INCONGRUITY OF HOMONYMOUS VISUAL-FIELD DEFECTS

1. In 15 of 22 patients with unilateral damage to the geniculo-cortical part of the visual pathway, perimetrical examination revealed an incongruity of visual field defects. The incongruity was mostly due to a larger sparing of the residual temporal visual half-field. 2. In order to test whether there is a relationship between incongruity and cortical organization principles, frequency and extent of incongruity were related to the position of the defect borders in the upper or lower quadrant of the visual field, to the eccentricity in the visual field, and to the position of the lesion in the anterior or posterior portion of the geniculocalcarine pathway. 3. The results indicate that incongruity is dependent on the organization of the optic radiation as welt as on cortical organization principles. The first conclusion is supported by the observation that the degree of incongruity depends on the position of the lesion (anterior--posterior) in the geniculo-calcarine pathway. The second conclusion is supported by the result that the degree of incongruity depends on eccentricity. 4. The results are discussed in the context of a ''divergence model'' of geniculo-cortical projection and, thus, cortical organization.