Synchronous functional magnetic resonance eye imaging, video ophthalmoscopy, and eye surface imaging reveal the human brain and eye pulsation mechanisms

Recent research shows the eye has a paravascular solute transport pathway driven by physiological pulsations resembling the brain. we developed synchronous multimodal imaging tools aimed at measuring the driving pulsations of the human eye. We used an eye-tracking functional eye camera (FEC) compatible with magnetic resonance imaging (MRI) for measuring eye surface pulsations. Special optics enabled the integration of the FEC with a magnetic resonance compatible video ophthalmoscopy (MRcVO) for simultaneous retinal imaging along with functional eye MRI imaging (fMREye) reflecting BOLD (blood oxygen level dependent) contrast. Upon optimizing the fMREye parameters, we thus measured the power of the physiological (vasomotor, respiratory, and cardiac) eye and brain pulsations by fast Fourier transform (FFT) power analysis. The human eye proved to pulsate in all three physiological pulse bands, most prominently in the respiratory (RESP) band. The FFT power means of physiological pulsation for two adjacent slices was significantly higher than in one-slice scans (RESP1 .vs RESP2; df = 5, p = 0.0174). FEC and MRcVO confirmed the respiratory pulsations at the eye surface and retina. we conclude that the human eye has three pulsation mechanisms, and multimodal imaging offers non-invasive monitoring of their effects in driving eye fluidics.