الفهرس 
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Abstract
Diabetes mellitus (DM) is a major medical problem throughout the world. Patients with diabetes often develop ophthalmic complications, such as corneal abnormalities, glaucoma, iris neovascularization, cataracts, retinopathy and neuropathies.
The exact mechanism by which diabetes causes retinopathy remains unclear, but several theories have been postulated to explain the typical course and history of the disease.
Optical coherence tomography angiography (OCTA) allows three-dimensional visualization of retinal, choroidal and optic disc vascular networks. This technology depends on the detection of motion-related signals from back-reflected light from the fundus. The advantage enables visualization of 4-retinal capillary layers, which allows physicians to determine in which layer the capillary pathologies, such as microaneurysms, capillary dilation, and capillary non-perfusion area, are present in diabetic maculopathy and vein occlusive diseases.
The aim of the study is to compare the optical coherence tomography angiography findings in diabetic patients with either no or early diabetic changes in the form of NPDR according to ETDRS classification and comparing them with age matched healthy controls.
This prospective cross sectional study included a total of 78 eyes of 40 patients (27 eyes of 13 healthy participants, 25 eyes of 13 diabetic patients without diabetic changes on fundus examination, and 26 eyes of 14 patients with mild non-proliferative diabetic retinopathy “NPDR” on fundus examination).
All patients subjected to history taking and full ophthalmological examination before performing OCTA.
In group A (healthy controls), the majority of them (76.9%) with age range 40-49 years old. The mean size of vessel density measurements of the Superficial layer is (Whole image 47.2 ± 5.5, fovea 30.8 ± 7.9 and parafovea 50.8 ± 4.9). The mean size of vessel density measurements of the deep layer is (Whole image 52.5± 8.1, fovea 33.9± 9.7and parafovea 59.6± 5.1).The mean size of vessel density measurements of the Choriocapillaries layer is (Whole image 66.0± 1.4, fovea 65.6± 4.0 and parafovea 65.8± 1.6). The mean HA1C is 4.83 ± 0.46.
In group B (No diabetic changes), the majority of them (46.2%) with age range 40-49 years old. The mean duration of DM is 6.62 ± 3.36 with significant difference with group C. About 69.2% of them are on oral hypoglycemic and 53.8% are hypertensive. The mean size of vessel density measurements of the Superficial layer is (Whole image 45.5 ± 3.8, fovea 27.7 ± 4.8 and parafovea 47.1 ± 4.4). The mean size of vessel density measurements of the deep layer is (Whole image 52.5± 6.8, fovea 28.1± 6.9 and parafovea 58.5± 5.1).The mean size of vessel density measurements of the Choriocapillaries layer is (Whole image 65.2± 1.6, fovea 64.4± 3.8 and parafovea 65.1± 1.6). The mean HA1C is 5.53 ± 0.64.
In group C (Mild NPDR), the majority of them (42.9%) with age range 40-49 years old. The mean duration of DM is 14 ± 4.30 with significant difference with group B. The majority of them (71.4%) are on insulin and 28.6% are hypertensive. The mean size of vessel density measurements of the Superficial layer is (Whole image 42.8 ± 3.9, fovea 27.1 ± 5.4 and parafovea 43.7 ± 4.9). The mean size of vessel density measurements of the deep layer is (Whole image 43.1± 7.9, fovea 24.91± 5.1 and parafovea 48.55± 6.6).The mean size of vessel density measurements of the Choriocapillaries layer is (Whole image 63.9± 1.6, fovea 61.7± 3.2 and parafovea 64.0± 1.9). The mean HA1C is 7.76 ± 1.01.
There is a statistically significant difference in HbA1C between all study groups. Gropu B and C have a significantly higher levels of HbA1C than group A, however, the difference in HbA1C between group B and C was not statistically significant. group B and C have significantly moderate inverse correlation with vessel density particularly in the choriocapillaries layer, but not in group A. Although group B and C have moderate inverse correlation with vessel density, it was only statistically significant in choriocapillaries layers in group B.