Retinal Vessel Oxygenation in Diabetic Retinopathy (2015)
Undergraduates: Teresa Martz, Abhi Guduru, B.S. Alexa Waters, B.S.
Faculty Advisor: Seema Garg
Department: Biology
Diabetic retinopathy (DR) is a disease caused by damage to the blood vessels in the retina as a result of chronic hyperglycemia, and thus has been linked to inner retina hypoxia as a result of blood supply deprivation. It is further suggested that poor oxygen distribution in the retina of DR patients leads to high SO2 (oxygen saturation) in retinal blood vessels. However, constraints in non-invasive measurement techniques have limited the understanding of this relationship. For this reason, retinal oximetry, a new noninvasive imaging method to measure retinal vessel hemoglobin oxygen saturation, may be an effective diagnostic tool to evaluate patients with a range of severity of diabetic retinopathy. In this study, retinal vessel oxygenation was found using retinal oximetry image analysis for six stages of disease: no diabetes, diabetes without DR, mild nonproliferative retinopathy (NPDR), moderate NPDR, severe NPDR and proliferative DR. Results indicated that there was a significant increase in both arteriole and venule oxygenation in patients with moderate NPDR, severe NPDR and PDR, with venous oxygenation values increasing more significantly. There is also a significant increase in arteriole and venule oxygen saturation in PDR patients in comparison to patients in the health control and DM w/o DR groups (venous: p=0.000 and 0.004; arterial: p=0.003 and 0.001), as well as a significant increase in venous oxygen saturation between healthy patients and moderate NPDR patients (p=0.038). The results indicate a decrease in the efficiency of the oxygen exchange due to ischemia and endothelial damage as the severity of diabetic retinopathy increases. However, significance was not found in the arterio-venous difference in oxygen saturation, suggesting that in response to the damaged endothelium of the vessels, there is a concomitant increase of arteriole saturation alongside the venous saturation. The significant correlation between increasing severity of DR and incr