This research was supported by National Institutes of Health grant R01EY023261 to T.L.A. and a Barry Goldwater Scholarship and NJIT Provost Doctoral Award to S.N.F.

<ol>
	<li>Alvarez, T. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disparity+vergence+differences+between+typically+occurring+and+concussion-related+convergence+insufficiency+pediatric+patients.">Disparity vergence differences between typically occurring and concussion-related convergence insufficiency pediatric patients.</a> Vision Research. 185, 58-67 (2021).</li><li>Alvarez, T. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Underlying+neurological+mechanisms+associated+with+symptomatic+convergence+insufficiency.">Underlying neurological mechanisms associated with symptomatic convergence insufficiency.</a> Scientific Reports. 11, 6545 (2021).</li><li>Scheiman, M., Kulp, M. T., Cotter, S. A., Lawrenson, J. G., Wang, L., Li, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interventions+for+convergence+insufficiency:+A+network+meta-analysis.">Interventions for convergence insufficiency: A network meta-analysis.</a> The Cochrane Database of Systematic Reviews. 12 (12), (2020).</li><li>Semmlow, J. L., Chen, Y. F., Granger-Donnetti, B., Alvarez, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correction+of+saccade-induced+midline+errors+in+responses+to+pure+disparity+vergence+stimuli.">Correction of saccade-induced midline errors in responses to pure disparity vergence stimuli.</a> Journal of Eye Movement Research. 2 (5), (2009).</li><li>Scheiman, M., Wick, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Clinical Management of Binocular Vision., 5th Edition. , (2019).</li><li>Kim, E. H., Vicci, V. R., Granger-Donetti, B., Alvarez, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Short-term+adaptations+of+the+dynamic+disparity+vergence+and+phoria+systems.">Short-term adaptations of the dynamic disparity vergence and phoria systems.</a> Experimental Brain Research. 212 (2), 267-278 (2011).</li><li>Labhishetty, V., Bobier, W. R., Lakshminarayanan, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+25Hz+enough+to+accurately+measure+a+dynamic+change+in+the+ocular+accommodation.">Is 25Hz enough to accurately measure a dynamic change in the ocular accommodation.</a> Journal of Optometry. 12 (1), 22-29 (2019).</li><li>Juhola, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+saccadic+eye+movements+using+a+non-recursive+adaptive+digital+filter.">Detection of saccadic eye movements using a non-recursive adaptive digital filter.</a> Computer Methods and Programs in Biomedicine. 21 (2), 81-88 (1985).</li><li>Mack, D. J., Belfanti, S., Schwarz, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+sampling+rate+and+lowpass+filters+on+saccades+-+A+modeling+approach.">The effect of sampling rate and lowpass filters on saccades - A modeling approach.</a> Behavior Research Methods. 49 (6), 2146-2162 (2017).</li><li>Ghahghaei, S., Reed, O., Candy, T. R., Chandna, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calibration+of+the+PlusOptix+PowerRef+3+with+change+in+viewing+distance,+adult+age+and+refractive+error.">Calibration of the PlusOptix PowerRef 3 with change in viewing distance, adult age and refractive error.</a> Ophthalmic &amp; Physiological Optics. 39 (4), 253-259 (2019).</li><li>Guo, Y., Kim, E. L., Alvarez, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=VisualEyes:+A+modular+software+system+for+oculomotor+experimentation.">VisualEyes: A modular software system for oculomotor experimentation.</a> Journal of Visualized Experiments. (49), e2530 (2011).</li><li>Convergence Insufficiency Treatment Trial Study Group. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Randomized+clinical+trial+of+treatments+for+symptomatic+convergence+insufficiency+in+children.">Randomized clinical trial of treatments for symptomatic convergence insufficiency in children.</a> Archives of Ophthalmology. 126 (10), 1336-1349 (2008).</li><li>Borsting, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Association+of+symptoms+and+convergence+and+accommodative+insufficiency+in+school-age+children.">Association of symptoms and convergence and accommodative insufficiency in school-age children.</a> Optometry. 74 (1), 25-34 (2003).</li><li>Sheard, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zones+of+ocular+comfort.">Zones of ocular comfort.</a> American Journal of Optometry. 7 (1), 9-25 (1930).</li><li>Hofstetter, H. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+longitudinal+study+of+amplitude+changes+in+presbyopia.">A longitudinal study of amplitude changes in presbyopia.</a> American Journal of Optometry and Archives of American Academy of Optometry. 42, 3-8 (1965).</li><li>Donders, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> On the Anomalies of Accommodation and Refraction of the Eye. , (1972).</li><li>Sravani, N. G., Nilagiri, V. K., Bharadwaj, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photorefraction+estimates+of+refractive+power+varies+with+the+ethnic+origin+of+human+eyes.">Photorefraction estimates of refractive power varies with the ethnic origin of human eyes.</a> Scientific Reports. 5, 7976 (2015).</li><li>Maddox, E. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Clinical Use of Prisms and the Decentering of Lenses. , (1893).</li><li>Yaramothu, C., Santos, E. M., Alvarez, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+visual+distractors+on+vergence+eye+movements.">Effects of visual distractors on vergence eye movements.</a> Journal of Vision. 18 (6), 2 (2018).</li><li>Borsting, E., Rouse, M. W., De Land, P. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prospective+comparison+of+convergence+insufficiency+and+normal+binocular+children+on+CIRS+symptom+surveys.+Convergence+Insufficiency+and+Reading+Study+(CIRS)+group.">Prospective comparison of convergence insufficiency and normal binocular children on CIRS symptom surveys. Convergence Insufficiency and Reading Study (CIRS) group.</a> Optometry and Vision Science. 76 (4), 221-228 (1999).</li><li>Maxwell, J., Tong, J., Schor, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+first+and+second+order+dynamics+of+accommodative+convergence+and+disparity+convergence.">The first and second order dynamics of accommodative convergence and disparity convergence.</a> Vision Research. 50 (17), 1728-1739 (2010).</li><li>Alvarez, T. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Convergence+Insufficiency+Neuro-mechanism+in+Adult+Population+Study+(CINAPS)+randomized+clinical+trial:+Design,+methods,+and+clinical+data.">The Convergence Insufficiency Neuro-mechanism in Adult Population Study (CINAPS) randomized clinical trial: Design, methods, and clinical data.</a> Ophthalmic Epidemiology. 27 (1), 52-72 (2020).</li><li>Leigh, R. J., Zee, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Neurology of Eye Movements. , (2015).</li><li>Alvarez, T. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+and+functional+imaging+changes+induced+from+vision+therapy+in+patients+with+convergence+insufficiency.">Clinical and functional imaging changes induced from vision therapy in patients with convergence insufficiency.</a> Annual International Conference of the IEEE Engineering in Medicine and Biology Society. 2019, 104-109 (2019).</li><li>Scheiman, M. M., Talasan, H., Mitchell, G. L., Alvarez, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Objective+assessment+of+vergence+after+treatment+of+concussion-related+CI:+A+pilot+study.">Objective assessment of vergence after treatment of concussion-related CI: A pilot study.</a> Optometry and Vision Science. 94 (1), 74-88 (2017).</li><li>Yaramothu, C., Greenspan, L. D., Scheiman, M., Alvarez, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vergence+endurance+test:+A+pilot+study+for+a+concussion+biomarker.">Vergence endurance test: A pilot study for a concussion biomarker.</a> Journal of Neurotrauma. 36 (14), 2200-2212 (2019).</li></ol>

The authors have no conflicts of interest to declare.

Applications of the method in research 
Innovations from the initial VisualEyes2020 (VE2020) software include the expansibility of the VE2020 to project onto multiple monitors with one or several visual stimuli, which allows the investigation of scientific questions ranging from the quantification of the Maddox components of vergence18 to the influence of distracting targets on instructed targets19. The expansion of the haploscope system to VE2020 alongside the complementary development of the VEMAP and AMAP provide a self-contained stimulus and analysis platform that is compatible with currently accessible eye movement and accommodation recording equipment. Following the successful creation of the VE2020 stimulus routine and subsequent recording, the conversion of raw eye movement position and accommodation data into meaningful and analyzable subsets of data enables researchers with the necessary non-invasive tools to holistically investigate prevalent and underlying vision dysfunctions, such as typically occurring or mild traumatic brain injury-induced dysfunction and convergence insufficiency, which can be compared with function in binocularly normal control participants1,2,13,20. Providing eye movement analysis with corresponding accommodative responses enhances the scientific understanding of the unknown interplays between the vergence and accommodative systems in both healthy participants and those with oculomotor dysfunction21.
As demonstrated, with VE2020, the VEMAP, and the AMAP jointly configured, the underlying neural control mechanisms in dysfunction can be better understood22,23. Through VE2020&#39;s repeatable visual stimulation, latent neurological dysfunctions that may have early biomarkers expressed through abnormal accommodative, vergence, or version responses can now be quantitatively assessed by the AMAP and VEMAP. Unifying the accommodative response analysis with coupled eye movement recordings from previously isolated vision experiments helps studies to obtain more complete and quantifiable analysis outcomes. Objective methods of analysis and stimulation provide the ability to compare the efficacy of current standards of care and their therapeutic outcomes24,25. These quantifications, coupled with subjective participant symptom surveying, can aid in identifying personalized remediation strategies that improve outcomes. Furthermore, by evaluating these principal components that may evoke symptoms, early methods for detecting injury26 and severity assessments can be established with heightened efficacy.
Critical steps in the protocol 
Eye movements are usually measured by the magnitude of rotation of the eye in degrees. As seen in Figure 5, the trigonometric conversion of a stimulus&#39;s translational movement to degrees requires a known inter-pupillary distance (IPD) and measured distance to the target. Utilizing known averages for the IPD can provide a generalized approximation for scripting the VE2020 stimulus sequences; however, these rely on proper calibrations. Sign conventions for the direction of movements can be altered; however, this will alter the application of gain values for the VEMAP. The VEMAP&#39;s current movement conventions are as follows for saccadic movements: rightward is positive, and leftward is negative. Additionally, for vergence movements, convergence (inward rotation) is positive, and divergence (outward rotation) is negative.
As seen in Figure 7, the stimulus targets were placed at 1&#176;, 3&#176;, and 5&#176;, representing an inward monocular angular rotation from optical infinity. The bottom-left plot demonstrates a three-point linear regression for the left eye positional data, where for a 5&#176; stimulus, the average recorded voltage was &#8722;1 V, for a 3&#176; stimulus, the average recorded voltage was approximately 0.4 V, and for a 1&#176; stimulus, the average recorded voltage was approximately 1.25 V. Similarly, for the right-eye position in the bottom-right plot, a 1&#176; stimulus had a corresponding voltage of &#8722;1.25 V, a 3&#176; stimulus had an average voltage of about 0 V, and a 5&#176; stimulus had an average voltage of 1.1 V.
Limitations of the method 
The current limitations of the method include the standardized output of the autorefractor and eye tracker data, as the AMAP and VEMAP are programmed to process these data formats. Another limitation includes the fact that if the experimentation is not engaging, participants may frequently blink (close) their eyes, leading to poor data recording quality. While other oculomotor dysfunctions such as strabismus, amblyopia, nystagmus, and suppression could leverage VE2020, the VEMAP, and the AMAP, modifications would need to be implemented for each of these specific oculomotor dysfunctions.

Concerted binocular coordination and appropriate accommodative and oculomotor responses to visual stimuli are crucial aspects of daily life. When an individual has reduced convergence eye movement response speed, quantified through eye movement recording, doubled vision (diplopia) may be perceived1,2. Furthermore, a Cochrane literature meta-analysis reported that patients with oculomotor dysfunctions, attempting to maintain normal binocular vision, experience commonly shared visual symptoms, including blurred/double vision, headaches, eye stress/strain, and difficulty reading comfortably3. Rapid conjugate eye movements (saccades), when deficient, can under-respond or over-respond to visual targets, thus meaning further sequential saccades are required to correct this error4. These oculomotor responses can also be confounded by the accommodative system, in which the improper focusing of light from the lens creates blur5. 
Tasks such as reading or working on electronic devices demand coordination of the oculomotor and accommodative systems. For individuals with binocular eye movement or accommodative dysfunctions, the inability to maintain binocular fusion (single) and acute (clear) vision diminishes their quality of life and overall productivity. By establishing a procedural methodology for quantitatively recording these systems independently and concertedly through repeatable instrumentation configurations and objective analysis, distinguishing characteristics about the acclimation to specific deficiencies can be understood. Quantitative measurements of eye movements can lead to more comprehensive diagnoses6 compared to conventional methods, with the potential to predict the probability of remediation via therapeutic interventions. This instrumentation and data analysis suite provides insight toward understanding the mechanisms behind current standards of care, such as vision therapy, and the long-term effect therapeutic intervention(s) may have on patients. Establishing these quantitative differences between individuals with and without normal binocular vision may provide novel personalized therapeutic strategies and heighten remediation effectiveness based on objective outcome measurements.
To date, there is not a single commercially available platform that can simultaneously stimulate and quantitatively record eye movement data with corresponding accommodative positional and velocity responses that can be further processed as separate (eye movement and accommodative) data streams. The signal processing analyses for accommodative and oculomotor positional and velocity responses have respectively established minimum sampling requirements of approximately 10 Hz7 and a suggested sampling rate between 240 Hz and 250 Hz for saccadic eye movements8,9. However, the Nyquist rate for vergence eye movements has yet to be established, though vergence is about an order of magnitude lower in peak velocity than saccadic eye movements. Nonetheless, there is a gap in the current literature regarding eye movement recording and auto-refractive instrumentation platform integration. Furthermore, the ability to analyze objective eye movement responses with synchronous accommodation responses has not yet been open-sourced. Hence, the Vision and Neural Engineering Laboratory (VNEL) addressed the need for synchronized instrumentation and analysis through the creation of VE2020 and two offline signal processing program suites to analyze eye movements and accommodative responses. VE2020 is customizable via calibration procedures and stimulation protocols for adaptation to a variety of applications from basic science to clinical, including binocular vision research projects on convergence insufficiency/excess, divergence insufficiency/excess, accommodative insufficiency/excess, concussion-related binocular dysfunctions, strabismus, amblyopia, and nystagmus. VE2020 is complemented by the VEMAP and AMAP, which subsequently provide data analysis capabilities for these stimulated eyes and accommodative movements.

<table><tbody><tr><td>Analog Terminal Breakout Box</td><td>National Instruments</td><td>2090A</td><td></td></tr><tr><td>Convex-Sphere Trial Lens Set</td><td>Reichert</td><td>Portable Precision Lenses</td><td>Utilized for autorefractor calibration</td></tr><tr><td>Graphics Cards</td><td>-</td><td>-</td><td>Minimum performance requirement of GTX980 in SLI configuration</td></tr><tr><td>ISCAN Eye Tracker</td><td>ISCAN</td><td>ETL200</td><td></td></tr><tr><td>MATLAB</td><td>MathWorks</td><td>v2022a</td><td>AMAP software rquirement</td></tr><tr><td>MATLAB</td><td>MathWorks</td><td>v2015a</td><td>VEMAP software requirement</td></tr><tr><td>Microsoft Windows 10</td><td>Microsoft</td><td>Windows 10</td><td>Required OS for VE2020</td></tr><tr><td>Plusoptix PowerRef3 Autorefractor</td><td>Plusoptix</td><td>PowerRef3</td><td></td></tr><tr><td>Stimuli Monitors (Quantity: 4+)</td><td>Dell</td><td>Resolution 1920x1080</td><td>Note all monitors should be the same model and brand to avoid resolution differences as well as physical configurations</td></tr></tbody></table>

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).

Group-level ensemble plots of stimulated eye movements evoked by VE2020 are depicted in Figure 11 with the corresponding first-order velocity characteristics.
<img alt="Figure 11" class="xfigimg" src="/files/ftp_upload/64808/64808fig11.jpg" /> 
Figure 11: Eye movement response ensembles. The ensemble plots of vergence steps (left) and saccades (right) stimulated using the VE2020 are shown. Each eye movement position trace (degrees) is plotted as a uniquely colored line and overlayed with the group-level velocity response in red. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/64808/64808fig11large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The exported features from the AMAP enable the visualization of both the participant-level and group-level movement plots (ensembles) and corresponding metrics (export) in an accessible spreadsheet (Table 4). The exported data tables provide a quantitative overview of the participants&#39; performances and can establish criteria for outlier removal.
Table 4:&#160;AMAP software analysis export. An example of the AMAP export function, in which individual eye movement responses are exported row-wise with the corresponding subject and movement type identification. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/64808/Table_4.xlsx" target="_blank">Please click here to download this Table.</a>
The visualization of the participant performances can also be accomplished within the AMAP, as shown in Figure 12, which shows an ensemble of 5&#176; convergent responses and the corresponding 1.5 diopter accommodative responses that are the result of data processing.
<img alt="Figure 12" class="xfigimg" src="/files/ftp_upload/64808/64808fig12.jpg" /> 
Figure 12: Accommodative movement response ensembles. The figure demonstrates the AMAP ensemble function, which creates overlays of each individual movement response trace (gray) and the average response (green). <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/64808/64808fig12large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Figure 11 and Figure 12 demonstrate the successful stimulation and recording of both vergence and saccadic eye movements as well as accommodative responses. Provided the calibration procedures from the VEMAP give the expected 4&#176; vergence and 5&#176; saccadic targets, Figure 11 shows that for a binocularly normal participant undergoing these visual tasks, the anticipated stimulation is met. For accommodative responses processed within the AMAP, Figure 12 demonstrates an approximate accommodative response of 1 diopter with an accommodative demand of 1.5 diopters, which is consistent with the variability of autorefractor systems for varying participant demographics17. These results can be further calibrated, utilizing a constant gain, following group-level statistics for various experimental participant groups with the export feature seen in Table 4. Hence, the establishment and successful implementation of VE2020, the VEMAP, and the AMAP can provide a quantitative understanding of the differences in stimulated eye movement and accommodative response metrics.

Watch this Scientific Journal Video about Quantification of Oculomotor Responses and Accommodation Through Instrumentation and Analysis Toolboxes at JoVE.com

Quantification of Oculomotor Responses and Accommodation Through Instrumentation and Analysis Toolboxes

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 ...

quantification-oculomotor-responses-accommodation-through

Universidad San Sebastian

Research

JoVE Journal

Bioengineering

837 Views.  New Jersey Institute of Technology. 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.

Video: Quantification of Oculomotor Responses and Accommodation Through Instrumentation and Analysis Toolboxes

VisualEyes: A Modular Software System for Oculomotor Experimentation

Eye movement studies have provided a strong foundation forming an understanding of how the brain acquires visual information in both the normal and dysfunctional brain.1 However, development of a platform to stimulate and store eye movements can require substantial programming, time and costs. Many systems do not offer the flexibility to program numerous stimuli for a variety of experimental needs. However, the VisualEyes System has a flexible architecture, allowing the operator to choose any background and foreground stimulus, program one or two screens for tandem or opposing eye movements and stimulate the left and right eye independently. This system can significantly reduce the programming development time needed to conduct an oculomotor study. The VisualEyes System will be discussed in three parts: 1) the oculomotor recording device to acquire eye movement responses, 2) the VisualEyes software written in LabView, to generate an array of stimuli and store responses as text files and 3) offline data analysis. Eye movements can be recorded by several types of instrumentation such as: a limbus tracking system, a sclera search coil, or a video image system. Typical eye movement stimuli such as saccadic steps, vergent ramps and vergent steps with the corresponding responses will be shown. In this video report, we demonstrate the flexibility of a system to create numerous visual stimuli and record eye movements that can be utilized by basic scientists and clinicians to study healthy as well as clinical populations.

Neural control and cognitive processes can be studied through eye movements. The VisualEyes software allows an operator to program stimuli on two computer screens independently using a simple, custom scripting language. The system can stimulate tandem eye movements (saccades and smooth pursuit) or opposing eye movements (vergence) or any combination.

Eye movement studies have provided a strong foundation forming an understanding of how the brain acquires visual information in both the normal and ...

Neuroscience

VisioTracker, an Innovative Automated Approach to Oculomotor Analysis

Investigations into the visual system development and function necessitate quantifiable behavioral models of visual performance that are easy to elicit, robust, and simple to manipulate. A suitable model has been found in the optokinetic response (OKR), a reflexive behavior present in all vertebrates due to its high selection value. The OKR involves slow stimulus-following movements of eyes alternated with rapid resetting saccades. The measurement of this behavior is easily carried out in zebrafish larvae, due to its early and stable onset (fully developed after 96 hours post fertilization (hpf)), and benefitting from the thorough knowledge about zebrafish genetics, for decades one of the favored model organisms in this field. Meanwhile the analysis of similar mechanisms in adult fish has gained importance, particularly for pharmacological and toxicological applications.
Here we describe VisioTracker, a fully automated, high-throughput system for quantitative analysis of visual performance. The system is based on research carried out in the group of Prof. Stephan Neuhauss and was re-designed by TSE Systems. It consists of an immobilizing device for small fish monitored by a high-quality video camera equipped with a high-resolution zoom lens. The fish container is surrounded by a drum screen, upon which computer-generated stimulus patterns can be projected. Eye movements are recorded and automatically analyzed by the VisioTracker software package in real time.
Data analysis enables immediate recognition of parameters such as slow and fast phase duration, movement cycle frequency, slow-phase gain, visual acuity, and contrast sensitivity.
Typical results allow for example the rapid identification of visual system mutants that show no apparent alteration in wild type morphology, or the determination of quantitative effects of pharmacological or toxic and mutagenic agents on visual system performance.

The VisioTracker is an automated system for the quantitative analysis of visual performance of larval and small adult fish based on the recording of eye movements. It features full control over visual stimulus properties and real-time analysis, enabling high-throughput research in fields such as visual system development and function, pharmacology, neural circuit studies and sensorimotor integration.

Investigations into the visual system development and function necessitate quantifiable behavioral models of visual performance that are easy to elicit, ...

Video-oculography in Mice

Eye movements are very important in order to track an object or to stabilize an image on the retina during movement. Animals without a fovea, such as the mouse, have a limited capacity to lock their eyes onto a target. In contrast to these target directed eye movements, compensatory ocular eye movements are easily elicited in afoveate animals1,2,3,4. Compensatory ocular movements are generated by processing vestibular and optokinetic information into a command signal that will drive the eye muscles. The processing of the vestibular and optokinetic information can be investigated separately and together, allowing the specification of a deficit in the oculomotor system. The oculomotor system can be tested by evoking an optokinetic reflex (OKR), vestibulo-ocular reflex (VOR) or a visually-enhanced vestibulo-ocular reflex (VVOR). The OKR is a reflex movement that compensates for "full-field" image movements on the retina, whereas the VOR is a reflex eye movement that compensates head movements. The VVOR is a reflex eye movement that uses both vestibular as well as optokinetic information to make the appropriate compensation. The cerebellum monitors and is able to adjust these compensatory eye movements. Therefore, oculography is a very powerful tool to investigate brain-behavior relationship under normal as well as under pathological conditions (f.e. of vestibular, ocular and/or cerebellar origin).
Testing the oculomotor system, as a behavioral paradigm, is interesting for several reasons. First, the oculomotor system is a well understood neural system5. Second, the oculomotor system is relative simple6; the amount of possible eye movement is limited by its ball-in-socket architecture ("single joint") and the three pairs of extra-ocular muscles7. Third, the behavioral output and sensory input can easily be measured, which makes this a highly accessible system for quantitative analysis8. Many behavioral tests lack this high level of quantitative power. And finally, both performance as well as plasticity of the oculomotor system can be tested, allowing research on learning and memory processes9.
Genetically modified mice are nowadays widely available and they form an important source for the exploration of brain functions at various levels10. In addition, they can be used as models to mimic human diseases. Applying oculography on normal, pharmacologically-treated or genetically modified mice is a powerful research tool to explore the underlying physiology of motor behaviors under normal and pathological conditions. Here, we describe how to measure video-oculography in mice8.

Video-oculography is a very quantitative method to investigate ocular motor performance as well as motor learning. Here, we describe how to measure video-oculography in mice. Applying this technique on normal, pharmacologically-treated or genetically modified mice is a powerful research tool to explore the underlying physiology of motor behaviors.

Eye movements are very important in order to track an object or to stabilize an image on the retina during movement. Animals without a fovea, such as the ...

Efficiently Recording the Eye-Hand Coordination to Incoordination Spectrum

The objective analysis of eye movements has a significant history and has been long proven to be an important research tool in the setting of brain injury. Quantitative recordings have a strong capacity to screen diagnostically. Concurrent examinations of the eye and upper limb movements directed toward shared functional goals (e.g., eye-hand coordination) serve as an additional robust biomarker-laden path to capture and interrogate neural injury, including acquired brain injury (ABI). While quantitative dual-effector recordings in 3-D afford ample opportunities within ocular-manual motor investigations in the setting of ABI, the feasibility of such dual recordings for both eye and hand is challenging in pathological settings, particularly when approached with research-grade rigor. Here we describe the integration of an eye tracking system with a motion tracking system intended primarily for limb control research to study a natural behavior. The protocol enables the investigation of unrestricted, three-dimensional (3D) eye-hand coordination tasks. More specifically, we review a method to assess eye-hand coordination in visually guided saccade-to-reach tasks in subjects with chronic middle cerebral artery (MCA) stroke and compare them to healthy controls. Special attention is paid to the specific eye- and limb-tracking system properties in order to obtain high fidelity data from participants post-injury. Sampling rate, accuracy, permissible head movement range given anticipated tolerance and the feasibility of use were several of the critical properties considered when selecting an eye tracker and an approach. The limb tracker was selected based on a similar rubric but included the need for 3-D recording, dynamic interaction and a miniaturized physical footprint. The quantitative data provided by this method and the overall approach when executed correctly has tremendous potential to further refine our mechanistic understanding of eye-hand control and help inform feasible diagnostic and pragmatic interventions within the neurological and rehabilitative practice.&#160;

Cerebral injury can damage both ocular and somatic motor systems. Characterization of motor control post-injury affords biomarkers that assist in disease detection, monitoring, and prognosis. We review a method to measure eye-hand movement control in health and in pathologic incoordination, with look-and-reach paradigms to assess coordination between eye and hand.

The objective analysis of eye movements has a significant history and has been long proven to be an important research tool in the setting of brain ...

Behavior

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, ...

In vivo Structural Assessments of Ocular Disease in Rodent Models using Optical Coherence Tomography

Spectral-domain optical coherence tomography (SD-OCT) is useful for visualizing retinal and ocular structures in vivo. In research, SD-OCT is a valuable tool to evaluate and characterize changes in a variety of retinal and ocular disease and injury models. In light induced retinal degeneration models, SD-OCT can be used to track thinning of the photoreceptor layer over time. In glaucoma models, SD-OCT can be used to monitor decreased retinal nerve fiber layer and total retinal thickness and to observe optic nerve cupping after inducing ocular hypertension. In diabetic rodents, SD-OCT has helped researchers observe decreased total retinal thickness as well as decreased thickness of specific retinal layers, particularly the retinal nerve fiber layer with disease progression. In mouse models of myopia, SD-OCT can be used to evaluate axial parameters, such as axial length changes. Advantages of SD-OCT include in vivo imaging of ocular structures, the ability to quantitatively track changes in ocular dimensions over time, and its rapid scanning speed and high resolution. Here, we detail the methods of SD-OCT and show examples of its use in our laboratory in models of retinal degeneration, glaucoma, diabetic retinopathy, and myopia. Methods include anesthesia, SD-OCT imaging, and processing of the images for thickness measurements.

Here, we describe the use of spectral-domain optical coherence tomography (SD-OCT) to visualize retinal and ocular structures in vivo in models of retinal degeneration, glaucoma, diabetic retinopathy, and myopia.

Spectral-domain optical coherence tomography (SD-OCT) is useful for visualizing retinal and ocular structures in vivo. In research, SD-OCT is a valuable ...

Using Optical Coherence Tomography and Optokinetic Response As Structural and Functional Visual System Readouts in Mice and Rats

Optical coherence tomography (OCT) is a fast, non-invasive, interferometric technique allowing high-resolution retinal imaging. It is an ideal tool for the investigation of processes of neurodegeneration, neuroprotection and neuro-repair involving the visual system, as these often correlate well with retinal changes. As a functional readout, visually evoked compensatory eye and head movements are commonly used in experimental models involving the visual function. Combining both techniques allows a quantitative in vivo investigation of structure and function, which can be used to investigate the pathological conditions or to evaluate the potential of novel therapeutics. A great benefit of the presented techniques is the possibility to perform longitudinal analyses allowing the investigation of dynamic processes, reducing variability and cuts down the number of animals needed for the experiments. The protocol described aims to provide a manual for acquisition and analysis of high quality retinal scans of mice and rats using a low cost customized holder with an option to deliver inhalational anesthesia. Additionally, the proposed guide is intended as an instructional manual for researchers using optokinetic response (OKR) analysis in rodents, which can be adapted to their specific needs and interests.

A detailed protocol for the assessment of structural and visual readouts in rodents by optical coherence tomography and optokinetic response is presented. The results provide valuable insights for ophthalmologic as well as neurologic research.

Optical coherence tomography (OCT) is a fast, non-invasive, interferometric technique allowing high-resolution retinal imaging. It is an ideal tool for ...

Evaluating Optokinetic Reflex Responses in Mice: A New High-Precision Protocol

Quantification of Visual Feature Selectivity of the Optokinetic Reflex in Mice

The optokinetic reflex (OKR) is an essential innate eye movement that is triggered by the global motion of the visual environment and serves to stabilize retinal images. Due to its importance and robustness, the OKR has been used to study visual-motor learning and to evaluate the visual functions of mice with different genetic backgrounds, ages, and drug treatments. Here, we introduce a procedure for evaluating OKR responses of head-fixed mice with high accuracy. Head fixation can rule out the contribution of vestibular stimulation on eye movements, making it possible to measure eye movements triggered only by visual motion. The OKR is elicited by a virtual drum system, in which a vertical grating presented on three computer monitors drifts horizontally in an oscillatory manner or unidirectionally at a constant velocity. With this virtual reality system, we can systematically change visual parameters like spatial frequency, temporal/oscillation frequency, contrast, luminance, and the direction of gratings, and quantify tuning curves of visual feature selectivity. High-speed infrared video-oculography ensures accurate measurement of the trajectory of eye movements. The eyes of individual mice are calibrated to provide opportunities to compare the OKRs between animals of different ages, genders, and genetic backgrounds. The quantitative power of this technique allows it to detect changes in the OKR when this behavior plastically adapts due to aging, sensory experience, or motor learning; thus, it makes this technique a valuable addition to the repertoire of tools used to investigate the plasticity of ocular behaviors.

Author Spotlight: An Accurate and Quantitative Approach to Study Visual Feature Selectivity of the Optokinetic Reflex in Mice 

Here, we describe a standard protocol for quantifying the optokinetic reflex. It combines virtual drum stimulation and video-oculography, and thus allows precise evaluation of the feature selectivity of the behavior and its adaptive plasticity.

The optokinetic reflex (OKR) is an essential innate eye movement that is triggered by the global motion of the visual environment and serves to stabilize ...

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 ...

Medicine

Python-Based Tool for Quantitative Optokinetic Reflex Assessment in Animals

PyOKR: A Semi-Automated Method for Quantifying Optokinetic Reflex Tracking Ability

The study of behavioral responses to visual stimuli is a key component of understanding visual system function. One notable response is the optokinetic reflex (OKR), a highly conserved innate behavior necessary for image stabilization on the retina. The OKR provides a robust readout of image tracking ability and has been extensively studied to understand visual system circuitry and function in animals from different genetic backgrounds. The OKR consists of two phases: a slow tracking phase as the eye follows a stimulus to the edge of the visual plane and a compensatory fast phase saccade that resets the position of the eye in the orbit. Previous methods of tracking gain quantification, although reliable, are labor intensive and can be subjective or arbitrarily derived. To obtain more rapid and reproducible quantification of eye tracking ability, we have developed a novel&#160;semi-automated analysis program, PyOKR, that allows for quantification of two-dimensional eye tracking motion in response to any directional stimulus, in addition to being adaptable to any type of video-oculography equipment. This method provides automated filtering, selection of slow tracking phases, modeling of vertical and horizontal eye vectors, quantification of eye movement gains relative to stimulus speed, and organization of resultant data into a usable spreadsheet for statistical and graphical comparisons. This quantitative and streamlined analysis pipeline, readily accessible via PyPI import, provides a fast and direct measurement of OKR responses, thereby facilitating the study of visual behavioral responses.

Author Spotlight: A Streamlined and Accessible Analysis Method to Quantify Optokinetic Reflex Tracking Responses

We describe here PyOKR, a semi-automated quantitative analysis method that directly measures eye movements resulting from visual responses to two-dimensional image motion. A Python-based user interface and analysis algorithm allows for higher throughput and more accurate quantitative measurements of eye-tracking parameters than previous methods.

The study of behavioral responses to visual stimuli is a key component of understanding visual system function. One notable response is the optokinetic ...