrafish to glucose-treated pdx1 +/− mutants zebrafish of both sexes. Further single-cell transcriptomic analysis revealed cones as the most vulnerable retinal neuron type that underwent three developmentally progressive cell states (States 1-3), predominantly present in WT animals, pdx1 +/− mutants, and glucose-treated pdx1 +/− mutants, respectively. Mechanistically, the expression of hcn1 was progressively decreased in cones during its transition from State 1 to State 3. Furthermore, genetic hcn1 disruption r...