Journal of Eye Movement Research

3 pages, 138 KiB

Open AccessArticle

Vergence Eye Movements: From Basic Science to Clinical Application—Foreword to the Special Issue

by Wolfgang Jaschinski and Rudolf Groner

J. Eye Mov. Res. 2019, 12(4), 1-3; https://doi.org/10.16910/jemr.12.4.0 - 11 Mar 2020

Cited by 1 | Viewed by 73

The abstract book of the last European Conference on Eye Movements [1] lists abstracts of 373 presentations, but less than five percent investigate vergence eye movements, i.e., the coordination of the right and left eye. Why then a special issue on this neglected [...] Read more.

The abstract book of the last European Conference on Eye Movements [1] lists abstracts of 373 presentations, but less than five percent investigate vergence eye movements, i.e., the coordination of the right and left eye. Why then a special issue on this neglected issue? Human vision under natural conditions involves both eyes in coordination controlled by interacting processes subsumed under the concept of vergence. Further, vergence is important for people in their daily lives since disorders of vergence can have serious consequences: ophthalmologists deal with squinting patients on the basis of heterophoria and heterotropia testing, eye strain or visual complaints can be related to impaired vergence dynamic or less accurate static vergence, remediation by optometrist includes vergence training or prism eye glasses, etc. Full article

10 pages, 451 KiB

Open AccessArticle

The Influence of Vergence Facility on Binocular Eye Movements During Reading

by Remo Poffa and Roland Joos

J. Eye Mov. Res. 2019, 12(4), 1-10; https://doi.org/10.16910/jemr.12.4.9 - 16 Dec 2019

Cited by 3 | Viewed by 50

Abstract

Optometrists regularly use binocular measurements in patients with asthenopic complaints when performing close-up work. The focus of this work was therefore on the correlation of optometric parameters and objective fixation disparity (FD) measured by an eye tracker. In our investigation, 20 participants (6 [...] Read more.

Optometrists regularly use binocular measurements in patients with asthenopic complaints when performing close-up work. The focus of this work was therefore on the correlation of optometric parameters and objective fixation disparity (FD) measured by an eye tracker. In our investigation, 20 participants (6 male, 14 female) were subjected to a classical optometric procedure. Subsequently, these subjects read various sentences on a screen and eye movements were registered by using a RED500 eye tracker. The experiment was performed under two reading distance conditions. In order to be comparable with previous work, the present study was conducted under dark illumination conditions [12]. FD values were deduced from objective eye tracking data during reading. Data analysis was done using linear mixed-effects models. FD was found to depend on vergence facility (t = 3.3, p = 0.004). Subjects with a low vergence facility showed more eso fixation disparity than subjects with a normal vergence facility. If studies of binocular coordination using eye tracking methods are performed under dark illumination conditions, vergence facility is an important parameter and should be accounted for. Neglecting this parameter may mask other important parameters. Vergence facility in context of reading difficulties may be important. Full article

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11 pages, 983 KiB

Open AccessArticle

Effects of Aligning Prisms on the Objective and Subjective Fixation Disparity in Far Distance

by Volkhard Schroth, Roland Joos, Ewald Alshuth and Wolfgang Jaschinski

J. Eye Mov. Res. 2019, 12(4), 1-11; https://doi.org/10.16910/jemr.12.4.8 - 11 Dec 2019

Cited by 3 | Viewed by 60

Abstract

Fixation disparity (FD) refers to a suboptimal condition of binocular vision. The oculomotor aspect of FD refers to a misadjustment in the vergence angle between the two visual axes that is measured in research with eye trackers (objective fixation disparity, oFD). The sensory [...] Read more.

Fixation disparity (FD) refers to a suboptimal condition of binocular vision. The oculomotor aspect of FD refers to a misadjustment in the vergence angle between the two visual axes that is measured in research with eye trackers (objective fixation disparity, oFD). The sensory aspect is psychophysically tested using dichoptic nonius lines (subjective fixation disparity, sFD). Some optometrists use nonius tests to determine the prisms for constant wear aiming to align the eyes. However, they do not (yet) use eye trackers. We investigate the effect of aligning prisms on oFD and sFD for 60 s exposure duration of prisms determined with the clinically established Cross test in far distance vision. Without prisms, both types of FD were correlated with the aligning prism, while with prisms the FD was close to zero (these analyses included all base-in and base-out cases). The effect of base-in prisms on oFD was proportional to the amount of the aligning prism for the present 60 s exposure, similar as for the 2–5 s exposure in Schmid et al. (2018). Thus, within 1 min of prism exposure, no substantial vergence adaptation seems to occur in the present test conditions. Further studies may investigate intra-individual responses to different exposure times of aligning prisms in both prism directions. Full article

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10 pages, 1109 KiB

Open AccessArticle

Binocular Advantages in Reading Revisited: Attenuating Effects of Individual Horizontal Heterophoria

by Stephanie Jainta and Joëlle Joss

J. Eye Mov. Res. 2019, 12(4), 1-10; https://doi.org/10.16910/jemr.12.4.10 - 9 Dec 2019

Cited by 5 | Viewed by 51

Abstract

Reading with two eyes necessitates efficient processes of binocular vision, which provide a single percept of the text. These processes come with a binocular advantage: binocular reading shows shorter average fixation durations and sentence reading times when compared to monocular reading. A couple [...] Read more.

Reading with two eyes necessitates efficient processes of binocular vision, which provide a single percept of the text. These processes come with a binocular advantage: binocular reading shows shorter average fixation durations and sentence reading times when compared to monocular reading. A couple of years ago, we showed for a small sample (N = 13) that binocular advantages critically relate to the individual heterophoria (the resting state of vergence). In the present, large-scale replication we collected binocular eye movements (Eyelink II) for 94 participants who read 20 sentences monocularly and 20 sentences binocularly. Further, individual heterophorias were determined using three different optometric standards: objective eye tracking (EyeLink II at 60 cm), Maddox wing test (at 30 cm) and measures following the “Guidelines for the application of the Measuring and Correcting Methodology after H.-J. Haase” (MCH; at 6 m). Binocular eye movements showed typical pattern and we replicated (1) binocular advantages of about 25 ms for average fixation durations and (2) a reduction in binocular advantages when heterophoria increased – but only when heterophoria was identified by EyeLink II or Maddox wing measures; MCH measures of heterophoria did not affect binocular advantages in reading. For large heterophorias binocular reading even turned into a disadvantage. Implications for effect estimations and optometric testing will be discussed. Full article

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11 pages, 1218 KiB

Open AccessArticle

Dynamics of the Disparity Vergence Slow (Fusion Sustaining) Component

by John L. Semmlow, Chang Yaramothu and Tara L. Alvarez

J. Eye Mov. Res. 2019, 12(4), 1-11; https://doi.org/10.16910/jemr.12.4.11 - 4 Dec 2019

Cited by 7 | Viewed by 40

Abstract

The stereotypical vergence response to a step stimulus consists of two dynamic components: a high velocity fusion initiating component followed by a slower component that may mediate sustained fusion. The initial component has been well-studied and is thought to be controlled by an [...] Read more.

The stereotypical vergence response to a step stimulus consists of two dynamic components: a high velocity fusion initiating component followed by a slower component that may mediate sustained fusion. The initial component has been well-studied and is thought to be controlled by an open-loop mechanism. Less is known about the slow, or fusion sustaining component except that it must be feedback controlled to achieve the positional precision of sustained fusion. Given the delays in disparity vergence control, a feedback control system is likely to exhibit oscillatory behavior. Vergence responses to 4 deg step changes in target position were recorded in eight subjects. The slow component of each response was isolated manually using interactive graphics and the frequency spectrum determined. The frequency spectra of all isolated slow vergence movements showed a large low frequency peak between 1.0 and 2.0 Hz and one or more higher frequency components. The higher frequency components were found to be harmonics of the low frequency oscillation. A feedback model of the slow component was developed consisting of a time delay, an integral/derivative controller and an oculomotor plant based on Robinson’s model. Model simulations showed that a direction dependent asymmetry in the derivative element was primarily responsible for the higher frequency harmonic components. Simulations also showed that the base frequencies are primarily dependent on the time delay in the feedback control system. The fact that oscillatory behavior was found in all subjects provides strong support that the slow, fusion sustaining component is mediated by a feedback system. Full article

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10 pages, 398 KiB

Open AccessArticle

Changes in the Disparity Vergence Main Sequence After Treatment of Symptomatic Convergence Insufficiency in Children

by Mitchell Scheiman, Chang Yaramothu and Tara L. Alvarez

J. Eye Mov. Res. 2019, 12(4), 1-10; https://doi.org/10.16910/jemr.12.4.6 - 4 Dec 2019

Cited by 3 | Viewed by 42

Abstract

This study investigates the underlying physiological mechanisms that may lead to improved outcomes for symptomatic convergence insufficiency (CI) patients after 12 weeks of office-based vergence/accommodation therapy (OBVAT) by evaluating the change in the main sequence of vergence and saccadic eye movements. In this [...] Read more.

This study investigates the underlying physiological mechanisms that may lead to improved outcomes for symptomatic convergence insufficiency (CI) patients after 12 weeks of office-based vergence/accommodation therapy (OBVAT) by evaluating the change in the main sequence of vergence and saccadic eye movements. In this prospective trial, 12 participants with symptomatic CI were recruited and treated with 12 weeks of OBVAT. Outcome measures included the objective assessment of the following: peak velocity, time to peak velocity, latency, response amplitude, and clinical changes in the near point of convergence (NPC), positive fusional vergence (PFV) and symptoms via the Convergence Insufficiency Symptom Survey (CISS). Ten of the twelve participants (83%) were categorized as “successful” and two were “improved” based on pre-determined published criteria (CISS, NPC, PFV). There were statistically significant changes in peak velocity, time to peak velocity, and response amplitude for both 4° and 6° symmetrical convergence and divergence eye movements. There was a significant change in the main sequence ratio for convergence post-OBVAT compared to baseline measurements (p = 0.007) but not for divergence or saccadic responses. Phasic/step vergence movements adjust the underlying neural control of convergence and are critical within a vision therapy program for CI patients. Full article

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9 pages, 678 KiB

Open AccessArticle

Target Eccentricity and Form Influences Disparity Vergence Eye Movements Responses: A Temporal and Dynamic Analysis

by Chang Yaramothu, Rajbir S. Jaswal and Tara L. Alvarez

J. Eye Mov. Res. 2019, 12(4), 1-9; https://doi.org/10.16910/jemr.12.4.7 - 3 Dec 2019

Cited by 3 | Viewed by 50

Abstract

This study sought to investigate whether stimulation to the fovea or the parafovea with different color combinations influenced the temporal and dynamic features of 4° disparity vergence step responses. Twelve unique types of stimuli were displayed within a haploscope presented along the participant’s [...] Read more.

This study sought to investigate whether stimulation to the fovea or the parafovea with different color combinations influenced the temporal and dynamic features of 4° disparity vergence step responses. Twelve unique types of stimuli were displayed within a haploscope presented along the participant’s midsagittal plane. Vergence eye movement responses from fifteen naïve participants were recorded using video-based infrared eye tracking instrumentation. Latency and peak velocity from left and right eye movement responses were quantified. Results show that the type of stimulus projection (foveal versus parafoveal) significantly (p < 0.001) influences the vergence response latency but did not impact peak velocity. Vergence responses to eccentric circles with 6° eccentricity targeting the parafovea resulted in a significantly faster response latency compared to vergence responses to a cross with 2° eccentricity stimuli targeting the fovea. Results have implications for the stimulus design of a variety of applications from virtual reality to vision therapy interventions. Full article

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8 pages, 472 KiB

Open AccessArticle

The Effect of Target Speed and Verbal Instruction on NPC Measures in a Young, Healthy, and Active Population

by Ian McGinnis, Ryan Tierney, Jamie Mansell and Jacqueline Phillips

J. Eye Mov. Res. 2019, 12(4), 1-8; https://doi.org/10.16910/jemr.12.4.5 - 23 Oct 2019

Cited by 1 | Viewed by 42

Abstract

Purpose: Evaluate the effect of target speed and verbal instruction on near point of convergence (NPC) measurements in a young, healthy, and active population. Methods: NPC was measured in 20 individuals with three target speeds and two sets of verbal instruction. The [...] Read more.

Purpose: Evaluate the effect of target speed and verbal instruction on near point of convergence (NPC) measurements in a young, healthy, and active population. Methods: NPC was measured in 20 individuals with three target speeds and two sets of verbal instruction. The target speeds used were 1 cm/s, 3 cm/s, 5 cm/s, and participant self-paced. The verbal instruction given was either to indicate when the target became “double” or “blurry”. Results: Paired-samples t-tests revealed significant differences between 5 cm/s (5.44 ± 2.01) and 1 cm/s (6.72 ± 2.39, p = 0.003), 3 cm/s (6.10 ± 2.36, p = 0.030) and self-paced (6.63 ± 2.26, p = 0.005). A significant difference (p < 0.001) was also found between the “double” (6.72 ± 2.39) and “blurry” (10.82 ± 3.08) conditions. Conclusions: For young, healthy and active individuals, target speed and verbal instruction matter when measuring NPC. Full article

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15 pages, 6748 KiB

Open AccessArticle

Influence of Artificially Generated Interocular Blur Difference on Fusion Stability Under Vergence Stress

by Miroslav Dostalek, Jan Hejda, Karel Fliegel, Michaela Duchackova, Ladislav Dusek, Jiri Hozman, Tomas Lukes and Rudolf Autrata

J. Eye Mov. Res. 2019, 12(4), 1-15; https://doi.org/10.16910/jemr.12.4.4 - 11 Sep 2019

Cited by 2 | Viewed by 59

Abstract

The stability of fusion was evaluated by its breakage when interocular blur differences were presented under vergence demand to healthy subjects. We presumed that these blur differences cause suppression of the more blurred image (interocular blur suppression, IOBS), disrupt binocular fusion and suppressed [...] Read more.

The stability of fusion was evaluated by its breakage when interocular blur differences were presented under vergence demand to healthy subjects. We presumed that these blur differences cause suppression of the more blurred image (interocular blur suppression, IOBS), disrupt binocular fusion and suppressed eye leaves its forced vergent position. During dichoptic presentation of static grayscale images of natural scenes, the luminance contrast (mode B) or higher-spatial frequency content (mode C) or luminance contrast plus higher-spatial frequency content (mode A) were stepwise reduced in the image presented to the non-dominant eye. We studied the effect of these types of blur on fusion stability at various levels of the vergence demand. During the divergence demand, the fusion was disrupted with approximately half blur than during convergence. Various modes of blur influenced fusion differently. The mode C (isolated reduction of higher-spatial frequency content) violated fusion under the lowest vergence demand significantly more than either isolated or combined reduction of luminance contrast (mode B and A). According to our results, the image's details (i.e., higher-spatial frequency content) protects binocular fusion from disruption by the lowest vergence demand. Full article

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27 pages, 755 KiB

Open AccessArticle

The Mean Point of Vergence Is Biased Under Projection

by Xi Wang, Kenneth Holmqvist and Marc Alexa

J. Eye Mov. Res. 2019, 12(4), 1-27; https://doi.org/10.16910/jemr.12.4.2 - 9 Sep 2019

Cited by 9 | Viewed by 48

Abstract

The point of interest in three-dimensional space in eye tracking is often computed based on intersecting the lines of sight with geometry, or finding the point closest to the two lines of sight. We first start by theoretical analysis with synthetic simulations. We [...] Read more.

The point of interest in three-dimensional space in eye tracking is often computed based on intersecting the lines of sight with geometry, or finding the point closest to the two lines of sight. We first start by theoretical analysis with synthetic simulations. We show that the mean point of vergence is generally biased for centrally symmetric errors and that the bias depends on the horizontal vs. vertical noise distribution of the tracked eye positions. Our analysis continues with an evaluation on real experimental data. The estimated mean vergence points seem to contain different errors among individuals but they generally show the same bias towards the observer. And it tends to be larger with an increased viewing distance. We also provided a recipe to minimize the bias, which applies to general computations of gaze estimation under projection. These findings not only have implications for choosing the calibration method in eye tracking experiments and interpreting the observed eye movements data; but also suggest to us that we shall consider the mathematical models of calibration as part of the experiment. Full article

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13 pages, 1068 KiB

Open AccessArticle

Variance Components Affecting the Repeatability of the Alternating Cover Test

by Marius M. Paulus, Andreas Straube and Thomas Eggert

J. Eye Mov. Res. 2019, 12(4), 1-13; https://doi.org/10.16910/jemr.12.4.3 - 28 Aug 2019

Cited by 1 | Viewed by 43

Abstract

In within-subject and within-examiner repeated measures designs, measures of heterophoria with the manual prism cover test achieve standard deviations between 0.5 and 0.8 deg. We addressed the question how this total noise is composed of variable errors related to the examiner (measurement noise), [...] Read more.

In within-subject and within-examiner repeated measures designs, measures of heterophoria with the manual prism cover test achieve standard deviations between 0.5 and 0.8 deg. We addressed the question how this total noise is composed of variable errors related to the examiner (measurement noise), to the size of the heterophoria (heterophoria noise), and to the availability of sensory vergence cues (stimulus noise). We developed an automated alternating cover test (based on a combination of VOG and shutter glasses) which minimizes stimulus noise and has a defined measurement noise (sd = 0.06 deg). In a within-subject design, 19 measures were taken within 1.5 min and multiple such blocks were repeated either across days or across 45 min. Blocks were separated by periods of binocular viewing. The standard deviation of the heterophoria across blocks from different days or from the same day (sd = 0.33 deg) was 6 times larger than expected based on the standard deviation within the block. The results show that about 42% of the inter-block variance with the manual prism cover test was related to variability of the heterophoria and not to measurement noise or stimulus noise. The heterophoria noise across blocks was predominantly induced during the intermediate binocular viewing periods. Full article

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J. Eye Mov. Res., Volume 12, Issue 4 (October 2019) – 11 articles

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