New paper: ageing effects on peripheral vision

We have recently published the first paper from Menaka’s PhD, investigating how healthy ageing affects the perception of visual stimuli in the presence of surrounding features in peripheral vision. In particular, we are interested in the area of our field of view that is just outside of the centre (the fovea), which we refer to as the parafoveal area. Studying parafoveal vision is important in older adults, especially as foveal damage occurs in age-related conditions like macular degeneration, which may lead to increased reliance on parafoveal vision.

One aspect of vision that occurs in the parafovea is crowding, which is typically described as reduced object recognition in a cluttered scene. Another visual phenomenon that occurs in the parafovea is surround suppression. An example of suppression occurs when a person’s ability to detect that a visual target is present is worse when there are surrounding features. We measured crowding and surround suppression effects in 20 older and 21 younger adults. Observers focused on the centre of a computer screen and visual stimuli were presented in their peripheral vision (8 degrees from where they were fixating). Examples of what were presented are shown in the figure below.

menaka-stimuli

Top: To measure the effect of crowding, we presented a target (right, striped pattern) next to an extra piece of clutter known as a flanker (left, cross hatched pattern) Bottom: To measure the effect of surround suppression, the target (right, centre striped pattern) is presented with or without a surrounding half annulus. The white dot is the fixation spot for both tasks.

We found that older adults have reduced ability to detect a visual target when it was surrounded (more surround suppression) compared to the younger observers, but crowding was unaffected by the type of stimuli used in our study. This suggests that crowding and surround suppression may be distinct visual phenomena, despite both occurring in parafoveal vision.

An extra question we asked was: given previous reports of decreased visual attention with healthy ageing, could altered performance on the crowding and surround suppression tasks be explained by changes to visual attention? Our specific measure of attention was a visual search task. Indeed, our group of older adults showed decreased visual attention but neither crowding nor surround suppression showed a relationship to the attentional aspect.

Advancing our knowledge on the ageing effects on peripheral visual function is useful for future remediation strategies using peripheral vision in older individuals where foveal vision is hindered. The article can be viewed online here.

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