Eyeworld

EW NEWS & OPINION 20 July 2017 by Liz Hillman EyeWorld Staff Writer Amniotic membrane: Expanding thoughts on when to use these products An article in the May 2017 issue of EyeWorld provided a brief history of the use of amniotic membrane in oph- thalmology and delved into how some physicians are using amniotic mem- brane to improve the ocular surface prior to cataract surgery. This article expands perspectives on this topic and explores how amniotic membrane can be used in other applications for ocular healing. The graft is tucked into the subconjunctival space to provide its antifibrotic effects to Tenon's fascia, from which pterygium recurrence might arise. Source: John Hovanesian, MD Freeze-dried human amniotic membrane is cut into a C-shaped graft. continued on page 23 B arry Schechter, MD, direc- tor of the cornea and cat- aract service, Florida Eye Microsurgical Institute, Boynton Beach, Florida, said amniotic membrane (AM) has been "invaluable" in many thera- peutic areas of ophthalmology. "It has been successful in facilitation of epithelialization, maintenance of normal cellular phe- notypes, and reduction of inflamma- tion, vascularization, and scarring when treating corneal ulcers; in treatment of corneal erosions; and extremely helpful in surgical treat- ment of ocular surface disorders. I have been utilizing AM in its various forms for more than 15 years," Dr. Schechter said. "Any treatment that necessitates the prolongation and maintenance of epithelial stem cells, promotion of conjunctival goblet cell differenti- ation, and exclusion of inflammato- ry cells with anti-protease activities would benefit from the inclusion of AM," he said. John Hovanesian, MD, Harvard Eye Associates, Laguna Hills, Cali- fornia, a cornea specialist, said the most common condition he treats as it pertains to AM is pterygium. Dr. Hovanesian said his use of amniotic membrane to promote healing and prevent reoccurrence in pterygia cas- es dates back to 2004 when he was looking for a method gentler than mitomycin-C. "Amniotic membrane provided that answer," he said. "I started do- ing a procedure that involved doing a conjunctival autograft but addi- tionally taking amniotic membrane and placing it just in the subcon- junctival space surrounding that graft. … Tuck it in underneath the surrounding conjunctiva—it's like a protective barrier in that space—to prevent recurrence. Then you glue down the graft in the normal fash- ion. The graft is not sitting on top of amniotic membrane; it's sitting on top of sclera as it usually is, but then around it in the subconjunctival space is this amnion. The rationale for that technique is when we think about recurrence of pterygium, it doesn't come from the bare sclera site, it comes from the tissue under- neath the surrounding conjunctiva," Dr. Hovanesian explained. A non-comparative study coau- thored by Dr. Hovanesian published in the Canadian Journal of Ophthal- mology detailed use of amniotic membrane in 101 pterygia cases. 1 Recurrence using this technique at 6 months of follow-up was 1%. Dr. Hovanesian said other reports suggest recurrence rates without am- niotic membrane being closer to 5%. Similarly, research coauthored by Dr. Schechter, presented at the 2017 ASCRS•ASOA Symposium & Congress, involving 493 eyes in an ethnically diverse population—8% Caribbean/African American, 27% Hispanic, and 15% Caucasian/ Asian—found a 1.22% recurrence rate with the adjunctive use of amniotic membrane for conjunctival autograft for pterygia cases. 2 "The importance of the study is in showing that these patients who phenotypically have a much higher rate of pterygium recurrence did extremely well with a low recurrence rate when conjunctival stem cell grafting was augmented by the use of amniotic membrane," Dr. Schechter said. Drs. Schechter and Hovanesian said they've used cryopreserved and dehydrated amniotic membranes, finding both varieties efficacious. Dr. Schechter said he prefers cryo- preserved AM when he wants the membrane to be incorporated into the healing tissue, for example in cases of Stevens-Johnson syndrome or in neurotrophic disease. When he wants AM to function as a scaffold for reepithelialization, he prefers dehydrated AM. "As far as healing, I think they both work well," Dr. Hovanesian said, adding that in some cases he thinks thinner dehydrated mem- branes held in place with a soft contact lens can be easier to deal with than the cryopreserved prod- ucts that have a self-retaining ring, although there are times self-reten- tion is an advantage as well. Research presented as a poster at the 2015 ASCRS•ASOA Symposium & Congress compared Prokera (Bio-Tissue, Doral, Florida), a cryopreserved amniotic mem- brane, and AmbioDisk (IOP Oph- thalmics/Katena, Denville, New Jersey), a dehydrated amniotic membrane, for different indications of corneal epithelial defects. 3 Of the 40 eyes in the study, 28 received

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