الفهرس 
Anatomy of the cornea
ResultsOnly 14 pages are availabe for public view
 |  | from | 109 |  |  |
| | | from | 109 | | |
Abstract
Amniotic membrane is the innermost layer of the placenta which is semi-transparent, resilient, avascular tissue and consists histologically of a single epithelial layer, a thick basement membrane, and an avascular stroma. (1,2) Amniotic membrane has many beneficial characteristics; it promotes epithelialization, reduces formation of scars and new vessels, and reduces inflammation. It contains nerve growth factor, therefore promotes nerve regeneration, (3) and collagen types 3, 4, 5 and 7 and other substances as fibronectin, laminin and growth factors. The basement membrane of amniotic membrane resembles that of the conjunctiva and cornea. (4) Amniotic membrane is believed to be non-immunogenic. It doesn’t express the human leukocyte antigen (HLA). Hence immunological rejection after its transplantation does not occur and there is no need for immunosuppression. This feature along with the transparent structure and ability to be preserved for prolonged periods make the amniotic membrane an ideal substract for ocular surface transplantation. (5) Infected corneal ulcers that don’t show any healing within two weeks despite proper medical treatment are considered resistant and need surgical intervention. Possible causes of resistant corneal ulcers include: persistent infection, neurotrophic keratopathy, exposure keratopathy, dry eye, and treatment toxicity. (6) In Ophthalmology, the amniotic membrane transplantation has been used to treat resistant corneal ulcers because it acts as a bioactive substratum which accelerates the epithelial healing. Amniotic membrane also reduces the pain caused by friction of eyelids over the ulcer surface and has antimicrobial properties that decrease the risk of infection either through inherent chemical properties or through its function as a physical barrier.