Retinal oximetry in vascular diseases

Abstract

Retinal oximetry imaging of retinal blood vessels measures oxygen saturation of haemoglobin. The imaging technology is non‐invasive and reproducible with remarkably low variability on test–retest studies and in healthy cohorts. Pathophysiological principles and novel biomarkers in several retinal diseases have been discovered, as well as possible applications for systemic disease. The aim of this presentation is review of state of the art knowledge of us of retinal oximetry in vascular diseases and its possible clinical application.In diabetic retinopathy, retinal venous oxygen saturation is elevated and arteriovenous difference progressively reduced in advanced stages of retinopathy compared with healthy persons. This correlates with pathophysiology of diabetic retinopathy where hypoxia stimulates VEGF production. Laser treatment and vitrectomy both improve retinal oximetry values, which correlate with clinical outcome. The oximetry biomarker may allow automatic measurement of severity of diabetic retinopathy and predict its response to treatment.Central retinal vein occlusion is characterized by retinal hypoxia, which is evident in retinal oximetry. The retinal hypoxia seen on oximetry correlates with the extent of peripheral ischemia, visual acuity and thickness of macular oedema. This biomarker may help diagnose and measure severity of vein occlusion and degree of retinal ischemia.Retinal oxygen metabolism is altered in uveitis associated with VKH disease. Oxygen saturation profile is abnormal in acute uveitic phase of the disease and returns to normal in those who recover with normal fundus appearance, but not in eyes that suffer permanent anatomical damage with “sunset glow fundus” and chorioretinal atrophy. Retinal oximetry may be of value in evaluating vascular and metabolic aspects of posterior uveitis.