An ocular parasympathetic nerve pathway of facial nerve origin and its influence on intraocular pressure

Abstract

Fine autonomic nerves were observed by dissection to enter the eyeball in close proximity to ciliary arteries and ciliary nerves in monkeys. The name rami oculares is introduced to identify these nerves. The rami oculares were derived from the retro-orbital plexus of autonomic nerves and they entered the orbit through the superior orbital fissure. Division of nerves from the plexus occurred frequently within the orbit and several branches followed the course of each of the major branches of the ophthalmic artery. Up to 27 rami oculares were found at the eyeball, a few of which anastomosed with ciliary nerves usually shortly before entering the sclera. Finer rami passed to the adventitia of ciliary arteries. The sources of unmyelinated nerve fibre bundles of the rami oculares were determined by employing appropriate nerve or ganglion lesions and by observing the subsequent degeneration of fibres. Electron microscopical inspection of the rami revealed that the fibre bundles were derived from the pterygopalatine ganglion and that probably none were derived from the superior cervical ganglion. Pterygopalatine neurones in addition to cervical sympathetic neurones innervated the ciliary arteries, and it is suggested that nerve fibres probably enter the eyeball in the adventitia of the arteries. The study establishes the existence of a parasympathetic nerve pathway to the eyeball additional to the oculomotor supply; it is of facial nerve origin with a relay in the pterygopalatine ganglion. Surgical interruption of the facial nerve parasympathetic pathway either at the greater petrosal nerve or at the pterygopalatine ganglion induced a reduction of intraocular pressure which persisted for the full experimental periods up to 1 year.