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Thomas H. Heflin, Junko Yoshida, Andrea Zambrano, Albert Jun, Huan Meng, Qing Pan, Walter Stark, Yassine Daoud; Gamma-irradiated Sterile Cornea for use in Penetrating Keratoplasty: A Novel Approach. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6679.
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© ARVO (1962-2015); The Authors (2016-present)
Penetrating keratoplasty (PK) is the most common and successful tissue transplant. Unfortunately, the shortage of corneal supply and 14-day shelf life complicate emergency cases. Vision Graft Sterile Cornea®, a sterile gamma-irradiated cornea, has been shown effective as a lamellar graft. Its benefit is in its one-year shelf life and availability for emergencies and remote areas. We postulated that the collagen cross-linking by radiation would strengthen the stroma and keep it clearer and thinner than non-irradiated cornea. If our hypothesis is true, these properties may allow the sterile cornea to serve as a practical substitute to fresh, perishable donor cornea.
Our experiment consisted of three groups of three male New Zealand White rabbits receiving PK in the right eye. The first group received fresh allogeneic corneal graft. The second received fresh grafts with endothelium removed. The third received gamma-irradiated sterile cornea. Slit lamp examination and photographs were taken one and two weeks after surgery, and two examiners scored of clarity (C), edema (E), and vascularization (V) of the grafted corneas according to the Holland method, scoring C, E, & V on a 0-4 scale.
The average score of the three groups (fresh with endothelium, fresh without endothelium, and sterile) at postoperative week (POW) 1 was C0E0V0, C2.7E2V0.71 and C1E0.7V0.3 respectively; at POW2 the scores were C0E.3V1.8, C2.8E2.2V1.3, C2.8E2.7V1.7. Fresh grafts with endothelium stayed clear and thin, while those without endothelium showed advanced haze and diffuse stromal edema. Meanwhile, sterile cornea stayed clear and thin with decreased vascular response until POW1 but developed corneal opacity and edema by POW2.
Grafts of sterile cornea stayed clearer and thinner than the grafts of fresh cornea without endothelium up to one week postoperatively. We postulate that the decreased edema was due to radiation-mediated cross-linkage of the collagen lamellae. The effect decreased by POW2 and PK graft of sterile cornea saw no improvement over the intact-endothelium group. Thus, sterile cornea appears to stay clearer and thinner than the standard endothelium-removed fresh cornea, but not sufficiently for use as PK graft. In conclusion, favorable results coupled with extended shelf life may make sterile cornea the superior candidate for patch graft of corneal defects compared to preserved corneas without endothelium.
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