OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FEATURES OF DIABETIC RETINOPATHY

Diabetic retinopathy is a microangiopathy that causes capillary occlusion, vascular hyperpermeability, and neovascularization in the retinal vasculature.1 Detailed clinical examination for grading disease severity for risk of progression and vision loss is the standard of care2, but ophthalmic angiography has played a critical role in understanding and care of the disease. Early Treatment of Diabetic Retinopathy Study (ETDRS) examined the fluorescein angiographic features of the posterior pole of patients with non-proliferative diabetic retinopathy and correlated the specific features with their risk of disease progression. 3,4 Fluorescein angiography (FA) is also used to identify retinal neovascularization (RNV) in situations where clinical examination cannot detect RNV or distinguish from other anomalous appearing vessels on the retinal surface. While angiography provides valuable additional information compared to clinical examination or fundus photography, it is not part of the routine diabetic eye examination. FA requires venipuncture and intravenous injection of a dye that has a moderate risk of nausea and a rare but well documented risk of anaphylaxis and death. 5 Also, a standard protocol FA acquires images over 10 minutes with repeated exposure to a very bright light source, 6 which can cause significant discomfort for patients. Optical coherence tomography (OCT) angiography, a novel imaging technique that uses decorrelation between resampled images to detect flow to construct 2- and 3-dimensional images of blood flow within the eye, offers an alternative angiographic technique without some of the drawbacks of FA. Our group has developed the split-spectrum amplitude decorrelation algorithm (SSADA) for efficiently detecting flow signals for angiography. 7 Applying this algorithm, an OCT angiogram in areas up to 6 × 6 mm area can be acquired in 3.5 seconds without intravenous injection. This study describes features of diabetic retinopathy as seen on OCT angiography.