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Y. Liang, L. Wang, G. Cull, H. Fujii, J. C. Downs; Systemic Blood Pressure Determines the Magnitude of IOP-Induced Blood Flow Change in the Optic Nerve Head of Non-Human Primate. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3265.
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© ARVO (1962-2015); The Authors (2016-present)
To use laser speckle flowgraphy (LSFG) to quantify the relationship between the Optic Nerve Head (ONH) blood flow velocity (BFV) and the ocular perfusion pressure (OPP) by independently adjusting systemic blood pressure (BP) and IOP in non-human primate (NHP).
In NHPs, the anterior chamber in one eye was cannulated using a 27-G needle connected to a saline reservoir, which was used to set IOP. The systemic BP was measured by a noninvasive BP monitor, which was calibrated against an arterial line pressure transducer. For each experiment, mean arterial pressure (MAP) was adjusted to one of four ranges (Table) by controlling the level of anesthesia. ONH BFV was measured with LSFG every 20-60 seconds while IOP was set to 10, then 30, and back to 10 mm Hg (15-20 minutes at each IOP level). 120 LSFG image frames captured over 4 seconds are combined into a composite BFV image (Fig. A) that represents average BFV at each time point (note that SBR is an arbitrary unit proportional to BFV). For BF analyses, only the pixels representing the ONH capillaries were included; all visible blood vessels and pixels outside the disc margin were masked out (Fig. B).Results: 1) The 20 mm Hg increase/decrease of OPP induced a two-phase BFV response, a transient phase and a steady phase. The transient phase started immediately after OPP transition, reached a peak in approximately 10-20 seconds, and stabilized to the steady phase in 3-5 minutes (Fig. D). 2) When MAP was below 70±6.1 mm Hg, OPP changes induced a significant BFV decrease/increase, the higher the MAP, the smaller the BFV changes (Table). 3) When MAP>70 mm Hg, no significant BFV change was induced. 4) In all experiments, the BFV returned to baseline (variation < 5%) after IOP was lowered to 10 mm Hg.Conclusions: At high MAP (OPP > 40 mm Hg), there is a full ONH blood flow autoregulation. At mid and low MAP, ONH BFV changes significantly with IOP perturbation, indicating incomplete autoregulation at OPP < 40 mm Hg.
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