Microstructural Visual Pathway White Matter Alterations in Primary Open-Angle Glaucoma: A Neurite Orientation...

Area of Science:

• Neuroscience
• Ophthalmology
• Medical Imaging

Background:

• Primary open-angle glaucoma (POAG) involves degeneration beyond the retina, affecting the entire visual pathway.
• Previous diffusion tensor imaging (DTI) studies show widespread visual pathway damage in POAG.
• The precise microstructural nature of this degeneration remains poorly understood due to DTI parameter interpretation limitations.

Purpose of the Study:

• To utilize neurite orientation dispersion and density imaging (NODDI) to characterize microstructural changes in the pregeniculate optic tracts and postgeniculate optic radiations in POAG patients.
• To elucidate the underlying mechanisms of visual pathway degeneration in POAG.

Main Methods:

• Acquired T1- and multishell diffusion-weighted scans from 23 POAG patients and 29 controls.
• Generated NODDI parametric maps and used probabilistic tractography to delineate optic tracts and radiations.
• Computed NODDI parameters for tracked pathways and compared between groups, assessing retinal nerve fiber layer thickness and visual field loss in POAG patients.

Main Results:

• POAG patients exhibited higher orientation dispersion index and lower neurite density index in optic tracts compared to controls (P < .001 and P = .001).
• POAG patients showed a higher orientation dispersion index in optic radiations compared to controls (P = .003).

Conclusions:

• Pregeniculate visual pathways in POAG show loss of axonal coherence and density.
• Postgeniculate pathways in POAG demonstrate loss of axonal coherence only.
• Longitudinal studies are recommended to track NODDI alterations in the visual pathways of POAG patients over time.