Abstract
It is commonly believed that the intra-ocular tension is sustained by the blood pressure in the intra-ocular blood vessels, especially by those in the iris; and that it may be lowered either by fall of the general blood pressure, or by constriction of the vessels locally. Results achieved following administration of drugs have not been uniform; for instance, after cocaine, the intraocular tension may remain unchanged or may be raised or lowered.
We measured the intra-ocular tension with the Souter-tonometer and later with the mercury manometer, by insertion of a needle subconjunctivally into the anterior chamber. All drugs were injected into the common carotid artery. The experiments were made on dogs under ether anesthesia.
After injection into the carotid artery of 5 minims or more of chloroform, we several times noticed forced position of the eyes, (a) enophthalmos, (b) exophthalmos, (c) deviation of the globe. At the same time there was an hemolysis, edema of the retina, retinal and iridic hemorrhages, and increase in the intraocular tension to plus 3.
Following this administration of chloroform the general blood pressure falls, and a local vasoconstriction occurs in the retina, the two factors, which it is believed, ordinarily are followed by a lowering of the intra-ocular pressure. We found, however, without exception, that the intra-ocular tension rose from a normal of 15 to 23 mm. Hg. to 70 or more mm. of Hg. in the eye on the side of the injection, returning to 40 mm. of Hg. in 20 minutes, and gradually decreasing to normal. There was no change in the depth of the anterior chamber.
Ether.–2 cc. was followed similarly by immediate blanching of the retinal vessels and increase in tension. There were these differences: (a) increase in tension is not quite as rapid as with chloroform (tension rose to 70+ mim., however); (b) there are not as marked changes in the eye, although hemorrhages were occasionally seen.
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