الفهرس 
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Abstract
Summary and Conclusion
Diabetic retinopathy is a chronic progressive, potentially sight-threatening disease of the retinal microvasculature associated with the prolonged hyperglycaemia and other conditions linked to diabetes mellitus such as hypertension.
Diabetic retinopathy falls into two main classes: nonproliferative and proliferative. The word “proliferative” refers to whether or not there is neovascularization (abnormal blood vessel growth) in the retinaEarly disease without neovascularization is called nonproliferative diabetic retinopathy (NPDR). As the disease progresses, it may evolve into proliferative diabetic retinopathy (PDR), which is defined by the presence of neovascularization and has a greater potential for serious visual consequences.
Ganglion Cell Layer
This layer contains about 1.2 million ganglion cells as well as a number of other cell types, including “displaced” amacrine cells, astrocytes, endothelial cells, and pericytes. The thickness of the ganglion cell layer is greatest in the perifoveal macula consisting of between eight and ten rows of nuclei (60–80 μm), decreases to a single row outside the macula (10–20 μm), and is absent from the foveola itself.
Nerve Fiber Layer
Ganglionic axons travel towards the optic nerve head within the nerve fiber layer. Thin and difficult to discern in the far periphery, the nerve fiber layer becomes hicker towards the disc as a result of the convergence of all retinal ganglion axon fibers on the optic disc. 44 G.D. Hildebrand and A.R. Fielder The axons are accompanied by astrocytes in the nerve fiber layer and are separated into small bundles by the cellular processes of Müller cells and the internal limiting membrane. The exact cross-sectional ordering of the axonal fibers of the peripheral and central ganglion cells in the retina remains controversial. Temporal to the disc lies the macula, which has the highest density of ganglion cells. Axons from the macula project straight to the disc, forming the papillomacular “bundle.” The remaining axons of the temporal retina reach the optic disc only by arcing around the papillomacular bundle. As a result, all temporal ganglion cell axons originating from outside the macula are compressed into the superotemporal and inferotemporal sectors of the optic nerve, above and below the temporal entry of the papillomacular bundle fibers. The superior and inferior nerve fibers are therefore much thicker (almost 200 mm) compared to the papillomacular bundle (65 mm) and easier to see on clinical examination, especially in red-free light. Nasally, axons enter the nasal half of the optic disc more or less straight. In addition, ganglion axon fibers do not cross the horizontal meridian (the horizontal raphe).
OCT has made its most significant clinical contribution in the field of ophthalmology, where it has become a key diagnostic technology in the areas of retinal diseases and glaucoma. Retinal OCT imaging provides high-resolution imagery of subsurface retinal features that were previously inaccessible with fluorescein angiography and ophthalmic ultrasound. The contrasting structure and reflectivity in the retinal layers allow for differentiation of the retinal nerve fiber layer _RNFL_, nuclear layers, plexiform layers, external limiting membrane, retinal pigment epithelium, photoreceptor layers, and choriocapillaris. In OCT images of the retina, horizontal cell orientation is correlated with high reflectivity, while nuclei and vertical structures have low reflectivity. OCT has been used to diagnose a number of vitreoretinal conditions. In addition to the evaluation of normal vitreous separation caused by aging.
Macular edema, a thickening and swelling occurring when fluid and protein deposits collect on or under the macula, is often a complication of diabetic retinopathy and can be caused by fluid leakage from abnormal blood vessels or traction by the vitreous gel. While fluorescein angiography remains the only method for the identification of leaking vessels, it cannot identify cases of nonvascular macular edema. OCT, however, has been extensively employed for the identification of cystoid macular edema and the monitoring of macular thickness, which is correlated to a decrease in central vision.
In our study we evaluate the NFL and GCC thickness in type II diabetic patients comparing the thickness among the control group, diabetic group with no diabetic retinopathy. NPDR group and PDR group. Our study was conducted on sixty eyes of randomly selected Egyptian healthy subjects, 30 males and 30 female with the age group between 20-65 (, they equally divided into four groups control group, Diabetic group with no diabetic retinopathy, NPDR group and PDR group. A method called enhanced depth imaging spectral-domain optical coherence tomography (EDI OCT) has been developed that enables in vivo cross-sectional imaging of the NFL and GCC thickness. As an accurate evaluation of NFL and GCC thickness is obtained by measuring the distance between the ILM and INL/IPL and compare it to quietly averaged normative database obtained from control group and comparing it with the other 3 groups.
A method called enhanced depth imaging spectral-domain optical coherence tomography (EDI OCT) has been developed that enables in vivo cross-sectional imaging of the NFL and GCC thickness. As an accurate evaluation of NFL and GCC thickness is obtained by measuring the distance between the ILM and INL/IPL and compare it to quietly averaged normative database obtained from control group and comparing it with the other 3 groups. We found that NFL and GCC thickness was thickest in inferior 6 mm, nasal 6mm, temporal 3mm. and temporal 6mm. and thinnest in the nasal 3 mm.