Joseph Lappin - US grants

The principal function of vision is to provide information about the geometrical structure of the environment--about the 3-D shapes, locations, and motions of objects and about the location and motion of the observer. Precise and globally consistent measures of this environmental structure are obtained from changing stimulus patterns distributed both spatially and temporally over two retinal surfaces. This basic visual achievement remains poorly understood, however. A central empirical and theoretical problem is to specify the visually detected geometrical properties that carry information about environmental structure. Analysis of the physiological processes underlying spatial vision depends on an understanding of the specific geometric relationships to which vision is sensitive. The objective of this research project is to identify the geometric relationships in spatially and temporally varying stimulus patterns that permit precise and globally consistent discriminations of spatial structure. The specific aim is to quantify the acuities of human observers in discriminating both local and global spatial relations in changing stimulus patterns. The proposed experiments focus on stimulus patterns in which the local spatial structure of 2-D images is changing due to motion in 3-D space and to stereoscopic projection. The strategy is to evaluate the visual acuity for spatial relations that are intrinsic to the geometric structure of the stimulus pattern versus those that are based on retinal positions. The optical stimulus patterns consist of points and line segments presented on cathode ray tube displays under computer control, with precise control of the spatial and temporal parameters of the patterns. Human observers discriminate patterns with slightly different geometric structures. Visual performance is measured by the psychometric function relating discrimination accuracy to the magnitude of a geometrical variable, providing separate measures of the gain and threshold for obtaining visual information about a particular geometrical variable.

[unreadable] DESCRIPTION (provided by applicant): The integrity of the visual field may be impaired in children with low vision, demanding compensatory strategies for acquiring and integrating visual information over central and peripheral regions of the field. Observations of children with low vision suggest that often they are unresponsive to peripheral information relevant to orientation and mobility, even though standard visual assessments indicate that such stimulus patterns should be visible. The present project is motivated by several key gaps in currently available knowledge relevant to this problem: Currently available visual assessments do not evaluate motion sensitivity, attention, and pattern recognition in the peripheral field; knowledge is still limited about the impact of various types of visual impairments on the processes and mechanisms for integrating information about motion and spatial patterns over the panoramic visual field; and too little is known about the developmental plasticity of visual skills for integrating changing spatial information over the central and peripheral fields. [unreadable] [unreadable] To address these problems, the present study is designed to (a) develop a method for testing peripheral visual functions beyond those describing photosensitivity, (b) determine whether differences in peripheral visual function exist among children with and without low vision and those with different low vision etiologies, and (c) determine whether peripheral visual skills can be improved by training. [unreadable] [unreadable] This study should contribute (a) knowledge about several basic mechanisms of visual function in both normal and low vision populations, (b) tools for assessing visual function in children with low vision, and (c) training strategies for improving visual functioning of children with low vision, especially as related to the use of peripheral vision for mobility and spatial orientation. [unreadable] [unreadable] [unreadable]