Infectious Disease Risk Factors of Corneal Graft Donors

Research Objective

To investigate how donor health status affects the risk of infection after corneal transplant.

Study Design

Matched case-control study.

Relevant Methodology

An adverse reaction surveillance registry was used to conduct a matched case-control study among transplanted donor corneas from January 1, 1994, to December 31, 2003. Cases comprised 162 reports of endophthalmitis after penetrating keratoplasty. Two controls were matched to each case by surgery date. Conditional logistic regression estimated adjusted odds ratios with 95% confidence intervals according to the premortem status of decedent donors.

Outcome Measures

The presence of endophthalmitis.

Results

Postkeratoplasty endophthalmitis was associated with recent hospitalization and fatal cancer among donors. Endophthalmitis appeared more likely with tissues transplanted longer than five days after. The prevalence of concordant microbial isolates from donors and recipients was greater among fungal endophthalmitis than among bacterial endophthalmitis.

Conclusions

Corneal grafts with eye tissue obtained from donors dying in the hospital or with cancer may have an increased risk of postsurgical endophthalmitis, possibly due to donor-to-host microbial transmission. Together with donor screening and processing, improvements in microbiological control may reduce infection associated with corneal transplant.

Breakout: Hassan and Wilhelmus's paper will unfortunately unnecessarily raise concerns about donor safety from a microbial point of view, which is not justified.

Comment

William Dixon, MD

University of Toronto Toronto, ON Canada

Hassan, Wilhelmus et al conclude in their article “infectious Disease Risk Factors of Corneal Graft Donors (Arch Ophthalmol Vol 126 No. 2 Feb 2008 p 235 - 239) that “Corneal grafts with eye tissue obtained from donors dying in the hospital or with cancer may have an increased risk of post surgical endophthalmitis, possibly due to donor-to-host microbial transmission.” Their study however covered the time period January 1, 1994 to December 31, 2003

The decision to use tissue for corneal transplantation is ultimately up to the operating surgeon. The eye bank provides tissue it believes to be suitable and safe, but it is not guaranteed to be sterile.

Current EBAA standards require all donor tissue to be treated with povidone iodide during the preparation for transplant. This may be in the donor if the tissue is being prepared in situ, or in the laminar flow hood if the tissue is being prepared in the eye bank. This requirement, however, became a medical standard only in January 2006.ⁱ Prior to this time, the use of povidone iodine was an individual eye bank decision according to its standard operating procedure. Thus, in the current study, there was not consistent use of povidone iodine. Povidone iodine at a 5% concentration for two minutes has been shown to significantly reduce microbial contamination of donor corneas without penetrating into the corneal layers.ⁱⁱ

Hassan and Wilhelmus's paper will unfortunately unnecessarily raise concerns about donor safety from a microbial point of view, which is not justified. Although there is no anti-fungal in the Optisol GS, the gentamycin and streptomycin are excellent antibacterial agents. The use of povidone iodide in all cases on the intact globe significantly reduces the microbial load, and comparison of the microbial load of tissue from 2008 with that from 1994 - 2003 is not justifiable. In fact, in a study by Spelsberg et al, no patient who received a graft from a septic donor developed endophthalmitis.ⁱⁱⁱ

Cancer as a cause of death for the donor is extremely common. Eyes are the one tissue which can be donated by a donor dying of cancer - bone banks, heart valve banks, and skin banks do not accept tissues from these donors. The authors state “dying…with cancer”. Many donors have had cancer in the past and die from some other event such as a myocardial infarction, cerebral hemorrhage, and so on. It is totally unjustified to include them in a group who might be immune compromised because of treatment for terminal cancer. The authors refer to a paper by Rehany et al ^iv which states “malignancy may be a risk factor for corneal button contamination because of prolonged hospitalization of the patient and the use of cytotoxic agents… surprisingly, donor corneal buttons from donors who died of cardiac disease had significant higher contamination rate than the rest of the corneas.”

The risk of developing endophthalmitis after penetrating corneal transplant is fortunately very low - 0.1 - 0.41%. Current methods of donor care - soaking the globe in 5% povidone iodine for two minutes, rinsing with sterile saline, storing in Optisol GS, and using the donor as expeditiously as possible, reduces the risk of transmitting microbacterial agents from the donor to the recipient.