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Master Thesis

Optic-nerve-head blood-flow response to increase in arterial blood pressure in humans

Abstract : Purpose. Autoregulation in ocular tissues ensures constant blood flow despite variations in ocular perfusion pressure and may be impaired in ocular diseases. The purpose of this study was to investigate the effect of increased blood pressure (BP) and ocular perfusion pressure (OPP) during isometric exercise on optic-nerve-head blood flow (ONH-BF). Methods. In 21 healthy subjects, aged 18-40 years, BP was measured using a Nexfin™ pneumatic transcutaneous sensor and blood flow was measured using laser Doppler flowmetry (LDF). OPP was defined as (0.74 × mean BP) − intraocular pressure. Handgripping consisted of static contraction of the finger flexors at 30% maximum contraction force using a hand dynamometer for 2 min. Results. Data were analyzed in 15 healthy subjects, exhibiting a homogeneous response of BP to handgripping (linear regression of BP versus time). A large increase, up to 50%, in OPP during exercise was not associated with a proportional increase in ONH-BF; vascular resistance increased about 30%. The blood flow-pressure relationship showed blood flow significantly increased by approximately 30%, mainly due to the rise in velocity. Conclusion. These new data strongly support the notion of autoregulation in ocular blood flow, protecting the eye from overperfusion. However, the increase in OPP is not completely counterbalanced despite the regular increase in vascular resistance. This blood flow regulation is possibly due to vasoconstriction, taking place outside of the sampled volume, probably in the arterioles proximal to the capillary bed of the neuroretinal rim. In the future, real-time measurements of vascular resistance during handgripping could be investigated in glaucoma patients.
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Master Thesis
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Submitted on : Friday, September 2, 2011 - 3:26:38 PM
Last modification on : Tuesday, May 11, 2021 - 11:36:16 AM
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  • HAL Id : dumas-00618682, version 1

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Tiffany Lacharme. Optic-nerve-head blood-flow response to increase in arterial blood pressure in humans. Médecine humaine et pathologie. 2011. ⟨dumas-00618682⟩

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