PURPOSE. The importance of processing speed for explaining age-differences in cognitive performance has been well-documented. The hypothesis of this study is that, like speed of processing, vision affects the quality and efficiency of encoding. The mechanism by which speed of processing affects memory and learning in old age may also be affected by visual factors when cognitive tests are presented visually. METHOD. 62 subjects between 60 and 87 years recruited from the Optometry Clinic. They were excluded if they had central visual field defects, significant eye disease, poor English language skills, or a self-reported history of a neurological disorder.
Visual tests (higher and lower cognitive demand respectively): Visual acuity (LogMar and Landolt C), contrast sensitivity (AO H-R-R style contrast threshold test, Melbourne Edge Test) and colour vision (AO H-R-R and FM D-15).
Cognitive tests: Raven's Progressive matices, Similarities (part of Weschler Adult Intelligence Scale Devices), Stroop (Black-and-White, Colour and Colour-Word) RESULTS. Visual acuity test correlate well with one another and show the expected age decline. Only the Stroop Colour-Word showed a highly significant decline with age, other effects were less striking. The most marked associations were of the Stroop Colour-Word (a visually undemanding task but cognitively the most demanding) with visual acuity and of the Raven's Progressive Matrices (a test of non-verbal reasoning) with the FM D-15.
CONCLUSIONS. 1 In general, visual acuity and contrast sensitivity do not contribute to apparent cognitive losses until the cognitive task is highly demanding.
2 Non-verbal reasoning skill affect performance on the FM D-15.
3 In common with all correlating variables, a causative relationship cannot be assumed without furher investigation.