الفهرس 
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Abstract
Diabetic Retinopathy is mostly a vascular disease where the development of macular oedema and proliferative retinopathy are major causes of visual impairment. Over the last years a lot of work has been done on early diagnosis of DR and on looking for new ocular diagnostic tools useful in evaluating patients affected by diabetes. (Mastropasqua, et al., 2017)
It has been reported that retinal blood flow decreases in patients with type 2 diabetes mellitus who have no or mild DR, suggesting that the retinal microvasculature becomes impaired in early-stage DR, even in patients with no evidence of retinopathy. (Al-Sheikh,et al., 2016)
The FAZ is extremely sensitive to biological events and tracking the morphology of this region can provide insights into possible pathologic processes, specifically FAZ enlargement in DR. Therefore, exploring the relationship between the FAZ characteristics and onset and progression of disease may offer an early diagnostic tool that might allow for early detection before irreversible changes occur. (Bates,et al., 2018)
Enlargement of the foveal avascular zone (FAZ) is associated with visual deterioration in patients with diabetic retinopathy. (Lynch, et al., 2018)
DMI is an irreversible category of diabetic maculopathy, and its presence limits the potential benefits of treatments for DR. (Garcia, et al., 2016) and clinically, DMI is defined by an enlargement of the foveal avascular zone (FAZ) and paramacular areas of capillary non-perfusion. (Bradley, et al., 2016)
Introduction of optical coherence tomography angiography (OCTA) has allowed the opportunity both to study retinal vasculature without the need for dye injection and to image the two plexuses. Moreover, OCTA is able to image and evaluate both the presence of retinal vascular abnormalities and neovascularization associated to diabetes. (Ishibazawa, et al., 2015)
The results of our study showed that the FAZ area at the levels of the superficial and deep vascular networks of eyes with DR was found to be larger compared with those of age-matched healthy controls. And as would be expected, control eyes had higher vascular density in both networks compared with the diabetic eyes. Furthermore, eyes with worse DR stage showed larger FAZ area and lower vascular density values. This study also showed that angiographic parameters, namely FAZ area and VD correlated with best corrected visual acuity.