Washington: Donated corneas can be safely stored for 11 days without negatively impacting the success of transplantation surgery to restore vision in people with eye diseases, study has found.

Currently, donor corneas are generally not used for surgery if they have been preserved for longer than seven days. Expanding the window in which donor tissues can be considered suitable by even just a few days should help safeguard quality donor tissue and access to vision-saving transplantation procedures.

For the research by Case Western Reserve University in the US Patients were randomly assigned to one of two treatment groups. The first received corneas preserved up to seven days, and the second received corneas preserved for eight to 14 days. The US Food and Drug Administration has approved the use of solutions to preserve donated corneas for 14 days.

"The current practice of surgeons to use corneas preserved for no longer than seven days is not evidence-based, but rather a practice based on opinion, which hopefully will change with this new evidence," said Jonathan Lass at University Hospitals Eye Institute in the US. Researchers looked at three-year graft success rates among a total of 1,090 individuals who underwent transplantation via Descemet's stripping automated endothelial keratoplasty by 70 surgeons at 40 surgical sites.

Most of the patients underwent transplantation for Fuchs' endothelial corneal dystrophy, a progressive disease that causes cells to die in the innermost layer of the cornea called the endothelium. Death of corneal endothelial cells is a normal part of ageing. However, Fuchs' accelerates this cell death. Corneal transplantation is the only treatment available to restore vision.

Overall, the investigators were unable to conclude that three-year success rates were the same for corneas preserved for eight to 14 days compared with up to seven days (92.1 per cent versus 95.3 per cent). However, parsing out the data, they found that much of the difference between the groups was accounted for by those who received corneas preserved 12 to 14 days.

There was no meaningful difference between those who received corneas preserved up to seven days and those who received corneas preserved eight to 11 days. While it is true that patients who received corneas preserved 12 to 14 days had comparably lower success rates, Lass emphasised that even their success was impressively high at 89.3 per cent, which may support the use of these tissues as logistics dictate.