The protocol was conducted at the Laboratory of Brain Imaging at the Nencki Institute of Experimental Biology, Warsaw, Poland and was supported by a grant 2018/29/B/NZ4/02435 from the National Science Centre (Poland) awarded to K.B and J.S.

All procedures were performed following the relevant guidelines and regulations and were approved by the Ethical Committee, WUM (KB/157/2017). Written consent was obtained from all participants, ensuring that they understood the general aim of the experiment and that they understood the inclusion of their data for statistical analysis purposes. All presented visual stimuli are generated using a Java-based desktop application (Viscacha2) created for the purpose of these experiments.&#160;
1. Setup
<ol>
	<li>Secure a quiet, dimmed room. Build a setup consisting of a computer, a keyboard, a flat display, an eye tracker (optional, depending on the research question and aims; see Table of Materials), a desk, a chinrest, and a chair. Arrange it so that the participants can sit with the chin resting on the chinrest, eyes directly in front of the center of the upper half of the display, and hands reaching the arrow keys on the keyboard. The horizontal distance between the display and the eyes should be 85 cm. 
	NOTE: Although the participants are trained and specifically asked to fixate the central fixation cross during the entire procedure, testing with an eye tracker may constitute an additional control for filtering during analyses of those participants who exhibit too many fluctuations with their gaze. Moreover, depending on the aim of the study, eye tracker results may provide interesting insight into the fixation patterns, pupil size, or location of interest of different cohorts of participants.&#160;</li>
	<li>Visit https://github.com/grimwj/Viscacha2 and download the software by clicking the Code button and downloading ZIP. Extract the zip file and save it in the working directory.</li>
	<li>Follow the installation steps described in the README.txt file. In case of testing with an eye tracker, follow the software installation steps for the eye tracker. Mount the eye tracker as per instruction.</li>
	<li>To perform an initial check, run the program by double-clicking the Viscacha2.jar file. After the initial screen is displayed, press ESC on the keyboard to exit the program.</li>
	<li>Navigate through newly created folders &#8211; experiment_data, TestPatient, Shape_Brt. Open the .csv file using a spreadsheet editor (set semicolon as field separator). Verify that the parameters, such as screen dimensions and the distance from the screen, are correct. 
	NOTE: From here, the protocol is based on the assumption that a 1920 x 1080, 31.5 inch display is used and the distance between the patient and the screen is 85 cm. This implies that the screen occupies 44.6&#176; of visual space horizontally. If these parameters cannot be met, one can refer to step 5 for reconfiguring the program.</li>
</ol>
2. Determining the initial difficulty of the test
<ol>
	<li>Open the config.txt file and find a line containing patient_name=TestPatient. Replace the TestPatient with a text identifying the subject being examined.</li>
	<li>In the config.txt file, find the line filename=Shape_Brt.txt. Make sure that this line does not begin with a hash symbol # (uncommented line).&#160;</li>
	<li>Ask the subject to sit in front of the display, with his/her chin rested and eyes directly in front of the center of the upper half of the display. Verify that the distance from the screen is correct. Make sure that the keyboard keys are easily accessible for the subject to use.&#160;</li>
	<li>Navigate to the Viscacha2.jar directory and run the program. Teach the participant to focus the sight on the fixation cross at the center of the screen for the entire duration of the experiment.&#160;&#160;</li>
	<li>On each side of the screen, either a circle or an ellipse will be presented at the same distance from the central fixation cross. The task is to select the circle over an ellipse using the left and right arrow keys on the keyboard. Explain the task to the participant, and when he/she is ready, press the s key to begin the experiment. The experiment continues till the participant presses one of the arrow keys.&#160;</li>
	<li>The program ends&#160;after four reversals have occurred or a maximum number of trials has been reached. A reversal occurs when the subject selects the wrong response after previously selecting the correct one or vice versa. 
	NOTE: This is a staircase-type procedure. The difficulty of each trial increases after each correct response and decreases after a wrong response. Figure 1 displays how the staircase level changes over trials for one representative participant.&#160;&#160;&#160;</li>
	<li>Note the four reversals after which the task is finished and the detection threshold has been established. Open the corresponding .csv file containing results. Locate the THRESHOLD columns near the end of the file. Use the value in this column to calculate the initial difficulty for subsequent tasks.&#160; 
	NOTE: The test can also be presented in a constant paradigm, where the level of the difficulty is fixed and does not change, by removing the hash symbol from the Experiment_Type=Constant line in the init.txt files and by adding a hash symbol before the line Experiment_Type=Staircase.&#160;</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/66272/66272fig1.jpg" /> 
Figure 1: Change in the staircase level over the duration of the Shape_Brt experiment (subsequent trials). The red plot depicts the staircase level, which translates to the aspect ratio of the S- (ellipse). After 4 reversals have occurred (blue bars), the subject&#8217;s detection threshold has been established, and the task is finished. <a href="https://www.jove.com/files/ftp_upload/66272/66272fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="8">
	<li>Use the newly obtained threshold as the baseline for the next stimuli presentation (steps 2.3&#8211;2.5). To replace the new threshold in all the stimuli definition files, use the Python script inside the replacer folder and follow the instructions on the screen.&#160;&#160;</li>
</ol>
3. Stimuli procedure
NOTE: A total of 10 experiments will be conducted: 5 with white dots on a black background and 5 with black dots on a white background.
<ol>
	<li>Coherence task
	<ol>
		<li>When the subject is ready, open the config.txt file and comment (i.e., insert the hash symbol) the line filename=Shape_Brt.txt and uncomment the line below, including the shape_dotsB_C.txt task. In this task, the circle and the ellipse consist of dots moving randomly with a velocity of 10&#176;/s. The background is built of dots moving coherently upward with the same velocity as in the circle and ellipse. 
		NOTE: It is possible to define a different movement direction of the background dots by editing the Direction parameter inside the definition file for each task.&#160;&#160;</li>
		<li>Run Viscacha2.jar. Explain the task to the subject in simple words, for example, Please always point to the circle. When the participant is ready, press the s key to begin the experiment. Wait until the experiment is completed.&#160;</li>
		<li>Open the config.txt file, comment the line filename=shape_dotsB_C.txt, and uncomment the line below including the shape_dotsW_C.txt task. Repeat step 3.1.2.&#160;</li>
	</ol>
	</li>
	<li>Direction task&#160;
	<ol>
		<li>&#160;When the subject is ready, open the config.txt file and comment on the previously selected filename. Uncomment the line containing filename=shape_dotsB_D.txt task. In this task, the circle and the ellipse consist of dots moving coherently upward with a velocity of 10&#176;/s. The background consists of dots moving coherently leftward with the same velocity as in the circle and ellipse.&#160;</li>
		<li>Run Viscacha2.jar. Explain the task to the subject. When the participant is ready, press the s key to begin the experiment. Wait until the experiment is completed.&#160;</li>
		<li>Open the config.txt file, comment the line filename=shape_dotsB_D.txt, and uncomment the line below, including the shape_dotsW_D.txt task. Repeat step 3.2.2.&#160;</li>
	</ol>
	</li>
	<li>Velocity task&#160;
	<ol>
		<li>&#160;When the subject is ready, open the config.txt file and comment the previously selected filename. Uncomment the line containing filename=shape_dotsB_V10_20.txt task. This task involves three conditions. The circle and ellipse and the background consist of dots moving coherently upward, and dots within the circle and the ellipse always move slower than the background dots: i) 10&#176;/s versus 20&#176;/s; ii) 5&#176;/s versus 10&#176;/s; and iii) 1&#176;/s versus 2&#176;/s.</li>
		<li>Run Viscacha2.jar. Explain the task to the subject. When the participant is ready, press the s key to begin the experiment. Wait until the experiment is completed.&#160;</li>
		<li>Open the config.txt file and comment on the line shape_dotsB_V10_20.txt and uncomment the line below, including the shape_dotsW_V10_20.txt task. Repeat step 3.2.2.&#160;</li>
		<li>Repeat steps 3.3.1 - 3.3.3 2x, for tasks shape_dotsB_V5_10.txt and shape_dotsW_V5_10.txt, as well as for shape_dotsB_V1_2.txt and shape_dotsW_V1_2.txt.&#160;
		<ol>
			<li>To avoid manually changing the filename for each task after the task is done, use a sweep_file option. In the config.txt file, set the sweep_files field to 0 to end the procedure after each task procedure is over.&#160;&#160;</li>
			<li>Use this setting for the Shape_Brt.txt task to define the initial baseline threshold value. Once the baseline is set, for running multiple tasks in succession, set the sweep file to an integer between 1 and 9. The integer here determines the number of changes between consecutive tasks (e.g., if set to 1 and shape_dotsB_D.txt is uncommented, the program will run this task and the next one. If set to 9, all tasks will be run). Internally, this will result in regenerating a new config file after each experiment is completed, with a previously selected filename commented and the subsequent filename selected for the upcoming experiment.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
4. Goggles limiting vision
<ol>
	<li>To transiently remove the peripheral visual field, use swimming goggles (Figure 2), where transparent lenses are replaced with white opaque ones. The lenses had an aperture of 1.4 mm that limited the visual field to the central 10&#176;. To make the goggles suitable for every subject and to account as best as possible for the natural individual interocular distance, make 14 pairs of goggles with holes spacing from 58 mm to 72 mm (with a step of 1 mm between each pair of goggles).</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/66272/66272fig2.jpg" /> 
Figure 2: Narrowing goggles. The central holes have a diameter of 1.4 mm. We had 14 pairs of goggles with distances between holes of 58 mm to 72 mm. <a href="https://www.jove.com/files/ftp_upload/66272/66272fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Use a ruler to define the distance between the participant&#8217;s eyes. Place the ruler just above the eyes, in line with the eyebrows, with the value 0 on top of one eye. Calculate how far in mm, is the second pupil by checking the value on top of the second eye. During the procedure, ask the participant to maintain the gaze as stable as possible.</li>
	<li>After the more suitable pair has been chosen, give a break of 15 min. During this time, ask the participants to move freely in the room, use their telephone, or read to let the eyes become accustomed to the new visual condition.&#160;</li>
	<li>Start the procedure again from step 3.&#160;&#160;</li>
</ol>
5. Reconfiguration
<ol>
	<li>Screen size and distance calibration
	<ol>
		<li>If a different display is being used, insert the screen dimensions (resolution and diagonal) into the config file (resolution_v for vertical resolution, resolution_h for horizontal resolution, diagonal_inch for the screen diagonal in inches).&#160;</li>
		<li>Run Viscacha2.jar. Once the initial screen displays, press ESC to terminate. Open the .csv file containing the results.&#160;</li>
		<li>Find the line containing Distance mm text and write down the value.&#160;</li>
		<li>Readjust the experimental setup so that the subject can be seated at the newly calculated distance. Calculate the distance so that the screen width occupies 44.6&#176; of visual space horizontally. This is defined by the full_angle_h parameter, which can also be changed in the config.txt file. 
		NOTE: Calibration can be also performed for screen height using the full_angle_v parameter. Please note that only one of these parameters can be set, the other one has to be commented with a # prefix.&#160;&#160;</li>
	</ol>
	</li>
	<li>Stimuli definition&#160;
	<ol>
		<li>Define the stimuli parameters in separate files (e.g., shape_dotsB_C.txt). Some values, such as dimensions of the S- (Ellipse_X, Ellipse_Y) are given in pixels. To calculate from pixels to visual degrees, multiply the value by the Pixel to angle multiplier extracted from the csv file containing results.&#160; 
		NOTE:&#160; Stimuli parameters, such as the coherence of the dots are predefined and adjustable for each layer (background, shape S+, shape S-, noise). In the coherence task, for example, the circle and the ellipse consist of dots moving randomly with a velocity of 10&#176;/s (coherence = 0.0). The background is built of dots moving coherently upward with the same velocity as in the circle and ellipse (coherence = 1.0). Viscacha2 does not have an official user manual as of yet. For further information regarding the stimuli definition refer to the stimuli_description.ods file in the Viscacha2 repository.</li>
	</ol>
	</li>
</ol>

Assessing Vision via Shape Recognition in Random Dot Kinematograms

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The authors have nothing to disclose.

Here, a novel method is described for measuring visual motion acuity using a set of stimuli based on random dot kinematograms. The result is given as a minimal perceived difference between a circle and an ellipse, and it allows one to see when the subject stopped distinguishing shapes from each other. The smaller the difference achieved, the better acuity: it means that the subject can still detect where the circle is, even though it is almost identical to the ellipse. The motion-acuity test presented here brings the res...

<a href="https://app.jove.com/t/6597">This corrects</a> the article <a href="https://dx.doi.org/10.3791/66272">10.3791/66272</a>

An erratum was issued for: <a href="https://www.jove.com/t/66272">Motion-Acuity Test for Visual Field Acuity Measurement with Motion-Defined Shapes</a>. The Authors section was updated.

Erratum: Motion-Acuity Test for Visual Field Acuity Measurement with Motion-Defined Shapes

Most of the available visual tests are directed to examine the features processed by central vision, relying on the input deriving from the central retina1. The central retina has the densest cone-photoreceptor population for maximal visual acuity and lacks rod photoreceptors, which dominate the peripheral retina2. The presence of densely packed photoreceptors is also reflected in an increased density of ganglion cells, which means a greater number of axons are directed to the optic nerve and, eventually, to the visual cortex. Outside the fovea towards the periphery, rods outnumber the cone photoreceptor3. With the rods&#39; wider bodies and the sparser mosaic of photoreceptors, the peripheral retina is primarily responsive to night vision and motion awareness4.
Classically, it was believed that visual processing, depending on stimulation of the central part of the visual field, is devoted to the fine analysis of stationary objects, and its peripheral part is specialized in detecting motion and bringing objects to the central, foveal vision, where it is further analyzed5,6. However, now we have emerging evidence showing that on the cortical level, the fine analysis of the stationary pathway is not fully separated from the motion-sensitive one6,7,8. Testing form and motion perception simultaneously is classically performed using moving gratings9 and glass patterns10 and also concentric rings motion11. Our goal is to introduce a test that is close to the normal life of visually disabled people, which can lower their frustrations and give hope by explicitly showing them that some features of their visual processing might still be preserved and even strengthened. The proposed motion-acuity test based on random dot kinematograms (RDKs) combines motion and shape perception analysis and simultaneously tests the functioning of the motion and shape perception. Within the motion-acuity test, there are many possibilities of psychophysical features to test, such as different velocities, directions, and contrasts of the RDKs. By changing the parameters, we can manipulate the strength of stimulation, either specific for the central processing or peripheral. For example, detecting fast-moving objects is a well-described feature specific to peripheral visual processing12, whereas the processing of the darks on the bright background is preferentially processed by central vision13. This test was initially performed on patients with retinal degeneration of photoreceptors, either specifically located within the central or peripheral retina14. Retinitis pigmentosa (RP) is manifested with peripheral damage and prevails in ~1/5000 patients worldwide15. Stargardt disease (STGD), with a prevalence of ~1/10000, is the most common cause of juvenile macular degeneration (MD)16. Damage to the photoreceptors at the central retina, as in macular degeneration or as in retinitis pigmentosa at the peripheral retina, results in corresponding visual field losses. Those visual field losses are reflected in the impairments of the features specific to the given visual system regions17. Importantly, the regions of the visual system that receive inputs from unaffected parts of the retina are also affected. It was previously shown in animal models of macular degeneration18 that after binocular central retinal damage, not only is acuity aggravated, but motion perception, a feature characteristic of peripheral processing, is reinforced. The motion-acuity testing described here provides an important insight for planning visual rehabilitation procedures. A complete view of the interplay between central and peripheral parts of the visual field has a crucial role in understanding how lost functions might be taken over by the spare parts of the visual system and how this process can be supported by visual training rehabilitation procedures. Inline, the knowledge of how regional retinal degeneration affects visual processing, especially beyond its damaged parts, still remains incomplete. Optical tests are based on the measurements of the stationary shape features. For instance, the visual acuity measurements rely on stationary stimuli, either letters (Snellen charts), grating charts, or vernier acuity charts.
For the purpose of widening the insight into the dynamics between central and peripheral vision in healthy eyes and eyes that have impaired central/peripheral visual functions, a motion-based acuity test measuring the shape and motion perception simultaneously was introduced. The motion-acuity test is based on the detection of centrally located shapes in negative or positive contrast (dark or light dots), an ellipse and circle with matching surfaces, built from random dot kinematograms (RDK) and separated from the same RDK background by velocity, coherence, or direction. Acuity is measured as the minimal difference perceived between circle and ellipse dimensions, and the results are given in visual degrees at which the subject stops to perceive the difference. Additionally, to check if the luminance contrast influences the measured motion acuity, stimuli can be presented in negative (black dots on white background) or in positive contrast (white dots on black background). All the available information about positive contrast (ON type) and negative contrast (OFF type) processing in the visual system comes from the stationary stimulation of the central visual field19,20. But how peripheral processing of motion signals depends on contrast remains fairly unknown14,21. It was only established that sensitivity to high velocities is specific for peripheral processing, whereas central motion processing engages slow velocities at higher spatial frequencies presented in positive contrast (ON type)12. The positive and negative contrast versions of the motion-acuity stimuli, as well as the ability to modify the velocity of dots, as well as the coherence or direction, is crucial for a more detailed description of the full visual field. Additionally, a mechanical narrowing of the visual field to central 10 degrees is proposed using goggles with lenses replaced with opaque ones with centrally located holes. This easily replicable narrowing system, suitable for fMRI and TMS protocols, allows further investigations of the functions of the peripheral visual input and how visual peripheries influence centrally measured acuity. A similar system was initially validated in previous studies14, in which it was found that motion acuity tests in negative contrast and in fast motion, strongly activating visual peripheries, are the most difficult for all participants. For patients with Stargardt disease, they were unmanageable. Importantly, attenuation of visual periphery stimulation, by diminishing the velocity of RDKs, improves acuity thresholds in all tested subjects. In conclusion, we propose the task with motion-acuity measurement based on simple shape discrimination. Therefore, the results are straightforward and easy to understand also for patients and their caregivers. The motion-acuity test presented here is also addressed for users outside academia. The task is easy to explain to a broad range of ages and patient groups.

<table><tbody><tr><td>Chinrest</td><td></td><td></td><td>custom-made</td></tr><tr><td>Computer</td><td></td><td></td><td>Windows 10 or higher</td></tr><tr><td>Display</td><td></td><td></td><td>1920 &amp;times; 1080, 31 inches</td></tr><tr><td>EyeLink 1000 Plus</td><td>SR Research</td><td></td><td>desktop mount</td></tr><tr><td>USB Keyboard</td><td></td><td></td><td></td></tr><tr><td>USB mouse</td><td></td><td></td><td></td></tr></tbody></table>

motion-acuity test for visual field acuity measurement with motion-defined shapes

The standard visual acuity measurements rely on stationary stimuli, either letters (Snellen charts), vertical lines (vernier acuity) or grating charts, processed by those regions of the visual system most sensitive to the stationary stimulation, receiving visual input from the central part of the visual field. Here, an acuity measurement is proposed based on discrimination of simple shapes, that are defined by motion of the dots in the random dot kinematograms (RDK) processed by visual regions sensitive to motion stimulation and receiving input also from the peripheral visual field. In the motion-acuity test, participants are asked to distinguish between a circle and an ellipse, with matching surfaces, built from RDKs, and separated from the background RDK either by coherence, direction, or velocity of dots. The acuity measurement is based on ellipse detection, which with every correct response becomes more circular until reaching the acuity threshold. The motion-acuity test can be presented in negative contrast (black dots on white background) or in positive contrast (white dots on black background). The motion defined shapes are located centrally within 8 visual degrees and are surrounded by RDK background. To test the influence of visual peripheries on centrally measured acuity, a mechanical narrowing of the visual field to 10 degrees is proposed, using opaque goggles with centrally located holes. This easy and replicable narrowing system is suitable for MRI protocols, allowing further investigations of the functions of the peripheral visual input. Here, a simple measurement of shape and motion perception simultaneously is proposed. This straightforward test assesses vision impairments depending on the central and peripheral visual field inputs. The proposed&#160;motion-acuity test advances the capability of standard tests to reveal spare or even strengthened vision functions in patients with injured visual system, that until now remained undetected.

The motion acuity task generates, for each participant, one result file for each stimuli procedure. An exemplary log file for a test participant has been included in the repository inside the doc folder. From row 1 to row 31, various settings are reported, such as the name of the patient and the configuration settings. The task block starts from row 34 and reports important information necessary for further analysis: event time, event type, trial, duration, selection, correct, success, experimenter, external stimuli, rev...

Watch this Scientific Journal Video about Assessment of Visual Acuity in Central Vision Loss Through Motion-Based Peripheral Vision Testing at JoVE.com

Author Spotlight: Assessment of Visual Acuity in Central Vision Loss Through Motion-Based Peripheral Vision Testing

A novel motion-based acuity test that allows the assessment of central and peripheral visual processing in low-vision and healthy individuals, along with goggles limiting peripheral vision compatible with MRI protocols, are described here. This method offers a comprehensive vision assessment for functional impairments and dysfunctions of the visual system.

Motion-Acuity Test for Visual Field Acuity Measurement with Motion-Defined Shapes

The standard visual acuity measurements rely on stationary stimuli, either letters (Snellen charts), vertical lines (vernier acuity) or grating charts, ...

motion-acuity-test-for-visual-field-acuity-measurement-with-motion

Research

JoVE Journal

Neuroscience

482 Views.  Polish Academy of Sciences. A novel motion-based acuity test that allows the assessment of central and peripheral visual processing in low-vision and healthy individuals, along with goggles limiting peripheral vision compatible with MRI protocols, are described here. This method offers a comprehensive vision assessment for functional impairments and dysfunctions of the visual system.

Video: Author Spotlight: Assessment of Visual Acuity in Central Vision Loss Through Motion-Based Peripheral Vision Testing

Methods to Test Visual Attention Online

Online data collection methods have particular appeal to behavioral scientists because they offer the promise of much larger and much more representative data samples than can typically be collected on college campuses. However, before such methods can be widely adopted, a number of technological challenges must be overcome &#8211; in particular in experiments where tight control over stimulus properties is necessary. Here we present methods for collecting performance data on two tests of visual attention. Both tests require control over the visual angle of the stimuli (which in turn requires knowledge of the viewing distance, monitor size, screen resolution, etc.) and the timing of the stimuli (as the tests involve either briefly flashed stimuli or stimuli that move at specific rates). Data collected on these tests from over 1,700 online participants were consistent with data collected in laboratory-based versions of the exact same tests. These results suggest that with proper care, timing/stimulus size dependent tasks can be deployed in web-based settings.

To replicate laboratory settings, online data collection methods for visual tasks require tight control over stimulus presentation. We outline methods for the use of a web application to collect performance data on two tests of visual attention.

Online data collection methods have particular appeal to behavioral scientists because they offer the promise of much larger and much more representative ...

Behavior

A Method to Quantify Visual Information Processing in Children Using Eye Tracking

Visual problems that occur early in life can have major impact on a child's development. Without verbal communication and only based on observational methods, it is difficult to make a quantitative assessment of a child's visual problems. This limits accurate diagnostics in children under the age of 4 years and in children with intellectual disabilities. Here we describe a quantitative method that overcomes these problems. The method uses a remote eye tracker and a four choice preferential looking paradigm to measure eye movement responses to different visual stimuli. The child sits without head support in front of a monitor with integrated infrared cameras. In one of four monitor quadrants a visual stimulus is presented. Each stimulus has a specific visual modality with respect to the background, e.g., form, motion, contrast or color. From the reflexive eye movement responses to these specific visual modalities, output parameters such as reaction times, fixation accuracy and fixation duration are calculated to quantify a child's viewing behavior. With this approach, the quality of visual information processing can be assessed without the use of communication. By comparing results with reference values obtained in typically developing children from 0-12 years, the method provides a characterization of visual information processing in visually impaired children. The quantitative information provided by this method can be advantageous for the field of clinical visual assessment and rehabilitation in multiple ways. The parameter values provide a good basis to: (i) characterize early visual capacities and consequently to enable early interventions; (ii) compare risk groups and follow visual development over time; and (iii), construct an individual visual profile for each child.

A method is described to quantify the quality of visual information processing based on reflexive eye movements in response to specific visual modalities. Reaction times and fixation output parameters are used to characterize visual performance in children with and without visual impairments from 6 months of age.

Visual problems that occur early in life can have major impact on a child's development. Without verbal communication and only based on observational ...

Three Dimensional Vestibular Ocular Reflex Testing Using a Six Degrees of Freedom Motion Platform

The vestibular organ is a sensor that measures angular and linear accelerations with six degrees of freedom (6DF). Complete or partial defects in the vestibular organ results in mild to severe equilibrium problems, such as vertigo, dizziness, oscillopsia, gait unsteadiness nausea and/or vomiting. A good and frequently used measure to quantify gaze stabilization is the gain, which is defined as the magnitude of compensatory eye movements with respect to imposed head movements. To test vestibular function more fully one has to realize that 3D VOR ideally generates compensatory ocular rotations not only with a magnitude (gain) equal and opposite to the head rotation but also about an axis that is co-linear with the head rotation axis (alignment). Abnormal vestibular function thus results in changes in gain and changes in alignment of the 3D VOR response.
Here we describe a method to measure 3D VOR using whole body rotation on a 6DF motion platform. Although the method also allows testing translation VOR responses 1, we limit ourselves to a discussion of the method to measure 3D angular VOR. In addition, we restrict ourselves here to description of data collected in healthy subjects in response to angular sinusoidal and impulse stimulation.
Subjects are sitting upright and receive whole-body small amplitude sinusoidal and constant acceleration impulses. Sinusoidal stimuli (f = 1 Hz, A = 4&deg;) were delivered about the vertical axis and about axes in the horizontal plane varying between roll and pitch at increments of 22.5&deg; in azimuth. Impulses were delivered in yaw, roll and pitch and in the vertical canal planes. Eye movements were measured using the scleral search coil technique 2. Search coil signals were sampled at a frequency of 1 kHz.
The input-output ratio (gain) and misalignment (co-linearity) of the 3D VOR were calculated from the eye coil signals 3.
Gain and co-linearity of 3D VOR depended on the orientation of the stimulus axis. Systematic deviations were found in particular during horizontal axis stimulation. In the light the eye rotation axis was properly aligned with the stimulus axis at orientations 0&deg; and 90&deg; azimuth, but gradually deviated more and more towards 45&deg; azimuth.
The systematic deviations in misalignment for intermediate axes can be explained by a low gain for torsion (X-axis or roll-axis rotation) and a high gain for vertical eye movements (Y-axis or pitch-axis rotation (see Figure 2). Because intermediate axis stimulation leads a compensatory response based on vector summation of the individual eye rotation components, the net response axis will deviate because the gain for X- and Y-axis are different.
In darkness the gain of all eye rotation components had lower values. The result was that the misalignment in darkness and for impulses had different peaks and troughs than in the light: its minimum value was reached for pitch axis stimulation and its maximum for roll axis stimulation.
Case Presentation
Nine subjects participated in the experiment. All subjects gave their informed consent. The experimental procedure was approved by the Medical Ethics Committee of Erasmus University Medical Center and adhered to the Declaration of Helsinki for research involving human subjects.
Six subjects served as controls. Three subjects had a unilateral vestibular impairment due to a vestibular schwannoma. The age of control subjects (six males and three females) ranged from 22 to 55 years. None of the controls had visual or vestibular complaints due to neurological, cardio vascular and ophthalmic disorders.
The age of the patients with schwannoma varied between 44 and 64 years (two males and one female). All schwannoma subjects were under medical surveillance and/or had received treatment by a multidisciplinary team consisting of an othorhinolaryngologist and a neurosurgeon of the Erasmus University Medical Center. Tested patients all had a right side vestibular schwannoma and underwent a wait and watch policy (Table 1; subjects N1-N3) after being diagnosed with vestibular schwannoma. Their tumors had been stabile for over 8-10 years on magnetic resonance imaging.

A method is described to measure three-dimensional vestibulo ocular reflexes (3D VOR) in humans using a six degrees of freedom (6DF) motion simulator. The gain and misalignment of the 3D angular VOR provide a direct measure of the quality of vestibular function. Representative data on healthy subjects are provided

The vestibular organ is a sensor that measures angular and linear accelerations with six degrees of freedom (6DF). Complete or partial defects in the ...

Dynamic Visual Tests to Identify and Quantify Visual Damage and Repair Following Demyelination in Optic Neuritis Patients

In order to follow optic neuritis patients and evaluate the effectiveness of their treatment, a handy, accurate and quantifiable tool is required to assess changes in myelination at the central nervous system (CNS). However, standard measurements, including routine visual tests and MRI scans, are not sensitive enough for this purpose. We present two visual tests addressing dynamic monocular and binocular functions which may closely associate with the extent of myelination along visual pathways. These include Object From Motion (OFM) extraction and Time-constrained stereo protocols. In the OFM test, an array of dots compose an object, by moving the dots within the image rightward while moving the dots outside the image leftward or vice versa. The dot pattern generates a camouflaged object that cannot be detected when the dots are stationary or moving as a whole. Importantly, object recognition is critically dependent on motion perception. In the Time-constrained Stereo protocol, spatially disparate images are presented for a limited length of time, challenging binocular 3-dimensional integration in time. Both tests are appropriate for clinical usage and provide a simple, yet powerful, way to identify and quantify processes of demyelination and remyelination along visual pathways. These protocols may be efficient to diagnose and follow optic neuritis and multiple sclerosis patients.
In the diagnostic process, these protocols may reveal visual deficits that cannot be identified via current standard visual measurements. Moreover, these protocols sensitively identify the basis of the currently unexplained continued visual complaints of patients following recovery of visual acuity. In the longitudinal follow up course, the protocols can be used as a sensitive marker of demyelinating and remyelinating processes along time. These protocols may therefore be used to evaluate the efficacy of current and evolving therapeutic strategies, targeting myelination of the CNS.

Object From Motion (OFM) and Time-constrained stereo protocols are sensitive tools to identify monocular and binocular dynamic visual function deficits, which are uniquely affected in optic neuritis patients. Furthermore, these tests may be used as quantitative noninvasive tools to assess the extent of myelination along visual pathways.

In order to follow optic neuritis patients and evaluate the effectiveness of their treatment, a handy, accurate and quantifiable tool is required to ...

Medicine

Assessing Binocular Central Visual Field and Binocular Eye Movements in a Dichoptic Viewing Condition

Macular degeneration typically results in heterogeneous binocular central visual defects. Currently available approaches to assess central visual field, like the microperimetry, can test only one eye at a time. Therefore, they cannot explain how the defects in each eye affect the binocular interaction and real-world function. Dichoptic stimulus presentation with a gaze-controlled system could provide a reliable measure of monocular/binocular visual fields. However, dichoptic stimulus presentation and simultaneous eye-tracking are challenging because optical devices of instruments that present stimulus dichoptically (e.g., haploscope) always interfere with eye-trackers (e.g., infrared video-based eye-trackers). Therefore, the goals were 1) to develop a method for dichoptic stimulus presentation with simultaneous eye-tracking, using 3D-shutter glasses and 3D-ready monitors, that is not affected by interference and 2) to use this method to develop a protocol for assessing central visual field in subjects with central vision loss. The results showed that this setup provides a practical solution for reliably measuring eye-movements in dichoptic viewing condition. In addition, it was also demonstrated that this method can assess gaze-controlled binocular central visual field in subjects with central vision loss.

Presented here is a protocol for assessing binocular eye movements and gaze-controlled central visual field screening in participants with central vision loss.

Macular degeneration typically results in heterogeneous binocular central visual defects. Currently available approaches to assess central visual field, ...

An Automated Assessment of Visual Acuity in Infants and Toddlers

An Automated Method for Assessing Visual Acuity in Infants and Toddlers Using an Eye-Tracking System

Visual acuity measurement is an important visual function test to perform in infancy and childhood. However, accurate visual acuity measurement in infants is difficult because of deficiencies in their communication ability. This paper presents a novel automated method to assess visual acuity in children (5-36 months old). This method, the automated acuity card procedure (AACP), uses a webcam for eye tracking and recognizes children's watching behaviors automatically. A two-choice preferential-looking test is performed when the tested child watches the visual stimuli shown on a high-resolution digital display screen. When the tested child watches the stimuli, their facial pictures are recorded by the webcam. These pictures are used by the set computer program to analyze their watching behavior. With this procedure, the child's eye movement responses to different stimuli are measured, and their visual acuity is assessed without communication. By comparing the results with grating acuity obtained by Teller Acuity Cards (TACs), AACP performance is deemed comparable to that of TACs.

Author Spotlight: An Automated Method for Assessing Visual Acuity in Infants and Toddlers Using an Eye-Tracking System  

In this paper, we present a novel automated method for assessing visual acuity in infants and toddlers by using an eye-tracking system.

Visual acuity measurement is an important visual function test to perform in infancy and childhood. However, accurate visual acuity measurement in infants ...

Quantification of Oculomotor Responses and Accommodation Through Instrumentation and Analysis Toolboxes

Through the purposeful stimulation and recording of eye movements, the fundamental characteristics of the underlying neural mechanisms of eye movements can be observed. VisualEyes2020 (VE2020) was developed based on the lack of customizable software-based visual stimulation available for researchers that does not rely on motors or actuators within a traditional haploscope. This new instrument and methodology have been developed for a novel haploscope configuration utilizing both eye tracking and autorefractor systems. Analysis software that enables the synchronized analysis of eye movement and accommodative responses provides vision researchers and clinicians with a reproducible environment and shareable tool. The Vision and Neural Engineering Laboratory&#39;s (VNEL) Eye Movement Analysis Program (VEMAP) was established to process recordings produced by VE2020&#39;s eye trackers, while the Accommodative Movement Analysis Program (AMAP) was created to process the recording outputs from the corresponding autorefractor system. The VNEL studies three primary stimuli: accommodation (blur-driven changes in the convexity of the intraocular lens), vergence (inward, convergent rotation and outward, divergent rotation of the eyes), and saccades (conjugate eye movements). The VEMAP and AMAP utilize similar data flow processes, manual operator interactions, and interventions where necessary; however, these analysis platforms advance the establishment of an objective software suite that minimizes operator reliance. The utility of a graphical interface and its corresponding algorithms allow for a broad range of visual experiments to be conducted with minimal required prior coding experience from its operator(s).

VisualEyes2020 (VE2020) is a custom scripting language that presents, records, and synchronizes visual eye movement stimuli. VE2020 provides stimuli for conjugate eye movements (saccades and smooth pursuit), disconjugate eye movements (vergence), accommodation, and combinations of each. Two analysis programs unify the data processing from the eye tracking and accommodation recording systems.

Through the purposeful stimulation and recording of eye movements, the fundamental characteristics of the underlying neural mechanisms of eye movements ...

Bioengineering

A New Optokinetic Testing Method to Measure Rat Vision

Optokinetic nystagmus (OKN) is a reflexive eye movement initiated by the motion of visual stimuli in the field of vision. The head-tracking movement associated with OKN is commonly used as a measure of visual function in rodents. To record OKN responses in normal and experimental rats, a simple and inexpensive apparatus has been developed. This setup uses two tablet screens to display the OKN visual stimulus consisting of high contrast black and white stripes generated using the OKN Stripes Visualization Web Application, a freely available software. The rat is placed inside a clear Plexiglass holder that limits&#160;movement so that the&#160;rat&#39;s head continuously faces the OKN display screen. The position of the rat holder can be changed to adjust the distance between the rat and the display screen. A micro-camera positioned above the rat holder is used to record the rat&#39;s visual activities. These recordings can be used for quantitative assessments. Based on the presence or absence of clear head-tracking, the OKN responses at different spatial frequencies can be determined. The collected data demonstrates a novel technique for reliable measurement of visual acuity in normal and retinal degenerate rats.

The Optokinetic Nystagmus (OKN) behavioral testing method is used for the assessment of visual acuity in rodents. Here a simple method is demonstrated that can be easily set up in research laboratories for a reliable assessment of visual function in both normal and experimental rats.

Optokinetic nystagmus (OKN) is a reflexive eye movement initiated by the motion of visual stimuli in the field of vision. The head-tracking movement ...

Binocular Dynamic Visual Acuity in Eyeglass-Corrected Myopic Patients

Current clinical visual assessment mainly focuses on static vision. However, static vision may not sufficiently reflect real-life visual function as moving optotypes are frequently observed daily. Dynamic visual acuity (DVA) might reflect real-life situations better, especially when objects are moving at high speeds. Myopia impacts static uncorrected distance visual acuity, conveniently corrected with eyeglasses. However, due to peripheral defocus and prism effects, eyeglass correction might affect DVA. The present research demonstrates a standard method to examine eyeglass-corrected DVA in myopia patients, and aimed to explore the influence of eyeglass correction on DVA. 
Initially, standard subjective refraction was performed to provide the eyeglass prescription to correct the refractive error. Then, binocular distance vision-corrected DVA was examined using the object-moving DVA protocol. Software was designed to display the moving optotypes according to the preset velocity and size on a screen. The optotype was the standard logarithmic visual chart letter E and moves from the middle of the left to the right side horizontally during the test. Moving optotypes with randomized opening direction for each size are displayed. The subjects were required to identify the opening direction of the optotype, and the DVA is defined as the minimum optotype that subjects could recognize, calculated according to the algorithm of logarithmic visual acuity.
Then, the method was applied in 181 young myopic subjects with eyeglass-corrected-to-normal static visual acuity. Dominant eye, cycloplegic subjective refraction (sphere and cylinder), accommodation function (negative and positive relative accommodation, binocular cross-cylinder), and binocular DVA at 40 and 80 degrees per second (dps) were examined. The results showed that with increasing age, DVA first increased and then decreased. When myopia was fully corrected with eyeglasses, a worse binocular DVA was associated with more significant myopic refractive error. There was no correlation between the dominant eye, accommodation function, and binocular DVA.

The present research demonstrates a method to accurately examine dynamic visual acuity (DVA) in myopic subjects with eyeglass correction. Further analysis indicated that the closer the refraction state to emmetropia, the better the eyeglass-corrected binocular DVA is at both 40 and 80 degrees per second.

Current clinical visual assessment mainly focuses on static vision. However, static vision may not sufficiently reflect real-life visual function as ...

Gaze-Contingent Framework for Studying and Training in Simulated Vision Loss

A Gaze-Contingent Display Framework for Perceptual Learning Research with Simulated Central Vision Loss

Macular degeneration (MD) is one of the leading causes of vision impairment in the Western world. Patients with MD tend to develop spontaneous eye movement strategies to compensate for their vision loss, including adopting a preferred retinal locus, or PRL, a spared peripheral region that they use more frequently to replace the damaged fovea. However, not all patients are successful in developing a PRL, and even when they do, it might take them months. Currently, no gold standard rehabilitative therapy exists, and MD research is further hindered by issues of recruitment, compliance, and comorbidity. To help address these issues, a growing body of research has used eye tracking-guided, gaze-contingent displays in a simulated central vision loss paradigm in individuals with intact vision. While simulated vision loss is qualitatively different than pathological central vision loss, our framework provides for a highly controlled model through which to study compensatory eye movements and test possible rehabilitation interventions in low vision. By developing a comprehensive framework, rather than relying on isolated and disconnected tasks, we create a cohesive environment where we can test larger-scale hypotheses, allowing us to examine interactions between tasks, assess training effects across multiple measures, and establish a consistent methodology for future research. Furthermore, participants in simulated central vision loss studies show similarities in their oculomotor compensatory behaviors compared to patients with MD. Here, we present a framework for conducting gaze-contingent studies related to simulated central vision loss. We emphasize the utilization of the framework to test behavioral and oculomotor performance of healthy individuals on a wide range of perceptual tasks encompassing different levels of visual processing. We also discuss how this framework can be adapted for training MD patients.

Development of a Gaze-Contingent Display Framework Designed for Perceptual and Oculomotor Research with Simulated Central Vision Loss

We present development of a gaze-contingent display framework designed for perceptual and oculomotor research simulating central vision loss. This framework is particularly adaptable for studying compensatory behavioral and oculomotor strategies in individuals experiencing both simulated and pathological central vision loss.