الفهرس 
Normal Anatomy and Histology of the RetinaOnly 14 pages are availabe for public view
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Abstract
Ageing has been associated with a decline in sensory function, as observed in animal and human studies. Age-related visual changes in humans include reduced visual acuity, visual field sensitivity, contrast sensitivity and delayed dark adaptation. These functional changes are associated with structural changes in the ageing eye, such as crystalline lens opacification, blood vessels calcification and an increased oxidative stress. Furthermore, there is evidence of a decline in the number of neurons with age in human eyes, including losses of photoreceptors, rod bipolar cells, retinal ganglion cells and retinal pigmented epithelial cells, which might explain some aspects of functional decline.
Taurine (2-aminoethanesulfonic acid) is an amino acid that has been described as an important modulator of mammalian cell function. It is considered a regulatory factor in the maintenance of osmotic pressure, in calcium ion (Ca2) flux and in the phosphorylation of proteins. One of the most interesting roles that have been proposed for taurine is regulation of retinal function. In experimental models, taurine deficiency has been manifested by visual dysfunction and changes in cellular morphology up to cellular damage in the retina.
So, the aim of our work was to study the alterations in retinal structure with ageing and to investigate the possible role of taurine in improving these changes.
Thirty male albino rats were used and divided into three equal groups (ten rats / group). Group I: control group consisted of ten adult rat aged 4- 6 months, group II: senile group consisted of ten rat aged 24 months left without any treatment, group III : ten senile rat (aged 24 months), received 1 gm / kg taurine as daily dose for 3 weeks. The doses were dissolved in distilled water and given to the rats orally by gastric intubation. At the end of the experiment, the animals were sacrificed and the eye balls were extracted and processed to be examined by light microscope, and photographed.
Examination of group II showed thinned out retina, The pigmented epithelial layer revealed loss of cell boundaries with wide areas of degeneration of the cytoplasm of the cells and marked depletion of the pigment granules, the layer of rods and cones showed disorganization with loss of parallel striations, especially in its outer segment, the outer nuclear layer showed marked thinning with loss of cell demarcation. Examination of semithin sections showed most cells had dark nuclei with dense chromatin, the picture of rod cells, some cells appear to be degenerating losing the normal cell density and looked like cell ghosts among the other cells. The outer plexiform layer was fading with partial loss of its reticular appearance. The inner nuclear layer revealed a decrease of cell density among the layer and on examination of semithin sections, its cells appeared irregular or oval without demarcation of its four types. The inner plexiform layer preserved its reticular appearance and the ganglion cell layer showed the large ganglion cells had pale cytoplasm, irregular nuclei with prominent nucleoli. Intermingled with large ganglion cells were small glial cells with deeply stained nuclei. Some regions showed increased cellularity and multilayering of the ganglion cell layer.
Examination of group III showed slight decrease in thickness of the retina. The layer of rods and cones retained its thickness and fibrillar appearance. The outer nuclear layer was still packed and the two cell types of this layer could be markedly differentiated. The outer plexiform layer was markedly thinned out, in many regions; it showed cellular infiltration giving a cellular continuity appearance between the outer and inner nuclear layers. The inner nuclear layer contained the usual four types of cells which could be distinguished from each other. The cell types were the Horizontal cell, this was the most lightly stained cell, Bipolar cell having moderate density with oval or rounded nucleus, and it was smaller than the horizontal cells, Muller cell was tall slender cell and darker than other cell types in this layer and the Amacrine cell, which was larger than Muller and Bipolar cell approaching horizontal cell in size, with pale indented nucleus, the inner plexiform layer preserved its reticular appearance and the ganglion cell layer showed the normal regular arrangement but few regions of discontinuity were observed.
Our results were discussed with the previous literature. The present study clarified that beside the previously documented functional visual disturbances occurring with aging, there were morphological alterations of the retinal structure. Some of these alterations were reversible after administration the drug. So, taurine can be used as a supportive element for the eye in senile persons.
Therefore, we can suggest that taurine may be beneficial in treatment of retinal complication as an anti-aging supplement. Also, it can protect and delay complications associated with age, however, this might need further studies.