The effect of hyperoxia and hypercapnia on fundus pulsations in the macular and optic disc region in healthy young men

The purpose of this study was to investigate the influence of hyperoxia and hypercapnia on fundus pulsations in the macular and optic disc region and determine a potential autoregulative capacity of the choroid under these conditions. In a randomized cross-over study 100% O-2 and a mixture of 5% CO2 with air was inhaled for 10 min by ten healthy male volunteers on different study days. Fundus pulsations were measured with a recently described laser interferometer. These results were compared to changes in systemic haemodynamics and Doppler-sonographic measurements of the radial artery. The fundus pulsation amplitude significantly decreased during hyperoxia and significantly increased during hypercapnia. These effects on fundus pulsations were stronger in the optic disc region than in the macular region. The systemic parameters showed only minor changes. Hence the amplitudes of fundus pulsations measured during hyperoxia and hypercapnia are assumed to be a consequence of metabolic autoregulative mechanisms. This autoregulative capacity is greater in the optic disc region than in the macular region, implying that the fundus pulsation amplitude in the papilla is influenced by both the choroidal and the retinal circulation. (C) 1995 Academic Press Limited