[Effect of decreased ocular perfusion pressure on iris blood flow measured by laser Doppler flowmetry].
OBJECTIVE
To determine whether iris blood flow (IBF) is regulated in response to an acute decrease in mean ocular perfusion pressure (PPm = MOAP-IOP, MOAP = mean ophthalmic arterial pressure) induced by increasing the intraocular pressure (IOP).


METHODS
Iris blood flow was measured using a slit lamp incorporating a laser Doppler flowmetry (LDF) module. The study was conducted on 12 normal volunteers (14 to 59 years old). IOP was raised using a scleral suction cup. In Exp. #1, the suction pressure was successively raised in steps of 50 to 100 mm Hg, each lasting about 10 sec, until IOP reached the MOAP level. In Exp. #2, the suction was raised to 200 mm Hg in 4 successive steps of 2 min duration.


RESULTS
In Exp. #1, no significant change of IBF was observed for small decreases of PPm (< 23%); greater decreases of PPm resulted in a linear IBF decrease (p < 0.01). In Exp. #2, such a IBF versus PPm decrease was also observed (p < 0.001). Immediately after release of suction, a significant, transient IBF increase of 79% above baseline level was observed.


CONCLUSIONS
These results suggest that some IBF regulation occurs for small PPm decreases (< 23%); no IBF compensatory mechanism appears to operate for further decreases of PPm (> 23%).
Institut de Recherche en Ophtalmologie, Sion.
S R
SR
Chamot
A
A
Movaffaghy
B L
BL
Petrig
C E
CE
Riva
D000293:Adolescent; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D005123:Eye / Q000098:blood supply*; D005260:Female; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D007498:Iris / Q000098:blood supply*; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D009887:Ophthalmoscopy
Effet d'une diminution de la pression de perfusion oculaire sur le flux sanguin dans l'iris mesuré par fluxmétrie laser Doppler.