Oculomotor responses and 3D displays

This thesis investigated some of the eye movement factors related to the development and use of eye pointing devices with three dimensional displays (stereoscopic and linear perspective). In order for eye pointing to be used as a successful device for input-control of a 3D display it is necessary to characterise the accuracy and speed with which the binocular point of foveation can locate a particular point in 3D space. Linear perspective was found to be insufficient to elicit a change in the depth of the binocular point of fixation except under optimal conditions (monocular viewing, accommodative loop open and constant display paradigm). Comparison of the oculomotor responses made between a stereoscopic 'virtual' and a 'real' display showed there were no differences with regards to target fixational accuracy. With one exception, subjects showed the same degree of fixational accuracy with respect to target direction and depth. However, close target proximity (in terms of direction) affected the accuracy of fixation with respect to depth (but not direction). No differences were found between fixational accuracy of large and small targets under either display conditions. The visual conditions eliciting fast changes in the location of the binocular point of foveation, i.e. saccade disconjugacy, were investigated. Target-directed saccade disconjugacy was confirmed, in some cases, between targets presented at different depths on a stereoscopic display. However, in general the direction of saccade disconjugacy was best predicted by the horizontal direction of the target. Leftward saccade disconjugacy was more divergent than rightward. This asymmetry was overlaid on a disconjugacy response, which when considered in relative terms, was appropriated for the level of vergence demand. Linear perspective depth cues did not elicit target-directed disconjugate saccades

Vision during manned booster operation Final report

Retinal images and accomodation control mechanism under conditions of space flight stres

Binocular coordination: reading stereoscopic sentences in depth

The present study employs a stereoscopic manipulation to present sentences in three dimensions to subjects as they read for comprehension. Subjects read sentences with (a) no depth cues, (b) a monocular depth cue that implied the sentence loomed out of the screen (i.e., increasing retinal size), (c) congruent monocular and binocular (retinal disparity) depth cues (i.e., both implied the sentence loomed out of the screen) and (d) incongruent monocular and binocular depth cues (i.e., the monocular cue implied the sentence loomed out of the screen and the binocular cue implied it receded behind the screen). Reading efficiency was mostly unaffected, suggesting that reading in three dimensions is similar to reading in two dimensions. Importantly, fixation disparity was driven by retinal disparity; fixations were significantly more crossed as readers progressed through the sentence in the congruent condition and significantly more uncrossed in the incongruent condition. We conclude that disparity depth cues are used on-line to drive binocular coordination during reading.<br/

Development of new methodologies for the clinical, objective and automated evaluation of visual function based on the analysis of ocular movements : application in visual health

Healthy visual function not only relies on good visual acuity. Other systems such as accommodation or binocular vision need to be effective. Binocular vision is the ability of the visual system to coordinate and integrate the information received separately from the two eyes into a single binocular percept. Anomalies in the binocular vision system lead to dysfunctions which are often associated with symptoms like asthenopia, diplopia, or ocular strain. The most prevalent non-strabismic binocular dysfunction is convergence insufficiency. The tests typically used to evaluate binocular vision and diagnose binocular dysfunctions essentially consist in eliciting eye movements and asking the patients to report when they perceive diplopia or single vision. In a conventional optometric clinical setting, they are generally run subjectively, as their results depend on the answers of the patients or on the examiner’s criteria. However, there exist instruments to determine the gaze position and measure ocular movements objectively, i.e. eye-trackers. These instruments are used as research tools in a wide range of applications (neuroscience, psychology, marketing, computer science, ophthalmology, etc.). Eye tracking systems are seldom used in optometric clinical practice, although it seems reasonable to think that the evaluation of binocular vision could better rely on eye tracking systems rather than subjective observations. In this context, the main objective of this thesis is to develop new methodologies for the clinical, objective and automated evaluation of visual function based on the analysis of ocular movements. This thesis is divided in 4 studies. In the first study, new methods for an eye tracking system based on multiple corneal reflections are proposed. The other 3 studies aim to analyze ocular movements in clinically interesting situations for the objective and automated evaluation of binocular vision. The results of the first study showed that the light sources configurations that produced the reflections in the lower region of the cornea showed higher accuracy. Vertical accuracy was slightly better with a higher number of corneal reflections. However, the proposed normalization methods improved vertical accuracy and counteracted the tendency for increasing accuracy with the number of glints. As a result, if the light sources are optimally positioned to avoid the interference of the eyelids and the normalization methods are applied, there is no need for more than two light sources. In the second study, an automated and objective method to measure phoria was proposed. It was significantly more repeatable than two other conventional clinical methods. However, the phoria results of the three tests were not interchangeable. This study brings to light several advantages of using eye-trackers in optometric clinical settings. The third study analyzes the characteristics of saccadic movements that occur during the near point of convergence test. The results showed that saccadic amplitude increased and rate decrease at closer viewing distances. These changes might be explained by the more rapid change of vergence demand and the greater angular size of the fixation target at near than at far. In general, saccades contributed to correct vergence errors and fixation position errors of the dominant eye. Finally, the fourth study focuses on the effects of the stimulus’ predictability on the latency and response time of vergence step movements. The results confirmed that vergence movements to predictable stimulus had shorter latency and response time than when the stimulus was random. Latency of convergence and divergence movements was influenced by the direction of the phoria. Other factors such as attention or voluntary effort might also affect vergence responses. All these effects might influence the final result of the vergence facility test, although further research is needed to specify the impact on the clinical test.Una bona funció visual no és sinònim exclusivament de bona agudesa visual. Cal que altres sistemes com l’acomodatiu o la visió binocular siguin eficaços. La visió binocular és la capacitat del sistema visual per coordinar i integrar la informació que reben els dos ulls en una única percepció. Anomalies en el sistema de visió binocular poden donar lloc a disfuncions associades a símptomes com astenopia, o visió doble. La disfunció no estràbica de la visió binocular més prevalent és la insuficiència de convergència. Els tests que normalment es fan per avaluar la visió binocular es basen en estimular moviments oculars i demanar als pacients que indiquin quan veuen doble i quan fusionen. A la pràctica clínica convencional, aquests tests solen ser subjectius. No obstant, hi ha instruments que serveixen per determinar objectivament la posició de mirada i mesurar els moviments oculars: els eye-trackers o instruments de seguiment de mirada. Aquests instruments s’utilitzen en recerca en moltes disciplines (neurociència, psicologia, marketing, oftalmologia, etc.). Tot i que una aplicació directa dels eye-trackers podria ser en l’avaluació de la visió binocular, els sistemes de seguiment de mirada gairebé no s’utilitzen en la pràctica clínica optomètrica. En aquest context, l’objectiu principal d’aquesta tesi és desenvolupar noves metodologies per a l’avaluació clínica, objectiva i automatitzada de la funció visual basades en l’anàlisi dels moviments oculars. La tesi està estructurada en 4 estudis. En el primer, es proposen nous mètodes per a un eye-tracker basat en múltiples reflexos corneals. Els altres 3 estudis tenen com a objectiu analitzar els moviments oculars en situacions d’interès clínic per avaluar objectiva i automàticament la visió binocular. Els resultats del primer estudi demostren que les configuracions d’il·luminació dels eye-trackers que formen les reflexions corneals a la zona inferior de la còrnia són més precises. La precisió vertical és lleugerament millor amb més fonts de llum. Tot i això, els mètodes de normalització proposats milloren considerablement la precisió vertical i contraresten la tendència de més precisió amb més fonts de llum. D’aquesta manera, si les fonts de llum no interfereixen amb les parpelles i s’apliquen els mètodes de normalització, no cal que els eye-trackers tinguin més de dues fonts de llum. En el segon estudi s’ha proposat un mètode automàtic i objectiu per mesurar la fòria. Aquest mètode és significativament més repetitiu que dos altres mètodes clínics. Tot i això, els resultats amb els tres mètodes no són intercanviables. Aquest estudi posa de manifest avantatges que podrien tenir els eye-trackers a la pràctica clínica optomètrica. En el tercer estudi s’analitzen les característiques dels moviments sacàdics que es produeixen durant la prova del punt proper de convergència. Els resultats demostren que l’amplitud dels sacàdics augmenta i la freqüència disminueix a mesura que s’escurça la distància. Aquests canvis poden ser deguts a que la demanda de vergència canvia més ràpid a distàncies properes que llunyanes, i a l’increment de la mida angular de l’objecte de fixació. En general, els sacàdics contribueixen a corregir els errors de vergència i els errors de fixació de l’ull dominant. Finalment, el quart estudi se centra en els efectes de la predictibilitat de l’estímul en la latència i temps de resposta dels salts de vergència. Els resultats confirmen que els moviments de vergència tenen una latència i temps de resposta més curts quan l’estímul es predictible que quan és aleatori. La latència dels moviments de convergència i divergència està influenciada per la direcció de la fòria. Altres factors com el grau d’atenció o d’esforç voluntari pot ser que afectin els moviments de vergència. Tots aquests efectes probablement influencien en el resultat final de la prova de la instal·lació de vergència, encara que es necessiten més investigacions per especificar l'impacte en la prova clínica

Engineering Data Compendium. Human Perception and Performance, Volume 1

The concept underlying the Engineering Data Compendium was the product an R and D program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design of military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by system designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is Volume 1, which contains sections on Visual Acquisition of Information, Auditory Acquisition of Information, and Acquisition of Information by Other Senses

Development of new methodologies for the clinical, objective and automated evaluation of visual function based on the analysis of ocular movements : application in visual health

Premi Extraordinari de Doctorat, promoció 2018-2019. Àmbit de CiènciesHealthy visual function not only relies on good visual acuity. Other systems such as accommodation or binocular vision need to be effective. Binocular vision is the ability of the visual system to coordinate and integrate the information received separately from the two eyes into a single binocular percept. Anomalies in the binocular vision system lead to dysfunctions which are often associated with symptoms like asthenopia, diplopia, or ocular strain. The most prevalent non-strabismic binocular dysfunction is convergence insufficiency. The tests typically used to evaluate binocular vision and diagnose binocular dysfunctions essentially consist in eliciting eye movements and asking the patients to report when they perceive diplopia or single vision. In a conventional optometric clinical setting, they are generally run subjectively, as their results depend on the answers of the patients or on the examiner’s criteria. However, there exist instruments to determine the gaze position and measure ocular movements objectively, i.e. eye-trackers. These instruments are used as research tools in a wide range of applications (neuroscience, psychology, marketing, computer science, ophthalmology, etc.). Eye tracking systems are seldom used in optometric clinical practice, although it seems reasonable to think that the evaluation of binocular vision could better rely on eye tracking systems rather than subjective observations. In this context, the main objective of this thesis is to develop new methodologies for the clinical, objective and automated evaluation of visual function based on the analysis of ocular movements. This thesis is divided in 4 studies. In the first study, new methods for an eye tracking system based on multiple corneal reflections are proposed. The other 3 studies aim to analyze ocular movements in clinically interesting situations for the objective and automated evaluation of binocular vision. The results of the first study showed that the light sources configurations that produced the reflections in the lower region of the cornea showed higher accuracy. Vertical accuracy was slightly better with a higher number of corneal reflections. However, the proposed normalization methods improved vertical accuracy and counteracted the tendency for increasing accuracy with the number of glints. As a result, if the light sources are optimally positioned to avoid the interference of the eyelids and the normalization methods are applied, there is no need for more than two light sources. In the second study, an automated and objective method to measure phoria was proposed. It was significantly more repeatable than two other conventional clinical methods. However, the phoria results of the three tests were not interchangeable. This study brings to light several advantages of using eye-trackers in optometric clinical settings. The third study analyzes the characteristics of saccadic movements that occur during the near point of convergence test. The results showed that saccadic amplitude increased and rate decrease at closer viewing distances. These changes might be explained by the more rapid change of vergence demand and the greater angular size of the fixation target at near than at far. In general, saccades contributed to correct vergence errors and fixation position errors of the dominant eye. Finally, the fourth study focuses on the effects of the stimulus’ predictability on the latency and response time of vergence step movements. The results confirmed that vergence movements to predictable stimulus had shorter latency and response time than when the stimulus was random. Latency of convergence and divergence movements was influenced by the direction of the phoria. Other factors such as attention or voluntary effort might also affect vergence responses. All these effects might influence the final result of the vergence facility test, although further research is needed to specify the impact on the clinical test.Una bona funció visual no és sinònim exclusivament de bona agudesa visual. Cal que altres sistemes com l’acomodatiu o la visió binocular siguin eficaços. La visió binocular és la capacitat del sistema visual per coordinar i integrar la informació que reben els dos ulls en una única percepció. Anomalies en el sistema de visió binocular poden donar lloc a disfuncions associades a símptomes com astenopia, o visió doble. La disfunció no estràbica de la visió binocular més prevalent és la insuficiència de convergència. Els tests que normalment es fan per avaluar la visió binocular es basen en estimular moviments oculars i demanar als pacients que indiquin quan veuen doble i quan fusionen. A la pràctica clínica convencional, aquests tests solen ser subjectius. No obstant, hi ha instruments que serveixen per determinar objectivament la posició de mirada i mesurar els moviments oculars: els eye-trackers o instruments de seguiment de mirada. Aquests instruments s’utilitzen en recerca en moltes disciplines (neurociència, psicologia, marketing, oftalmologia, etc.). Tot i que una aplicació directa dels eye-trackers podria ser en l’avaluació de la visió binocular, els sistemes de seguiment de mirada gairebé no s’utilitzen en la pràctica clínica optomètrica. En aquest context, l’objectiu principal d’aquesta tesi és desenvolupar noves metodologies per a l’avaluació clínica, objectiva i automatitzada de la funció visual basades en l’anàlisi dels moviments oculars. La tesi està estructurada en 4 estudis. En el primer, es proposen nous mètodes per a un eye-tracker basat en múltiples reflexos corneals. Els altres 3 estudis tenen com a objectiu analitzar els moviments oculars en situacions d’interès clínic per avaluar objectiva i automàticament la visió binocular. Els resultats del primer estudi demostren que les configuracions d’il·luminació dels eye-trackers que formen les reflexions corneals a la zona inferior de la còrnia són més precises. La precisió vertical és lleugerament millor amb més fonts de llum. Tot i això, els mètodes de normalització proposats milloren considerablement la precisió vertical i contraresten la tendència de més precisió amb més fonts de llum. D’aquesta manera, si les fonts de llum no interfereixen amb les parpelles i s’apliquen els mètodes de normalització, no cal que els eye-trackers tinguin més de dues fonts de llum. En el segon estudi s’ha proposat un mètode automàtic i objectiu per mesurar la fòria. Aquest mètode és significativament més repetitiu que dos altres mètodes clínics. Tot i això, els resultats amb els tres mètodes no són intercanviables. Aquest estudi posa de manifest avantatges que podrien tenir els eye-trackers a la pràctica clínica optomètrica. En el tercer estudi s’analitzen les característiques dels moviments sacàdics que es produeixen durant la prova del punt proper de convergència. Els resultats demostren que l’amplitud dels sacàdics augmenta i la freqüència disminueix a mesura que s’escurça la distància. Aquests canvis poden ser deguts a que la demanda de vergència canvia més ràpid a distàncies properes que llunyanes, i a l’increment de la mida angular de l’objecte de fixació. En general, els sacàdics contribueixen a corregir els errors de vergència i els errors de fixació de l’ull dominant. Finalment, el quart estudi se centra en els efectes de la predictibilitat de l’estímul en la latència i temps de resposta dels salts de vergència. Els resultats confirmen que els moviments de vergència tenen una latència i temps de resposta més curts quan l’estímul es predictible que quan és aleatori. La latència dels moviments de convergència i divergència està influenciada per la direcció de la fòria. Altres factors com el grau d’atenció o d’esforç voluntari pot ser que afectin els moviments de vergència. Tots aquests efectes probablement influencien en el resultat final de la prova de la instal·lació de vergència, encara que es necessiten més investigacions per especificar l'impacte en la prova clínica.Award-winningPostprint (published version

Deformable Beamsplitters: Enhancing Perception with Wide Field of View, Varifocal Augmented Reality Displays

An augmented reality head-mounted display with full environmental awareness could present data in new ways and provide a new type of experience, allowing seamless transitions between real life and virtual content. However, creating a light-weight, optical see-through display providing both focus support and wide field of view remains a challenge. This dissertation describes a new dynamic optical element, the deformable beamsplitter, and its applications for wide field of view, varifocal, augmented reality displays. Deformable beamsplitters combine a traditional deformable membrane mirror and a beamsplitter into a single element, allowing reflected light to be manipulated by the deforming membrane mirror, while transmitted light remains unchanged. This research enables both single element optical design and correct focus while maintaining a wide field of view, as demonstrated by the description and analysis of two prototype hardware display systems which incorporate deformable beamsplitters. As a user changes the depth of their gaze when looking through these displays, the focus of virtual content can quickly be altered to match the real world by simply modulating air pressure in a chamber behind the deformable beamsplitter; thus ameliorating vergence–accommodation conflict. Two user studies verify the display prototypes’ capabilities and show the potential of the display in enhancing human performance at quickly perceiving visual stimuli. This work shows that near-eye displays built with deformable beamsplitters allow for simple optical designs that enable wide field of view and comfortable viewing experiences with the potential to enhance user perception.Doctor of Philosoph

Effects of Lateral Motion on Stereoacuity Thresholds for Physically Moving Targets

The goal of this thesis was to determine the impact of lateral retinal motion on stereoacuity under natural viewing conditions. I found that stereoacuity thresholds remained stable when target velocities varied between 0 and 16 /s. These results do not agree with previous literature (Ramamurthy, Bedell & Patel, 2005) which found that stereoacuity degraded at higher velocities (greater than 3 deg/s). I suggest that depth is acquired very rapidly at target onset when targets are relatively broadband and have not been distorted by motion smear. Subsequent experiments ruled out the potential effects of monocular cues, retinal smear size and inter-stimulus delay enhancing perceived depth. I conclude that artefacts introduced by the graphical displays used by Ramamurthy et al. (2005) were responsible for the observed elevation of thresholds at higher velocities

Iterative Solvers for Physics-based Simulations and Displays

La génération d’images et de simulations réalistes requiert des modèles complexes pour capturer tous les détails d’un phénomène physique. Les équations mathématiques qui composent ces modèles sont compliquées et ne peuvent pas être résolues analytiquement. Des procédures numériques doivent donc être employées pour obtenir des solutions approximatives à ces modèles. Ces procédures sont souvent des algorithmes itératifs, qui calculent une suite convergente vers la solution désirée à partir d’un essai initial. Ces méthodes sont une façon pratique et efficace de calculer des solutions à des systèmes complexes, et sont au coeur de la plupart des méthodes de simulation modernes. Dans cette thèse par article, nous présentons trois projets où les algorithmes itératifs jouent un rôle majeur dans une méthode de simulation ou de rendu. Premièrement, nous présentons une méthode pour améliorer la qualité visuelle de simulations fluides. En créant une surface de haute résolution autour d’une simulation existante, stabilisée par une méthode itérative, nous ajoutons des détails additionels à la simulation. Deuxièmement, nous décrivons une méthode de simulation fluide basée sur la réduction de modèle. En construisant une nouvelle base de champ de vecteurs pour représenter la vélocité d’un fluide, nous obtenons une méthode spécifiquement adaptée pour améliorer les composantes itératives de la simulation. Finalement, nous présentons un algorithme pour générer des images de haute qualité sur des écrans multicouches dans un contexte de réalité virtuelle. Présenter des images sur plusieurs couches demande des calculs additionels à coût élevé, mais nous formulons le problème de décomposition des images afin de le résoudre efficacement avec une méthode itérative simple.Realistic computer-generated images and simulations require complex models to properly capture the many subtle behaviors of each physical phenomenon. The mathematical equations underlying these models are complicated, and cannot be solved analytically. Numerical procedures must thus be used to obtain approximate solutions. These procedures are often iterative algorithms, where an initial guess is progressively improved to converge to a desired solution. Iterative methods are a convenient and efficient way to compute solutions to complex systems, and are at the core of most modern simulation methods. In this thesis by publication, we present three papers where iterative algorithms play a major role in a simulation or rendering method. First, we propose a method to improve the visual quality of fluid simulations. By creating a high-resolution surface representation around an input fluid simulation, stabilized with iterative methods, we introduce additional details atop of the simulation. Second, we describe a method to compute fluid simulations using model reduction. We design a novel vector field basis to represent fluid velocity, creating a method specifically tailored to improve all iterative components of the simulation. Finally, we present an algorithm to compute high-quality images for multifocal displays in a virtual reality context. Displaying images on multiple display layers incurs significant additional costs, but we formulate the image decomposition problem so as to allow an efficient solution using a simple iterative algorithm

Optical Modeling of Schematic Eyes and the Ophthalmic Applications

The objectives of this dissertation are to advance and broaden the traditional average eye modeling technique by two extensions: 1) population-based and personalized eye modeling for both normal and diseased conditions, and 2) demonstration of applications of this pioneering eye modeling.The first type of representative eye modeling can be established using traditional eye modeling techniques with statistical biometric information of the targeted population. Ocular biometry parameters can be mathematically assigned according to the distribution functions and correlations between parameters. For example, the axial dimension of the eye relates to age, gender, and body height factors. With the investigation results from the studies of different population groups, population-based eye modeling can be established. The second type of eye model includes the optical components of the detailed corneal structure. Many of these structures, especially the corneal topography and wavefront aberration, are measured directly from the human eye. Therefore, the personalized eye models render the exact clinical measure and optical performance of the eye. In a sense, the whole eye, other than the identity of the individual, is quantified and stored in digital form for unlimited use for future research and industrial applications. The presentation of this dissertation is: Chapter 1 describes the background of the research in this area, the introduction of eye anatomy, and the motivation of this dissertation work. In Chapter 2, a comprehensive review of the contemporary techniques of measuring ocular parameters is presented and is followed by the review of literature and then the statistical analysis of the ocular biometry parameters. The goal of this chapter is to build a statistical base for population-based schematic eye modeling research. The analysis includes the investigation of the correlations between ocular parameters and ocular refraction, subject age, gender, ethnicity, and accommodation conditions. In Chapter 3, the tools and methods that are used in our optical eye modeling are introduced. The operation of the optical program ZEMAX is discussed. The detail of the optical eye modeling procedure and method of optical optimization, which is utilized to reproduce desired clinical measurement results, are described. The validation functions, which will be used to evaluate the optimization results, are also addressed. Chapter 4 includes the discussion of the population-based eye modeling and the personalized eye modeling. With the statistical information and the clinical measurements presented in Chapter 2 and the computation method described in Chapter 3, the two types of eye modeling technologies are demonstrated. The procedure, difficulty, and validation of eye modeling are included. The considerations of optical opacities, irregular optical surface, multiple reflection, scattering, and tear film breakup effects are discussed and the possible solutions in ZEMAX are suggested. Chapter 5 presents eye modeling applications of the simulations of ophthalmic instrument measurements. The demonstrated simulation results are retinoscopy and photorefraction. The simulation includes both normal eye model and diseased eye model. The close conformity between the simulation results with the actual clinical measurements further validates the eye modeling technique. The ophthalmic simulation application provides the potential for medical training and instrument development. The summary of the dissertation is given in Chapter 6