June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Oriented blur biases the perceived direction of motion
Author Affiliations & Notes
  • Cherlyn J Ng
    College of Optometry, University of Houston System, Houston, Texas, United States
  • Duje Tadin
    Brain and Cognitive Sciences, University of Rochester, Rochester, New York, United States
  • Randolph Blake
    Department of Psychology, Vanderbilt University, Nashville, Tennessee, United States
  • Martin S Banks
    School of Optometry, University of California Berkeley, Berkeley, California, United States
  • Geunyoung Yoon
    College of Optometry, University of Houston System, Houston, Texas, United States
  • Footnotes
    Commercial Relationships   Cherlyn Ng None; Duje Tadin None; Randolph Blake None; Martin Banks None; Geunyoung Yoon None
  • Footnotes
    Support  NIH Grant EY014999
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 2884. doi:
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    • Get Citation

      Cherlyn J Ng, Duje Tadin, Randolph Blake, Martin S Banks, Geunyoung Yoon; Oriented blur biases the perceived direction of motion. Invest. Ophthalmol. Vis. Sci. 2023;64(8):2884.

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

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Abstract

Purpose : Astigmatism is a common ocular problem that causes axial blur. Here, we study the effect of astigmatism on motion perception, a routine visual function that is seldom measured in the clinic. The hypothesis is that oriented blur may provide a non-directional signal that can be misinterpreted as motion streaks and bias the perceived direction.

Methods : Astigmatism was temporarily and artificially induced in four adult subjects between 28 and 40yo whose pupil sizes were restricted to 3mm. The manipulation resulted in 1.25D cylindrical power at either 45° or 135° blur orientation in the right eye. Motion perception was monocularly tested with random dot kinematograms (RDKs) presented for 500ms in a 3° diameter circular window at a density of 100 dots/deg2. Dots moved at either of three speeds (2, 7 or 18deg/s). In the unambiguous condition, 80% dots moved coherently. Only 5% were coherent in the ambiguous condition. Subjects turned a dial to report the perceived coherent direction that was randomly presented with equal probabilities in steps of 45°.

Results : In the unambiguously coherent RDK (e.g. 80% coherent, 2 deg/s), motion along the blur and orthogonal axes was reported with similar probabilities (27.3 and 22.6%, pooled from all subjects). However, perceived direction was biased towards the blurry axis when coherent motion was not readily perceivable. This happened at higher speeds and low (5%) coherence. 42.8% of all trials were reported to move along the blurry axis at 7deg/s as compared to 14.0% in the orthogonal. The effect was more pronounced with the fastest moving dots (18deg/s) where 70.0% of the motion was reported to be in the direction along the blurry axis. There were no reports of perceived movement along the orthogonal axis. Motion was also biased towards the blur axis when the fastest dots were presented at 80% coherence level (49.6 vs 17.4%). Such biases were minimal without oriented blur (25 vs 16.7%; 19.6 vs 21.1%; 21.7 vs 18.8% respectively).

Conclusions : Astigmatism could bias perceived motion at fast speeds. A possible reason may be that the visual system mistakes oriented blur for motion streaks. This finding may lend reasons to why uncorrected astigmats have problems with motion related activities such as nighttime driving.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

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