Abstract
In vision, there is surprisingly very little evidence for common factors. Using large scale test batteries, most studies have found that there are no or only weak correlations between performance levels in different visual tests. Factor analysis confirmed these results. This means that a participant excelling in one test may rank lowest in another test. In aging research, cross-sectional studies have repeatedly found that older adults show deteriorated performance in most visual tests compared to young adults. However, within the older population, there is no evidence for a common factor underlying visual abilities. To investigate further the decline of visual abilities due to age as well as the relationship between visual abilities, we performed a longitudinal study. Older adults performed a battery of 12 visual tests three times, with re-tests after about four and seven years. Performance in most visual tests is stable across the seven years, except for visual acuity as determined with the Freiburg visual acuity test, which shows strong decline. Our results suggest that the decline of most visual abilities due to age is slower than usually thought - biased by the decline in visual acuity. This paradoxical outcome provokes the question whether visual acuity is a misleading or a very good test.