Cortical blindness

Bilateral lesions of the primary visual cortex may cause blindness.

The cortically blind patient may have no vision but:

• pupillary responses are intact:
  • fibres terminate in the pretectal region of the midbrain and do not involve the cortex
• normal fundoscopy
• normal visual imagination and dreaming

Optokinetic nystagmus is absent. Visual evoked occipital potentials are absent.

Depending on the aetiology, patients may recover from cortical blindness. There are often several stages in the recovery from blindness to visual agnosia to minor visual impairments through to normal perception.

In patients with more extensive lesions there may be denial of cortical blindness, a condition termed Anton's syndrome.

When the primary visual cortex is intact but the visual association cortex is damaged the result is one of a number of incomplete cortical blindness syndromes.