Amnion graft closure surgery has become an established adjuvant therapy in ophthalmic clinical practice with successful results for many corneal, conjunctival, and scleral disorders. Amniotic graft closure surgery or amniotic membrane transplantation has a long tradition in ophthalmic surgery and has become very popular recently due to newly developed tissue preservation methods.
Amnion graft is a biological ocular transplantation graft used as adjunctive therapy by eye surgeons worldwide to treat ocular surface indications such as corneal ulcers, pterygium, mechanical dry eye tumor removal, chemical burns. The amniotic membrane graft is prepared from the placenta.
Transplantation of the amniotic membrane can be considered as one of the most important new developments in ocular surface surgery. Although the first ophthalmological use of amniotic graft closure surgery or amniotic membrane transplantation documented in the international literature occurred almost years ago, it has only been performed promisingly in a larger number of patients since 1995.
What is Amnion Graft Covering?
Amnion graft covering is one of the preferred methods in cases where medical treatments do not respond. It was first used as a skin graft by Davis in 1910. It was first used in ophthalmology by De Rotth in 1940. It has been used in fresh form and with the chorion layer in conjunctival surface reconstruction but without success.
Successful results were obtained in 1946 and 1947. Amnion graft has antiadhesive and bacteriostatic epithelization initiating effects, inhibiting angiogenesis and inflammation, and reducing pain. The amniotic membrane has non-immunogenic properties. The amniotic basement membrane is permeable and elastic due to its structural integrity. It is the most commonly used tissue in ocular surface reconstructions.
Which Area Is Considered by Amnion Graft Covering Surgery?
The main objectives of amnion graft closure are ocular surface reconstruction, promotion of epithelialization, symptomatic relief, and reduction of inflammation. There are three basic principles by which the final technique is personalized.
- Inlay or graft technique
- Overlay or patch technique
- Filling or layered technique
When the inlay or graft technique is tailored to the size of the defect and is intended to act as a scaffold for epithelial cells that subsequently fuse with the host tissue, it is termed a graft. Epithelial cells surrounding the basement membrane or epithelial side up are allowed to migrate across the membrane.
When the overlay or patch technique is used similarly to a biological contact lens to protect the underlying healing surface defect, it is referred to as patching. A patch also reduces inflammation by its barrier effect against chemical mediators. When used as a patch, the membrane is fixed epithelial side up or dropped or removed.
In the filling or layered technique, the entire depth of the ulcer crater is filled with small pieces of AM cut to the size of the defect. A larger graft is stitched inlays to the edges of the defect, and additional patching can help preserve the deeper layers longer. Ophthalmology clinic deals with amnion graft covering surgery.
What is Amnion Graft Covering Surgery?
The amniotic membrane or amnion is the innermost layer of the placenta and consists of a thick basement membrane and an avascular stromal matrix. Amniotic graft covering surgery or amniotic membrane transplantation are used as grafts or dressings in different surgical branches. In the field of ophthalmology, it is commonly used to reconstruct the ocular surface after various procedures.
It supports healing as a graft for ocular surface melts and as a bandage in cases of persistent epithelial defects or ocular surface inflammation. All these indications take advantage of the amniotic membrane's ability to promote healing.
How is Amnion Graft Covering Surgery Performed?
Many reports in the literature demonstrate the use of human amniotic membrane, which is removed from the placenta during cesarean section and preserved until use on the ocular surface. Cryopreserved amniotic membrane is available and widely used and preserves the histological and morphological features of fresh tissue. The amniotic membrane can be surgically adhered to the ocular surface with absorbable or non-absorbable sutures.
Biological tissue adhesives have also been used to attach the amniotic membrane to the ocular surface. Tissue preservation should always be done in an approved tissue bank and basically consists of washing the placenta in an antibiotic solution. In addition to giving written consent, the donor mother must also undergo serological tests to ensure that she does not suffer from any infectious disease.
These tests are done by an officially approved tissue bank. This treatment can also be used to increase the chances of success in some corneal surgeries, such as corneal transplants, and where post-surgical tissue regeneration or scarring problems are expected.
Amnion Graft Surgery
Amniotic graft closure surgery, or membrane transplant, consists of applying a piece of amniotic membrane to the surface of the eye. This piece is attached to the tissue, usually with fine stitches. There are two different application methods according to the type of injury. These are dressings or grafts. If there is only one defect in the epithelium but the stroma is healthy, the amniotic membrane is used as a full-surface dressing.
Amnion graft cover surgery causes the growth factors contained in the membrane to begin to grow under the epithelial cells. After a few days, the membrane can be easily removed without leaving any scars in the surgery. Amniotic membrane transplantation is especially indicated in acute phase burns caused by caustic substances such as bleach and lime, where the tissue becomes lifeless, inflamed or regeneration problems are encountered.
It is also used after extensive conjunctival resection, often for removal of tumors or scars, as well as for ulcers and defects of the cornea and conjunctival epithelium. It can also be used to increase the chances of success in some corneal surgeries such as corneal transplants and where post-surgical tissue regeneration or scarring problems are anticipated.
What are the Advantages of Amnion Graft Covering Surgery?
The basement membrane component of the amniotic membrane is similar in composition to the conjunctiva. Therefore, the current theory proposes that the amniotic membrane increases support for epithelial cells, limbal stem cells, and corneal temporal proliferative cells. While excluding inflammatory cells and their protease activity, clonogenicity is maintained, which promotes both goblet and non-goblet cell differentiation.
Moreover, the stromal surface of the amniotic membrane suppresses myofibroblast differentiation of normal fibroblasts to reduce scar and vessel formation. This action aids healing for conjunctival reconstruction, epithelial defects and stromal ulceration.
Post Amnion Graft Surgery Process
The amniotic membrane can act as a basement membrane replacement or a temporary graft in the eye. It has anti-inflammatory and anti-scarring effects and contains growth factors that promote epithelial wound healing on the eye surface. Amniotic membrane transplantation has been found to be a good alternative for corneal and conjunctival reconstruction in many clinical situations, including acute burns, permanent epithelial defects of the cornea, and diseases that cause conjunctival scarring.
However, to date there have been no more than a few randomized and controlled trials of amniotic membrane transplantation. Other studies have shown that the amniotic membrane can serve as a culture substrate to expand epithelial progenitor cells for use in ocular surface reconstruction. The amniotic membrane triggers a rapid wound healing process that can take 2 to 15 days, depending on the condition of the treated eye.
In cases of deeper injury involving loss of stroma, the membrane is grafted to fill the space left by the missing stroma. With this method, the cells do not grow on the bottom as when the cover is placed on the epithelium, but on the top until the slowly reabsorbed membrane is renewed. Inoculation involves a slower healing process that takes several months for the membrane to absorb. During this time, the amniotic membrane can make the eye opaque, which can temporarily limit vision.
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