Purpose

To correlate angiogenic cytokines in the aqueous humour with total retinal blood flow in subjects with type 2 diabetes with non-proliferative diabetic retinopathy (NPDR).

Methods

A total of 17 controls and 16 NPDR patients were recruited into the study. Aqueous humour was collected at the start of cataract surgery to assess the concentration of 14 angiogenic cytokines. Aqueous humour was analysed using the suspension array method. Six images were acquired to assess total retinal blood flow (TRBF) using the prototype RTVue^™ Doppler Fourier domain optical coherence tomography (Doppler FD-OCT) (Optovue, Inc., Fremont, CA) using a double circular scan protocol, 1 month postsurgery. At the same visit, forearm blood was collected to determine glycosylated haemoglobin (A1c).

Results

Transforming growth factor beta (TGF-β1, TGF-β2) and PLGF were increased while FGF-1 was reduced in NPDR compared to controls (Bonferroni corrected, p < 0.003 for all). Total retinal blood flow (TRBF) was significantly reduced in the NPDR group compared to controls (33.1 ± 9.9 versus 43.3 ± 5.3 μl/min, p = 0.002). Aqueous FGF-1 significantly correlated with TRBF in the NPDR group (r = 0.71, p = 0.01; r²  = 0.51). In a multiple regression analysis, A1c was found to be a significant predictor of aqueous TGF-β1 and FGF-1 (p = 0.018 and p = 0.020, respectively).

Conclusion

Aqueous angiogenic cytokines (TGF-β1, TGF-β2 and PLGF) were elevated in conjunction with a reduction in TRBF in patients with NPDR compared to controls. Non-invasive measurement of TRBF may be useful for predicting aqueous FGF-1 levels and severity of vasculopathy in DR.