Regulation of optic nerve head blood flow during combined changes in intraocular pressure and arterial blood pressure.
In the choroid, there is evidence that blood flow does not only depend on ocular perfusion pressure (OPP), but also on absolute mean arterial pressure (MAP) and intraocular pressure (IOP). The present study included 40 healthy subjects to investigate whether such behavior is also found in the optic nerve head (ONH). The ONH blood flow (ONHBF) was studied using laser Doppler flowmetry during a separate increase in IOP and MAP as well as during a combined elevation. Mean arterial pressure was increased by isometric exercise and IOP by the suction method. During both, the change in ONHBF was less pronounced than the change in OPP indicating autoregulation. Correlation analysis was performed for the combined experiments after pooling all data according to IOP and MAP values. A correlation between ONHBF and MAP was found at IOPs 25 mm Hg (P<0.001), but not at IOPs>25 mm Hg (P=0.79). Optic nerve head blood flow and IOP were significantly correlated (P<0.001), and ONHBF was only slightly dependent on MAP. The data of the present study indicate a complex regulation of ONHBF during combined changes in MAP and IOP. Our results may be compatible with myogenic mechanisms underlying autoregulation, and indicate better ONHBF regulation during an increase in MAP than during an increase in IOP.
1] Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria [2] Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
Agnes
A
Boltz
Doreen
D
Schmidl
René M
RM
Werkmeister
Michael
M
Lasta
Semira
S
Kaya
Stefan
S
Palkovits
Reinhard
R
Told
Katarzyna J
KJ
Napora
Alina
A
Popa-Cherecheanu
Gerhard
G
Garhöfer
Leopold
L
Schmetterer
D000293:Adolescent; D000328:Adult; D062186:Arterial Pressure; D018592:Cross-Over Studies; D005260:Female; D006439:Hemodynamics; D006706:Homeostasis; D006801:Humans; D007429:Intraocular Pressure; D017078:Laser-Doppler Flowmetry; D008297:Male; D009898:Optic Disk / Q000098:blood supply*; D011446:Prospective Studies; D012039:Regional Blood Flow; D055815:Young Adult