New procedure uses amniomembrane for eye reconstruction

Amniotic membrane transplantation helps manage patients in the acute stage of chemical burns.

SALZBURG, Germany — The use of preserved amniotic membrane can provide a favorable extracellular matrix substrate for epithelial migration and adhesion. Amniotic membrane can suppress inflammation and promote epithelial healing.

“Amniotic membrane has been used and studied for various ocular problems, including surface reconstruction of the cornea with persistent epithelial defects with progressive ulcer and painful bullous keratopathy,” Gunther Grabner, MD, said. “It has been used experimentally as a short-term bandage after photorefractive keratectomy and partial and total limbus insufficiency. Additionally, the membrane has been used for surface reconstruction of the conjunctiva with primary and secondary pterygium, large-scale tumor excision, fornix reconstruction and glaucoma surgery to reconstruct blebs.”

What it heals

Although it does take time for clinical results to be seen, the placement of amniotic membrane improved epithelialization, reduced inflammation, reduced vascularization and reduced scar formation. “This seems to be due to the fact that the life and the survival of precursor stem cells at the limbus can be improved if there is a substrate,” Dr. Grabner said.

“In the amniotic membrane, there are probably also cytokine and other compounds, such as protease inhibitors, which will reduce the inflammation proteins and will reduce cell death, but also proteins that prevent or reduce vascularization.” Fibroblasts and cytokines also can be affected and the membrane may suppress certain transforming growth factor beta signal pathways, he said.

Preparation of membrane

Prior to delivery, an expectant mother must grant consent for her amniotic membrane to be used. The placenta from a caesarean section is used for the reconstruction of the ocular surface instead of a placenta that has gone through the unsterile birth canal. The mother is checked for HIV, hepatitis B virus, hepatitis C virus and syphilis. The placenta and the amniotic membranes are cleaned under lamina flow and are put into a sterile environment. The tissue also is cleaned or purified with phosphate-buffered saline, penicillin and antibiotics.

Under sterile conditions, the tissue is applied to Merocel plates and cut to the required size of 4 × 4 cm, round or square. It is important that the orientation is maintained so that during surgery the amniotic membrane can be correctly placed onto the cornea and the ocular surface.

The amniotic membrane can be stored or frozen at –80° in sterile containers, with a shelf life of about 1 year, although Dr. Grabner admits it should not be stored for that length of time.

Surgical procedure

In a case of an ulcer-affected cornea, the epithelium is removed. The amniotic membrane, including a marginal zone, is fixed with 10-0 nylon individual sutures at the ulcer. According to Dr. Grabner, it is important to pay attention to the orientation of the graft, meaning that the single layer of epithelium that has died off during freezing is facing away from the eye so that you transplant or implant a basement membrane.

Initially, the total surface of the cornea is diluted and dissection is made from the contralateral healthy eye at 90° to the limbus stem cells. If the situation is very bad, a 90° stem cell graft can be removed from the fellow eye.

“With these grafts, you have to be very patient and draw the attention of the patient to the fact that for 2 or 3 weeks, he or she might have to wear a bandage,” Dr. Grabner said. “It would not be sufficient to just use a therapeutic contact lens.”

Other circumstances

In one case, a Downs syndrome patient with a keratoconus graft had suffered from a refractory ulcer. According to Dr. Grabner, there are not too many treatment options for this type of patient. Two weeks after a graft had been sutured, the ulcer had completely epithelialized with good stability and without irritation. In tougher cases where there is total loss of the stem cells in the limbus, ingrowth of conjunctival epithelium and recurring erosions, vascularization, neovascularization and subepithelial opacifications, often the corneal stroma is preserved. In these cases, especially lime acid burns, amniotic grafting will not be sufficient, but limbus grafting can improve the situation.

According to Dr. Grabner, it is much better if the doctor has an autogenous graft if the patient has an acid burn, or a burn in only one eye, or the disease has affected only one eye. In cases of bilateral involvement, which happens rather frequently if there is limbus insufficiency, a donor is needed and then immunosuppression is mandatory.

“In the first weeks after grafting, you must not be scared,” Dr. Grabner said. “It takes quite some time until the amniotic membrane is epithelialized.”

But you also have to think of further procedures, he said. With this type of acid burn treatment, vision can improve to 0.4. But because of an irregular corneal surface, further surgery is required, such as a lamellar keratoplasty or penetrating keratoplasty.

For Your Information:

• Gunther Grabner, MD, can be reached at Landesaugenklinik Salzburg, Mullner Hauptstrasse 48, Salzburg, Austria, A 5020; +(43) 662-4482-3702; fax: +(43) 662-4482-3701; e-mail: g.grabner@lkasbg.gv.at.