Corneal blood staining. An animal model.

Corneal blood staining was established in the rabbit cornea by injecting autologous, citrate-buffered blood in the anterior chamber. Increased intraocular pressure was maintained above 30 mm of Hg by self-sealing trans-limbal injections repeated every 12 hours. Typically, corneal edema developed in 3 days, followed several days later by a red discoloration that turned brown about 2 days later. Histopathologically, the edematous cornea disclosed endothelial swelling and attenuation with marked stromal edema. Histochemically, the red-stained cornea disclosed only extracellular hemoglobin particles; the brown-stained corneas showed extracellular and intracellular hemoglobin particles as well as intracellular hemosiderin in keratocytes. Spectrophotometric analysis of the keratectomy specimens suggested the presence of porphyrins in all stages of blood staining, including the edematous cornea. Oxyhemoglobin was found in red-stained corneas, while methemoglobin was present in the brown-stained corneas. It was concluded that endothelial degeneration uniformly accompanied corneal blood staining in this model and that keratocytes are actively involved in hemoglobin degradation.