Altered Whole Brain Gray Matter Volume in High Myopia Patients - A Narrative Review

High myopia (HM) is a refractive error caused by axial elongation, with its prevalence impacting the quality of life and the socioeconomic well-being of nations. Due to the intimate ties between the brain’s visual-related areas and the eye’s associated structures, aberrant visual function alters the brain’s functional connections and morphology. This narrative review, which contains pertinent publications and studies from 2018 to 2022, outlines the advancement of research connecting changes in gray matter volume in patients with extreme myopia and other microstructural alterations caused by this condition. Numerous techniques, including optical coherence tomography (OCT), voxel-mirrored homotopic connectivity (VMHC), and DKI, were employed in the studies, but research confirmed that functional magnetic resonance imaging (fMRI), is the preferred imaging technique for examining spontaneous brain activity. Gray Matter Volume (GMV) values in High Myopic patients (HM) were significantly lower, according to a study that used MRI data that was processed using the SPM8 software. In contrast, increased GMV values were found in the brain stem, left Para hippocampal gyrus/thalamus, right Para hippocampal gyrus/thalamus and the left and right putamen. Furthermore, spectral domain OCT has demonstrated that excessive myopia causes thinning of the choroidal layer. Different dReHo values in various brain regions are observed in HM patients, which may indicate that HM significantly alters brain activity. The potential ramifications of this should highlight the need for additional study and therapeutic management of high myopia, to showcase the important pathological effects of this condition on the brain and its functional roles amongst society.

Keywords:Gray matter volume; high myopia; fMRI; Magnetic resonance imaging; Voxel-based morphometry; White matter

Abbreviations:HM: High Myopia; OCT: Optical Coherence Tomography; VMHC: Voxel-Mirrored; Homotopic Connectivity; DKI: Diffusion Kurtosis Imaging; Fmri: Functional Magnetic Resonance Imaging; GMV: Gray Matter Volume; Cu: Cuneus; Hcs: Healthy Controls; HM: High Myopia: LG: Lingual Gyrus; Parahg: Parahippocampal Gyrus; Put: Putamen; Tha: Thalamus; AD: Axial Diffusivity; DKI: Diffusion Kurtosis Imaging