الفهرس 
EPIDEMIOLOGY AND PATHOPHYSIOLOGY OF DIABETIC MACULAR EDEMAOnly 14 pages are availabe for public view
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Abstract
D
iabetic retinopathy microangiopathy is characterized by formation of microaneurysms and breakdown of blood-retinal barrier with increased vascular permeability leading to the retinal swelling in DME. Because vascular endothelial growth factor (VEGF) is the most significant factor in the development of prolifrative diabetic retinopathy (PDR) and diabetic macular edema (DME), anti-VEGF agents are used as the primary therapy for DME, effectively improving macular odema and vision in most patients.
DME is the result of microvascular retinal changes due to the effects of hyperglycemia and hypoxia, which cause biochemical and structural changes, leading to damage of the BRB. This leads to increased vascular permeability and edema, with extravasation of fluid and plasma constituents. Subsequently, lipoproteins accumulate in the macula forming hard exudates
VEGF is a proinflammatory cytokine, which is important in causing vascular leakage in diabetic eyes. Thus, anti-VEGF drugs are delivered as intravitreal injections in order to treat center-involving DME
Optical coherence tomography (OCT)-angiography is a new method of analysis based on high-resolution imaging techniques whereby the retinal and choroidal circulation can be visualized without the need to injection of any contrast agent. This new technology is therefore noninvasive, unlike fluorescein angiography that is currently still considered to be the gold standard of retinal vascular imaging. Angio-OCT is capable of detecting endoluminal flow at any time, is thus independent of time, and of administration of the contrast medium as instead occurs with fluorangiography.
Numerous studies demonstrated quantitative OCTA metrics on SCP and DCP are correlated with severity of DR, suggesting that the extent of microvascular damage in individual capillary plexus can be quantified from OCTA. These studies generally reported that enlarged FAZ area, decreased FAZ circularity and lower VD are significantly associated with worsening DR. For example, a decreased VD is associated with worsening DR and other studies showed an enlarged FAZ area, decreased FAZ circularity, lower VD on SCP, enlarged FAZ area and lower VD on DCP, were significantly associated with worsening DR.
In the present study we investigated the changes in OCT angiography biomarkers which are the FAZ area, FAZ perimeter, the acircularity index and the vessel density in the superficial and deep capillary plexus in patients with DME under treatment with antiVEGF injections.
There was a statistically significant decrease in the FAZ area and FAZ perimeter during the follow up period denoting improved vascular perfusion, and the FAZ AI decreased significantly denoting that the FAZ regained its regularity.
There was a statistically significant increase in the vessel density in the parafoveal area of the superficial plexus during the follow up period, this might be explained by decreased artifacts due to macular edema.
There was a statistically significant difference in the parafoveal vessel density in the SCP, FAZ area, FAZ perimeter, and AI at baseline between good and poor responders. These biomarkers could be used as predictors for response after treatment with anti VEGF in eyes with DME.
CONCLUSION
I
n our study we found that parafoveal vessel density in the SCP, FAZ area, FAZ perimeter, and AI at baseline were independent predictors for a better response after ranibizumab treatment in eyes with DME. OCT angiography could be used to predict the prognosis of anti-VEGF treatment in DME. Future advancements in OCTA hardware and software will enable the identification of more precise predictors for the treatment outcomes of DME.