Amniotic membrane in ophthalmology Amniotic membrane contains a unique structure: an avascular matrix and a thick basement membrane. The avascular stroma prevents the formation of fibrous scar tissue and controls the occurrence of rejection. The thick basement membrane facilitates epithelial cell migration, increases basal epithelial cell adhesion, promotes epithelialization, and prevents epithelial cell apoptosis. It is these characteristics of amniotic membrane that make it useful for the treatment of severe ocular surface disorders or as a first step in reconstructing a healthy ocular surface in combination with corneal rim transplantation. Therefore, the application and use of amniotic membrane in the ophthalmic clinic is bound to become a closely watched area in modern ophthalmology to solve some difficult ophthalmic problems. The human amniotic membrane is 0.02-0.5 mm thick, transparent, tough, and composed of a thick basement membrane and a stroma with no blood vessels, nerves or lymphatic vessels. It is divided into 5 layers from inside to outside: epithelial cell layer, basement membrane, dense layer, fibroblast layer, and spongy layer. There is a potential gap between the basement membrane surface and the choriocapillaris, which is easily separated bluntly. Animal experiments and clinical studies have shown that the amnion is an ideal support for epithelial growth, prolonging its life and maintaining its cloning. The amniotic membrane stroma stimulates the differentiation of conjunctival cupped cells, promotes the differentiation of conjunctival stem cells into conjunctival epithelial cells, promotes the conversion of conjunctival epithelium to corneal epithelium, and promotes the proliferation of corneal limbal stem cells and corneal epithelial cell migration. A component of the amniotic stroma inhibits β-transforming growth factor (TGF-β) signaling, inhibits the proliferation and differentiation of normal human corneal limbal fibroblasts into fibroblasts, reduces scarring, and inhibits neovascularization. Different forms of protease inhibitory factors in the amniotic stroma remove inflammatory cells and promote rapid apoptosis by altering protease activity. Preservation of human amniotic membrane under normal environmental conditions does not express human leukocyte antigens and therefore no immune rejection occurs. Preparation and preservation of amniotic membranes The placenta is obtained from a cesarean section or a sterile delivery, and the donor (maternal) is examined prenatally to exclude those with human immunodeficiency disease (HIV), hepatitis B virus (HBV), and syphilis; and the maternal (donor) is negative for gonococci and chlamydia in the birth canal. The placenta is sterilized upon removal. The freeze-dried amniotic membranes used in our center are provided by Jiangxi Ruiji Biological Engineering Technology Co. Ruiji bio-amniotic membrane 3. Application mechanism 1. promote epithelial cell differentiation and prevent apoptosis of epithelial cells: provide a healthy matrix environment, express a variety of growth factors 2. inhibit inflammation and neovascularization, containing protease inhibitors: express a variety of anti-angiogenic and anti-inflammatory proteins 3. have a strong anti-fibrotic, anti-adhesive effect: down-regulate the expression of transforming growth factor β and its receptors 4. clinical applications as Conjunctival substitute for reconstruction of ocular surface Ocular chemical injury Infected and non-infected corneal ulcers Pterygium, conjunctival mass excision No eye conjunctival sac stenosis molding Prosthetic exposure Infected and non-infected corneal ulcers As therapeutic contact lens for corneal epithelial defects Relief of symptoms of large vesicular keratopathy V. Our center has carried out pterygium, conjunctival mass excision combined with amniotic membrane transplantation, infected and non-infected corneal The center has performed amniotic membrane shielding for infected and non-infected corneal ulcers, etc. The recurrence and pain after pterygium excision can be well resolved. The recurrence of pterygium is associated with surgical trauma that accelerates fibroblast proliferation. In contrast, amniotic membrane has the ability to prevent the proliferation of subconjunctival fibrous tissue, inhibit the inflammatory response, and form a continuous smooth collagen membrane on the surface of the sclera, which acts as a mechanical membrane and prevents the proliferation of fibrous tissue, thus preventing the recurrence of pterygium after excision. The surgery is less invasive, and amniotic membrane transplantation can effectively protect the corneal wound and promote corneal epithelial regeneration. Amniotic membrane transplantation can promote corneal epithelial regeneration, inhibit neovascularization, reduce the self-fusion and inflammatory response of the cornea after burn, effectively prevent perforation, and have a biological barrier function to prevent and treat lid adhesions. VI. Contraindications Fungal corneal ulcer