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Nikita Wong, Sara Rafique, Krista Kelly, Stefania Moro, Jennifer Steeves; DTI reveals asymmetry in the optic radiations following early monocular enucleation. Journal of Vision 2016;16(12):773. https://doi.org/10.1167/16.12.773.
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Introduction. Early monocular enucleation (surgical eye removal) results in enhanced visual spatial processing (Steeves et al., 2008) and better sound localisation (Hoover et al., 2012). These behavioural findings are supported by recent neuroimaging studies that demonstrate morphological changes in visual and auditory processing regions, including decreased lateral geniculate nuclei (LGN) volumes, and increased surface area and gyrification in visual, auditory and multisensory cortices (Kelly et al., 2015). Given the existing behavioural and morphological differences following early eye enucleation we investigated how the loss of one eye affects the development of connectivity within the visual system, particularly in the optic radiations. Methods. Participants were scanned using diffusion tensor imaging (DTI) and probabilistic tractography was performed to delineate the optic radiations. Seeds were placed at the LGN with waypoints and termination points in primary visual cortex in order to generate the optic radiations. Tract-based spatial statistics were used to extract the skeletonised fractional anisotropy (FA) values of the reconstructed optic radiations. Mean FA values were compared between individuals who had undergone early monocular enucleation and binocularly intact controls. Results. Unlike controls, people with one eye exhibited a hemispheric asymmetry, with significantly larger FA values in the right optic radiation compared to the left, independent of eye of enucleation. Conclusions. The asymmetry suggests structural changes to the optic radiations in people with one eye. This difference in FA may reflect compensatory changes in the right hemisphere in order to preserve normal function, however, it may also be the result of a deficit in a left lateralised function. Overall, this asymmetry could indicate accommodation for the loss of an eye early in life.
Meeting abstract presented at VSS 2016
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