Abstract
Impaired visual function is often described by reduced visual acuity, with effects thought to be qualitatively similar for various types of stimuli. Visual fields may be locally impaired, but little is known about how such local field deficits might interact with different visual discrimination tasks. Now, we report that (a) children with different low-vision etiologies may have differing deficits for static and moving patterns, and (b) these deficits may differ in the central and peripheral fields.
Vision was evaluated simultaneously in central and peripheral fields, using three adjacent monitors, each perpendicular to the visual direction - one central and two peripheral displays, at ±30 deg eccentricity. Stimuli were Gabor patches. Static form perception was measured by orientation discrimination thresholds; and motion perception was measured by temporal thresholds for direction discrimination. In addition to single-stimulus discrimination tasks in which a test pattern appeared in a randomly selected field, attentional selection was also studied with multiple simultaneous Gabor patches and a spatial cue designating an individual target patch. Children with several different types of low vision have been tested, as well as normally sighted children and adults in the same visual tasks.
Normally sighted children and adults exhibited little or no difference in performance on these tasks. Low-vision children, however, exhibited dramatically different deficits not predictable from previous knowledge about acuity, visual fields, or etiology — deficits substantially different for static forms and moving patterns, and different for the central and peripheral fields. Evidently, perception of static forms and motion entail qualitatively different mechanisms and visual skills that differ between central and peripheral fields.