Purchase this article with an account.
Cindy Y Teng, Ian Conner, Matthew C. Murphy, Richard Bilonick, Seong-Gi Kim, Gadi Wollstein, Joel S Schuman, Kevin C Chan; Visual cortex activity is impaired prior to visual field loss in glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1697.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Glaucoma involves transsynaptic degeneration in the visual cortex. Retinal structure and visual function relationships in glaucoma have been described by a broken-stick model, in which detectable visual field (VF) functional loss emerges after substantial retinal degeneration reaches a tipping point. This study examined relationships among visual cortex activity, retinal morphology and visual function in glaucoma using both linear and broken-stick analyses.
Blood-oxygen-level-dependent (BOLD) functional MRI was collected for 26 subjects including 10 advanced glaucoma (age=65.5±7.8yrs), 9 early glaucoma (age=62.9±7.1yrs) and 7 healthy control (age=64.1±8.0yrs) on a 3 Tesla scanner. Checkerboard stimuli were presented to the superior/inferior hemifield of each eye separately. BOLD % signal changes between rest and stimulation periods within Brodmann Areas (BA) 17, 18 and 19 were compared to OCT-measured peripapillary retinal nerve fiber layer (RNFL) thickness and macular ganglion cell-inner plexiform layer (GCIPL) thickness, and to VF mean deviation using linear and broken-stick analyses based on data distribution.
Using linear modeling, superior/inferior RNFL/GCIPL thicknesses and VF were most strongly correlated with BOLD activity for corresponding hemifields in BA17 (superior RNFL/GCIPL/VF p=0.006/0.003/0.001, inferior p=0.001/<0.001/0.001 respectively), less in BA18 (p=0.31/0.001/0.13, p=0.02/0.02/0.04), and not significantly correlated in BA19 (p>0.05). Our data confirmed previously reported broken-stick model relating RNFL/GCIPL thickness and VF function at a tipping point of 82µm for RNFL and 66µm for GCIPL (p<0.001). Our data also demonstrated a broken-stick model relationship between BOLD signal in BA17 and VF function for the superior hemifield at a tipping point of BOLD=0.54% (p<0.001).
Our results from linear modeling showed that glaucomatous degeneration of inner retinal structure and visual function were more closely associated with reduced activity in the primary visual cortex than higher-order visual areas. Current data also supported previously described broken-stick models for structural OCT vs functional VF correlations. More importantly, a tipping point also existed between regional primary visual cortex activity and VF function, suggesting substantial reduction in brain activity before detectable VF functional loss.
This PDF is available to Subscribers Only