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Angelo Arleo, Marcia Bécu, Guillaume Tatur, Denis Sheynikhovich; Impact of healthy aging on ocular fixation stability and microsaccades during optic flow. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5925.
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© ARVO (1962-2015); The Authors (2016-present)
Aging alters the processing of dynamic visual cues. However, the influence of optic flow on fixational eye movements remains partially understood across the life span. This study aims at characterizing the effect of healthy aging on ocular fixation stability and fixational microsaccades in the presence of optic flow (i.e., the pattern of visual motion that projects to the retina due to the relative motion between an observer and the environment).
A population of 119 adults (range: 21-83 yo) was used in this study. Participants were enrolled in the French cohort study SilverSight and they were ascertained to be healthy by visual, vestibular, sensorimotor, and cognitive clinical examination. The experiment was performed in the dark and in head-fixed condition with a chinrest. The protocol included a fixation task with a target presented at 57 cm from the subject’s eye. The target was presented either alone or superimposed on 3 optic flow patterns: two radial flows at speed of 1.38 m/s and 6 m/s, respectively, and a tangential flow with a speed of 1.38 m/s. Eye movements were recorded monocularly at 1 KHz on the dominant eye. All experiments were carried out at the Institute of Vision, Paris. Microsaccades were analyzed using a custom-made unsupervised clustering method that permits reliable detection in the presence of high-frequency pupil detection noise.
Our results show that the previously reported age effect on fixation stability disappears when saccades and blink-related artifacts are accurately removed from the data. Additionally, optic flow increases fixation stability to a greater extent in older adults, and this effect is not specific to the motion pattern providing the optic flow. Our microsaccade analysis shows that healthy aging significantly increases the frequency, amplitude, and peak velocity of fixational microsaccades. Tangential and radial optic flow significantly trigger microsaccades in the opposite direction to the flow. Importantly, this directional bias seems to be stronger in older adults as compared to young subjects.
This study can provide normative healthy aging data with respect to fixational eye movements in the presence of optic flow, a condition relevant to mobility and visuo-spatial behavior. These data can thus contribute to the research related to microsaccadic dysfunctions as biomarkers of age-related pathological conditions.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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