SPECIAL CORNEA ISSUE

Eye Banks Doing More for Surgeons

As procedures evolve, regional eye banks are keeping pace

BY STEVEN M. SILVERSTEIN, MD, FACS, WITH TONY BAVUSO

With the number of full- and partial-thickness corneal transplant procedures performed each year in the US nearing 50,000, along with anticipated increasing use of glaucoma shunts following the release of data from the Tube vs Trabeculectomy (TVT) study, the demand for pre-cut tissue for ophthalmic surgery will certainly continue to grow.

Over the past two decades, the most common disease states necessitating corneal transplantation have changed. In the 1970s and 1980s, aphakic and pseudophakic bullous keratopathy topped the list, due to several iterations of lens implants that proved to be detrimental to the corneal endothelium, and because of more traumatic or less sophisticated methods of cataract extraction. With current IOLs and less traumatic phacoemulsification techniques, the incidence of surgically induced bullous keratopathy has declined considerably. The top three diseases requiring corneal transplant today are: traumatic or infectious corneal scarring (particularly caused by herpes simplex virus), Fuchs' dystrophy and keratoconus.

Though a handful of higher-volume transplant surgeons still continue to cut their own tissue, most doctors will be working with — and depending on — local and regional eye banks to meet the need for tissue that can be used with a high degree of confidence. As a cornea transplant surgeon who has worked with the Heartland Lions Eye Bank (HLEB) in Kansas City, Mo., for many years, I believe that HLEB is representative of the high-quality local and regional eye banks that are moving ahead, just as surgeons are advancing in terms of rapidly adopting newer and better procedures.

Eye Banks Have Progressed

Many aspects of current day eye banking have evolved, particularly in the areas of consent, recovery, storage, processing and distribution of eye tissue. This is primarily due to several new initiatives, such as the Eye Bank Association of America (EBAA) Cornea Collaborative, modeled after the Break through Organ Donation Collaborative.

The Cornea Collaborative initiative is a major step forward. It involves sharing data, identifying best practices and implementing positive change. Other recent changes in eye bank operations have centered upon adapting to the needs of corneal surgeons as new surgical techniques have emerged, particularly with regard to the science of targeted keratoplasty.

Previously, consent for eye donation had typically involved contacting the deceased's legal next of kin soon after death and requesting permission to retrieve eye tissue from the donor. More recently, many eye banks have begun acting on First Person Consent (FPC), which is usually documented on the back of a person's driver's license, donor card or on a state donor registry.

This advance came about as a result of changes to the Uniform Anatomical Gift Act (UAGA) found in many states. The UAGA originated in 1968, but has gone through multiple revisions in order to strengthen its language and allow the process of eye, organ and tissue donation to occur more seamlessly.

FPC has not been without controversy, as it can often be difficult to carry out the wishes of the deceased if the surviving family is opposed. However, legal opinion holds that recovery agencies (eye, tissue and organ banks) are obligated to proceed with donation, and no person may interfere if the deceased properly documented his or her decision to be a donor.

Historically eye banks performed enucleations, followed by corneo-scleral excisions and preservation. It is now more common for eye banks to perform in situ corneal excisions and preservation onsite at the hospital, morgue or funeral home. This approach saves time and money, allowing the tissue to be obtained in a more cost-effective manner.

Additionally, disposable surgical instruments are commonly used instead of reusable instruments to avoid the risk associated with cross-contamination from a donor with a transmissible spongiform encephalopathy and to make it easier to comply with CFR Title 21 Part 1271 Current Good Tissue Practices regulations enforced by the FDA.

Tissue Preservation

Though tissue procured from eye banks is always best used within a week of harvesting, preservatives can help to extend the useful life of ocular tissue a bit longer.

Optisol GS has been the standout choice of most eye banks for tissue preservation for many years now, but some have tried newer products such as Eusol-C, which is entirely synthetic and does not contain any ingredients derived from animal components (e.g., the chondroitin sulfate found in Optisol GS). Other new products are also under development, including LifeForce media and some generic forms of Optisol GS. However, Optisol GS remains the most popular corneal storage media in the US to date. Glycerin is also being used for long-term preservation of corneas not suitable for penetrating keratoplasty (PKP) or Descemet's stripping automated endothelial keratoplasty (DSAEK). Glycerinpreserved corneas can be used as tectonic grafts, anterior lamellar grafts or glaucoma shunt coverings.

A technician at Heartland Lions Eye Bank in Kansas City, Mo., at left, processes tissue for use in corneal transplant procedures. At right is a close-up look, showing the precision nature of providing pre-cut tissue to ophthalmic surgeons.

Providing Tissue for DSAEK and ALK

DSAEK has truly changed many aspects of keratoplasty for corneal surgeons as well as for eye banks. Nearly 65 percent of the 2,770 corneas that Heartland Lions Eye Bank provided for transplant in 2009 were for DSAEK procedures. The vast majority of those were pre-cut by the eye bank.

HLEB also pre-cuts tissue for 12 other eye banks. In total, HLEB prepares more than 1300 corneas per year for DSAEK in its Kansas City-based laboratory.

In order to obtain precise graft thicknesses, HLEB uses Fourier-domain OCT to determine the corneal thickness prior to resection with the Moria CBm microkeratome system. Microkeratome heads of various thicknesses (200 μm to 350 μm) are used to obtain a targeted graft thickness of 140 μm with a standard deviation of 26 μm (although thinner or thicker grafts can be prepared upon request). Fourier-domain OCT is also used after resection, in addition to slit-lamp and specular microscopy, as a quality-control measure to ensure that a smooth, even graft of acceptable thickness is obtained and the endothelium is not harmed during the procedure.

The post-processing OCT image is then provided to the trans planting surgeon for review prior to transplant (see figures below). While not all eye banks have an OCT, they do evaluate the tissue's suitability and provide detailed information regarding the specifications of tissue prepared for DSAEK, including graft thickness, graft-bed diameter (maximum trephination diameter), cell count and slit-lamp microscopy observations.

Because preferences regarding DSAEK tissue specifications vary widely among surgeons, it is important to communicate with the eye bank whether thinner or thicker grafts are preferred and what markings are desired on the donor tissue. While eye banks can accommodate most requests for anterior cap or stromal bed markings, most avoid placing excessive markings on the tissue because of concerns about endothelial damage as described by Ide et al. in Cornea (http://journals.lww.com/corneajrnl/Abstract/2008/06000/Descemet_stripping_Automated_Endothelial.11.aspx).

Given that eye banks are very proficient in preparing tissue for DSAEK, there is still some inherent variability in the process and in donor tissue. To date, no definite link has been proven between donor graft thickness and postop BCVA. Therefore, it is suggested that surgeons be willing to accept pre-cut DSAEK tissue of any reasonable thickness according to the eye bank's standards for tissue suitability.

HLEB also uses the Moria CBm microkeratome system to prepare tissue for anterior lamellar keratoplasty (ALK) trans plants, although the demand from US surgeons for pre-cut ALK tissue is much lower than the demand for precut DSAEK tissue.

The Vision Share Network

To meet the growing and evolving needs of surgeons, 20 eye banks across the US founded a consortium called Vision Share. These non-profit eye banks provide more than 50 percent of corneal tissue transplanted in the United States and collaborate to share best practices in providing the highest quality donor tissue and comprehensive services. Vision Share eye banks have served as leaders in pre-cutting tissue for DSAEK and ALK, offering femtosecond laser-prepared corneas for PKP, and are the only eye banks to offer prepared tissue for Descemet's membrane (automated) endothelial keratoplasty (DMAEK/DMEK) and can provide donor tissue for procedures such as deep anterior lamellar keratoplasty (DALK) and kerato-limbal allograft (KLAL). This is in addition to providing tissue that meets all Eye Bank Association of America standards for PKP.

Vision Share allows HLEB to utilize the services of other member eye banks, which provide unique and innovative services to meet the needs of surgeons and patients:

► Vision Share eye banks in Iowa and Washington state use IntraLase femtosecond laser systems to prepare tissue for customized IntraLase-enabled keratoplasty in configurations such as zig-zag, mushroom and top hat.

► Vision Share eye banks in Indiana and Iowa are the first in the world to offer preparation of tissue for DMEK/DMAEK and are working with researchers and other eye banks to perfect the technique for this challenging type of donor tissue preparation.

► Through the Global Sight Network program, the Vision Share eye bank in Alabama provides glycerin-preserved corneas, which may be used for glaucoma shunt coverage, anterior lamellar keratoplasty, tectonic keratoplasty and as support tissue for the Boston KPro artificial cornea.

Vision Share's distribution staff allows HLEB to access tissue from other eye banks when necessary, as well as share tissue to meet the needs of surgeons and patients across the United States and worldwide, with a single point of contact. The distribution center and eye bank staff handle all logistics in an effort to place the tissue where it needs to be, on time, via myriad logistics resources, including airlines, courier services, and shippers such as FedEx, DHL and UPS.

Handling Corneal Tissue Upon Receipt

As eye banks are regulated by the FDA, they must uphold strict standards regarding the handling and storage of tissue. Corneal tissue must be maintained on wet ice or in a monitoring refrigerator at 2 to 8 degrees centigrade and used as soon as possible. Deviations from these conditions will result in the eye bank being unable to accept returned tissue in the event that surgery is canceled.

Corneal tissue and the accompanying documentation should always be thoroughly inspected prior to transplantation as the final responsibility for determining the suitability of the tissue always rests with the transplant surgeon.

A technician at Heartland Lions Eye Bank (above) performs OCT imaging on tissue processed by the eye bank to determine its suitability for use by surgeons. The surgeons receive a printout, shown at right, which is helpful in planning the procedure.

Serology

► Currently, serologic screening requirements are as follows.
HIV-1/HIV-2: anti-HIV-1, anti-HIV-2 (or combination test)
HIV-1 NAT (or combination NAT)
HBV: Hepatitis B surface antigen (HBsAg)
Total antibody (IgG + IgM) to Hepatits B core antigen (anti-HBc)
HCV: anti-HCV
HCV NAT (or combination NAT)
Treponema pallidum (RPR, STS)
► Non-required tests:
HTLV-1/HTLV-2

Serologic testing results and the screening of the donor's medical history should be reviewed, the seal and the integrity of the tissue vial or chamber should be inspected, and the media color should be within the manufacturer's recommendations (from pink to orange for Optisol GS from Bausch + Lomb). Eye banks do not normally culture donor tissue and while Optisol GS contains gentamicin and streptomycin, the tissue should not be assumed to be sterile. Any positive culture results should be reported to the eye bank.

More Flexible Scheduling is Possible

As recently as the early 1980s, storage media and tissue transportation and distribution were so inconsistent that potential transplant recipients were assigned a beeper and paged to the hospital day or night once tissue became available.

Currently, non-emergent transplants are successfully scheduled electively, with only rare cancellations due to a lack of quality tissue availability. As the result of heightened national awareness due to volunteer organizations such as The Gift of Life, located in Kansas City, as well as the Lions Clubs of America, high-quality tissue available for transplantation is much more accessible than is seen by patients and surgeons in most other countries around the world. Even in similarly developed countries in Europe, there is a desperate need for tissue, including corneal tissue, largely as the result of differences in cultural philosophy, religious protests and a fundamental lack of public awareness. Surgeons are often forced to use transplant tissue rejected by US surgeons based upon the age or quality of the tissue. One corneal surgeon from Germany described a proposal that, based on tissue shortages, would permit only patients registered as organ donors to receive donated tissue.

Lastly, the economic recession and healthcare reform legislation are presenting new challenges to ophthalmic surgeons and eye banks alike. Reimbursement from third-party payers has become an issue when ambulatory surgery centers sign contracts with private health insurers that bundle surgeon fees, facility fees and tissue-processing fees together into a single reimbursement that does not fully cover each of these fees individually. Surgeons can help alleviate this problem by ensuring that their ASCs negotiate contracts with insurers that sufficiently cover all of the fees for a transplant procedure. OM

Steven M. Silverstein, MD, FACS (pictured) is in practice at Silverstein Eye Centers in Kansas City, Mo. Tony Bavuso is director Heartland Lions Eye Bank, also in Kansas City. Dr. Silverstein can be reached at ssilverstein@silversteineyecenters.com.