Today, eye banking services are provided in an environment of stringent quality assurance standards, often with increasing government regulation or oversight. All of these systems have as their basis the identification and minimisation of risk so as to ensure and improve the quality and safety of transplanted tissue. Quality management systems and risk assessment have become important aspects of eye banking where the emphasis is now not only on quantity of tissue provided but also where quality of tissue and quality of service have become priorities.

Different recovery procedures, storage techniques, and in more recent years tissue processing techniques, have been introduced and each have their own benefits and risks. These will be compared in this chapter. However, the adoption or choice of a particular procedure needs to be considered within the context of a practitioner’s local conditions to ensure an efficient, safe and quality service. Ultimately, the objective of eye banking remains – the delivery of ocular tissue, donated for transplantation, in order to allow the ophthalmic surgeon to restore sight in a safe and high-quality procedure.

Retrieval of Donor Tissue

Either the corneoscleral button is removed in situ and directly transferred to a storage or collection solution, or the eye is enucleated and the corneoscleral button excised later in the eye bank laboratory. Legal requirements will vary between jurisdictions, with some legislature requiring that only medical practitioners be authorised to perform the donor procedure, and still some others specifying that only in situ excision rather than enucleation be allowed. The suggested procedures for enucleation and in situ excision are described in the Medical and Technical Standards of many eye banks and eye banking organisations. Ultimately, the preferred method is dependent on local/national conditions and considerations and legalities but the persons performing the donor surgery must use their professional judgment and satisfy themselves that all reasonable steps and normal surgical precautions have been taken to minimise contamination or damage to the tissue.

Technical Aspects

The benefits and risks of both procedures are summarised in Table 6.1. In situ excision is more technically demanding and also requires the time to perform a careful in situ examination by penlight or handheld slit lamp. The introduction of the artificial anterior chamber also means that lamellar surgical techniques can be performed on the corneoscleral button obviating need for a whole eye. The enucleation procedure is more invasive with the risk of haemorrhages from the optic vessels and the orbit affecting the appearance of the donor, although this is not a common problem [4].

Upon the death of the donor, the corneal endothelium is subject to warm ischemia and is in contact with stagnant aqueous humour. This results in progressive cytolysis and cell death and this may also progress during subsequent storage.

Limiting the time between the cessation of donor circulation and storage of the cornea results in a more viable endothelium, but an absolute acceptable time interval has not yet been defined. Recommended death to enucleation times for corneas intended for organ culture storage tend to be more liberal than those for hypothermic storage. The normothermic temperatures of organ culture storage provide for an in-built viability assay on the “health” of the cornea, and evaluation at the end of the storage period allows for a discard of those corneas they may have suffered from ischaemic damage following the donor’s death. A period of 24 h (or beyond) death to enucleation is often a recommended benchmark. Conversely, hypothermic storage doesn’t provide for this type of assessment and thus more conservative maximum death to enucleation times of 12–18 h are often used as a benchmark.

Microbiological Aspects

The normal ocular flora that is present during life multiplies with the lack of lid movement and lyzosomal enzymes in the tear film. Before removal of the tissue, bacterial contamination from both exogenous sources and from the ocular flora post-mortem [5] has to be removed. For in situ excision, one must be especially aware of the bacteriologic considerations, as no further decontamination of the tissue is possible. In general, the procedure consists of vigorous rinsing with balanced salt solution, moistening of the eye and eye lashes with a broad-spectrum antibiotic/ antifungal solution and disinfection of the lids and the surrounding eye tissue and skin with povidone–iodine solution. In the case of enucleation, many eye banks will forego extensive donor preparation, opting instead to decontaminate the globe within the laboratory. This is usually done by vigorous rinsing with a balanced salt solution, immersion of the eye in a 0.5–1% povidone–iodine solution, followed by a subsequent rinse with balanced salt (See technical guidelines EBAA, EBAANZ and EEBA). Comparative studies support the validity of both procedures [5].

The overall rate of post-operative endophthalmitis following penetrating keratoplasty has been found to be around 0.4% in a literature review of 90,549 cases [6].