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R.O. Duncan, P.A. Sample, R.N. Weinreb, L.M. Zangwill; Retinotopic Organization of Primary Visual Cortex Correlates With Visual Function and Optic Nerve Head Structure in the Diagnostic Innovations in Glaucoma Study (DIGS) . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3987.
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© ARVO (1962-2015); The Authors (2016-present)
To quantify the relationship between visual function, optic nerve head structure, and the retinotopic organization of primary visual cortex in patients with glaucoma.
Six patients from a longitudinal study of glaucoma (DIGS) participated in our study. Patients presented with asymmetric primary open–angle glaucoma. Visual function of both eyes was tested using three types of automated perimetry: standard automated perimetry using the Swedish Interactive Threshold Algorithm (SITA–SAP), short–wavelength automated perimetry (SITA–SWAP), and frequency doubling technology perimetry (FDT 24–2). Measurements of retinal nerve fiber layer (RNFL) thickness were collected using scanning laser polarimetry (GDx VCC), optical coherence tomography (Stratus OCT), and confocal scanning ophthalmoscopy (HRT II). Functional magnetic resonance imaging (fMRI) was used to compare cortical responses to visual stimulation of the glaucomatous vs. fellow eye. Cortical responses were elicited by alternately presenting each eye with a full–field flickering checkerboard pattern. Regions of visual space were computationally projected onto the flattened representation of cortex and defined as regions of interest (ROIs). For the visual functions tests, the difference between the pattern deviation (PD) values for the glaucomatous and fellow eye was computed at 12 test locations within the most damaged visual quadrant. These difference scores were compared to the fMRI amplitude within 12 corresponding ROIs. For the structural tests, fMRI responses for an entire quadrant were compared to the difference in the mean RNFL thickness between eyes for a similar region.
For all three visual function tests, we observed a correlation between the difference in PD values and the fMRI amplitude within the corresponding cortical ROIs (all p < 0.001). For all three structural tests, we observed a trend between fMRI amplitude and difference in RNFL thickness between eyes. A statistical bootstrapping approach revealed that simultaneously observing the three correlations between the fMRI data and the three structural tests was unlikely (p < 0.0001).
FMRI reliably measures the effects of glaucoma in the cortex, and fMRI may help determine the long–term effects of treatment on post–retinal function.
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