Measurement of discrimination of separation in elderly persons using a liquid-crystal display and grating method

This study analyzed psychophysical data from younger and elderly people on the influence of spacing between vertical lines, exposure time, and number of vertical lines in a stimulus for visual performance. A total of 50 elderly people and 31 graduate students participated in the experiment. Nine levels of spacing between lines (3, 6, 9, 12, 15, 18, 21, 24, and 29 points), three exposure times (0.2, 0.6, and 1.0 sec.), and five sets of numbers of lines (4, 5, 6, 7, and 8) were manipulated. Analysis showed enhanced spacing between lines and exposure time improved discrimination of separation. However, although performance on discrimination of separation increased as spacing between lines increased up to 21 points, it was degraded at higher values. A positive effect of number of lines on discrimination of separation was also observed, and performance increased as the number of lines decreased. The effect of age group, i.e., elderly versus younger, on performance was significant. The accuracy of the younger was greater than that for the elderly group. Moreover, three interactive two-way effects were found: group x spacing between lines, number of lines x spacing between lines, and number of lines x exposure time. The present findings could be used as a practical reference in the design of instrument displays in which the operator has to consider the scale and markings on a dial, especially if the display is operated in an emergency or is manipulated by elderly people.