Introduction

Cortical blindness refers to a total loss of vision caused by a bilateral lesion or dysfunction of the occipital lobe. It represents a subset of cerebral blindness, a more general term which indicates blindness from any damage to both visual pathways posterior to the lateral geniculate bodies. Cortical blindness results typically from direct insult to both the primary visual areas lying in the calcarine cortex. As the responsible lesion does not usually limit to the cortex, but also encompasses the posterior part of the optic radiations and variably the extrastriate visual areas, both de-afferentation and de-efferentation of the primary visual cortex may also contribute to the visual dysfunction that is observed at the acute and at the recovered stages as well. Ischemic strokes are the major cause of cortical blindness.

Description

Clinical symptoms

By definition, cortical blindness is defined by a bilateral and total loss of vision. Thus, affected subjects can no longer identify visual forms, colors, location, orientation or movement of objects, nor even differentiate light from dark. They are usually distressfully aware of their deficit. At the acute stage, however, degree of awareness is variable. Patients may not report spontaneously their problem or seem indifferent to it. A minority of patients may even deny any visual loss or attribute their faulty performance to external factors, such as unfitted eyeglasses or poor room illumination.