الفهرس 
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Abstract
Diabetic retinopathy (DR) is one of the leading causes of blindness especially in patients between 20 and 60 years of age. Early detection of DR is important to prevent loss of vision in patients with diabetes mellitus (DM). DR classically presents with micro-aneurysms and small hemorrhages in an early stage of the disease, and detected with slit- lamp biomicroscopy and fundus photography.
Although DR is generally regarded as a vascular disease, several studies have indicated that neural loss may .also occur in a very early stage of DR, even before any sign of vasculopathy can be observed .Human and experimental animal studies have shown apoptosis of neural and glial cells in the retina in a very early stage of retinopathy. Functional deficits in patients with DM have been described, such as a disordered multifocal electroretinogram, color vision disturbances and abnormal microperimetry. These abnormalities were present in the earliest stages of DR, even before development of micro-aneurysms or hemorrhages. However, gross neuroglial cell loss, as observed in rodents with experimental DM, has not been confirmed in humans as yet.
A loss of neuroglial tissue should decrease retinal thickness (RT) in the macular area. This effect of neuroglial loss would be most pronounced in the pericentral ring around the fovea, where the neuroglial cell layer is thickest. Optical coherence tomography (OCT) is the most sensitive, clinically available, non-invasive method to measure RT, able to detect even very small changes.
To investigate whether neuroglial loss is a very early manifestation of DM. OCT was used to compare pericentral retinal thickness in patients with DM, with no DR, to a healthy control group.
Eighty subjects were included in the study and divided into 2 equal groups:
Diabetics without diabetic retinopathy (DR) group(40n), and healthy control group(40n).
Full ophthalmic examination was done, slit lamp biomicroscopy, stereoscopic fundus photograph, OCT and fluorescein angiography. And also all patients underwent a physical examination, with review of medical history and current medication. Age, gender and onset of DM were recorded. The following parameters were measured: glycosylated haemoglobin (HbA1c), total cholesterol, triglycerides, serum creatinine.
Mean RT measured by OCT was calculated for the fovea, the pericentral and the paracenteral area of the macula, and compared to healthy controls.
As we go to the more thicker fovea the retinal thickness is decreased significantly (P<0.05) until it became highly significant (P<0.01)in the pericentral area which represent the thickest area in the retina after that going further to the less thicker retina , the peripheral zone the difference in retinal thickness is lessened between groups (P>0.05).
So in this study a significantly decreased pericentral RT was measured in diabetic patients with no DR compared to healthy controls. This could be explained by a loss of intraretinal neural tissue in the earliest stage of DR. and these measures could be helpful in finding a surrogate for following development of retinopathy that could affect vision.