Comparison of choroidal and optic nerve head blood flow regulation during changes in ocular perfusion pressure.
OBJECTIVE
We compared the response of choroidal and optic nerve head blood flow (ChBF, ONHBF) in response to an increase in ocular perfusion pressure (OPP) during isometric exercise and during a decrease in OPP during an artificial increase in intraocular pressure (IOP).


METHODS
We included 96 healthy subjects in our study. In 48 subjects OPP was increased by 6 minutes of squatting, and either ONHBF (n = 24) or ChBF (n = 24) was measured continuously. In 48 other healthy subjects either ONHBF (n = 24) or ChBF (n = 24) was measured continuously during a period of artificial increase in IOP using a suction cup. All blood flow measurements were done using laser Doppler flowmetry.


RESULTS
During all experiments the response in blood flow was less pronounced than the response in OPP, indicating for flow regulation. During isometric exercise ChBF regulated better than ONHBF (P = 0.023). During artificial IOP increase ONHBF regulated better than ChBF (P = 0.001). Inter-individual variability in blood flow responses was high. During squatting ONHBF decreased considerably below baseline ONHBF when OPP fluctuated in 3 subjects, although OPP still was much higher than at baseline. This phenomenon was not observed in the choroid.


CONCLUSIONS
Our data indicate that regulation of ChBF and ONHBF during changes in OPP is different and complex. In some subjects performing squatting, considerable ONHBF reductions were observed during OPP fluctuations, although OPP still was high. Whether this predisposes to ocular disease remains unclear.
Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
Doreen
D
Schmidl
Agnes
A
Boltz
Semira
S
Kaya
Rene
R
Werkmeister
Nikolaus
N
Dragostinoff
Michael
M
Lasta
Elzbieta
E
Polska
Gerhard
G
Garhöfer
Leopold
L
Schmetterer
D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D002829:Choroid / Q000098:blood supply*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D017078:Laser-Doppler Flowmetry; D008297:Male; D009798:Ocular Hypertension / Q000503:physiopathology*; D009898:Optic Disk / Q000098:blood supply*; D012039:Regional Blood Flow / Q000502:physiology; D055815:Young Adult