Superficial and deep vascular structure of the retina in diabetic macular ischaemia: OCT angiography

Diabetic macular ischaemia (DMI) is a major cause of visual loss in patients with diabetic retinopathy. Although the incidence is not well known, some clinical studies have reported an estimate of approximately 7% of all patients with diabetic retinopathy. The DMI is morphologically appreciable by means of fluorescein angiography (FA) that shows an enlargement of the foveal avascular zone (FAZ) as well as the interruption of capillaries all around the foveal region. However, FA needs dye injection to observe retinal circulation and might have significant adverse events ranging from discomfort and nausea to, in rare cases, anaphylaxis. Optical coherence tomography (OCT) has introduced a new method to visualize the retina by means of cross-sectional images with increased speed and sensitivity over time. This method, known as OCT angiography based on split spectrum amplitude decorrelation angiography (SSADA), is able to detect small changes in retinal vascular microcirculation (Jia et al. 2012). The SSADA has been successfully reported for retinal circulation assessment in healthy eyes (Savastano et al. 2015). The capillary perfusion density values in diabetic eyes were evaluated by Agemy et al. (2015). However, they reported limited information available about OCT angiography changes in DMI. The aim of this study was to evaluate the perifoveal vascular structure in DMI eyes using OCT angiography (OCT-A).