Abstract
Purpose:
To investigate the relationship between retinal blood oxygen saturation (SO2) and aqueous humor (AH) concentrations of protein biomarkers in diabetic patients with non-proliferative diabetic retinopathy (NPDR) and to compare them with those of control subjects.
Methods:
The sample comprised 14 participants with mild-to-moderate NPDR (66.3 ± 9.1 years) and 17 age-matched controls (69.1 ± 5.7 years); all participants were previously scheduled for routine cataract extraction with intraocular lens implantation. At the start of surgery, AH was collected using a Sautter hydrodissection cannula (27G, 0.4x22mm; Geuder, Heidelberg, Germany). Multiplex cytokine analyses of 26 biomarkers, including Angiopoietin 2 (Ang 2), Epidermal Growth Factor (EGF), Hepatocyte Growth Factor (HGF) and Interleukin-8 (IL-8) were performed by BioPlex 200 system (Bio-Rad Laboratories, Inc., Hercules, CA, USA). Four weeks after uncomplicated surgery and 2 weeks after cessation of any anti-inflammatory eyedrops, non-invasive hyperspectral retinal (HR) imaging (prototype H-8.5 HR Camera, Optina, QC, Canada) was undertaken. Six repeated retinal images were acquired centered on the optic nerve head at wavelengths of 586 and 605nm using the HR camera for each subject.
Results:
Mean venular retinal blood oxygen saturation (p<0.001) and AH levels of HGF (p=0.018), Ang 2 (p=0.005), EGF (p=0.030) and IL-8 (p=0.034) were significantly higher in NDPR when compared to controls. This study demonstrated a correlation between venular retinal blood oxygen saturation and pro-angiogenic factors HGF (r=0.584, p=0.030), Ang 2 (r=0.592, p=0.026), and EGF (r=0.523, p=0.050), but did not find any correlation for IL-8 (r=0.435, p=0.120) even though this biomarker was significantly higher in the diabetic group.
Conclusions:
The results of this study revealed a direct relationship between retinal blood SO2 and Ang 2, EGF and HGF but not IL-8.