Effects of intraocular pressure changes on the afferent activity of ciliary nerves

Abstract In order to study the existence of afferent activity in the ciliary nerves, related to changes in the intraocular pressure, the electrical activity in the peripheral out end of such nerves was studied in 59 cats. Spontaneous afferent activity was observed in 19 animals; in 9 cats modifications of frequency of impulses could be obtained both with sudden and gradual increases and decreases of the intraocular pressure; a relationship seems to exist between intraocular pressure values and frequency of impulses. The decrease of intraocular pressure by occlusion of the homolateral carotid artery was usually accompanied by a decrease in the spike frequency; however, when intraocular pressure was artificially elevated previous to the occlusion, the frequency did not change, or increased slightly with the occlusion. Scleral tactile fibers responded in a different manner to intraocular pressure variations. These results suggest the presence of specific mechanoreceptors (baroreceptors) in the eye which adapt slowly to intraocular pressure changes and that could be able also to measure ocular blood pressure reductions.