Abstract
ObjectiveDetection of vascular endothelial growth factor (VEGF) levels in ocular tissue may perhaps provide insight into the role of VEGF in the pathogenesis and progression of diabetic retinopathy (DR). The aim of this study was to evaluate the levels of VEGF in tears and serum amongst type 2 diabetes mellitus (DM) patients.MethodsA comparative cross-sectional study was conducted between August 2016 and May 2018 involving type 2 DM patients with no DR, non-proliferative DR (NPDR), and proliferative DR (PDR). Tear samples were collected using no.41 Whatman filter paper (Schirmer strips) and 5 mL blood samples were drawn by venous puncture. VEGF levels in tears and serum were measured by enzyme-linked immunosorbent assay.ResultsA total of 88 type 2 DM patients (no DR: 30 patients, NPDR: 28 patients, PDR: 30 patients) were included in the study. Mean tear VEGF levels were significantly higher in the NPDR and PDR groups (114.4 SD 52.5 pg/mL and 150.8 SD 49.7 pg/mL, respectively) compared to the no DR group (40.4 SD 26.5 pg/mL, p < 0.001). There was no significant difference in the mean serum VEGF levels between the three groups. There was a fair correlation between serum and tear VEGF levels (p = 0.015, r = 0.263).ConclusionVEGF levels in tears were significantly higher amongst diabetic patients with DR compared to those without DR and were significantly associated with the severity of DR. There was a fair correlation between serum and tear VEGF levels. Detection of VEGF in tears is a good non-invasive predictor test for the severity of DR. A large cohort study is needed for further evaluation.
Highlights
Diabetic retinopathy (DR) is the leading cause of blindness in the working-age population and has a considerable economic burden on society, especially on healthcare systems [1,2]
Mean tear Vascular endothelial growth factor (VEGF) levels were significantly higher in the non-proliferative DR (NPDR) and proliferative diabetic retinopathy (PDR) groups (114.4 Standard deviation (SD) 52.5 pg/mL and 150.8 SD 49.7 pg/mL, respectively) compared to the no DR group (40.4 SD 26.5 pg/mL, p < 0.001)
There was no significant difference in the mean serum VEGF levels between the three groups
Summary
Diabetic retinopathy (DR) is the leading cause of blindness in the working-age population and has a considerable economic burden on society, especially on healthcare systems [1,2]. Microvasculopathy and inflammation are the main pathways involved in the pathogenesis of DR [4]. Studies have shown that the breakdown of the blood-retinal barrier is due to high levels of inflammatory mediators and cytokines [5,6,7,8]. Vascular endothelial growth factor (VEGF) is involved in the angiogenesis process of DR. VEGF has been associated with many other neovascular retinopathies, such as ischemic retinal vein occlusion and retinopathy of prematurity [9]. VEGF levels are reduced during the quiescent phase of proliferative diabetic retinopathy (PDR) and diminish after successful laser therapy [10]
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