Disorders of Awareness of Vision or Visual Deficit
Patients with Anton syndrome characteristically have cortical blindness but deny having any visual problem. These patients have no demonstrable visual behavior, but they hallucinate and confabulate visual images, claiming the ability to see. Anton syndrome is most common with bilateral occipital infarctions but has been described with blindness from bilateral optic nerve lesions.
Figure 6-2 The patient is asked to describe what is occurring in this drawing, the “cookie theft picture,” modified from the Boston Diagnostic Aphasia Examination. A patient with simultanagnosia will describe one part of the scene and not see anything else.
(Used with permission from Kline LB, Bajandas FJ. Neuro-Ophthalmology Review Manual. Rev. 5th ed. Thorofare, NJ: Slack; 2004:227.)
Preservation of the perception of motion in a blind hemifield is termed staticokinetic dissociation, or the Riddoch phenomenon. When present in an otherwise complete homonymous hemianopia, it is thought to portend a better visual prognosis.
Cortically blind patients may have an unconscious rudimentary visual perception (blindsight). This condition manifests in the presence of damage to retrogeniculocalcarine visual pathways.
Patients with hemispatial neglect (hemineglect) will not acknowledge seeing objects in one hemifield (usually the left) if presented with simultaneous stimuli in both hemifields; however, they will see the stimulus if it is presented in that hemifield alone. Confrontation visual field testing using double simultaneous stimulation may be used to verify this condition (see Chapter 3). Hemispatial neglect usually results from damage in the right hemisphere (eg, the posterior parietal cortex, frontal eye fields, cingulate gyrus) that mediates attention in both hemifields.
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.