Abstract
Contrary to our perceptual impression, visual processing is not homogeneous across the visual field. While foveal vision offers fine spatial detail with high precision, peripheral vision provides coarser yet crucial previewing that helps direct our attention and future saccades. Together, the two types of visual processing allow us to perform everyday visual tasks, such as reading or visual search. Thus, the question arises as to how the oculomotor system would adapt when one or the other processing is compromised. Here, using a gaze-contingent display, we simulated scotomas with various shapes, sizes, and locations to see whether/how different disruptions in the visual field would impact the pattern of eye movements during reading. Simulated scotoma was induced in 12 young normally-sighted adults and their eye movements were continuously recorded during reading. Our visual-field defects included no scotoma, central scotomas with diameters ranging from 2 – 10 degrees, peripheral scotomas (with the intact central visual-field ranging from 2 – 10 degrees in diameter), and hemifield scotomas that induce left, right, upper, or lower visual-field loss. Eye movements were analyzed in terms of forward and backward saccades, microsaccades, and fixations. As expected, under severe peripheral and central scotoma, reading speed decreased by 47% and 51%. Compared to no scotoma, severe peripheral scotoma induced increased fixation duration (17%), decreased saccade amplitude (37%), increased number of fixations (71%), and increased rate of microsaccades (150%). When blocking the right visual hemifield, saccade amplitude decreased by 26% and showed the largest increase in the number of forward saccades (186%) compared to other hemifield scotomas. Eye movements often represents active choices of sampling the environment required to accomplish visual tasks. Our findings suggest that, during reading under various disruptions of the integration of information in the visual field, the oculomotor system exhibits changes in strategies to optimize the information uptake.