NEW YORK, Apr 13 (Reuters Health) -- Grafts made of amniotic membrane -- one of the protective layers surrounding the fetus -- can be used to stimulate the regrowth of damaged corneas, according to researchers.
"Amniotic membrane transplantation was effective to promote corneal healing in patients," report Dr. Augusto Azuara-Blanco and colleagues at the University of Nottingham in Nottingham, UK. Their findings are published in the April issue of the British Journal of Ophthalmology.
Injury to the eye can result in serious damage to corneal tissue. In milder cases, physicians simply apply medications and wait for the damaged tissue to heal and regrow.
However, surgical interventions are required in situations in which this type of spontaneous healing fails to occur, such as cases due to chemical burns, or where the cornea is severely infected.
The amniotic membrane, which surrounds the fetus in the womb, is a unique source of 'biological dressing' that has been used in wound healing for decades. According to the researchers, these membranes appear to contain large amounts of growth factors (which encourage tissue regeneration), as well as anti-bacterial and anti-scarring properties. They are especially useful as tissue grafts because they do not encourage autoimmune rejection (as happens in organ transplant, for example).
In their study, the UK team surgically covered the damaged corneas of 10 patients with small patches of amniotic membrane, which "were obtained under sterile conditions (from human placenta) after elective cesarean delivery," the authors explain.
They report that, in cases of milder corneal damage (due to abscess, radiation damage, or chemical burns), "rapid corneal healing occurred in four of five cases 1 to 4 weeks after amniotic membrane transplantation." The original wound defect reoccurred in the fifth patient.
Amniotic membrane transplant was also successful in promoting the growth of corneal tissue in a patient whose scarring had caused the eyelid to adhere to the eye. The authors explain that 'antiadhesive' compounds in amniotic membrane tissue appear to help prevent this type of scarring.
The procedure was not successful, however, in patients with more severely damaged corneas, such as perforations. These patients went on to receive corneal transplants.
In all the successful cases, the amniotic membrane graft "dissolved" away within 2 months, leaving healed corneal tissue in its stead. Most patients did require further corrective surgeries before regaining full vision.
Based on their findings, the researchers advocate the use of amniotic membrane transplantation in patients with relatively mild corneal damage unresponsive to traditional 'wait and see' therapies. They caution, however, that "a controlled clinical trial will be necessary to evaluate whether amniotic membrane transplantation has a better or worse outcome than conventional surgical options to treat persistent epithelial defects."
SOURCE: British Journal of Ophthalmology 1999;83:399-402.
