PURPOSE: To investigate possible correlations between vitreous and/or serum levels of platelet-derived growth factor isoforms (PDGF-AA, -AB and -BB) with parameters associated with non-proliferative diabetic retinopathy (NPDR) and clinically significant macula oedema (CSMO); to compare the results to relevant results regarding vascular endothelial growth factor (VEGF), which is an established growth factor affecting NPDR.METHODS: Fifteen patients with NPDR, 31 patients with proliferative diabetic retinopathy (PDR) and 15 non-diabetic patients were included in the study. Vitreous and serum samples were obtained during vitrectomy. PDGF-AA, -AB and -BB, as well as VEGF, were measured by enzyme-linked immunosorbent assay (ELISA).RESULTS: PDGF-AA, -AB and -BB and VEGF were all expressed in the serum and vitreous of controls and patients with NPDR. The levels of PDGF-AA, PDGF-AB and VEGF in vitreous were significantly increased in the NPDR group compared to controls, while PDGF-BB levels were significantly decreased in the NPDR group compared to controls. The levels of all PDGF isoforms and VEGF in vitreous were significantly increased in the PDR group compared to the NPDR group. No such differences were evident in serum. PDGF-AA and VEGF correlated significantly to the severity of NPDR. PDGF or VEGF in vitreous of NPDR patients did not correlate with retinal photocoagulation (RP) or the serum levels of haemoglobin A1c (HbA1c). There was no correlation between the vitreous and serum levels of VEGF or PDGF in patients with PDR. Only PDGF-AB vitreous levels correlated significantly with PDGF-BB vitreous levels in the NPDR group.CONCLUSION: It appears that in addition to VEGF, almost all PDGF isoforms in the vitreous are also correlated with NPDR and CSMO.