Amniotic membrane in ocular surface disease

Human amniotic membrane is a unique collagenous membrane derived from the innermost submucosa of the placenta, the area in which the human fetus grows and develops within the mother’s uterus. Human amniotic membrane is composed of a single epithelium layer, a thick basement membrane, and an avascular stromal matrix.  

The innate properties of amniotic membrane make it ideal for wound healing/tissue regeneration and in eye care, the management of corneal and conjunctiva disease/reconstruction. A 2007 article by Baradaran-Rafii gives historical perspective, property review, and preparation processes of amniotic membrane.¹

In 1940, De Roth first reported use of fetal membranes on the ocular surface using amnion and chorion as a biological dressing for the management of conjunctival defects.^2,3 Although found to be of some benefit in the treatment of ocular surface disorders at that time, the use of amniotic membrane therapy has become popular only in the past two decades. It has been proposed that the poor clinical outcomes with amniotic membrane in the early 20^th century was a function of inefficient tissue processing that compromised the biologic properties of the amnion.

What makes it special?

Amniotic membrane contains collagen types I, III, IV, V, and VII, and specialized proteins such as fibronectin, laminins, proteoglycans, and glycosaminoglycans. In addition, it contains essential, active, growth factors such as epidermal growth factor (EGF), transforming growth factor beta (TGF-b), fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) that promotes and accelerates epitheliazation. It facilitates epithelial cell migration, reinforces adhesion of basal epithelial cells, promotes epithelial differentiation, and prevents epithelial apoptosis. Amniotic membrane therefore can act as a bandage contact lens, allowing corneal epithelialization beneath it. Additionally, it provides cytokines that diminish inflammation and fibrosis, thereby aiding to maintain corneal clarity. Dogru demonstrated that amniotic membrane improves corneal sensation and tear stability.3 Additionally, the basement membrane of amnion can also support the expansion of progenitor cells, making it useful for the treatment of partial limbal stem cell deficiency. 

Amniotic membrane inhibits inflammation and angiogenesis and the presence of proteinase inhibitors may facilitate wound healing.4^,5 It has antimicrobial properties and prevents wound surface drying, thereby accelerating healing.

Amniotic membrane preparation

Human amniotic membrane is harvested under sterile conditions from the placenta of elective cesarean section after full-term pregnancy in medically cleared donors. Amnion can be prepared for implantation a number of ways. Heat- or air-dried amniotic membrane loses some of its biologic properties and is not ideal for ocular surface rehabilitation. The tissue can be lyophilized (freeze-dried), which induces minimal change in its properties-the dehydrated tissue then can be stored at room temperature-for treatment of the ocular surface. For example, AmbioDisc (IOP Ophthalmics) is dehydrated via a proprietary (Purion) process that preserves the key elements associated with healing. Amnion can be preserved in cold glycerol and cryo-preserved and stored frozen at -80 degrees (AmnioGraft, AmnioGuard, ProKera [BioTissue]).

In the optometric office

Amniotic membrane can easily be applied in the office to manage corneal disease. The AmbioDisc dehydrated membrane is positioned on the corneal surface and then retained beneath a soft contact lens. Briefly, a speculum is positioned to retract the eyelids, the dehydrated sheet of amniotic membrane is placed and smoothed over the corneal surface, then a large-diameter contact lens is situated atop the membrane to secure it in place. The ProKera device (a self-retaining, cryo-preserved amniotic membrane secured in a thin, 16 mm flexible ring) is inserted in a one-step process; the ring-encircled amnion is simply slipped in under the upper eyelid which positions and holds the membrane over the cornea.

Indications for amniotic membrane therapy include:

• Neurotrophic corneal epithelial defects

• Shield ulcers

• Corneal abrasions

• Corneal ulcers

• Corneal burns

• Filamentary keratitis

• Dry eye and exposure keratopathy

• Recurrent corneal erosion

• Salzmann’s nodular degeneration

• Chemical and thermal burns

• Post-infectious keratitis

Topical therapeutic agents and fluorescein stain can be applied over the ProKera device.

Applied amniotic membrane will disintegrate/be absorbed at different rates, depending on the amount of surface information present: determining when to remove amniotic membrane is patient and case dependent. Varying membrane thicknesses are available commercially in multiple amnion graft designs for more severe pathology or conditions that require therapy for longer periods of time.

Active amniotic membrane can be employed in-office as a biologic bandage that reduces inflammation and minimizes scarring in ocular surface/corneal pathology. Optometrists are qualified to utilize this advanced, well-reimbursed treatment modality. Check with your amnion graft distributor and your state licensing board for specific details.ODT

References

1. Baradaran-Rafii A, Aghayan HR, Arjmand B, Javadi MA. Amniotic Membrane Transplantation. Iran J Ophthalmic Res. 2007;2(1): 58-75.

2. De Roth A. Plastic repair of conjunctival defects with fetal membranes. Arch Ophthalmol. 1940;23:522-5.

3. Dogru M, Yildiz M, Baykara M. Corneal sensitivity and ocular surface changes following preserved amniotic membrane transplantation for non-healing ulcers. Eye (Lond). 2003 Mar;17(2):139-48.

4. Hao Y, Ma DH, Hwang DG, et al. Identification of antiangiogenic and anti-inflammatory proteins in human amniotic membrane. Cornea. 2000 May;19(3):348-52.

5. Kim JS, Kim JC, Na BK, et al. Amniotic membrane patching promotes healing and inhibits proteinase activity on wound healing following acute corneal alkali burn. Exp Eye Res. 2000 Mar;70(3):329-37.

Side bar

Indications for amniotic membrane therapy include:

• Neurotrophic corneal epithelial defects

• Shield ulcers

• Corneal abrasions

• Corneal ulcers

• Corneal burns

• Filamentary keratitis

• Dry eye and exposure keratopathy

• Recurrent corneal erosion

• Salzmann’s nodular degeneration

• Chemical and thermal burns

• Post-infectious keratitis