Corneal transplantation

The COVID-19 pandemic created logistical challenges for maintaining corneal transplantation activity and raised questions about the risk of transmitting the SARS-CoV-2 virus to graft recipients. In a EuCornea Educational Webinar moderated by Jesper Hjortdal MD, PhD, Aarhus, Denmark, speakers reported data on European corneal donor procurement and transplantation procedures during the pandemic and discussed research designed to support evidence-based strategies for maintaining the safety of corneal grafting. A concluding remark from Diego Ponzin MD, aptly summarised the key message. He said: “Corneal transplantation can be performed in this COVID-19 era if done properly with the current safe procedures.” Characterising the pandemic’s impact Mor Dickman MD, PhD, Maastricht, The Netherlands, and Gilles Thuret MD, PhD, Saint-Etienne, France, presented findings from surveys sent to European eye banks to gather information on corneal procurement, assignment and donor selection algorithms. Results from a first survey, which was returned by 64 of 110 eye banks, showed overall transplantation activity during March through May 2020 decreased by 50% when compared to the same period in the previous two years. Overall procurement decreased significantly in March and April and increased in May, but there were significant disparities between eye banks such that the increases were only observed in small eye banks with few donors, reported Dr Dickman. The surveys also showed significant differences in donor screening algorithms between countries that correlated mainly with the stringency of national recommendations for donor selection and not according to pandemic severity in each country. Dr Thuret presented initial findings from a second survey covering the months of June through December 2020 that analysed responses received from 48 eye banks. He reported that the results showed major differences between the first and second waves of the pandemic, indicating that the corneal transplantation chain was able to adapt rapidly to the impact of COVID-19. Similar to the findings of the first survey, there was large variation among eye banks that was mainly related to eye bank size. A quarter of the responding eye banks indicated that their algorithm for donor selection changed after May 30, 2020, and the changes occurred at different dates in different countries. Two-thirds of the eye banks reported doing systematic PCR testing on donors. “The utility of this systematic testing seems to be very low. Very few donors were found to be positive, probably because donors are clinically selected as being asymptomatic and having no contact with positive cases,” Dr Thuret said. EYE BANK SURVEY The findings of the first survey were reflected by data from the Veneto Eye Bank, Venice, Italy, that were presented by its medical director, Dr Ponzin. He also shared some of the measures his eye bank used to address the challenges created by COVID-19. Dr Ponzin said that to prolong the storage time for procured tissue, his eye bank adopted a previously described dehydration process. In addition, he cited a study investigating various biocidal agents for inactivating the coronavirus as providing reassuring evidence for his eye bank’s existing practice of using povidone-iodine to disinfect the enucleation site and donor eye. RESEARCH ON VIRAL TRANSMISSION Dr Ponzin described a study investigating viral infectivity in corneal transplants using tissue from donors that had recovered from COVID-19. He reported that although genomic SARS-CoV-2 RNA was detected, subgenomic RNAwas absent, indicating absence of replicative potential. Dr Thuret presented findings from a series of laboratory studies designed to investigate whether the ocular surface can host the virus ex vivo. The results showed that a minority of corneas from COVID-19 positive donors (3/14, 21%) were positive for the virus by RT-PCR. In no case did both corneas from any one donor test positive, indicating that unilateral contamination is very likely, Dr Thuret said. Additional studies investigated the presence of viral receptor and activators in the corneal, limbal and conjunctival epithelium and the ability of SARS-CoV-2 to infect and proliferate in corneal and scleral tissues ex vivo. Dr Thuret reported that proteins for SARS-CoV-2 infectious routes were present in the ocular surface, but the complete set of molecules for both the internal and external routes of infection were present only in the conjunctiva. Using supraoptimal conditions to induce ocular surface infection, viral replication was obtained in the conjunctiva and to a lesser extent in the cornea. “It is very important to understand that we infected the tissue with a very high viral load and kept the virus in contact with tissue for 30 minutes. These conditions are probably not compatible with what is occurring in real life,” said Dr Thuret. “Furthermore, whether the virus isolated in these tissues could infect another person remains to be proven.” ADDRESSING PATIENT CONCERNS Dr Dickman observed that cornea transplant patients are asking whether it is safe to get the COVID-19 vaccine. “The answer is categorically yes,” he said. Dr Dickman mentioned that as a precautionary measure, Drs Francis and Marian Price, Indianapolis, USA, suggest increasing the use of topical steroid treatment to four times daily beginning two days before vaccination and continuing for two weeks. He also advised informing patients about “RSVP”. “Patients should know to consult their ophthalmologist if they develop Redness, Sensitivity to light, Visual blurring or Pain,” Dr Dickman said.

Tags: corneal translation