Eyeworld

EW CORNEA 66 July 2016 by Michelle Dalton EyeWorld Contributing Writer Dr. Hovanesian indicated that in extensive use of both types of amniotic membrane, he has not seen a difference in biologic activity, and assays of dehydrated AM have shown the presence of biological- ly active components similar to cryopreserved tissue. Furthermore, because the dehydrated form comes in various thicknesses, it can be used for conjunctival reconstruction or to form a new conjunctiva where a thicker membrane is advantageous, Dr. Hovanesian said. Dr. Desai uses the dehydrated forms in cases of neurotrophic ulcers that are already scarred or in infec- tious keratitis. "In many cases, though, I may need to reapply a dehydrated mem- brane twice or 3 times before the cornea is fully healed," he said. He also advised against using PROKERA in patients with previous filtering surgery "where the PROKERA ring would rub against that bleb and cause potential problems." Misperceptions AM is sometimes perceived as useful only in "train wreck" situations, but "we don't want to wait until there's already a scarring process or inflam- matory process underway before we utilize this technology," Dr. Desai said. and dehydrated membrane," Dr. Desai said. For the dehydrated mem- brane to be self-retaining, it has to use a contact lens in conjunction. The PROKERA's design means it is self-retaining. The cryopreserved versions need to be stored in a freezer for pro- longed storage, whereas the dehy- drated version is "shelf stable," and typically has a long shelf life, Dr. Hovanesian said. Drs. Hovanesian and Desai said both types of AM work well, but for potentially different scenarios. Dr. Desai uses cryopreserved AM when patients have "excellent vision potential and I need to ensure the defect or corneal dystrophy is re- solved quickly and without scarring with 1 single intervention." When he's more concerned with providing some extracellular matrix with the membrane and the vision potential is limited, then he will consider the dehydrated form. "The biological activity of the cryopreserved tissue means I get fast- er healing more consistently with less scarring and haze than I do with the dehydrated versions," Dr. Desai said. "In eyes that I'm not trying to improve for refractive cataract surgery, a dehydrated membrane is great because it provides wound cov- erage, and it gets the cornea healed eventually." ophthalmology and chief of the cor- nea and uveitis division, Jules Stein Eye Institute. "Other uses that are less common include the manage- ment of painful, bullous keratopathy in eyes with poor visual potential," Dr. Aldave said. There are 2 types of commercial- ly available AM—cryopreserved and dehydrated. The cryopreserved version (PROKERA, Bio-Tissue, Doral, Florida) includes a solid plastic ring that encompasses the cornea and sits on the conjunctiva; AmnioGraft (Bio-Tissue) does not. The dehydrated form (AmbioDisk, IOP Ophthalmics, Costa Mesa, California) is a sutureless overlay AM disk. PROKERA is available in 3 versions (slim, traditional, and plus), and the dehydrated form also includes Ambio2 and Ambio5, with various thicknesses and diameters. In the last 30 years there has been no reported case of bio-incom- patibility, rejection, or allergic reac- tion to AM, said Neel Desai, MD, partner, the Eye Institute of West Florida, Largo, Florida. "Both types of AM are very safe." Differences between types of AM There are "very clear differences in the function and the cellular archi- tecture and the biological activity between cryopreserved membrane Cornea experts caution about using the tissue as a cure-all for every corneal disorder A mniotic membrane (AM) is designed for use with specific corneal and conjunctival diseases, with proposed uses in- cluding persistent epithelial defect, prevention of ocular complications associated with Stevens-Johnson syndrome, primary/recurrent pte- rygia, cicatricial pemphigoid, and conjunctival forniceal reconstruc- tion. AM assists in wound healing and prevents scar tissue formation as it has powerful antifibrotic and anti-scarring properties. But what it is not, experts say, is a substitute for a bandage contact lens. "For disadherence problems, AM is not the solution because it doesn't address the disadherence. It only gets surface defects to heal, but there will still be problems with adher- ence," said John Hovanesian, MD, clinical instructor, Jules Stein Eye Institute, Los Angeles, adding some- thing like a neurotrophic cornea would be an appropriate use of AM. Persistent corneal defects are the most common use of AM for Anthony Aldave, MD, professor of To use or not to use amniotic membrane Amniotic membrane graft and patch placed for management of a persistent epithelial defect Contact lens and lateral tarsorrhaphy placed following amniotic membrane grafting Device focus

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