Abstract

A recent study (Odom et. al., 1989) has suggested that the vernier acuity of an observer is independent of the individual's age. This is somewhat surprising given the evidence of an age-related decline in other measures of visual performance such as visual acuity, contrast sensitivity (Elliott, Whitaker and MacVeigh, 1990) and indeed other types of hyperacuity such as displacement detection (Elliott, Whitaker and Thompson, 1989). This type of study is, however, fraut with methodological problems. As an example, if observers are allowed the freedom to set their own level of threshold, criterion differences between observers manifest themselves as actual threshold differences. Therefore, quite justifiably, it has been suggested that a method of adjustment, the technique used by both Odom et. al. (1989) and Elliott et. al. (1989), should be avoided for age-related studies of vision (Higgins et. al., 1988). This is especially true for vernier acuity in which a method of adjustment introduces many unquantifiable variations due to the technique adopted by different individuals. For these reasons we felt that a study employing a forced-choice method of threshold measurement for several different hyperacuity tasks was important.

© 1991 Optical Society of America