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Elisabeth von dem Hagen, Antony B Morland; Extent of abnormal retinal projection in human albinism correlates with pigmentation levels. Journal of Vision 2005;5(12):11. doi: https://doi.org/10.1167/5.12.11.
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© ARVO (1962-2015); The Authors (2016-present)
In albinism a large proportion of nerve fibres originating in temporal retina cross the midline at the chiasm and project to the contralateral hemisphere. Studies in animals with albinism have suggested that the extent of this misrouting at the chiasm is inversely proportional to pigmentation levels. Here, we examine whether there is evidence for a similar relationship in humans with albinism. FMRI was performed on 18 subjects with albinism and 17 control subjects in a Siemens 3T Trio as they underwent hemifield visual stimulation of nasal or temporal retina. Functional activation in 16 coronal slices beginning at the posterior occipital lobes were analysed and the extent of hemispheric response lateralisation at each slice position was determined. During temporal retina stimulation, the control response was ipsilateral for all slices. In albinos, the response in posterior slices was predominantly contralateral, consistent with misrouting of temporal retina fibres. However as slice location became progressively anterior, response lateralisation in all subjects reverted to the ipsilateral hemisphere. The slice location at which the transition from contra- to ipsilateral lateralisation occurred provided an estimate of the extent of fibre misrouting in the individual. The slice transition location correlated negatively with pigmentation level, a result consistent with previous work on hypopigmented mice.
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