Abstract
Purpose: :
Detection Thresholds (DT), Contrast Acuity (CA), Motion Perception (Mot) and Colour Vision (Col) were tested in 200 subjects at the fovea and in the periphery (6° away from fixation into each quadrant) to establish age-matched control data of different aspects of visual performance.
Methods: :
Ageing is known to affect visual performance, due to changes in the optics in the eye and the retina. Visual performance was assessed in a number of normal healthy subjects (spread evenly from 20 to 80 years of age). All subjects had Visual Acuity (VA) of 20/20 or better. The tests were carried out on the P_SCAN system and fixation stability was monitored using eye-movements. Target size was adjusted in size for peripheral locations to account for retinal and cortical magnification (Landolt ring for DT and CA from 14 min of arc to 38 min of arc). Colour vision assessment employed the CAD test and was restricted to yellow-blue and red-green axes.
Results: :
Absolute DT showed a significant dependence on age both in the fovea and the periphery for each subject group (decades). CA data for fovea and periphery could be statistically combined (size adjusted) with an increase in threshold with age. Motion thresholds were less influenced by age. Subjects showed no significant statistical difference below 50 years of age in combined data. Red-green and yellow-blue colour thresholds were analysed separately at the fovea and in the periphery and showed no effect of ageing below 60 years.
Conclusions: :
Gradual loss of DT and CA was found, confirming a reduction in VA with age. Motion (<50) and colour (<60) thresholds were less affected. Selective loss of visual functions with ageing was found to have a significant impact on central and peripheral threshold data. Our findings have clinical relevance in differentiating disease processes and making early diagnosis, this is crucial when disease tends to be more frequent with advancing age. Selective age ranges allowed performance limits to be established, providing a basis on which to assess the differential effect of ageing on different visual mechanisms.
Keywords: perception • aging • visual cortex