Effect of Third Cranial Nerve on Intraocular Pressure

Introduction  The factors responsible for the precise control of the ocular pressure remain an enigma despite extensive research concerning the various neural, vascular, hormonal, humoral, and local mechanical influences. While much interest in the effect of ocular innervation upon intraocular pressure is apparent in the literature, no adequate demonstrations have been made of any sustained controlling influence.The influence of the third cranial nerve and the parasympathetic outflow to the eye upon ocular hydrodynamics is somewhat confused despite the well-known effects of the various parasympathomimetic drugs. Schmerl and Steinberg (1949),¹ in one of a series of interesting experiments in rabbits, concluded that faradic stimulation in the region of the ciliary ganglion resulted, among other things, in an elevation in the ocular pressure. Perhaps more significantly, they noted a fall in the ocular pressure when destructive currents were applied in the same area. On occasion, this latter effect lasted for