Abstract
Purpose :
Recent research indicates a potential connection between glaucoma, a neurodegenerative disease, and changes in cerebrospinal fluid (CSF) dynamics, which may be detected by visual stimulation. Here, we investigated the influence of visual stimulation on CSF dynamics in healthy older adults and glaucoma patients.
Methods :
Eighteen early glaucoma patients [age: 66.00±1.89yrs (mean±S.E.M.)], twenty-four advanced glaucoma patients [66.63±1.36yrs] and twenty-three healthy controls [64.52±1.59yrs] underwent comprehensive ophthalmic evaluation including visual field perimetry and optical coherence tomography as well as anatomical and functional MRI (fMRI) (Fig.1A) at 3T. Patients were categorized as either early or advanced stage based on visual field mean deviation, using a cut-off threshold of -6.0 dB. During fMRI scans, a flickering checkerboard was presented on the entire screen (Fig.1B).
We extracted the blood-oxygenation-level-dependent (BOLD) signals from the visual cortex, and the fourth ventricle mask, which we delineated from the first slice of fMRI images. The BOLD signals derived from the fourth ventricle represent the incoming CSF flow, whereas those from the visual cortex reflect neural activity (Fig.1C).
Results :
We observed that an increase in visual cortex BOLD is followed by a decrease in CSF inflow, and that a decrease in visual cortex BOLD is followed by an increase in CSF inflow with a time delay in healthy individuals (Fig.1D). However, this pattern was shown to be disrupted in glaucoma patients (Fig.1E,F).
We also examined the temporal relationship between visual cortex BOLD and CSF inflow using cross-correlation. In healthy individuals, the strongest coupling (in terms of absolute value of correlation coefficient) was observed at a lag of 1 second (Fig. 2A). Nevertheless, this coupling was weaker among early and advanced glaucoma patients. Furthermore, the strength of coupling was found to be associated with other ophthalmic parameters (Fig. 2B-G). Specifically, weaker coupling was related to worse visual field mean deviation, thinner peripapillary retinal nerve fiber layer thickness, thinner macular ganglion cell-inner plexiform layer thickness, and smaller neuroretinal rim area, as well as a higher cup-to-disc ratio, but not with intraocular pressure.
Conclusions :
Our results suggest that the impact of visual stimulation on CSF inflow is gradually disrupted with increasing glaucoma severity.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.