Stereopsis and unilateral brain disease.

Performance on a random-letter stereoscopic task has been reported to be affected by right but not left cerebral disease. Subsequent studies employing a conventional stereoacuity test have challenged these results and proposed that dementia may be the primary determinant of impaired stereopsis in the patients with brain disease. The latter investigators have failed to distinguish between local and global stereopsis. The present study confirms the original findings, rules out dementia as a potential artifact, and attempts to reconcile the conflicting series of reports.