Assessment of spatial acuity at the fingertip with grating (JVP) domes: validity for use in an elderly population

JVP domes are of a set of small grating surfaces recently introduced for cu taneous spatial resolution measurement. The gratings are placed on the skin and subjects are required to identify the orientation of grooves and bars. The finest grating whose orientations are discriminated reliably (75% corr ect) provides an estimate of the spatial resolution limit in the tested are a, In the present study, we sought to determine the capacity of elderly sub jects to resolve such grating stimuli in order to obtain normative data for this population. Thirty-two elderly individuals in good health (range: 60- 88 years) were assessed for their ability to perceive grating orientation a t the tip of the dominant index finger. Testing proceeded from the widest g rating dome (3 mm) to the next (e.g., 2 mm), until the performance level dr opped below 75% correct discrimination. The grating orientation task proved to be very difficult for most subjects and only a minority (14/32) was abl e to provide reliable reports of grating orientation even with presentation of the widest dome available (3 mm). Accordingly, individual grating resol ution thresholds were often considerably higher (> 2.5 mm, n = 26) than val ues previously reported in young adults for the fingertip region (approxima te to 1 mm). These results suggest that the current set of grating domes ma y not be adequate for spatial acuity measurement at the fingertip of older adults. New larger grating dimensions should be added to the set presently available to improve their sensitivity for an older population.