Mucous Membrane Graft

It is important to understand the anatomy of the conjunctiva when considering the reconstruction and replacement of the conjunctiva. The human conjunctiva is an epithelial layer that is a non-keratinized stratified squamous and stratified columnar epithelium. The conjunctiva has goblet cells. The conjunctiva is a complex structure that contains lymphatic channels, blood vessels, fibrous tissue, melanocytes, T- and B-cell lymphocytes, accessory lacrimal glands, and Langerhans cells. Glands of Krause are found within the deep fibrous layer of the conjunctiva and the goblet cells, which are greatest in the fornices, secrete mucin. The conjunctiva contributes to the protection of the eye with the production of mucus and tears. It provides mechanical protection to the eye and assists in the free movement of the globe and the eyelids. The conjunctiva lines the tarsus (or palpebral conjunctiva), where it lines the eyelid margin of the tarsus and the Tenon's capsule. The flexibility of the forniceal conjunctiva is important in the free movement of the globe and the eyelids.  Loss or scarring of the conjunctiva from injury or disease can result in eyelid malposition, restriction of ocular movement with double vision, and dryness. When replacing the injured conjunctiva, materials such as amniotic membrane, hard palate grafts, nasal septal mucosa, autogenous conjunctiva, and tarsus with conjunctiva have been used. Ideally, it is wise to replace like for like. Unfortunately, except for small defects, autogenous conjunctiva is limited by availability. Oral mucosal grafts are used in two forms: 1. Oral mucous membrane grafting (MMG). 2. Minor salivary gland grafting (MSGG) for the treatment of severe dryness. Oral mucosa has multiple advantages: It has similar biological properties to the conjunctiva. The donor site is easily accessible and universally available. Obtaining donor tissue is technically easy. Obtaining tissue is cheap. Repeat harvesting is possible. Complications are few. It is an autograft avoiding the risks of allogeneic grafts. In 1912, Denig first described the use of mucous membrane for lime burns; later, mucous membrane grafts were used by Weeks for the correction of trichiasis and symblepharon. The mucous membrane acts as a scaffold for the proliferation of growing epithelial cells. The membrane does not contain the goblet cells which are present in the conjunctiva. Hence it does not help in treating dry eyes unless transplanted with minor salivary glands. Moreover, in patients with concurrent limbal stem cell deficiency of more than 3-4 clock hours, a limbal stem cell transplant procedure should be performed in the same sitting. The oral mucosal membrane is rich in elastin, making it resistant to shearing and compression, and being highly vascular, and the graft can be easily taken up. It is histo-compatible and has minimal contraction in the transplanted site. Indications for the use of mucous membrane grafts in Ophthalmology include the following: After removal of pterygia. Repair of contracted anophthalmic sockets. Globe surface and fornix reconstruction after tumor resection. Deformities of the eyelids (cicatricial entropion, keratinization of the eyelid margin after chemical burns, or Stevens-Johnson syndrome). Repair of erosions over glaucoma drainage devices. Repair over scleral buckle exposure. Support of keratoprosthesis associated with corneal melt. Formation of the lining during conjunctivodacryocystorhinostomy or dacryocystorhinostomy.