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Heather R M Connor, Sarah L Hosking, David F Abbott; Age-related structural changes to the human visual pathway determined using in vivo clinical imaging techniques. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):595.
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© ARVO (1962-2015); The Authors (2016-present)
To determine effects of normal ageing on visual pathway structures in the human brain using in vivo imaging techniques including 3T Magnetic Resonance Imaging (MRI)
83 healthy participants (mean age 58.6 ± 11y, range 40-82y, 37 female) were included. Imaging the retinal nerve fibre layer (RNFL) and optic nerve head (ONH) was conducted using Heidelberg HRTII and Stratus OCT instrumentation. 71 participants (mean age 57.8 ± 11y, range 40-82y, 31 female) completed 3T MRI imaging (Siemens Trio). T1, T2 and diffusion images were acquired and retrobulbar optic nerve diameter (ROND), optic radiations volume (ORV), fractional anisotropy (FA) mean diffusion (MD), radial diffusion (RD)(MRTrix software) and visual cortex volume (VCV: SPM8 software) determined. Linear regression analysis was used to determine effects of ageing for each structure (SPSS20).
RNFL thickness reduced by 4% per decade (pd) in right eyes (RE) (p < 0.01) and 3.5% in left eyes (LE) (p < 0.02). ONH measurements showed reduction in Horizontal Integrated Rim Width of 4.1% pd (p<0.05) RE and 5.9% pd (p<0.01) LE. Vertical Integrated Rim Area showed 17.4% reduction pd for LE (p < 0.03) but the 11.4% reduction RE was not statistically significant. HRTII measurements showed rim volume reduced 10.8% pd RE (p < 0.03) and 8.8% LE (p < 0.05). Height variation contour reduced 8.1% pd RE (p < 0.01) and 5.6% LE (p < 0.01). Only RE 15mm behind-the-globe ROND showed significant reduction of 2.4% pd (p < 0.05). ORV did not show significant change, but FA reduced by 2.2% pd (p < 0.02) and diffusion measures increased by between 2.1% - 2.9% pd (p < 0.01). VCV showed ageing effects only in males, with volume loss of 0.3% pd right (p = 0.028) and 0.4% pd (p = 0.015) left.
The posterior visual pathway appears more robust to structural changes compared to the anterior pathway, where normal ageing changes may confound diagnosis of degenerative diseases such as glaucoma.
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