Retinal blood oxygen saturation and aqueous humour biomarkers in early diabetic retinopathy

Purpose The aim of this study was to assess the relationship between retinal blood oxygen saturation ( SO 2 ) and specific aqueous humour ( AH ) concentrations of proangiogenic biomarkers in diabetic patients with nonproliferative diabetic retinopathy ( NPDR ) and to compare them with those of matched control subjects. Methods The sample comprised 14 participants with mild‐to‐moderate NPDR (69.1 ± 6.6 years) and 17 age‐matched healthy controls (69.7 ± 6.3 years); all participants were previously scheduled for routine cataract extraction with intraocular lens implantation. Multiplex cytokine analyses of specific biomarkers, including vascular endothelial growth factor A ( VEGF ‐A), angiopoietin2 (Ang2), epidermal growth factor ( EGF ), hepatocyte growth factor ( HGF ) and interleukin‐8 ( IL ‐8) were performed by BioPlex 200 system. Six non‐invasive hyperspectral retinal images were acquired. Results Mean SO 2 was significantly higher in both arterioles (94.4 ± 1.9 versus 93.0 ± 1.6) and venules (64.4 ± 5.6 versus 55.9 ± 4.8) of NPDR than in the healthy controls (p < 0.001). AH levels of HGF (p = 0.018), Ang2 (p = 0.005) and IL ‐8 (p = 0.034) were significantly higher, and EGF (p = 0.030) was significantly lower in NPDR subjects. The study demonstrated a correlation between venular retinal blood oxygen saturation and proangiogenic factors HGF ( r  = 0.558, p = 0.038), Ang2 ( r  = 0.556, p = 0.039) and EGF ( r  = −0.554, p = 0.040), but did not find any correlation for IL ‐8 ( r  = 0.330, p = 0.249) even though this biomarker was significantly higher in the diabetic group. Conclusion To our knowledge, the present study is the first report considering the association between SO 2 and AH concentrations of protein biomarkers in diabetic retinopathy. The biomarkers of interest have been shown to participate in cell death, which may explain higher oxygen saturation in NPDR .