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. 2020 Apr 9;9(5):3. doi: 10.1167/tvst.9.5.3

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Figure 3. — Axial corneal position was affected by cardiovascular pulsations in the time domain and frequency domain. The pulse amplitude was plotted in an arbitrary unit (a.u.). (a) A clear correlation was observed between the corneal position and the heartbeat frequency. Fast Fourier Transform results for the analysis window demonstrates the corresponding frequency components from eye motion (b) and heartbeat (c). A band-pass filter that included the main frequency components was utilized. Panel (d) compares the raw and filtered signals (corneal position and heartbeat) over time for the selected window. Results were normalized and shifted along the Y-axis for comparison. The time delay between the heartbeat and heartbeat-related eye motion was measured as 171.3 ± 22.3 ms (mean ± 95% CI).