Similar clinical outcomes have been observed with fresh and frozen corneal graft carriers for Boston Keratoprosthesis (KPro) type 1 implantation procedures, according to research published in the Canadian Journal of Ophthalmology. 

Researchers conducted a prospective, nonmasked, randomized controlled trial (ClinicalTrials.gov identifier NCT01950598) to compare the outcomes of Boston KPro type 1 fresh vs frozen graft carrier implants at 10 years follow-up. 

Thirty-seven eyes from 37 patients enrolled were enrolled in the initial 24-month study protocol; from there, 26 patients initially enrolled in the 60- and 120-month extension phases, with 7 lost to follow-up, resulting in 19 eyes in the final cohort. 


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Mean follow-up duration was 118 months vs 114 months in the fresh vs frozen groups, and no significant differences were noted in terms of age, gender, or disease category. The most common indication from surgery was prior graft failure. For the current surgery, 58% had a fresh corneal graft carrier and 42% had a frozen corneal graft carrier. 

The primary study outcome was device retention. Results showed overall device retention of 84% at 10 years, with no statistically significant differences between the 2 treatment groups (91% and 75% retention in the fresh vs frozen groups). Three patients failed to retain the device: 1 in the fresh carrier group who had a preoperative diagnosis of Stevens-Johnson Syndrome and experienced corneal melt and subsequent phthisis at 8 years, and 2 in the frozen carrier group, 1 with aniridia who experienced device extrusion, and one with a preoperative chemical burn diagnosis who experienced corneal melt and endophthalmitis at 8 and 9 years, respectively. 

Mean preoperative best-corrected visual acuity (BCVA) increased from counting fingers to 20/300 and 20/125 in the fresh and frozen groups, respectively. Improvement of mean BCVA was demonstrated in both treatment arms, with no statistically significant difference between the groups. 

Complications occurred at a rate of 2.36 and 2.37 per patient in the fresh and frozen carrier groups, respectively, in the 10-year follow-up period. New or progressive glaucoma was the most common complication, occurring in 54.5% and 87.5% of patients in the fresh and frozen groups. Four and 3 eyes in each group experienced corneal melt, retroprosthetic membrane, and uveitis. One eye in each group experienced endophthalmitis or cystoid macular edema, and 2 patients in the fresh carrier group experienced retinal detachment.

Study limitations include the small sample size, an inability to mask the surgeons to the tissue type, and an inability to extend the 10-year follow-up for all initially recruited patients, as well as a potential for selection bias regarding the follow-up duration. 

“The results of this study support the use of frozen corneal graft carriers in Boston KPro type 1 surgery, showing no statistically significant differences in outcomes in terms of device retention, visual rehabilitation, or incidence of complications over 10 years of follow-up,” the research says. “This evidence can help advise optimal use of corneal donor tissue, specifically if fresh tissue can be spared by using frozen tissue even for the relatively small number of KPros performed per year.”

Disclosure: One study author declared affiliations with the biotech or pharmaceutical industries. Please see the original reference for a full list of authors’ disclosures. 

Reference

Sabeti S, Daoud R, Robert M, Harissi-Dagher M. Randomized controlled trial of frozen versus fresh corneal graft carriers in Boston keratoprosthesis type 1 surgery: 10-year outcomes. Can J Ophthalmol. Published online March 26, 2021. doi:10.1016/j.jcjo.2021.02.003