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    Frozen, fresh corneal donor carriers yield similar clinical outcomes

    Use of frozen tissue may increase availability of fresh tissue for other procedures while increasing accessibility of KPro surgery

    Take-home message: Five-year results from a study of the Boston keratoprosthesis type 1 implant suggest that frozen and fresh corneal donors offer similar clinical outcomes—with no significant differences in device retention, visual rehabilitation or complication rates.




    Montréal—Patients undergoing Boston keratoprosthesis type 1 implantation (KPro, Massachusetts Eye and Ear Infirmary) do not need to wait for fresh corneal graft carriers to become available, according to researchers.

    A recent study with 5 years of follow-up demonstrated that use of frozen corneal graft carriers offers similar clinical outcomes to fresh tissue in terms of visual rehabilitation and complication rates. Recognition of this could impact that amount of fresh tissue available for use in other procedures, as well as increase the availability of KPro surgery worldwide.

    Study investigators, led by Adam K. Muzychuk, MD, noted there has been a significant increase in the number of devices implanted annually over the past two decades.

    “The vast majority of cases require allogenic tissue in the form of a donor corneal button, which acts as a peripheral device carrier and an interface to facilitate suturing of the device to the host,” Dr. Muzychuk said. “As such, optical clarity of donor tissue is not required.”

    He was joined in this study by Marie-Claude Robert, MD, Stanley Dao, MD, and Mona Harissi-Dagher, MD.

    Dr. Muzychuk explained that because fresh donor tissue can at times be difficult to obtain in Canada, his colleagues from the University of Montéal had previously conducted a study in which they compared frozen with fresh tissue. After a mean postoperative follow-up of 9.7 months, they found that visual rehabilitation and complication rates did not differ significantly between the two approaches.

    In light of more recent data suggesting an increase in the risk of certain complications with longer follow-up, the present study set out to evaluate the clinical outcomes of fresh versus frozen carrier grafts up to the 24 months of the initial study protocol, and further looked at the long-term outcomes of fresh versus frozen carrier grafts in a subset of these patients up to 60 months postoperatively.

    In this prospective, single-center, single-surgeon, non-blinded, randomized controlled trial, all patients who underwent implantation of the KPro device with an allograft carrier between October 2008 and December 2009 were included. All surgeries were performed using the standard KPro technique. The device used was the KPro type 1 threadless design with a 16-hole polymethylmethacrylate plate.

    According to Dr. Muzychuk, who was a clinical and surgical fellow at the University of Montréal, the cryopreserved or frozen tissue arrived at the operating room as whole globe on the morning of the scheduled surgeries and was then thawed in a sterile container under running water. The surgeon used a Westcott scissors to fashion a corneoscleral rim that was cut into a donor corneal button using the standard trephination technique.

    The primary study outcome was retention of the device at 24 and 60 months postoperatively. Secondary outcomes were the surgical feasibility, visual acuity, and complication rates.

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