April 2009

 

OPHTHALMOLOGY NEWS

 

Effective membrane patch possible in office


by Rich Daly EyeWorld Contributing Editor

 

 

Readily available patch for chemical burns hurries healing and saves money

Injured eye that has received an amniotic membrane graft

Pre-op image of an eye that has suffered a chemical burn prior to placement of an amniotic membrane graft

Post-op image of sutureless amniotic membrane graft placed in an injured eye

A close-up image of an injured eye that has received a sutureless amniotic membrane graft Source: James V. Aquavella, M.D.

The clock is ticking when a chemical injury occurs. A new office-based amniotic membrane patch (AMP) can jumpstart the healing process and save victims of one of the most difficult ocular emergencies significant pain and money.

The prognosis for eyes suffering from chemical burns depends not only on the severity of injury but also on the rapidity and mode of treatment. Conventional acute stage management has focused on promoting epithelialization and reducing inflammation to prevent progressive tissue melting. This approach also aims to prevent cicatricial complications in the chronic phase.

Previous approaches in these patients included topical and systemic uses of ascorbate, citrate, tetracycline, progesterone, and steroids, application of a glued-on hard contact lens, tenonplasty to correct severe ischemia, oral mucosa graft, and application of an AMP.

Previous research has found that the use of AMP as a permanent surgical graft promotes epithelialization and reduces inflammation, scarring, and neovascularization. Acute burn cases have also benefited from the AMP when it is used as a temporary patch or biological bandage.

The patch has performed best when used as part of early intervention in mild or moderate chemical burns, resulting in a sharp reduction of symptoms, rapid restoration of the ocular surface, and improved visual acuity, while also preventing cicatricial complications in the chronic stage.

However, the use of AMP has been limited because sutures were required to be placed in an operating room, which entailed high costs and delays that could affect the clinical outcome. The problem was further complicated by the frequent need for multiple sessions of AMP for a single eye with acute chemical burns.

“Therefore, a simple bedside or office method of AMP is needed to obviate these problems,” wrote Daniel Johnson, M.D., assistant professor and chief, Cornea and Uveitis Services, Department of Ophthalmology, University of Texas Health Science Center, San Antonio, and co-investigators in a recent AMP study.

A retrospective review of a new patch used in five eyes of five patients with grades I to III acute alkaline burns was published by Dr. Johnson and colleagues in the August 2008 issue of the Archives of Ophthalmology. The study examined the use of the ProKera (Bio-Tissue, Miami), a Food and Drug Administration-approved device that aims to provide a temporary AMP to help heal the corneal surface without using sutures. The device contains a piece of cryopreserved amniotic membrane clipped into a concave polycarbonate dual-ring system that conforms to the corneal and limbal surface like a contact lens.

In the study, the device was inserted within eight days of injury and included repeated applications.

The researchers found the conjunctival defects reepithelialized within 5 to 17 days, while limbal and corneal defects healed between 5 and 25 days.

“The latter was completed with circumferential closure of limbal defects followed by centripetal healing of corneal defects,” wrote Dr. Johnson and co-investigators.

The authors found that in three eyes, the early peripheral corneal neovascularization was followed by marked regression on completion of healing.

The findings led the authors to conclude that early placement of the sutureless patch “may help preserve remaining limbal stem cells for rapid expansion and prevent late cicatricial complications” in eyes with chemical burns.

The research findings fit with at least one other surgeon experienced with such cases.

James V. Aquavella, M.D., professor of ophthalmology, University of Rochester Eye Institute, Rochester, N.Y., said the effectiveness of temporary patches in chemical burn cases has been limited by the severity of the injury and the speed with which the amniotic membrane was delivered.

He noted that the ready-to-use design of the ProKera patch is simpler than standard AMPs, which will also increase its use.

“If it means that you have to get the patient anesthetized or into an operating room environment in order to do it, it is going to take a longer period of time, and we all agree that the sooner you get this protective covering over the surface of the eye, the better it is,” Dr. Aquavella said.

The concept of putting membranes on a carrier ring has been used for several years, said Dr. Aquavella, who has used such devices. However the ProKera design that allows their placement in a recently injured and inflamed eye with just a few drops of topical anesthetic is “definitely worthwhile stressing and putting out there because many people may not have thought of using them in that way.”

More study needed

The importance of the recent patch research is limited by the small number of cases and the lack of study of large eyes. Dr. Aquavella noted that chemical injuries to larger eyes produce significantly more lid swelling, which may complicate getting the ProKera or similar devices into the eye. In some cases, the device may also prove too uncomfortable for patients to keep it in the eye. The effectiveness of the device also may be limited in injuries with more irritated lids and in cases where the surgeon is aiming for an excess of membrane to be sutured deliberately in the inferior aspect of the conjunctiva and draped over the outside of the lid. The device appears best suited to address stem cell damage around the limbus of the eye—the central 10 or 11 mm around the cornea—whereas many chemical burns include damage to the conjunctiva and the lid margin.

Such wider injuries might lead surgeons to apply such a patch “right away” and then add more amniotic membrane over the following days in areas not protected by this device.

Another important point in the use of such devices is that surgeons need to have ready access to them to stop the ticking clock. Such patches require storage equipment that most physicians’ offices outside of a medical center or hospital complex probably lack.

“Ease of application is fine, but you if you can’t get it available, then it doesn’t make any difference,” he said.

Editors’ note: Dr. Aquavella has no financial interests related to his comments.

Contact information

Aquavella: 585-275-8957, James_Aquavella@URMC.Rochester.edu

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