Vascular occlusion of the retina: an experimental model. I. Leukocyte aggregates.

A new technique was developed to study the pathogenesis of retinal arteriolar occlusion in the pig. Using a catheter with its tip in front of the exit of the ophthalmic artery, autologous microparticles could be injected directly into the retinal arterial system. These microparticles were C5a-des-Arg stimulated leukocytes, which were aggregated to pellets of different sizes ranging from 0.26 to 1.0 mm. For better adhesion of the aggregates to the endothelium, endothelial damage was induced by the injection of additional substances, including methomidate and endothelial antibodies. In a further series of experiments systemic hypoxemic conditions were created over several hours prior to injection of the leukocyte aggregates. This resulted in cotton-wool spots and arterial branch occlusions with retinal edema. Furthermore, retinal hemorrhages occurred. This experimental model seems to be appropriate for mimicking retinal arteriolar occlusion syndromes.