West Texas #1 Dry Eye Treatment Center
West Texas #1 Dry Eye Treatment Center
Human amniotic membrane (AM) has been shown to provide a substantial benefit in treating certain types of conjunctival and corneal disease. While AM has traditionally been transplanted using sutures or fibrin glue in an operating room, the in-office application of sutureless AM is emerging as a less invasive alternative with promising clinical outcomes. In-office availability of AM allows clinicians to treat a variety of ocular surface conditions rapidly and effectively.
Amniotic membrane is an avascular fetal membrane that lies deep to the chorion and is harvested in a sterile environment from placental tissue obtained during elective cesarean sections. Donors are screened for transmissible diseases, and the AM is further treated with broad-spectrum antibiotics immediately after collection.
AM is made up of three layers: epithelium, basement membrane, and stroma. Several types of collagen make up the basement membrane, including type VII collagen, which is also present in the conjunctival and corneal basement membranes. The stroma of AM can be subdivided further into a compact layer, a fibroblast layer, and an outer spongy layer.
Beneficial properties of AM. Several characteristics contribute to the efficacy of AM in treating ocular surface problems. First, AM acts as a physical barrier to protect conjunctival and corneal epithelium as it heals, and it reduces pain caused by friction of the eyelids over the surface. In addition, the AM basement membrane promotes epithelial growth through cell migration, adhesion, and differentiation, while also inhibiting cell death. Furthermore, the stroma of AM, which contains fetal hyaluronic acid, inhibits fibroblast growth and reduces inflammation through decreased expression of cytokines.
Research has also shown AM to block angiogenesis and have antimicrobial properties. The mechanism of the antimicrobial effect is controversial, but AM may decrease the risk of infection either through inherent chemical properties or through its function as a physical barrier.
AM is universally tolerated due to its lack of histocompatibility antigens HLA-A, B, or DR; it can be implanted without concern for rejection.
Currently, two main types of AM are commercially available for in-office use: cryopreserved and dehydrated. Both types come in a variety of tissue thicknesses and sizes, depending on clinical needs.
Cryopreserved AM. Cryopreservation of AM involves slow freezing at –80°C using DMEM/glycerol preservation media to allow for slow-rate freezing without ice formation. This preservation technique retains the extracellular matrix components, such as heavy-chain hyaluronic acids, growth factors, fibronectin, and collagen, all of which promote anti-inflammatory effects and healing. The tissue is stored in a –80°C freezer and brought to room temperature when needed for use.
ProKera (BioTissue) is a cryopreserved form of AM in which the membrane is secured around a polycarbonate ring or an elastomeric band. It requires no assembly and is inserted into the eye in a manner similar to contact lens placement. This form of AM has been cleared by the FDA as a class II medical device, and product claims approved by the FDA include protective, wound healing, and antiinflammatory effects.
Dehydrated AM. Dehydrated AM is preserved using vacuum with low temperature heat to retain devitalized cellular components. FDA-approved claims for this type of AM are limited to wound coverage. Unlike cryopreserved tissue, dehydrated AM is kept at room temperature, but it must be rehydrated for clinical use.
AmbioDisk (IOP Ophthalmics) is a dehydrated AM commercially available for in-office use; it is applied directly to the ocular surface and covered with an overlying bandage contact lens.
The convenience, safety, and effectiveness of sutureless AM are helping to produce excellent clinical outcomes and revolutionize the treatment of a variety of ocular surface diseases. In-office AM is easy to use and could become a part of treatment algorithms earlier in the disease course to improve patient outcomes.