الفهرس 
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Abstract
Diabetic retinopathy (DR), which is a typical complication of diabetes mellitus (DM), is the leading cause of blindness in 20–70 year-old patients [1].
Retinal functional abnormalities could be detected in diabetic patients before microvascular lesions can be detected in ophthalmologic examination [2].
It is becoming increasingly clear that neuronal cells of the retina are affected by diabetes, resulting in dysfunction and even degeneration of some neuronal cells. Retinal ganglion cells (RGCs) are the best studied of the retinal neurons with respect to the effect of diabetes[5].
It is thought that chronic hyperglycemia causes Cellular affection; in the form of increased intracellular glycation end products and, oxidative stress ,activation of protein kinase C isoforms.These stresses eventually lead to apoptosis and proinflammatory events [83-85].
Several reports showed specific cellular defects in the neurosensory retina . These studies included evidence of Müller cell activation , abnormal glutamatemetabolism and microglial cell activation [133-135].
The use of spectral domain OCT (SD-OCT) makes it possible to measure individual layers at higher resolution and indicates that the thinning of the inner retina in the macula is primarily due to loss of ganglion cells [3].
The aim of this study was to assess the effect of diabetes mellitus on the retinal ganglion cells through Comparing the ganglion cell complexGCC thickness –as measured using the RTVue® SD-OCT(Optovue, Inc.)machine-between a study group of diabetic patients and a control group of non diabetic subjects,and correlating this thickness with type and duration of DM,with central foveal thickness,IOP,C/D ratio,refraction and best corrected visual acuity.
The study included 62 eyes of 33 subjects , divided into two groups;
group 1 :22 diabetic patients (41 eyes) free from diabetic retinopathy (Normal fundus fluorescein angiography).
group 2 :11 non-diabetic subjects (21 eyes) , free from any ocular pathology.
The study results showed that:
- The focal loss volume (FLV%) -which is used by the RTVue® machine to measure the average amount of focal loss over the entire GCC map-was significantly more in the diabetic eyes than normal eyes.
- The global loss volume GLV% -which is used by the RTVue® machine to measure the average amount of GCC loss over the entire GCC map- was significantly more in type I DM eyes than type II DM eyes (but both types were disproportionate in number of eyes).
- The average GCC was significantly less in type I DM eyes than type II DM eyes.
- The FLV% was negatively correlated to the refraction and level of HbA1C, C/D ratio was negatively correlated to the GCC thickness, and positively correlated to the GLV% .
This results support the concept that the retina is affected as a part of the generalized process of diabetic neurodegeneration.
This concept was also supported by older studies evaluating retinal nerve fiber layer in diabetic eyes ,using autopsy samples [192,193], red-free photography [194], streptozotocin induced diabetes in rats [195] and also by using scanning laser polarimetry [196,197] or Heidelberg retina tomography [203].
Other recent studies; used SD-OCT to measure the thickness of retinal layers in diabetic eyes and comparing it to normal. The results also supported the concept of early diabetic retinal neurodegeneration [3,199,201].
The different about our study regarding the methods was the combination of both types of DM eyes in one study, correlating the results with refraction ,correlating the results with C/D ratio . While the main difference regarding results was describing the diabetic ganglion cell loss as a focal rather than diffuse loss.
Further studies of this diabetic GCC focal loss are needed to confirm and understand this focal pattern of loss.
It is recommended to include a larger number of eyes in the future studies to allow better studying of the ganglion cell loss, and to compare both type I and II DM eyes, and to take refractive error into consideration while assessing retinal layers thickness.