Background.Previously, isotonic solution (IS) enriched with β-hydroxybutyrate, a nonlactate-generating substrate, was shown to be efficacious in maintaining tissues' ATP and metabolic activity under cold storage. The objective of this study was to verify these findings in terms of tissue viability in vivo.Methods.Using a rabbit cornea transplantation model, efficacy of IS was studied and compared with McCarey-Kaufman medium, with or without β-hydroxybutyrate, and other known media (Optisol and Likorol), with different properties and without β-hydroxybutyrate. After storage at 4°C for 6, 7, and 11 days, the corneas were grafted, and postoperative changes in corneal thickness, and endothelial cell density and morphology were monitored with a pachymeter and specular microscope.Results.The experiments revealed that before grafting, IS effectively controlled tissue swelling for 7 days or longer, comparable to Optisol. When grafted, the IS-stored corneas deturgesced at high rates, with a short half-time (t1/2) for the de-swelling process, and the grafts remained thin and clear with an intact endothelium. This reflects excellent tissue viability. In the controls, the deturgescence process was extremely sluggish, with significantly lower rates and longert1/2(P=>0.01-0.05). Immediate swelling for 3-5 days after grafting was also observed with Optisol. These grafts had significant endothelium cell loss of 24-30% after 12 weeks (P=>0.01-0.02).Conclusions.IS is more efficacious than currently used media for sustaining the viability of donor corneas under cold storage. These findings may serve as a useful basis for future tests of IS in other organ storage systems.