While most positional acuity tasks exhibit an age-related decline in performance, the effect of ageing upon vernier acuity continues
to be the subject of some debate. In the present study we employed a stimulus design that enabled the simultaneous
determination of bisection and vernier acuities in 36 subjects, aged between 22 and 84 years. This approach provided a means for
directly testing the hypothesis that ageing affects bisection acuity but not vernier acuity by ensuring that differences in stimulus
configuration and in the subject’s task were kept to an absolute minimum. Optimum thresholds increased as a function of age for
both bisection and vernier tasks. Inter-subject threshold variability also increased with age. Issues surrounding the comparison of
absolute vernier thresholds across different studies are discussed and two important methodological factors are identified: the precise
statistical method used to estimate thresholds, and the magnitude, in angular terms, of the smallest spatial offset of the elements of
the vernier stimulus which can be displayed. Comparison with previously published data indicates that the discrepancy between this
study and most previous investigations with respect to the effect of age upon vernier performance can be at least partly accounted for
by differences in the minimum displayable vernier offset. Vernier thresholds do increase with age. The increased variability of vernier
thresholds in older subjects would appear to limit the diagnostic value of the test as a means of enabling normal ageing to be
distinguished from visual loss due to pathology of the eye or visual system.
2004 Elsevier Ltd. All rights reserved