Albinism: a model of adaptation of the brain in congenital visual disorders

Congenital visual abnormalities can lead to profound differences in the organisation of the visual pathways compared with normal developmental organisation. Knowledge of different cortical organisations is important for understanding the plasticity of the developing brain. Recent advances in functional brain imaging have allowed insights into such functional changes in humans. For example, a large-scale developmental reorganisation of the visual pathway was shown in rod monochromats (achromatopsia, colour blind people who lack cone photoreceptor function). In rod monochromats, the cortical region that normally responds only to cones during functional magnetic resonance imaging activation responded powerfully to rod-initiated signals.1 Another fascinating example is that the visual cortex can be activated by Braille reading in blind people.2 One of the most profound reorganisations of the visual pathway occurs in albinism. In this issue of British Journal of Ophthalmology, Hoffmann et al3(see page 509) report on their investigation of visual field function of abnormally wired optic nerve fibres in patients with albinism.

In patients with oculocutaneous and ocular albinism, there is a continuous range of hypopigmentation.4 Accordingly, patients have variable degrees of reduction in visual …