Regulation Of Optic Nerve Head Blood Flow During Combined Changes In Intraocular Pressure And Arterial Blood Pressure

Abstract

Purpose: : We have previously shown that choroidal blood flow in healthy subjects regulates better during isometric exercise-induced changes in mean arterial blood pressure (MAP) than during suction cup-induced changes in intraocular pressure (IOP). The present study tested the hypothesis that human optic nerve head blood flow (ONHBF) may not only depend on ocular perfusion pressure (OPP), but also on the absolute values of MAP and IOP.

Methods: : Two study days were performed in 20 healthy young subjects. On the first study day the effect of squatting and IOP elevation on ONHBF was investigated separately. On the second study day the effect of combined IOP increase and squatting was studied. IOP was raised in stepwise increments using the suction cup method. ONHBF was measured using laser Doppler flowmetry. OPP was calculated as 2/3*MAP-IOP. For correlation analysis all values from all subjects were pooled according to IOP and MAP values.

Results: : When data were grouped according to MAP values a highly significant correlation was found between ONHBF and IOP (p < 0.001). The correlation between ONHBF and MAP was much less pronounced when data were grouped according to IOP levels (p < 0.05).

Conclusions: : Our data confirm previously published observations that ONHBF shows some autoregulatory capacity during changes in OPP. In addition, our data indicate that ONHBF regulates better during exercise-induced changes in MAP than during a suction cup-induced increase in IOP.

Clinical Trial: : http://www.clinicaltrials.gov NCT00912665

Keywords: blood supply • intraocular pressure • optic disc