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B. Lorenz, P. Seufert, M.N. Preising, M.B. Hoffmann; Assessment of Representation Abnormalities in the Human Visual Cortex With Multifocal Visual Evoked Potentials . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1679.
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© ARVO (1962-2015); The Authors (2016-present)
Visual evoked potentials (VEPs) are a routine tool to detect the partial abnormal projection of the temporal retina to the contralateral hemisphere, which is typical for human albinism . Multifocal VEPs (mfVEPs) open the possibility to screen a large number of distinct visual field locations for such abnormal cortical representations.
Using VERIS 4.8 (EDI) pattern–reversal mfVEPs were recorded during monocular stimulation of each eye to 60 locations comprising a visual field of 44° diameter in 5 controls, 5 carriers of X–linked ocular albinism (OA1), and 3 patients with albinism but negligible nystagmus. The differences of the VEPs recorded over opposing hemispheres were calculated to assess the lateralisation of the responses . Based on a signal–to–noise–ratio criterion ‘silent’ visual field locations were eliminated from further analysis. The difference traces obtained for each eye were correlated with each other to differentiate between normal and abnormal projections of the optic nerves: Positively correlated traces indicate that both eyes project as normal to the same cortical regions, negatively correlated traces indicate that both eyes project abnormally to opposing hemispheres.
In the patients with albinism negatively correlated traces were predominant at visual field locations along the central vertical meridian. In both controls and carriers of OA1 VEPs traces were positively correlated for the vast majority of visual field locations.
In the patients with albinism and negligible nystagmus, mfVEPs indicated an abnormal representation mainly of visual field locations along the central vertical meridian, which is in close correspondence to recent reports [2,3]. In the carriers of OA1 tested, mfVEPs did not indicate a projection abnormality.  Apkarian et al. (1983) Electroenceph Clin Neurophysiol 55:513–531;  Hoffmann et al. (2003) J Neurosci 23:8921–8930;  Hoffmann et al. (2004) Invest Opthalmol Vis Sci 46:3906–3912
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