Andrew Freedman¹ (), Preeti Verghese¹; ¹Smith-Kettlewell Eye Research Institute

The healthy fovea acts as an oculomotor reference for the control of eye movements and is closely coupled with attention, with the goal of an upcoming saccade showing greater sensitivity. Individuals with macular degeneration (MD) develop a preferred retinal locus (PRL) for fixation, but it is unclear to what extent the PRL adopts the control and attentional role of the fovea. Utilizing a naturalistic search task, we evaluated whether participants with MD employed their PRL in the same manner as controls with an intact fovea. Two participants with MD and 5 controls with intact vision searched for generic cylindrical targets among similar distractors, distributed throughout a realistic indoor scene, while their gaze was tracked. Participants visually searched the scene and indicated when they detected the target. Target contrast, eccentricity, and whether the border was enhanced for visibility, and number of distractors were randomized across trials. Targets and distractors were twice the minimum size necessary for participants to discriminate between them. Participants were shown a preview of the target before each trial. Our results show that fixations of MD participants using a PRL were centered on the target, with a spatial distribution of 11.82 – 22.4 degrees squared, similar to that of controls using the fovea (4.81 – 30.42 degrees squared). The temporal distribution of fixations relative to the detection response was also similar for MD and controls. For all participants, fixations immediately prior to reporting a detection were significantly more likely to be on target, compared to off target, Tx1, x2 = 3.2528 – 9.3664, all p ≤ .001. Thus, the PRL mirrored how the fovea was used by controls, suggesting that the PRL is utilized as an oculomotor reference point during visual search in MD, adopting the close coupling with attention typically associated with the fovea.

Acknowledgements: Funding: This work was supported by the NIH grants T32EY025201 and R01EY027390