Here we attempt to incorporate both ‘neurological’ and ‘psychiatric’ disorders into a single classificatory scheme using an anatomical network approach. This omission is understandable given that these types of symptoms are often transient and thus difficult to study directly, and may occur without an obvious associated brain lesion. 1 2 Visual symptoms more likely to be found in psychiatric or neurodevelopmental disorders such as visual hallucinations, illusions and visual perceptual distortions, are typically only mentioned in passing or not at all in such schemes. Current classificatory schemes focus on disorders traditionally considered neurological (ie, based on static visual deficits typically related to brain lesions), relating each disorder to a specific brain region or its connections. If visual perception is the day-to-day experience of ‘seeing’-or put another way, the conscious, visual experience of the world we have when we open our eyes-a visual perceptual disorder might be considered a deviation from this experience. The wider perspective forces us to consider what visual functions underlie a range of symptoms sidelined by previous classificatory schemes and helps generate novel hypotheses for further research in the area. Guided by clinical and neuroimaging evidence, visual perceptual disorders are classified by the functional anatomical networks likely to be involved and the class of underlying dysfunction, whether topological (a localised deficit or region of hyperfunction) or hodological (a disconnection or hyperconnection). Here, the authors attempt a functional anatomical classification of all disorders linked to visual perception, whatever the clinical context in which they arise, including those disorders that bridge vision, emotion, memory, language and action. Visual perceptual disorders are often presented as a disparate group of neurological deficits with little consideration given to the wide range of visual symptoms found in psychiatric and neurodevelopmental disease.

Visual depth perception definition