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Tiffany Arango, Nicole C. Ross, Peter J. Bex; Fixation characteristics with Central Vision Loss at different gaze postures in a CSF task. Journal of Vision 2020;20(11):1574. https://doi.org/10.1167/jov.20.11.1574.
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Patients with central vision loss adopt an eccentric preferred retinal locus (PRL) in the absence of functioning foveae. Early work examined PRL selection under monocular viewing in primary gaze, and recommends patients adopt one PRL in the inferior visual field to optimize visual function. Less is known about PRL use during binocular gaze at different gaze postures. We examined fixation behavior under binocular and monocular viewing, in 9 different gaze positions, while observers completed a contrast sensitivity task.
Subjects were recruited with bilateral central scotomas (n=7) defined with a MAIA microperimeter who have not received fixation training. Subjects completed a 9 point fixation task (8X8 degree grid) in binocular and monocular viewing conditions. Fixation stability (68% BCEA) was calculated for each eye at each location. A contrast sensitivity task was then completed in the gaze postures with highest and lowest fixation stability. Subjects identified band-pass filtered letters, whose spatial frequency and contrast were controlled with a quick CSF algorithm (Hou et al, 2017). Binocular eye movements were tracked using the Eyelink eye tracker, through a neutral density filter for monocular conditions. The fixation distance from the target center and estimated gaze center was calculated for each condition. PRL changes were estimated from differences among these distributions with one- and two-sample t tests.
Under binocular viewing conditions, fixation stability was associated with higher accuracy in the CSF task in the more (p=.05) but not the less (p=.85) stable fixation location. Fixation stability was not associated with accuracy in the CSF task in either monocular viewing condition (p>.05). PRL location significantly differed in most gaze postures (Bonferroni corrected, p’s < .001) for binocular and monocular conditions. Results demonstrate PRLs are highly dependent on the conditions used to measure them, and this malleability suggests that they may be amenable to rehabilitation training.
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