The relationships between visual acuity, crowding and spatial attention in the selection of the PRL during simulated central vision loss

Patients suffering from pathologies leading to central vision loss, such as macular degeneration (MD), tend to spontaneously develop compensatory oculomotor strategies to overcome their lack of foveal vision. One of the most commonly used strategies is the adoption of a preferred retinal locus, or PRL, a peripheral area outside the region of vision loss (scotoma) which they use for tasks such as reading, recognizing faces and fixation. The mechanisms underlying PRL development and its spatial location are still not completely understood: studies in MD patients show that the PRL is not necessarily the peripheral region with the highest resolution, while studies using simulated central vision loss seem to suggest that pre-existing attentional capabilities might be relevant in selecting the PRL location. The process of PRL development most likely involves multiple components, some related to resolution, others to integration and attention. In this study we measured visual acuity, visual crowding and spatial attention in four peripheral locations (‘PRL candidate regions’) before training participants to perform a demanding visual discrimination task in conditions of simulated central vision loss. We examine the extent to which these measures of visual performance across peripheral locations individually and jointly predict which of the PRL candidate regions the participant would use during the simulated scotoma task. Additionally, we measured how visual performance predicts PRL locations in a transfer task that allowed participants to place the target anywhere within a ring around the simulated scotoma. Similar to previous findings in the clinical literature, our results show individual differences in patterns across participants that will be discussed.