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Wolf C, Belopolsky AV, Lappe M. Current foveal inspection and previous peripheral preview influence subsequent eye movement decisions. iScience 2022; 25:104922. [PMID: 36060066 PMCID: PMC9429799 DOI: 10.1016/j.isci.2022.104922] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 06/20/2022] [Accepted: 08/09/2022] [Indexed: 11/25/2022] Open
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Mestre C, Bedell HE, Díaz-Doutón F, Pujol J, Gautier J. Characteristics of saccades during the near point of convergence test. Vision Res 2021; 187:27-40. [PMID: 34147850 DOI: 10.1016/j.visres.2021.06.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 06/04/2021] [Accepted: 06/04/2021] [Indexed: 10/21/2022]
Abstract
The near point of convergence test is widely used to evaluate binocular vision. It assesses the ability of the eyes to converge at short distances. Although the test consists of a pure symmetrical vergence task, small involuntary saccades occur concurrently. The main goal of this study was to analyze saccadic characteristics as a function of vergence demand when testing the near point of convergence. To this purpose, the eye movements of 11 participants were registered with an eye-tracker while they performed the near point of convergence test by following a target that traveled forward and backward on a motorized bench. Saccade amplitude increased and, on average, saccade rate decreased with vergence demand. In general, the direction of the concurrent vergence movement had no significant effect on saccade characteristics. However, each individual subject showed idiosyncratic behavior. Most saccades tended to be corrective in terms of both binocular disparity and individual fixation position errors. In particular, most participants tended to correct the fixation position error of the dominant eye.
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Affiliation(s)
- Clara Mestre
- Centre for Sensors, Instruments and Systems Development (CD6), Universitat Politècnica de Catalunya, Rambla Sant Nebridi, 10, 08222 Terrassa, Barcelona, Spain.
| | - Harold E Bedell
- College of Optometry, University of Houston, 4800 Calhoun Rd, Houston, TX 77004, USA
| | - Fernando Díaz-Doutón
- Centre for Sensors, Instruments and Systems Development (CD6), Universitat Politècnica de Catalunya, Rambla Sant Nebridi, 10, 08222 Terrassa, Barcelona, Spain
| | - Jaume Pujol
- Centre for Sensors, Instruments and Systems Development (CD6), Universitat Politècnica de Catalunya, Rambla Sant Nebridi, 10, 08222 Terrassa, Barcelona, Spain
| | - Josselin Gautier
- School of Optometry, University of California, 380 Minor Ln, Berkeley, CA 94720, USA
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Abstract
Due to its reported high sampling frequency and precision, the Tobii Pro Spectrum is of potential interest to researchers who want to study small eye movements during fixation. We test how suitable the Tobii Pro Spectrum is for research on microsaccades by computing data-quality measures and common properties of microsaccades and comparing these to the currently most used system in this field: the EyeLink 1000 Plus. Results show that the EyeLink data provide higher RMS precision and microsaccade rates compared with data acquired with the Tobii Pro Spectrum. However, both systems provide microsaccades with similar directions and shapes, as well as rates consistent with previous literature. Data acquired at 1200 Hz with the Tobii Pro Spectrum provide results that are more similar to the EyeLink, compared to data acquired at 600 Hz. We conclude that the Tobii Pro Spectrum is a useful tool for researchers investigating microsaccades.
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4
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Abstract
Eye trackers are sometimes used to study the miniature eye movements such as drift that occur while observers fixate a static location on a screen. Specifically, analysis of such eye-tracking data can be performed by examining the temporal spectrum composition of the recorded gaze position signal, allowing to assess its color. However, not only rotations of the eyeball but also filters in the eye tracker may affect the signal’s spectral color. Here, we therefore ask whether colored, as opposed to white, signal dynamics in eye-tracking recordings reflect fixational eye movements, or whether they are instead largely due to filters. We recorded gaze position data with five eye trackers from four pairs of human eyes performing fixation sequences, and also from artificial eyes. We examined the spectral color of the gaze position signals produced by the eye trackers, both with their filters switched on, and for unfiltered data. We found that while filtered data recorded from both human and artificial eyes were colored for all eye trackers, for most eye trackers the signal was white when examining both unfiltered human and unfiltered artificial eye data. These results suggest that color in the eye-movement recordings was due to filters for all eye trackers except the most precise eye tracker where it may partly reflect fixational eye movements. As such, researchers studying fixational eye movements should be careful to examine the properties of the filters in their eye tracker to ensure they are studying eyeball rotation and not filter properties.
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Abstract
Despite recent advances on the mechanisms and purposes of fine oculomotor behavior, a rigorous assessment of the precision and accuracy of the smallest saccades is still lacking. Yet knowledge of how effectively these movements shift gaze is necessary for understanding their functions and is helpful in further elucidating their motor underpinnings. Using a combination of high-resolution eye-tracking and gaze-contingent control, here we examined the accuracy and precision of saccades aimed toward targets ranging from [Formula: see text] to [Formula: see text] eccentricity. We show that even small saccades of just 14-[Formula: see text] are very effective in centering the stimulus on the retina. Furthermore, we show that for a target at any given eccentricity, the probability of eliciting a saccade depends on its efficacy in reducing the foveal offset. The pattern of results reported here is consistent with current knowledge on the motor mechanisms of microsaccade production.
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Affiliation(s)
- Martina Poletti
- Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY, 14627, USA.
- Department of Neuroscience, University of Rochester, Rochester, NY, 14627, USA.
- Center for Visual Science, University of Rochester, Rochester, NY, 14627, USA.
| | - Janis Intoy
- Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY, 14627, USA
- Center for Visual Science, University of Rochester, Rochester, NY, 14627, USA
- Graduate Program for Neuroscience, Boston University, Boston, MA, 02215, USA
| | - Michele Rucci
- Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY, 14627, USA
- Center for Visual Science, University of Rochester, Rochester, NY, 14627, USA
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Essig P, Leube A, Rifai K, Wahl S. Microsaccadic rate signatures correlate under monocular and binocular stimulation conditions. J Eye Mov Res 2020; 11. [PMID: 33828709 PMCID: PMC8008506 DOI: 10.16910/jemr.13.5.3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Microsaccades are involuntary eye movements occurring naturally during fixation. In this
study, microsaccades were investigated under monocularly and binocularly stimulated
conditions with respect to their directional distribution and rate signature, that refers to a
curve reporting the frequency modulation of microsaccades over time. For monocular
stimulation the left eye was covered by an infrared filter. In both stimulation conditions,
participants fixated a Gabor patch presented randomly in orientation of 45° or 135° over a
wide range of spatial frequencies appearing in the center of a monitor. Considering the
microsaccadic directions, this study showed microsaccades to be preferably horizontally
oriented in their mean direction, regardless of the spatial characteristics of the grating.
Furthermore, this outcome was found to be consistent between both stimulation conditions.
Moreover, this study found that the microsaccadic rate signature curve correlates between
both stimulation conditions, while the curve given for binocular stimulation was already
proposed as a tool for estimation of visual performance in the past. Therefore, this study extends the applicability of microsaccades to clinical use, since
parameters as contrast sensitivity, has been measured monocularly in the clinical attitude.
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Affiliation(s)
- Peter Essig
- Institute for Ophthalmic Research, Eberhard Karls University Tuebingen, Germany
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Hauperich AK, Young LK, Smithson HE. What makes a microsaccade? A review of 70 years of research prompts a new detection method. J Eye Mov Res 2020; 12. [PMID: 33828754 PMCID: PMC7962681 DOI: 10.16910/jemr.12.6.13] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
A new method for detecting microsaccades in eye-movement data is presented, following a review of reported microsaccade properties between the 1940s and today. The review focuses on the parameter ranges within which certain physical markers of microsaccades are thought to occur, as well as any features of microsaccades that have been stably reported over time. One feature of microsaccades, their binocularity, drives the new microsaccade detection method. The binocular correlation method for microsaccade detection is validated on two datasets of binocular eye-movements recorded using video-based systems: one collected as part of this study, and one from Nyström et al, 2017. Comparisons between detection methods are made using precision-recall statistics. This confirms that the binocular correlation method performs well when compared to manual coders and performs favourably compared to the commonly used Engbert & Kliegl (2003) method with subsequent modifications (Engbert & Mergenthaler, 2006). The binocular correlation microsaccade detection method is easy to implement and MATLAB code is made available to download.
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Perquin MN, Bompas A. Reliability and correlates of intraindividual variability in the oculomotor system. J Eye Mov Res 2019; 12:10.16910/jemr.12.6.11. [PMID: 33828751 PMCID: PMC7962678 DOI: 10.16910/jemr.12.6.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Even if all external circumstances are kept equal, the oculomotor system shows intraindividual variability over time, affecting measures such as microsaccade rate, blink rate, pupil size, and gaze position. Recently, some of these measures have been associated with ADHD on a between-subject level. However, it remains unclear to what extent these measures constitute stable individual traits. In the current study, we investigate the intraindividual reliability of these oculomotor features. Combining results over three experiments (> 100 healthy participants), we find that most measures show good intra-individual reliability over different time points (repeatability) as well as over different conditions (generalisation). However, we find evidence against any correlation with self-assessed ADHD tendencies, mind wandering, and impulsivity. As such, the oculomotor system shows reliable intra-individual reliability, but its benefit for investigating self-assessed individual differences in healthy subjects remains unclear. With our results, we highlight the importance of reliability and statistical power when studying between-subject differences.
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Abstract
The inability of current video-based eye trackers to reliably detect very small eye movements has led to confusion about the prevalence or even the existence of monocular microsaccades (small, rapid eye movements that occur in only one eye at a time). As current methods often rely on precisely localizing the pupil and/or corneal reflection on successive frames, current microsaccade-detection algorithms often suffer from signal artifacts and a low signal-to-noise ratio. We describe a new video-based eye tracking methodology which can reliably detect small eye movements over 0.2 degrees (12 arcmins) with very high confidence. Our method tracks the motion of iris features to estimate velocity rather than position, yielding a better record of microsaccades. We provide a more robust, detailed record of miniature eye movements by relying on more stable, higher-order features (such as local features of iris texture) instead of lower-order features (such as pupil center and corneal reflection), which are sensitive to noise and drift.
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Affiliation(s)
- Aayush K Chaudhary
- Carlson Center for Imaging Science, Rochester Institute of Technology, NY, USA
| | - Jeff B Pelz
- Carlson Center for Imaging Science, Rochester Institute of Technology, NY, USA
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Hooge ITC, Hessels RS, Nyström M. Do pupil-based binocular video eye trackers reliably measure vergence? Vision Res 2019; 156:1-9. [PMID: 30641092 DOI: 10.1016/j.visres.2019.01.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 12/19/2018] [Accepted: 01/05/2019] [Indexed: 10/27/2022]
Abstract
A binocular eye tracker needs to be accurate to enable the determination of vergence, distance to the binocular fixation point and fixation disparity. These measures are useful in e.g. the research fields of visual perception, binocular control in reading and attention in 3D. Are binocular pupil-based video eye trackers accurate enough to produce meaningful binocular measures? Recent research revealed potentially large idiosyncratic systematic errors due to pupil-size changes. With a top of the line eye tracker (SR Research EyeLink 1000 plus), we investigated whether the pupil-size artefact in the separate eyes may cause the eye tracker to report apparent vergence when the eyeballs do not rotate. Participants were asked to fixate a target at a distance of 77 cm for 160 s. We evoked pupil-size changes by varying the light intensity. With increasing pupil size, horizontal vergence reported by the eye tracker decreased in most subjects, up to two degrees. However, this was not due to a rotation of the eyeballs, as identified from the absence of systematic movement in the corneal reflection (CR) signals. From this, we conclude that binocular pupil-CR or pupil-only video eye trackers using the dark pupil technique are not accurate enough to be used to determine vergence, distance to the binocular fixation point and fixation disparity.
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Affiliation(s)
- Ignace T C Hooge
- Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, the Netherlands.
| | - Roy S Hessels
- Experimental Psychology, Helmholtz Institute, and Developmental Psychology, Utrecht University, Utrecht, the Netherlands
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11
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Abstract
Small saccades, known as microsaccades, occur frequently during fixation. Several recent studies have argued that a considerable fraction of these movements are present in the traces from one eye only. This claim contrasts with the findings of older reports, which concluded that microsaccades, like larger saccades, are virtually always binocular events. Here we examined the characteristics of small saccades by means of two of the most established high-resolution eye-tracking techniques available. A binocular Dual Purkinje Image eye-tracker was used to record eye movements while observers fixated, with their head immobilized, on markers displayed on a monitor. A specially designed eye-coil system was used to measure eye movements during normal head-free viewing, while subjects fixated on markers at various distances. Monocular microsaccades were virtually absent in both datasets. In the head-fixed data, not a single monocular microsaccade was observed. In the head-free data, only one event appeared to be monocular out of more than a thousand saccades. Monocular microsaccades do not seem to occur during normal head-free or head-immobilized fixation.
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Affiliation(s)
- Yu Fang
- Department of Psychological & Brain Sciences, Boston University, Boston, MA, USA
| | - Christopher Gill
- Department of Psychological & Brain Sciences, Boston University, Boston, MA, USA
| | - Martina Poletti
- Department of Neuroscience, University of Rochester, Rochester, NY, USA.,Center for Visual Science, University of Rochester, Rochester, NY, USA
| | - Michele Rucci
- Center for Visual Science, University of Rochester, Rochester, NY, USA.,Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY, USA
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