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Monika E. Danielewska, Daniel Szlag, D. Robert Iskander, Maciej Wojtkowski; Spectral and Phase Analyses of Ocular Hemodynamics using Combined STdOCT and Ultrasonic Method. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5649.
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© ARVO (1962-2015); The Authors (2016-present)
To propose a new approach to eye’s hemodynamic measurement for the assessment and diagnosis of ocular diseases of vascular aetiology.
Ocular pulse amplitude of the right eye was measured noninvasively as longitudinal corneal apex displacements (LCAD) using ultrasonic transducer, functioning at a frequency of 0.8 MHz. At the same time the retinal vessels of the left eye were registered using typical spectral optical coherence tomography (SOCT) setup. The cross-sectional images were measured in the same position within a small lateral range. To examine in-vivo retinal hemodynamic, blood flow velocity in selected retinal vessel was retrieved using combined spectral and time domain STdOCT method. The SOCT was synchronized with heart activity signals: ECG and pulse wave measured with pulseoximeters, placed on the right earlobe and right index finger. To compare signal of retinal blood flow (RBF) velocity registered with STdOCT to signals of LCAD and cardiac activity, a technique to extract RBF velocity was applied. Spectral content of all signals were examined. Additionally, to receive phase relationships between RBV, the ocular pulse and heart activity signals correlation and coherence functions were used.
In all considered spectra, the frequency related to the heart rate could be noticed. The phase compliance for the fundamental frequency for all signals was high. This indicate, that pulsatile blood flow in retinal vessels is strongly correlated with the ocular pulse and the cardiac activity.
Combining noninvasive ultrasonic measurements of LCAD, STdOCT measurements of RBF velocity and the heart activity (ECG, pulse) helps to simultaneously observe pulsatile blood flow in vessels and the ocular pulse response. Investigating spectral correlation and time delays between RBF velocity and cardiac activity signals could lead to a better understanding of blood circulation on the way from heart to eye. The proposed technique may lead in future to a tool for the assessment of ocular hemodynamics and diagnosis of ocular vascular diseases.
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