ADVICE ON AMT

Preoperative ocular surface neoplasia (Courtesy Damian Lake FRCOphth)

Amniotic membrane transplantation (AMT) has a variety of useful ophthalmic applications and is now being used more due to increased Caesarean birth rates and improved preservation techniques, Damian Lake FRCOphth, The Queen Victoria Hospital, East Grinstead, UK, told the Joint Irish/UKISCRS Refractive Surgery Meeting in Dublin, Ireland.
Clinically AMT has many long-established uses including treatment of persistent epithelial defects, reconstructions post tumour resection, neurotrophic ulceration, post-herpetic ulcerations, for PRK haze, following excision of conjunctivochalasis or pterygium, in patients with superior limbic keratoconjunctivitis after Tenon layer resection, and after ocular surface burns from chemicals or heat, Dr Lake explained.
The two main surgical techniques using amniotic membrane are inlay AMT to act as a replacement basement membrane or to fill deep ulcerations, and onlay AMT to act as a bandage to promote epithelial healing, he added.
“The AMT may be multilayered, and we prefer the stroma side down. We use nylon sutures in a running style, as they are quicker to use and less inflammatory than Vicryl,” he stated.
AMT has many modes of action including inhibiting angiogenesis, antimicrobial and anti-fibroblastic. It does not produce an immunological response and it becomes incorporated within the host stroma.
There is some evidence that the AMT contains some pluripotent stem cells, but the evidence on growth factors and anti-inflammatory molecules is often contradictory, Dr Lake noted.
He advised that surgeons seek out clinical studies on AMT for definitive data, as mainstream media coverage and advertisements tend to exaggerate the benefits and potential of AMT.

Safety and storage
With increased Caesarean section rates has come increased availability of amniotic membrane in the Western world. The screening process when collecting amniotic membranes is exhaustive so as to exclude any possibility of transmissible diseases such as hepatitis or HIV, Dr Lake reassured the meeting.
The storage process has commonly been through cryopreservation but increasingly freeze-dried tissue is now available with the advantage of easier storage in operating facilities. 
Despite its many uses, however, Dr Lake cautioned that AMT is not a robust material. “It is soft and should not be used for patching or glaucoma drainage tube erosion as it is unlikely to be successful,” he said.
Summarising, Dr Lake said AMT is a useful tool but is not a “cure all”. The procedure may need to be repeated, particularly in burns, and surgeons must be vigilant regarding infections and continue to use antibiotics, he concluded.

Damian Lake: lakedamian@hotmail.com