Ocular volume and common carotid occlusion in the rabbit.

The influence of common carotid occlusion on intraocular pressure was studied in rabbits by perfusion and tonographic techniques. Bilateral common carotid occlusion caused a greater ocular volume change than homolateral occlusion. If homolateral occlusion was followed by contralateral occlusion, there was consistently an additional fall in intraocular pressure. The initial fall in intraocular pressure after homolateral or bilateral occlusion was not infrequently followed by a rise of the pressure level to a new plateau. A quantitative relationship was demonstrated between ocular volume change and common carotid occlusion. For intraocular pressures between 20 and 40 mm. Hg there is a semilogarithmic relationship between the ocular blood volume change induced by common carotid occlusion and either perfusion pressure or tonometric pressure. With intraocular pressures greater than 40 to 50 vim. Hg the semilogarithmic relationship no longer holds, probably due to critical closure of intraocular vessels.