الفهرس 
AcknowledgementsOnly 14 pages are availabe for public view
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Abstract
The cornea is the transparent, dome-shaped window covering the front of the eye. It is a powerful refracting surface, providing 2/3 of the eye’s focusing power. It is a transparent avascular connective tissue that acts as the primary infectious and structural barrier of the eye.
Corneal ulcer is a potentially sight threatening and the leading cause of monocular blindness in developing countries. Corneal ulcer may be infectious either bacterial, viral, fungal or protozoal organism and sometimes it is sterile ulceration, which may occur due to systemic dermatologic or connective tissue disease, chemical or thermal injuries.
Careful diagnosis of corneal ulcer and its cause is an important step for proper management. Careful history will reveal the nature of the problem as if there is a history of trauma, recurrence, herpetic epithelial disease or contact lens wear. Diagnosis includes routine examination with slit lamp or with vital stains, confocal microscopy and microbiological investigation.
Resistant infected corneal ulcer is a sight-threatening infection that may end in great visual impairment. There are many causes of resistant corneal ulcer which include: wrong diagnosis, inadequate therapy, drug toxicity, limbal stem cell deficiency, inflammation of underlying stroma, tear film insufficiency, infection with organisms of low virulence, and recurrent erosions.
Early and proper treatment is important for rapid and complete healing. Medical treatment includes: antibiotics, anti-viral, anti-fungal and anti protozoal. Other non specific medical treatment includes: tear substitute whichis important for epithelial healing. Therapeutic BCL promote epithelial migration and regeneration of the basement membrane by protecting the corneal epithelium from the friction created by the upper tarsal conjunctiva also from eye movements under the lids. Vitamin A playan essential role in epithelial growth and limbal stem cell differentiation and therefore promote corneal wound healing. Also, application of vitamin C, B complex, correction of obvious malnutrition and enhancement of general body-resistance are necessary.
The use of autologous serum in the form of eye drops has been reported as a new treatment for severe ocular surface disorders. Serum eye drops may be produced as an unpreserved blood preparation. Autologous serum supplies the eye surface with several substances that are essential for the recovery of the damaged epithelium, such as vitamin A, epidermal growth factor, transforming growth factor, fibronectin, and many other cytokines.
Novel therapies recently being investigated are beginning to show promise in the treatment of the non-healing corneal epithelium include regenerating agents (RGTAs) as a wound healing agent, which are biodegradable polymers which are engineered to mimic and replace the glycos-aminoglycan heparinsulfate in the extra-cellular matrix of damaged tissue. Limited data are available onThymosin beta 4which promotes cell migration and wound healing, has anti-inflammatory properties, and suppresses apoptosis.
Surgical techniques include corneal debridement which is surgical removal of corneal epithelium without causing injury to the basement membrane, keratectomy, cauterization, and tarsorrhaphy.
Cyanoacrylate tissue adhesive has shown promising results in arresting the progression of both, infective and non infective corneal ulcers. It is highly effective, easy to use, and can delay the need for urgent corneal transplantation.
Corneal collagen cross-linking with riboflavin and UVA is a technique of corneal tissue strengthening using riboflavin as a photo-sensitizer and UVA to increase the formation of intra-and inter fibrillar covalent bonds by photo-sensitized oxidation. This treatment has been used to treat infectious corneal ulcers with apparently favorable results.
Argon laser photo-therapy may be used as an adjunctive therapy for resistant infected corneal ulcers. The laser therapy procedure was combined with the specific anti-microbial agents according to the culture and sensitivity test results.The duration of the treatment was obviously shortened and this can be considered a good result.
Amniotic membrane patching and grafting have been shown to decrease inflammation, vascularization, and scarring of the cornea while promoting re- epithelialization of the cornea. It is thought to achieve this through the release of certain growth factors and proteins.
Conjunctival flaps have been used in the treatment of corneal diseases since the 1800s. It is used for corneal ulcerations and thinning disorders, such as neuro-paralytic keratitis, marginal ulcerations, relapsing erosions, and herpetic ulcers.
Stem cells are defined by their capacity of unlimited or prolonged self-renewal that can produce at least one type of highly differentiated cells. The stem cells of the corneal epithelium are located in the limbal basal layer and are the ultimate source of corneal epithelial renewal. A variety of techniques of limbal transplantation have been reported. All these procedures provide a new source of epithelium for a diseased ocular surface and the removal of the host’s altered corneal epithelium.
Therapeutic keratoplasty is indicated when inflammatory or infectious corneal disease is progressing despite maximal medical therapy, and the integrity of the globe is compromised. Keratoprosthesismay be useful for bilateral, sever chemical injury where the prognosis is hopeless for penetrating keratoplasty due to severe damage to the ocular surface or repeated immunological rejection.