Jun 14, 2023 — Michael Szkarlat, Senior Partner Development Director
Background & history
Natalie Cheung, MD, begins the webinar with a brief discussion of the history of using human amniotic membrane (AM) tissue in ophthalmology. Plastic surgeon John Staige Davis, MD, first used human AM as a skin substitute for treating open wounds at Johns Hopkins in the 1800s. The first in ophthalmic surgery, Dr. Andras de Rötth used fetal membranes to reconstruct the ocular surface. In the 1990s, popularity increased, particularly for repairing conjunctival defects and reconstructing the fornices of the eye. Cryopreservation of AM also played a crucial role in its rising popularity.
Structure & properties
Dr. Cheung then reviews the anatomy of AM, which consists of three layers: a monolayer of simple epithelium, basement membrane and stroma. It contains various beneficial bioactive components including anti-inflammatory, anti-fibrotic, anti-scarring, anti-angiogenic, and some antimicrobial properties, as well as having low immunogenicity and the ability to inhibit oxidative stress. It also acts as a mechanical barrier to protect healing corneal epithelium from frictional forces while simultaneously promoting epithelialization.
Procurement & preservation
AM is only procured from donors undergoing elective C-sections who have been screened for infectious diseases. Vaginally delivered placental tissue is not procured due to contamination risk. After procurement, it is washed and treated with antibiotics, then the AM is dissected from the chorion. There are three main methods of AM preservation:- Cryopreservation: The most common method involves freezing the AM at -80°C. It can be stored for up to two years.
- Freeze drying (lyophilization): The AM is freeze-dried, sublimated, irradiated and stored at room temperature for two to five years.
- Dehydration: The AM is dehydrated and gamma irradiated. This is the harshest method in terms of damage to the desirable bioactive components.
Dr. Cheung then walks us through some of the AM products that are currently on the market for different applications from the clinic to the OR.
Use in ophthalmology
Dr. Cheung reviews AM applications in the cornea, glaucoma, retina, strabismus surgery and oculoplastics, and concludes by answering audience questions.
Corneal conditions
Amniotic membrane has shown efficacy in reconstructing the ocular surface, treating persistent epithelial defects, non-healing corneal ulcers, mild to moderate cases of Stevens-Johnson syndrome and more. It can also be used for ocular chemical injuries and for conjunctival reconstruction after neoplasia. In severe dry eye disease, amniotic membrane can provide relief, although more research is needed to determine its long-term effects.
Dr. Cheung reviews the surgical techniques for AM transplant. She covers how to use AM in such a way that it will be incorporated into the host tissue, as well as a way that it will act as a bandage or barrier that will ultimately not be incorporated into the host tissue. She highlights current published literature and shares some personal experience supporting the use of AM for various indications including corneal ulcers, peripheral ulcerative keratitis (PUK), ocular burns, Stevens-Johnson Syndrome, pterygium surgery, neoplasia and dry eye disease.
Glaucoma
In glaucoma surgeries such as trabeculectomy and tube shunts, AM has been used to reduce post-operative fibrosis, leakage, and vascularity around the surgical site. Studies have shown that AM use may be associated with lower intraocular pressure (IOP) and prevention of complications like hypotony, shallow anterior chamber, choroidal detachment and bleb leaks. However, the evidence is still limited, and further research is needed to establish its role in glaucoma management.
Retinal disorders
AM has shown promise in retinal conditions such as macular holes and complex tears. It serves as a suitable matrix to retain retinal pigment epithelial (RPE) cells and has demonstrated good anatomical and functional outcomes in macular hole closure. Animal studies have shown that AM can support retinal regeneration and organization. However, more research is required to determine precise applications in retinal disorders.
Strabismus surgery
In strabismus surgery, amniotic membrane has been investigated for its potential to reduce muscle fibrosis and adhesions, particularly in complex or repeat cases. Although some studies report favorable outcomes in terms of limit of duction improvement, ocular alignment and cosmetically acceptable results. But again, the evidence remains limited, and larger studies are needed.
Oculoplastics
AM has found utility in oculoplastic procedures where there is a need for tissue reconstruction, lid revisions, orbital linings or branch reconstruction. Many studies have shown high success rates in fornix reconstruction, particularly for less severe cases. It can also be used for prosthesis retention. The combination of amniotic membrane and oral mucosal graft may be beneficial in severe cases, while mitomycin can help reduce recurrence.
Key takeaways include:
- Background & history
- Structure & properties
- Procurement & preservation
- Use in ophthalmology
- Summary and Q&A
About Natalie Cheung, MD
Natalie Cheung, MD is a cornea and external disease specialist practicing in Cleveland. She completed her ophthalmology residency at University Hospitals in Cleveland and fellowship in cornea and external disease at Wills Eye Hospital in Philadelphia. She returned to Cleveland and joined the staff at the Louis Stokes VA Medical Center. Her practice is focused on cataract and corneal surgery and she is passionate about teaching, working with ophthalmology residents in her faculty role at the Case Western Reserve University School of Medicine.
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