IS RETINAL VASCULAR AUTOREGULATION IN MAN CENTRALLY CONTROLLED?

Title IS RETINAL VASCULAR AUTOREGULATION IN MAN CENTRALLY CONTROLLED?
Author, Co-Author John Lovasik, Helene Kergoat, Marc Gagnon
Topic
Year
1992
Day
Monday
Program Number
Poster 35
Room
Great Hall
Affiliation
Abstract A transient decrease in the ocular perfusion pressure (OPP) decreases neural responsivity in the test eye, and is associated with supranormal responsivity of the contralateral retina (Kergoat and Lovasik, 1990). Here, we extended our measures of contralateral retinal function in a search for correlative changes in fundus structures. Fundus details were recorded on colored slides synchronized with the cardiac cycle in 4 subjects. Slides of the optic nerve head (ONH) were taken for baseline conditions in both eyes. Then the OPP was decreased by 20% in the test eye via scleral suction (SS) for 2 min. and slides taken again for each eye. The same steps were repeated for a 30, 40 & 50% reduction in the OPP. Slides were also taken right after SS was quickly released, and 2 & 4 min. later. All slides were then cropped and digitized to allow detailed analyses of changes in selected chromatic attributes (hue, saturation, brightness) of the ONH with a Nikon Microanalyst system (Gagnon and Lovasik, 1991). All subjects showed an increasing area of pallor in the ONH of the test eye during decreasing levels of OPP. Changes in the ONH chromaticity in the contralateral eye were more variable; for 3 subjects changes in the ONH redness paralleled changes seen in the test eye while the 4th subject showed an opposite response during decreased OPP. These reversible contralateral alterations in ONH chromaticity appeared to be mediated by changes in the volume of blood perfusing the ONH and surrounding structures. If this was the case, these data could explain the earlier electrophysiological findings reported by Kergoat and Lovasik, and would also support the notion of a central vs local mechanism for regulating the flow of blood to the eyes. The implications of our work for current understanding of the regulation of blood flow in the retina are discussed.
Affiliation of Co-Authors
Outline