Testing Functional Fields Of View With The Multi-screen Text Display Device RSG

Wearers of Progressive lenses, which have differing power as a function of the eyes' position, must sometimes make head movements in order to clearly see a target in space. The progressive lenses thus induce a "modified gaze field" which changes the required tradeoff between head and eye movement in shifts of gaze. This paper reports experiments using a multi-screen microcomputer text display device to test the effects of various modifications of the gaze field on reading performance. Subjects were asked to repeat aloud 3-word groups presented one word at a time on three CRTs separated by one of several visual angles. The number of words reported incorrectly as presentation rate is increased is a measure of the impairment of gaze-directed reading. Results of preliminary experiments describe the drop in performance under normal vision conditions as a function of target eccentricity. This data is the basis for comparison with the measured performance of subject wearing progressive lenses and illustrates the different gaze shift strategies among subjects.