What is eye banking and why is it relevant to me , the ophthalmic assistant?
Ophthalmic clinics will see patients with cornea disease. Some of those patients may require a cornea transplant to treat the diseased cornea. Other eye surgeries also require ocular tissue for transplant (glaucoma shunt patch, enucleation, and others). The eye bank provides corneas and other ocular tissue to surgery centers for transplantation ( Fig. 54.1 ).
Around the world, there are tens of millions requiring a cornea transplant. In more developed countries, the pre-valence is very low and transplant rate is very high, with nearly everyone being treated as needed. Whereas in low and middle-income countries, the incidence and prevalence is very high; there are patients who remain untreated for multiple structural reasons (cost, access, infrastructure, training, funding, etc.). In these cases, many patients in the clinic may be evaluated and diagnosed, but will not be treated to effectively restore sight in that eye.
For those able to be treated with a cornea transplant, the eye bank provides the cornea. This comprises 99% of the activity of an eye bank. Some eye banks also provide other ocular tissues. For glaucoma shunt surgeries, the eye bank provides a piece of sclera or cornea to cover the outer end of the tube. For enucleations, the eye bank provides a whole sclera as a globe-shaped envelope for a prosthesis. Because corneas are the primary focus of eye banking, this chapter will be focused on cornea donation and transplantation.
The eye bank
The eye bank serves as a community resource and a link between the person who donates their eye or cornea (the donor), and the surgeon who transplants it into the patient needing a transplant (the recipient). Some organs and tissues can be donated from living donors (blood donation or kidney donation), however most donations of organs and tissues only can occur after death (heart, lung, bone, etc.). Like the latter, eye donation can only occur after death. Once an individual passes away, they can be considered for eye donation. The surgical recovery and preservation of the cornea must occur soon after death. The eye bank manages the identification of potential donors, screening for eligibility of donation, surgical recovery, processing, testing for infectious diseases, and distribution to surgery—thus forming the link between the donor and the surgeon (and the surgeon is the link between the eye bank and the recipient).
The eye bank is uniquely specialized to cover all these key activities from death of the donor to distribution of donor’s cornea to the surgeon; the eye bank must maintain key relationships with community organizations for each step of the process.
For example, many potential donors pass away in hospitals. The hospital must provide the eye bank technician access to the donor’s family members to gain legal authorization (consent) for donation from the deceased, and then proceed to surgical recovery of the cornea. The eye bank then serves as a continuation of the hospital’s services, by providing additional services and options even after the patient’s death. This single event requires an ongoing relationship (and sometimes a written agreement) between the hospital and the eye bank. This same principle for hospital relationships is applied to any entity in control of the potential donor immediately after death (funeral home, mortuary, medical examiner, coroner, police morgue, etc.). Many eye banks employ staff members to manage the relationship with hospitals and the general public, ensuring there are appropriate procedures and trust within the community.
On the other end of the process, the surgeon and surgery centers are the primary purpose and driver for the eye bank. If there were no surgeries, there would be no eye bank—or said differently, eye banking activity is filling a demand of surgical activity. The eye bank can also be seen as an extension of surgery or the presurgical preparation. Indeed, many eye banks perform additional surgical processing steps to the cornea to reduce time, cost, and training required for the hospital, patient, and surgeon, respectively. These additional pretransplant surgical procedures done in the eye bank must be done to the surgeon’s specifications, and therefore requires cooperation between the eye bank and the surgeon. This surgeon-eye bank relationship is fruitful for both, and results in new innovations of products and services to reduce costs and advance the science and practice of cornea transplantation.
These two ends of the process, the hospital relationship and the surgeon relationship, exemplify the community nature of the eye bank, and how the eye bank links community resources together.
Between those two ends are the core eye bank processes. Once preserved, the cornea remains viable for 1 to 4 weeks (depending on how it is preserved) before it must be transplanted. All the processes must fit within this timeframe.
At the beginning of the process is the community at large. Individuals in the community must have awareness about donation and willingness to donate corneas. Government entities can assist with communications, support for legislation, or other positive support for eye donation. There is a common misconception that donation rates are driven by the donors—especially in low-donation environments. However, donation rates are driven more by coordinated systems, organizations, trained staff, and appropriate regulatory environments, than by the general population. It has been found that even in areas with very low donation rates, the relative willingness to donate is much higher, suggesting that something other than the donor consent is limiting actual donations. No major religion is opposed to donation, and in fact many religious leaders have stated support for donation. The eye bank’s role and obligation is to convert public sentiment and individual’s commitments into action, ethically stewarding the donated cornea from donor to patient.
There are best practices, guidelines, standards, and regulations applied to the process. These rules ensure that corneas are safe to transplant. As an example, the Eye Bank Association of America (EBAA) has set industry-leading medical standards since 1961 ( Fig. 54.2 ). In the United States, these standards, along with government regulations published by the U.S. Food and Drug Administration (FDA) (CFR 1271) ( Fig. 54.3 ), form a comprehensive and complimentary set of standards and regulations to ensure tissue safety and efficacy. Many countries have similar standards as set forth by their Ministry of Health and/or other government transplant agency.
Some of these procedures include aseptic technique and sterility, infectious disease testing, physical/microscopic evaluation, and organizational oversight requirements. Aseptic technique is a critical practice during the surgical recovery of tissue from the donor. Following this protocol greatly reduces the risk of introducing microorganisms to the tissue, and thereby reducing transfer to the recipient. In most countries, infectious disease testing includes human immunodeficiency virus, hepatitis B, and hepatitis C. Some countries require syphilis or human T lymphotropic virus. The infectious disease testing, along with a comprehensive review of the donor medical history, provides a medical assessment of eligibility for transplant. Only donors who pass these screening procedures and tests are eligible for transplant. Because corneas are avascular (no blood vessels within the tissue), the risk for transferring disease agents is lower than other organs and tissues, and therefore the testing requirements are usually different. As mentioned later, this can cause challenges when regulations are written for all organs and tissues, without considering unique differences between them.
The cornea must not only be safe, but also be effective and viable for transplant. A physical examination using two different microscopy techniques ensures viability and clarity. The first is a specular or light microscope to photograph and count the endothelial cell density ( Fig. 54.4 ). The specialized eye bank microscope is designed to view the endothelium through the sealed container and preservation fluid. This evaluative technique provides a quantitative assessment of the endothelial health. Slit-lamp biomicroscopy ( Fig. 54.5 ) gives a qualitative assessment of each layer of the cornea: the epithelium, stroma, Descemet’s membrane, and endothelium. Together, these techniques provide a comprehensive assessment of the cornea and a judgment on suitability can be made.