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Jintao Yu, Lin Wang, Simon Thompson, Grant Cull; Transfer Function Analysis of Blood Flow Autoregulation in Humans Optic Nerve Head. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2943.
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© ARVO (1962-2015); The Authors (2016-present)
The study used a novel transfer function analysis to test the hypothesis that BF autoregulation in the optic nerve head (ONH) is frequency-dependent in response to spontaneous changes in blood press (BP).
In fourteen healthy volunteers (45±14 y, 3 males; 11 females), beat-to-beat BP was recorded at 200 Hz sampling rate with a noninvasive blood press monitor (Finometer Pro®, Holland). The ONH BF in the left eye was measured continuously at 30 Hz sampling rate with a device of laser speckle flowgraphy (NAVI LSFG system, Softcare, Japan) for 3 minutes. The recordings of both BP and BF were smoothed to time series by averaging each pulse cycle, interpolating at both BP and BF at 100 Hz and re-sampled at 1 Hz. With BP as an input signal and BF as an output signal, transfer function was analyzed by using the Welch method to estimate the gain, phase and coherence between BP and ONH BF within a range of frequency from 0 to 0.4 Hz.
Average intraocular press (IOP) was 11.9 ±2.1 mmHg (ranging from 8 to 14 mmHg). The transfer function (mean ±SE) including gain, phase and coherence within the range of frequency studied are shown in Figure A, B and C, respectively. Transfer gain strengthened gradually with the increase in frequency from 0.03Hz to 0.30Hz in association with a gradual decrease in phase. The coherence was >0.5 within the frequencies ranging from 0.03 to 0.30 Hz, and <0.5 at very low (<0.03 Hz) and higher frequency (0.3-0.4 Hz).
The results demonstrate that the spontaneous fluctuation in the ONH BF at the frequency range of 0.03-0.30 Hz are strongly related to changes in BP and frequency-dependent, and that the regulation function of ONH BF with changes in BP symbolize the autoregulation as a high-pass filter in the frequency range of 0.03-0.30 Hz. The physiological importance of the observation and the relevance in diseases remain to be further investigated.
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