June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
Fixational Eye Movements depend on Fixation Task
Author Affiliations & Notes
  • Samantha Lin
    School of Optometry and Vision Science Graduate Group, University of California Berkeley, Berkeley, California, United States
  • Norick Bowers
    School of Optometry and Vision Science Graduate Group, University of California Berkeley, Berkeley, California, United States
  • Josselin Gautier
    School of Optometry and Vision Science Graduate Group, University of California Berkeley, Berkeley, California, United States
    Paris Eye Imaging, Quinze-Vingts National Hospital, INSERM, Paris, Île-de-France, France
  • Austin John Roorda
    School of Optometry and Vision Science Graduate Group, University of California Berkeley, Berkeley, California, United States
  • Footnotes
    Commercial Relationships   Samantha Lin, None; Norick Bowers, None; Josselin Gautier, None; Austin Roorda, C. Light Technologies (I), Rochester (P), University of Houston (P)
  • Footnotes
    Support  NIH T35EY007139, NIH R01EY023591
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 507. doi:
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      Samantha Lin, Norick Bowers, Josselin Gautier, Austin John Roorda; Fixational Eye Movements depend on Fixation Task. Invest. Ophthalmol. Vis. Sci. 2021;62(8):507.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Even when fixating on a stationary target, the eye is in constant motion. These fixational eye movements (FEM) consist primarily of drifts (slow, random-walk-like movements) and microsaccades (fast, ballistic movements). Understanding these movements is important for two reasons (i) determining their role in normal vision and (ii) to learn optimal strategies for maintaining stable fixation for imaging and/or vision testing. Here we compare FEMs during active and passive fixation tasks. Five fixation targets were selected: Maltese cross, Annular disk, Dynamic concentric circles, a two-bar Vernier target, and an E-letter. The Maltese cross and disk targets were stationary (passive) while the Vernier and E-letter targets varied in presentation and time, requiring subject response (active). The concentric circle target was an attention-grabbing task with continual inward moving rings but required no subject response.

Methods : An Adaptive Optics Scanning Laser Ophthalmoscope system (AOSLO) was used to present the fixation target and to collect retinal videos for subsequent retrieval of eye motion and fixated image position on the retina. This instrument provides high spatial (~ 0.1 arcmin) and temporal (960Hz) resolution. Data was collected on 8 subjects with normal. Five 30-second videos of the fixated target moving on the retina were collected for each condition. FEMs were extracted from the videos and analyzed using custom software. Saccades and drifts were automatically marked and any missed or mislabelled saccades were manually amended.

Results : Important differences between passive and active fixation targets were observed. FEMs were overall larger for active tasks, marked with larger saccades but lower saccade rate, larger and longer drifts, and a larger ISOA. Conversely, passive tasks had smaller FEMs, with more saccades and faster/shorter/smaller drifts. Furthermore, each subject consistently used the same preferred retinal locus for all targets.

Conclusions : The lower saccade rate for active tasks suggests saccadic suppression. This suppression, in turn, leads to longer drift segments, larger saccade magnitudes and an overall larger distribution (ISOA) for fixation. Passive fixation targets (eg Maltese cross or disk) are recommended if minimal FEMs are desired. This study emphasizes that the choice of fixation target is important when studying the fine structure and functional role of eye movements for human vision.

This is a 2021 ARVO Annual Meeting abstract.

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