The influence of local arterial blood pressure on aqueous humor and intraocular pressure; an experimental study of the mechanisms maintaining intraocular pressure; the recovery of intraocular pressure, arterial blood pressure and heat dissipation by the external ear after unilateral carotid ligation
Acta Ophthalmologica 25(1): 81-94
ISSN/ISBN: 0001-639X PMID: 20250970 Accession: 056382275
Unilateral closure of the carotid artery was performed by ligation. The intraocular tension was measured with a special calibrated tonometer (model Schiotz). The blood pressure was measured by compression in the artery of the external ear which corresponds to the ophthalmic artery, both being branches of the external carotid artery. Heat dissipation was determined by immersing the 2 ears in 2 separate calorimeters. The animals were repeatedly examined 10 days before and 40 days after unilateral carotid ligation. After the carotid had been ligated there was observed a fall both of the intraocular tension (3.5 mm.) and the blood pressure (from 60 to 30 mm.). During the next 1-3 wks., the intraocular tension slowly became normal although the blood pressure showed a significant deficit and was far below the normal. This points towards a special defense-mechanism of the intraocular tension against fall in blood pressure. Examinations of heat dissipation became normal almost simultaneously with the intraocular tension. The fact that 2 different circulatory areas (eye and ear) present identical courses of reaction to carotid ligation supports the view of a more general adaptation of the vascular bed to low blood pressure, while the special ocular defense-mechanism seems questionable.