الفهرس 
Introduction And Aim Of The WorkOnly 14 pages are availabe for public view
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Abstract
The cornea is an avascular transparent tissue located at the outermost part of the eye. It must remain transparent to properly refract light for normal vision. Ocular trauma resulting from a corneal alkali burn is a serious clinical problem and may cause severe and permanent visual impairment by inducing tissue inflammation, fibrosis, and scarring, leading to subsequent corneal opacification. the balance between angiogenic and antiangiogenic factors determines the regulation of corneal neovascularization (NV) after a corneal alkali burn.
Retinoids are biologically active derivatives of vitamin A (retinol) involved in essential physiological processes of the eye. Vitamin A was previously reported as playing a major role in mesenchyme and corneal morphogenesis.
This study is concerned with the description of structural changes in rat corneal tissue following administration of filter paper saturated with 0.01 m NaOH on it for 45 seconds and identification of different mechanisms involved in these changes.
In this study, 30 male albino rats were used. Rats were divided randomly into four groups: group I, the control group; included 3 rats, received distilled water. Each of group II, III, IV included 9 rats: group II, the nontreated group, injured and received distilled water. group III, the antibiotic treated group, received antibiotic eye drops (Oflox 3mg/ml) 3 times per day for 3 days. group IV, vitamin A treated group, received the same course of antibiotic and vitamin A eye gel (Hypotear gel 1000 IU/g) t.d.s. for 3 days. The right eyeball was taken out, rapidly fixed and processed for light microscopic, immunocytochemical and morphometrical studies. Specimens were taken after 24, 48, 72 hr postinjury.
The results of the current study revealed that:
-In hematoxylin and eosin stained sections: vitamin A administration after corneal injury caused lesser damage to tissues with absence of neavascular formation or cellar infiltration. While antibiotic treated group showed abnormal apoptotic cells, vacuolated ones and large keratocytes. In case of nontreated group there were abnormal apoptotic cells, large keratocytes, stromal edema, more cellular infiltration and neo-vascularization.
-Immunohistochemical studies using TGF-β antibodies; there was lesser expression in the epithelium and stroma of vit.A treated group than both nontreated and antibiotic groups.
-Immunohistochemical studies using Ki67 antibodies; showed a significant increase in the numbers of ki67-immuno positive cells in vit. A treated group at 24hr post-injury and significant decrease at 72hr post-injury. Positive cells crept from the limbus to the site of the ulcer.
Consequently, the above data indicated that vitamin A has a beneficial effect on the healing process of corneal ulcer. The decrease of TGF-β expression could be one of the mechanisms through which vit. A induces its beneficial effect. Also, its ability to stimulate proliferation and differentiation of limbal stem calls enhance the process of healing.