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Josselin Gautier, CARLES OTERO MOLINS, Jaume Pujol; Do fixational eye movements relate to accommodative fluctuations? Effect of viewing distance and peripheral cues. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4578.
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© ARVO (1962-2015); The Authors (2016-present)
Microsaccades and accommodative fluctuations have been shown separately to be influenced by the task and the cognitive load. We asked how these two critical components of fine discrimination might be intermingled at the neural level.
Fixational eye movements and accommodative fluctuations were recorded simultaneously on respectively the left and right eye of participants (fluctuations are known to be highly correlated in phase and amplitude in both eyes). A PowerRef II recording at 25 Hz was synchronized to an Eyelink 1000 Plus sampling at 1000Hz. The stimuli were displayed monocularly on the right eye whose accommodation response was measured. Six subjects (normal without glasses, age: 21-29) were asked to fixate during 10 sec a Maltese cross at 0 and 5 Diopters, in 4 scenarios involving various cues i.e. a Maltese cross presented within a real world scene, on a similar sharp or blurry printed image of this scene and on a white background image.
Overall, microsaccade rate appears to increase at shorter distance (from 2.49 to 3.66 microsaccades/sec.), in a similar fashion to accommodative fluctuations (from a mean variability of 0.17D to 0.34D). Complementary to these increases, microsaccade amplitude appears reduced (from an average size of 1.69° to 1.03°), in agreement for a role in fine discrimination at short accommodative distances. Between scenario however, a scene that will favor low variation in accommodative fluctuation (sharp stimuli) appears to increase microsaccade production and reversely (fixation without external cues). Thus the influences of peripheral and depth cues remain to be carefully evaluated.
Fixational eye movements and accommodation might be combined by the human visual system in an optimal fashion. Considering them together, as they act in practice, should give new insights about their role in visual processing in the variety of viewing distances and tasks they operate.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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