Objective: By means of neuropsychologic tests, to further analyse a specific chiasmal monocular visual testing behaviour, here labelled temporal blocking because of the elective ignorance of optotypes on the temporal side of the chart. Often it is combined with impairment of reading and other cognitive impairments.
Methods: Eighteen patients with lesions to the chiasm and some degree of temporal blocking aged 24 – 76 years underwent:
- tests for visual neglect (Gothenburg test; behavioural inattention tests: star cancellation; line bisection);
- visuo-perceptual tests; and
- a test involving reading a crowded ten-letter and cipher bar.
Results: The temporal blocking in two patients recovered after emergency neurosurgery and their results were normal when subsequently tested. Of the 16 patients with deficiencies, 14 had a poorer left eye (p < 0.01).
Conclusions: The best neuropsychologic tests appeared to be those for visual neglect and the crowded bar test. In most cases, the right cerebral hemisphere’s lack of some crossed information from the left eye, usually needed for normative saccades and adjustment to visual space, may be a factor underlying the specific visual behaviour.