Cortical blindness is a condition resulting from lesions in the primary visual cortex (V1) characterized by visual impairment but with an intact anterior visual pathway (normal pupillary reflexes and fundal appearance).
Clinical presentation
The degree of visual impairment is related to the extent of cortical involvement 1:
- complete lesions in both V1 areas lead to binocular blindness
- complete lesions in either the right or left V1 lead to a homonymous hemianopia
- incomplete lesions in V1 lead to scotomas in the visual field
Although patients lose any conscious visual awareness, at least 70% retain some functional awareness, known as 'blindsight' 1. These patients are able to discriminate the presence, location and movement of objects under forced-choice conditions despite denying any awareness of them 2.
Two subtypes have been reported 1:
-
type 1
- complete absence of visual awareness
-
type 2
- residual awareness of "feeling" or "knowing" of the presented visual stimuli
Associations
Associated syndromes:
-
Anton-Babinski syndrome 3
- bilateral cortical blindness
- visual anosognosia (denial of vision loss)
- visual confabulation
-
Riddoch syndrome 4
- preservation of light and motion perception but not static objects within hemianopic field
-
Dide-Botcazo syndrome 4
- Anton-Babinski syndrome associated with memory impairment
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