Imaging of Hypoxia in Retinal Vascular Disease

Abstract

Retinal tissue hypoxia is a key mediator in the pathogenesis of many leading causes of irreversible vision loss, including diabetic retinopathy. Retinal hypoxia in diabetic retinopathy has been shown to drive the production of pro-inflammatory cytokines and pro-angiogenic growth factors. Together, these factors contribute to disease progression by causing unregu-lated growth of new blood vessels, increased vascular permeability and cell death within the retina. Studies have shown that retinal hypoxia precedes many of the pathologic events that occur during the progression of diabetic retinopathy such as angiopathy, microaneurysms, and capillary dropout. Therefore, early detection of hypoxia in the retinas of diabetic patients could help clinicians identify problems in patients before irreversible damage has occurred. Currently, oxygen sensitive electrodes remain the gold standard for direct measurement of oxygen tension within the retinal tissue; however the procedure is highly invasive and is therefore limited in its applicability towards preclinical models. Less invasive techniques such as retinal oximetry, phosphorescence-lifetime imaging, and hypoxia-sensitive fluorescent probes have shown promising diagnostic value in facilitating detection of oxygen imbalance correlated with neurovascular dysfunction in DR patients. This review highlights the current progress and potential of these minimally invasive hypoxia-imaging techniques in diabetic retinopathy.