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Anat Fintzi, Eric Hintz, Duje Tadin, George Vates, Zoe Williams, Bradford Mahon; Retinotopic mapping in a patient with optic chiasm compression: converging evidence from visual field testing and fMRI. Journal of Vision 2012;12(9):1122. doi: 10.1167/12.9.1122.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: Visual information from the temporal hemifield of each eye crosses the optic chiasm before innervating the optic tracts. Compression of the chiasm by pituitary tumors may restrict the information flow, causing bi-temporal visual field deficits. Successful tumor removal largely reestablishes axonal conduction, which makes this condition a useful model for studying the effects of reversible, long-term visual deprivation. Here, we investigate the time-course of visual recovery following removal of a pituitary tumor using behavioral and functional magnetic resonance imaging (fMRI) methods in a case study. Method: The patient (age 63) had a pituitary tumor removed following severe chiasmal compression. She was tested three times: prior to surgery, one month and two months after surgery. All tests were performed monocularly on the eye showing the greatest initial visual field deficit. Visual field deficits were assessed at each time point. Retinotopy was measured by presenting arcs to one of two locations within each field quadrant (3º and 5º eccentricity). Mapping stimuli were either isoluminant, low or high contrast. Isoluminance was determined within the scanner using a flicker fusion task. Results: Following tumor removal, we observed a rapid recovery of visual function, as well as corresponding retinotopic reactivation of early visual areas. Conclusions: We report a rapid time course of visual recovery following prolonged (partial) visual deprivation. A close correspondence was observed between fMRI (retinotopy) and standard field tests. Additional analysis of retinotopy with low-contrast and isoluminant stimuli will allow us to determine whether pituitary tumors preferentially compress a given class of nerve fibers (i.e., parvocellular vs. magnocellular).
Meeting abstract presented at VSS 2012
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