Rheologic findings in patients with acute central retinal artery occlusion.

The most important rheologic parameters were examined in six patients with acute occlusion of the central retinal artery. Blood samples were taken as part of the initial clinical examination on the day of the occlusion before the onset of therapy, and the following parameters were studied: (1) yield shear stress; (2) hematocrit; (3) plasma viscosity; (4) extent of erythrocyte aggregation; (5) erythrocyte deformability; (6) plasma fibrinogen concentration. A definite shear stress could be measured in all patients, something not possible in rheologically healthy volunteers. Hematocrit values were in the upper normal range; plasma viscosity was significantly increased. The extent of erythrocyte aggregation was greater than normal, erythrocyte deformability was markedly reduced, and the plasma fibrinogen was markedly higher than the normal level. Aside from the well-known pathologic findings in the carotid arteries of many patients with acute retinal vascular occlusion, rheologic factors seem to be of great importance in this disease.