Comments on: variation in vernier acuity with age

Comments on: variation in vernier acuity with age Li, Edwards, and Brown (2000) recently reported variation in vernier acuity with age in Vision Research. We have addressed this issue using somewhat different test displays, test conditions, and paradigms. The paper by Li et al., kindly cites a number of papers presented by our research group; here we add only related non-There seems to be a sub-category of vernier threshold conditions and measurements which either are not affected by aging, or are minimally affected by aging. Rather small changes in displays, techniques, and settings can alter these very interesting findings and result in age-related findings. This applies both to the precision of settings (standard deviation of measurements, also called vernier acuity or vernier threshold), and the bias of settings (average of measurements) in vernier deter-minations. Li et al. (2000) come to the general conclusion that in parallel with degenerative changes occurring with aging, vernier precision judgements do change with aging, but bias judgements do not. This is just the opposite to Odom, Vasquez, Schwartz, and Linberg's (1989) earlier findings, and also contradicts our repeated results on vernier thresholds. We do not question the findings of these investigators, their capabilities, nor the complexities encountered in this form of test. Rather, differences employed in our studies and their recent work are of consequence. Thus, great care must be used when making generalizations. This research does not negate our repeated experiments or conclusions on this topic. We have trended towards clinical applications of the hyperacuities (vernier thresholds, bisections, etc.) in response to a suggestion made by Prof. Gerald Westheimer in 1978–79. Early on, we also used observer feedback, but due to objections raised by our statisticians, we dropped this technique. Li et al. (2000) used higher stimulus lu-minance levels, smaller gap (or feature) separations than we currently use, much smaller targets, higher spatial frequency targets, a method of constant stimuli which is often not practical in clinical settings (e.g., Reich, Lakshminarayanan, & Enoch, 1991), etc. Important additional technical issues arose in our recent studies (Fang et al., 2000). Individually, and collectively, differences in test format, settings, and paradigms are substantial between the Hong Kong Laboratory and the work of others in this scientific field. For example, when one considers the method of constant stimuli, does this totally differ from Whitaker and Elliotts jump displacement approach? That is, does a meaningful difference exist between changing …