COVID-19 and Corneal Transplantation

The available evidence suggests the risk of COVID-19 transmission through corneal transplantation is low. Nevertheless, with an abundance of caution, Eye Bank Association of America (EBAA) guidelines on donor screening should continue to be implemented as the understanding of SARS-CoV-2 and corneal transplantation evolves, according to Shahzad I Mian MD.

In his discussion of the impact of SARS-CoV-2 on corneal transplantation, Dr Mian presented research relating to viral presence in the cornea, the risk of COVID-19 transmission through corneal transplantation, and the effect of the pandemic on donor supply.

He noted studies of SARS-CoV-2 ocular infection show conjunctivitis, not keratitis, is the most common ocular manifestation in patients with COVID-19. However, there is a poor correlation between presence of ocular signs and symptoms and presence of SARS-CoV-2 on the ocular surface.

Other research on ocular infection shows SARS-CoV-2 entry proteins/receptors express in the limbus, conjunctiva, and corneal epithelium. In addition, researchers have detected SARS-CoV-2 in ocular tissues harvested from donors who died of COVID-19, those with signs and symptoms of COVID-19, and individuals without manifestations of the novel coronavirus infection who were otherwise surgically eligible.

“The important question, however, is whether the presence of the virus translates into infection transmission through the cornea. Currently, information relevant to this issue is limited. So far, however, there is no evidence that SARS-CoV-2 replicates in human corneal tissue, and there are no reports of transmission of infection through corneal transplantation,” Dr Mian said.

EFFICACY OF DONOR SCREENING Dr Mian noted there are zero reported cases of SARS-CoV-2 transmission from blood or blood components when screening excludes donation by individuals who recovered from COVID19 within the previous 14 days. In fact, the only published case of COVID-19 transmitted through donor tissue involved a lung transplant recipient who was given an organ from a donor that tested negative for COVID-19 by nasopharyngeal swab. The donor was determined to be infected with SARS-CoV-2 only after the completed lung transplant through testing of bronchoalveolar lavage fluid.

Most importantly, data from the EBAA show no cases of SARS-CoV-2 transmission among nine patients who underwent corneal transplantation using tissue from donors who were COVID-19 positive.

Emphasising the point that the risk of transmission through corneal transplantation is low, Dr Mian said, “Of the nearly 50,000 transplants performed in the US during the pandemic, there were only nine cases of inadvertent transplantation of a graft from a COVID-19-positive donor, and there [weren’t any] transmission events among any of the transplant recipients.” LOOKING AHEAD Asked during the discussion following his talk whether, in light of existing knowledge, he thought the EBAA might change its recommendations on protocols for donor screening, Dr Mian said only time will tell.

“Early in the pandemic, there seemed to be a great need to implement strict screening criteria to avoid using tissue from COVID-19-positive donors because we did not know anything about the risk of transmission to recipients. As we gain more clinical data, we are learning that the risk of transmission is likely extremely low, and we have a better understanding [of] which screening criteria are valid,” he said.

“Although this raises the question of whether there is really a need to screen for COVID-19, it seems the COVID-19 positivity of a donor is still a good indication not to use the corneal tissue. However, criteria for donor exclusion relating to close contact with an infected individual may need to drop because there is a growing concern for having a sufficient supply of tissue to meet demand.”

Dr Mian also observed EBAA guidelines on screening are only recommendations. Ultimately, individual eye banks establish their own protocols.

“What we are seeing now is that because the risk of COVID-19 transmission to cornea transplant recipients seems to be essentially zero, a lot of the testing policies and practices are being dropped,” he said.

The easing of restrictions would be welcome news for those involved with meeting the demand for transplant tissue. Dr Mian noted because elective surgeries were placed on hold early during the pandemic, demand for corneal tissue was very low. Thus, a surplus of corneal tissue accumulated despite the implementation of stricter donor criteria.

“For the 2020 calendar year, the EBAA processed about 56,000 grafts, about 30,000 fewer than the average number processed in recent pre-pandemic years. Even with that shortfall, the supply was adequate because of low global demand. Now, however, from a global perspective, the supply volume is approximately 15% below the need,” Dr Mian commented.