الفهرس 
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Abstract
D
iabetic retinopathy (DR) is one of the most common diabetic complications, which has become a leading cause for vision loss, mainly because of macular edema and vitreous hemorrhage.
from 1990–2010, DR ranked as the fifth most common cause of preventable blindness and fifth most common cause of moderate to severe visual impairment.
In 2010, of an estimated 285 million people worldwide with diabetes, over one-third have signs of DR, and a third of these are afflicted with vision-threatening diabetic retinopathy (VTDR), defined as severe non-proliferative DR or proliferative DR (PDR) or the presence of diabetic macular edema (DME).
OCT angiography (OCT-A), a dye-free imaging technique useful to visualize retinal and choroidal vasculature, has allowed to detect angiographic features of DR and changes in the macular capillary network, even before disease onset. In patients with DR, areas of nonperfusion and their localization in the superficial and deep plexuses, irregular capillaries and micro aneurysms have been clearly analyzed.
We conducted our study to use Optical Coherence Tomography(OCT) and Optical Coherence Tomography Angiography (OCT-A) for qualitative and quantitative assessment of retinal vascular density in superficial capillary plexus, quantitative assessment of foveal avascular zone, choroidal vascular density map, assessment of retinal thickness and choroidal thickness in normal individuals and diabetic patients with and without diabetic retinopathy (DR).
This study included 64 eyes. diabetics and control group were recruited from internal medicine clinic in Misr University for science and Technology Hospital and asked to participate in this study.
This study was designed as an observational and cross sectional study in the period from 9/2018 to 2/2019.
Study Population:
Eyes were divided into 4 groups:
Group1: consists of 16 eyes of normal healthy individuals (control group).
group 2: consist of 16 eyes with clinical diagnosis of non diabetic retinapathy,
Group3: consists of 16 eyes with clinical diagnosis of non proliferative diabetic retinopathy.
Group4: consists of 16 eyes with clinical diagnosis of proliferative diabetic retinopathy.
Inclusion criteria:
Both sex (males & females).
Best-corrected visual acuity (BCVA) greater than 0.5 logMAR in the study eye at baseline examination (to ensure proper execution of examination)
Age 30-60years old
Exclusion criteria:
Iop more than 21 mmHg
High myopia.
Media opacity in the study eye
All subjects participating in the study asked to sign consent before inclusion. Then they subjected to: full medical, family histories, and complete ocular examination (best corrected visual acuity, intraocular pressure and dilated fundus examination).
We defined diabetes according to World Health Organization guidelines as fasting plasma glucose ≥ 126 mg/dl or 2-h plasma glucose ≥ 200 mg/dl or being on antidiabetic medication. The controls (group N) had normal glycaemic values
DR was graded into non diabetic retinapathy, mild, moderate, and severe/very severe non-proliferative DR (NPDR) or proliferative diabetic retinopathy as per ETDRS classification (World Health Organization, 2006).
SS-OCT and OCT angiography image acquisition. During the same visit, all study subjects underwent swept-source (SS)-OCT examination (DRI Triton, Topcon, Tokyo, Japan), which contains a 1,050-nm-wavelength swept light source and has a scanning speed of 100,000 A-scans/second.
Optical coherence topography OCT was done to acquire:-
a- Retinal thickness at the fovea and para foveal area using a a six-line radial pattern scan (1,024 A-scans) centered on the fovea from each eye
b- Choroidal thickness measured (nasal, temporal, superior and inferior) at 2 mm from the fovea.
We obtained a six-line radial pattern scan (1,024 A-scans) centered on the fovea from each eye. The definition of choroidal thickness was the vertical distance between the posterior edge of the hyper-reflective retinal pigment epithelium and the choroid/sclera junction. The choroidal thickness was manually measured using a built-in caliper in the OCT software OCT –Angiography was done
To study (qualitatively and quantitatively)
Quantitative measuring of Foveal Avascular Zone (FAZ) area at SCP using the (3x3 mm scan) we outlined the FAZ area and perimeter manually along the innermost capillaries on OCT angiography images at the SCP.
Superficial capillary plexus (SCP) and Deep capillary plexus (DCP) (qualitative analysis) at the parafoveal area in (4.5x4.5 mm scan).
Quantitative measuring the retinal vessels density map at the SCP in the (4.5x4.5 mm scan) (measured automatically by the device).
Measuring the choroidal vessels density map in the (4.5x4.5 mm scan) (Measured manually by the operator by applying a superior line at the level of Bruchs membrane and an inferior line at the sclera –choroidal interface (SCI).
The OCT device automatically segments the layers using a built-in segmentation algorithm for the superficial plexus (2.6 μm below the internal limiting membrane to 15.6 μm below the junction between the inner plexiform and inner nuclear layers (IPL/INL) and deep plexus (15.6 μm below the IPL/INL to 70.2 μm below the IPL/INL). En face projections of volumetric scans allow for the visualization of structural and vascular details within segmented retinal layer boundaries. We only used OCT images with a signal strength index >60 and excluded scans with poor image quality. Scans with poor image quality met these criteria: (1) poor fixation resulting in a double vessel pattern and motion artifacts, (2) weak local signal or poor clarity, (3) macular edema, and (4) macular segmentation errors.
All data was collected and analyzed statistically.
The results showed that the 4 groups comparable in age, sex, and best corrected visual acuity
The results showed that:
There is decrease in choroidal thickness in diabetic patient
There is increase in FAZ area in diabetic patients.
There is decrease in vessel density at the superficial capillary plexus in diabetic patients.
There is decrease in Choroidal vascular density in diabetic patients.
There is decrease in retinal thickness in diabetic patients and there is no significant differences in the retinal thickness between control subjects and patients with NDR.