Pressure Effect on ERG and Optic Nerve Conduction of Visual Impulse

Abstract

The effects of increased intraocular pressure on optic tract responses and the electroretinogram (ERG) b-wave were studied in owl monkeys. Both responses showed a decrease in amplitude only if the intraocular pressures exceeded a certain critical level, which was about 30 mm Hg below mean femoral blood pressure. Above this intraocular pressure, the magnitude of the depressed ERG and optic tract responses were linearly related to the perfusion pressure. The maximum effect occurred within five minutes, and after the intraocular pressure was restored to normal, the optic tract response and ERG returned to normal in four to five minutes. It is not clear whether the phenomena studied here have any relationship to the optic nerve damage seen in chronic open-angle glaucoma, where the perfusion pressure is usually greater than 30 mm Hg.