Amniotic membrane has several applications in conjunctival diseases

Pterygium excision, fornix reconstruction and surface reconstruction are some of the situations that may call for amniotic membrane transplantation.

Amar Agarwal

Amniotic membrane was first used by De Roth in 1940, but it was not until 1995 that Kim and Tseng made its use widespread and popular.

Amniotic membrane is used for its anti-inflammatory and anti-angiogenic properties as well as its ability to promote epithelial differentiation, adhesion and migration. It also has antibacterial, wound-protecting, pain-reducing and fibrosis-suppressing effects. It can be used as a graft, in which it fills defects and promotes epithelialization, or it can be used as a patch, in which it is used for its anti-inflammatory and anti-angiogenic properties. It may also be used as a patch-graft simultaneously, according to the underlying condition being treated. The stromal side of the amniotic membrane is differentiated from the basement membrane by touching with a sponge. The stromal side is sticky whereas the basement membrane side is not sticky.

Pterygium excision

Pterygia are known to be associated with a high recurrence rate, and various modalities, including the use of mitomycin C and conjunctival autografts, have been reported to decrease the incidence of recurrence. Amniotic membranes have been used in pterygium surgery, especially in surgery for large double-headed pterygia and in patients with inadequate conjunctiva to perform a conjunctival autograft. Nevertheless, conjunctival autograft has been shown to have a lower incidence of postoperative inflammation and recurrence than amniotic membrane transplantation. The amniotic membrane graft provides anti-inflammatory effects as well as anti-fibrotic effects via down-regulation of transforming growth factor beta and is thus of benefit in preventing recurrence (Figures 1a to 1d).

Figure 1. A large pterygium (A) extending onto the cornea. The conjunctival component is being cut. The pterygium head (B) is being stripped off the underlying stroma. An amniotic membrane graft (C) is used to cover the conjunctival defect and is placed over the raw surface on the cornea. The amniotic membrane (D) is glued into place. Images: Agarwal A

Fornix reconstruction

Many cases of symblephara, fornix foreshortening and forniceal obliteration require correction of lid deformity and reformation of fornices. Simple dissection alone, even if combined with symblepharon rings, may not always succeed because the raw surfaces obtained after dissection easily adhere and fuse again if allowed to be in contact with each other. Amniotic membrane may be used to cover these raw surfaces. Once the fornix is dissected, the affected part of the bulbar, forniceal and palpebral conjunctiva is covered with amniotic membrane, which is held in place using a combination of glue and sutures. Glue alone is generally not sufficient. Fornix-forming sutures are then taken, in which double-armed sutures are passed through the fornix, through the orbital rim periosteum and tied down on the surface of the lids using bolsters.

Surface reconstruction

Amniotic membranes can be used for ocular surface reconstruction after removal of large lesions such as ocular surface squamous neoplasias, large pterygia or other surgeries that result in the loss of a large area of the conjunctival surface with inadequate conjunctiva available for autograft. It is also used for closing conjunctival defects in patients with pre-existing blebs or those who might require a trabeculectomy or valve surgery in the future. Placing an amniotic membrane graft in such patients leaves the superior conjunctiva untouched for possible future use.

Acute corneal, conjunctival insults

Stevens-Johnson syndrome, toxic epidermal necrolysis, mucous membrane pemphigoid, and chemical and thermal burns can all cause extensive damage to the limbal stem cells and the conjunctiva, resulting in a multitude of problems, including persistent epithelial defects, corneal ulceration, stem cell deficiency, conjunctival cicatrization, symblepharon formation and fornix foreshortening. In the early stages of these conditions, covering the ocular surface with an amniotic membrane graft decreases the chances of complications by means of its anti-inflammatory, anti-angiogenic, anti-scarring and pro-epithelial effects. The amniotic membrane graft prevents symblepharon formation by acting as a physical barrier; it also likely provides a scaffold for early re-epithelialization.

During the acute phase of Stevens-Johnson syndrome or toxic epidermal necrolysis, amniotic membrane is used as a patch graft covering the entire ocular surface, dipping into the fornix and out onto the eyelid margin. Delayed or inadequate coverage may result in substandard results. It is used in combination with intensive steroid therapy and a large diameter Kontur lens (Kontur Kontact Lens Co.) in order to maintain the fornices.

This technique can also be used similarly for acute chemical and thermal burns.

Bleb leaks and overfiltering blebs

Late bleb leaks and overfiltering blebs are generally seen after application of wound-modulating agents. The conjunctiva covering the bleb is often thin and avascular. Excision of the bleb and direct resuturing, conjunctival advancement or conjunctival autografts may be used, but these depend on availability of adequate mobile conjunctiva to cover the defect without shortening the fornix. Amniotic membrane graft may be used in such instances.

• Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Eye Hospital and Eye Research Centre. Prof. Agarwal is the author of several books published by SLACK Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; fax: 91-44-28115871; email: dragarwal@vsnl.com; website: www.dragarwal.com.
• Disclosure: The authors have no relevant financial disclosures.