and Scheffer Tseng, MD, PhD
Part 1: Introduction, general uses and techniques
Introduction
In this article, we will introduce the use of amniotic membrane transplantation (AMT) in ophthalmology. We will discuss the background of AMT, its conceptual uses, and ocular diseases where it has proven useful. In subsequent series, we will discuss specific surgical techniques and its use in specific ophthalmic specialties such as ocular surface disease, glaucoma, and strabismus surgery. It is provided for ophthalmic use as cryopreserved tissue (AmnioGraft and Prokera; Bio-Tissue, Inc, Miami, FL), or as a freeze dried tissue (AmbioDry; IOP, Inc, Costa Mesa, CA).
Amniotic membrane transplantation is a surgical procedure used to promote tissue healing, reduce inflammation, tissue scarring and growth of neovascular vessels. As a temporary graft, it can decrease inflammation that can lead to problems with wound healing and scarring. As a “permanent” graft, it can help to replace corneal and conjunctival tissue that is damaged as a result of disease or prior surgeries.
Amniotic membrane is the innermost layer of the placenta facing the fetus. It consists of an epithelial layer, basement membrane and avascular stroma. It has several mechanisms of action, including providing a new basement membrane, or a stroma that exhibits anti-inflammatory, anti-scarring and anti-angiogenic properties. The basement membrane component of AM, consisting of laminin 1 and 5, type IV and VII collagen, can provide a substrate for epithelial cell growth, adhesion, migration and survival. The stroma contains collagens (type I, III, V), glycosaminoglycans and fibronectin. In addition, AM contains several growth factors, anti-angiogenic and anti-inflammatory proteins, and neurotrophins, and exhibits anti-fibroblast activity.
Surgical Indications
AMT can be used as a temporary graft in order to promote healing and suppress inflammation due to various ocular surface diseases and traumas. This includes the following disease states:
- Chemical and thermal burns
- Stevens Johnson syndrome
- Neurotrophic keratitis (HZ, HSV)
- Persistent corneal epithelial defect
- Recurrent corneal erosion
- Eyelid fornix reconstruction
- High risk penetrating keratoplasty
The temporary graft can take the form of amniotic membrane tissue or in ProKeraTM, which is AM tissue mounted on a symblepharon conformer. The graft is attached to the outer surface of the eye with sutures, fibrin tissue glue or the conformer.
AMT can also be used as a permanent graft in order to replace or repair ocular surface tissue casued by disease or trauma, and to promote regeneration of tissue rather than repair of the ocular surface. Since the AM does not itself contain living cells, it promotes growth from surrounding healthy tissue and induces an ingrowth of healthy tissue. This includes the following disease states:
- Corneal Diseases:
- Persistent Epithelial Defects and Ulcers
- Descemetocele or Perforation
- Neurotrophic Keratitis
- Bullous Keratopathy
- Band Keratopathy
- Removal of scar
- Conjunctival Diseases:
- Primary & Recurrent Pterygia
- Pingueculae
- Tumors
- Conjunctivochalasis
- Superior Limbic Keratoconjunctivis
- Scars and Symblepharon
- Chemical Burns, Stevens Johnson Syndrome and Pemphigoid
- Leaking Blebs
- Other Diseases:
- Partial Limbal Stem Cell Deficiency
- Scleral Melt/Ischemia
- Fornix Reconstruction
- Socket Reconstruction
- Complicated strabismus surgery
In some cases, AMT should be performed in combination with other procedures in order to successfully heal ocular tissues. Eyes with total limbal stem cell deficiency cannot be healed with AMT only and may require conjunctival limbal autograft, keratolimbal autograft, conjunctival autograft, or limbal stem cell transplantation (donor graft).
In conclusion, amniotic membrane transplantation is a procedure that can improve the outcomes in a wide variety of ocular diseases, with a growing list of indications. It can be used as a temporary graft to promote ocular surface healing by suppressing damaging inflammation, fibrosis and neovascular growth As a permanent graft, it can promote the healing or replacement of damaged or missing tissue by providing a substrate for normal tissue growth. Further research will expand clinical applications and also give us greater insight into the mechanisms of action of this unique tissue.
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