Sensory mechanisms and intraocular pressure

Recordings from the long ciliary nerves of cats and monkeys demonstrated fibres which responded to a rise in intraocular pressure by an increase in frequency of potentials which decreased when the pressure was reduced. Such fibres were found in 6 out of 22 cats and 1 out of 4 monkeys. In no animal was there an exact parallel between the change in pressure and the frequency of the spikes. Using micro-electrodes the region of the spinal nucleus of the fifth cranial nerve subserving corneal sensation was explored in the cat. The only responses to changes in intraocular pressure recorded from this region were bursts of spikes after raising the intraocular pressure rapidly. No sustained disoharges were obtained. It is concluded that these experiments fail to demonstrate any direct afferent pathway for information concerning the level of intraocular pressure in the animals studied.