Occipital proton magnetic resonance spectroscopy (1H-MRS) reveals normal metabolite concentrations in retinal visual field defects

Abstract

Background: Progressive visual field defects, such as age-related macular degeneration and glaucoma, prevent normal stimulation of visual cortex. We investigated whether in the case of visual field defects, concentrations of metabolites such as N-acetylaspartate (NAA), a marker for degenerative processes, are reduced in the occipital brain region.

Methodology/principal findings: Participants known with glaucoma, age-related macular degeneration (the two leading causes of visual impairment in the developed world), and controls were examined by proton MR spectroscopic ((1)H-MRS) imaging. Absolute NAA, Creatine and Choline concentrations were derived from a single-voxel in the occipital region of each brain hemisphere. No significant differences in metabolites concentrations were found between the three groups.

Conclusions/significance: We conclude that progressive retinal visual field defects do not affect metabolite concentration in visual brain areas suggesting that there is no ongoing occipital degeneration. We discuss the possibility that metabolite change is too slow to be detectable.

Figure 1. Example of PRESS box position and spectra.

Left: To delineate the single-voxel, an elongated PRESS box was located in each hemisphere (here shown only in the left hemisphere) along the calcarine sulcus as far to the back of the occipital pole and the midline of the brain as possible while avoiding the inclusion of fat and vasculature. Right: Example of spectra with Choline, Creatine and NAA peaks.

Figure 2. Metabolite concentrations.

Averaged absolute concentrations (in nM) of each of the measured metabolites (NAA, Cr and Cho) for each group (controls, AMD and glaucoma). The ANOVA analysis between the three groups (AMD, glaucoma and controls) showed no significant differences for any of the three metabolites concentration.