Natural visual behavior in individuals with peripheral visual-field loss.

Retinitis pigmentosa (RP) is an inherited disease that causes progressive peripheral visual-field loss. In this study, we investigated how such loss affects visual exploration of natural images. Individuals with varying degrees of visual-field loss and healthy control participants freely observed images of different sizes while eye movements were recorded. We examined whether visual behavior differed when the scene content was shown in various extents of the visual field, and investigated the spatial bias, saccade amplitudes, and number and duration of fixations. We found that the healthy control group showed a central spatial bias during image viewing. The RP group showed similar biases on the group level, but with reproducible individual exploration patterns. For saccade amplitudes, the healthy control group and the RP group showed similar behavior throughout all image sizes. The RP group with severe loss of peripheral vision thus tended to target saccades toward blind areas of their visual field. The number of fixations did not change between the two groups, although fixation durations decreased in the RP group. In conclusion, the RP group scanned the images surprisingly similarly to the healthy control group; however, they showed individual idiosyncratic explorative strategies when the observed scene exceeded their visible field. Thus, although RP leads to a severe loss of the visual field, there is no general adaptive mechanism to change visual exploration. Instead, individuals rely on individual strategies, leading to high heterogeneity in the RP group.