Purchase this article with an account.
Michael B. Hoffmann, Birgit Lorenz, Markus Preising, Petra Seufert; Cortical visual field representations in patients with albinism and female carriers of ocular albinism assessed with multifocal visual evoked potentials. Journal of Vision 2006;6(6):544. doi: https://doi.org/10.1167/6.6.544.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: In human albinism part of the temporal retina projects abnormally to the contralateral hemisphere. We tested whether this abnormality can be identified with multifocal visual evoked potentials (mfVEPs) and whether it is evident in carriers of ocular albinism (OA1).
Methods: In 12 controls, 11 patients with albinism, and 5 female carriers of OA1 monocular pattern-reversal mfVEPs were recorded for 60 locations comprising a visual field of 44° diameter (VERIS 4.8; EDI). For each eye and each stimulus location inter-hemispheric difference potentials were calculated and correlated with each other to assess the lateralisation of the responses: positive and negative correlations indicate lateralisation on same or opposite hemispheres, respectively. Misrouted optic nerves are expected to yield negative interocular correlations. Silent visual field locations were excluded from the analysis using a signal-to-noise threshold. Our analysis also allowed for the assessment of the sensitivity and specificity of the detection of projection abnormalities.
Results: Sizable mfVEPs were obtained in all controls, carriers and the 3 albino patients with negligible nystagmus and visual acuity > 0.25. 97% and 98% of the visual field locations were identified as normal in controls and carriers, respectively. While this indicates a specificity of 97%, the sensitivity of the procedure was estimated to be 76%. Finally, in albinism 50% of the responses were abnormally represented.
Conclusion: In the absence of nystagmus mfVEPs are a powerful tool to identify, in a spatially resolved manner, abnormal visual field representations. No local representation abnormalities were evident in the female carriers of OA1 tested.
This PDF is available to Subscribers Only