Effects of water drinking test on ocular blood flow waveform parameters: A laser speckle flowgraphy study

Abstract

The water-drinking test (WDT) is a provocative test used in glaucoma research to assess the effects of elevated intraocular pressure (IOP). Defective autoregulation due to changes in perfusion pressure may play a role in the pathophysiology of several ocular diseases. This study aims to examine the effects of WDT on ocular blood flow (in the form of pulse waveform parameters obtained using laser speckle flowgraphy) to gain insight into the physiology of ocular blood flow and its autoregulation in healthy individuals. Changes in pulse waveform parameters of mean blur rate (MBR) in the entire optic nerve head (ONH), the vasculature of the ONH, the tissue area of the ONH, and the avascular tissue area located outside of the ONH were monitored over time. Significant increases in the falling rate of MBR over the entire ONH and its tissue area and decreases in blowout time (BOT) of the tissue area were observed only at 10 minutes after water intake. Significant increases in the skew of the waveform and the falling rate were observed in the vasculature of the ONH at 40 and 50 minutes after water intake, respectively. In the avascular region of the choroid, the average MBR increased significantly up to 30 minutes after water intake. Furthermore, the rising rate in this region increased significantly at 20 and 40 minutes, and the falling rate and acceleration-time index were both significantly increased at 40 minutes after water intake. Our results indicate the presence of effective autoregulation of blood flow at the ONH after WDT. However, in the choroidal region, outside of the ONH, effective autoregulation was not observed until 30 minutes after water intake in healthy study participants. These pulse waveform parameters could potentially be used in the diagnosis and/or monitoring of patients with glaucoma.

Characterization of laser speckle flowgraphy pulse waveform parameters for the evaluation of the optic nerve head and retinal circulation

“…Conversely, LSFG pulse waveforms themselves are relatively free from such effects; therefore, they could be more suited for inter-individual comparison of the ONH or retinal circulatory status than the MT or MV. Several LSFG pulse waveform parameters reportedly showed significant differences between normal and glaucoma eyes 24 – 26 , between various disease stages of glaucoma 24 , and a significant change after trabeculectomy 27 , 28 , and water drinking 29 . Further, a significant correlation of leukocyte glutathione levels, an indicator of mitochondrial dysfunction, was found with one LSFG pulse waveform parameter for MT in glaucoma patients 30 .…”

Increased Optic Nerve Head Capillary Blood Flow in Early Primary Open-Angle Glaucoma

“…As such, it is able to parameterize and hence quantify aspects of the pulsatile waveform, potentially revealing insights into pathophysiological changes in the response across the cardiac cycle. Though the physiological specifications of these parameters have not been systemically investigated, multiple studies have shown they can be used to reveal hemodynamic differences in glaucoma 10,13–15. This suggests that LSFG may provide a way to assess and quantify changes in both ONH blood flow and its pulsatile variation in vivo in human glaucoma.…”

Astrocyte-neuron lactate shuttle plays a pivotal role in sensory-based neuroprotection in a rat model of permanent middle cerebral artery occlusion

“…As spatial parameters for initial dip and overshoot are based on single 500 ms frame, temporal pro les were acquired from all the frames of a single selected peak value pixel within the area of the skull-dura slits. The timing parameters had previously been reported for the WFR and temporal pro le of perfusion and are now used for ISOI-WFR analysis 34,37 . The detailed analysis and results of all timings parameters are reported in supplementary materials (Figure S1-S2).…”