• We studied collagen shield heparin delivery to the rabbit eye utilizing radiolabeled heparin as well as a fibrin inhibition assay. Radiolabeled heparin studies revealed significant tritium delivery to the cornea, aqueous, and iris, with only trace levels detectable for the lens, vitreous, and sclera. An aqueous fibrin inhibition assay revealed that a single collagen shield soaked in heparin achieved anterior chamber anticoagulant levels that paralleled the time course of the radiolabeled heparin delivery and resulted in fibrin inhibition during the 6-hour study period. Subconjunctival heparin injection did not alter baseline aqueous anticoagulant activity. No complications related to collagen shield heparin delivery were encountered. These studies suggest that a heparin-hydrated collagen shield may prevent postoperative fibrin formation in eyes at risk for this complication, including eyes undergoing surgery for the complications of proliferative diabetic retinopathy proliferative vitreoretinopathy, and glaucoma filtration surgery.