885 research outputs found
Engineering data compendium. Human perception and performance. User's guide
The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and 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 the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use
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Astigmatism and Pseudoaccommodation in Pseudophakic Eyes
noAdvanced IOLs with circumferential zones of different power provide pseudoaccommodation. We investigated the potential for power variation with meridian, namely astigmatism, to provide pseudo-accommodation. With appropriate power and axis orientations, acceptable pseudo-accommodation can be achieved
Visual and control aspects of saccadic eye movements
Physiological, behavioral, and control investigation of rapid saccadic jump eye movement in human
Change blindness: eradication of gestalt strategies
Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task
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 funciĂł visual no Ă©s sinònim exclusivament de bona agudesa visual. Cal que altres sistemes com l’acomodatiu o la visiĂł binocular siguin eficaços. La visiĂł binocular Ă©s la capacitat del sistema visual per coordinar i integrar la informaciĂł que reben els dos ulls en una Ăşnica percepciĂł. Anomalies en el sistema de visiĂł binocular poden donar lloc a disfuncions associades a sĂmptomes com astenopia, o visiĂł doble. La disfunciĂł no estrĂ bica de la visiĂł binocular mĂ©s prevalent Ă©s la insuficiència de convergència. Els tests que normalment es fan per avaluar la visiĂł binocular es basen en estimular moviments oculars i demanar als pacients que indiquin quan veuen doble i quan fusionen. A la prĂ ctica clĂnica convencional, aquests tests solen ser subjectius. No obstant, hi ha instruments que serveixen per determinar objectivament la posiciĂł 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 aplicaciĂł directa dels eye-trackers podria ser en l’avaluaciĂł de la visiĂł binocular, els sistemes de seguiment de mirada gairebĂ© no s’utilitzen en la prĂ ctica clĂnica optomètrica. En aquest context, l’objectiu principal d’aquesta tesi Ă©s desenvolupar noves metodologies per a l’avaluaciĂł clĂnica, objectiva i automatitzada de la funciĂł visual basades en l’anĂ lisi dels moviments oculars. La tesi estĂ estructurada en 4 estudis. En el primer, es proposen nous mètodes per a un eye-tracker basat en mĂşltiples reflexos corneals. Els altres 3 estudis tenen com a objectiu analitzar els moviments oculars en situacions d’interès clĂnic per avaluar objectiva i automĂ ticament la visiĂł binocular. Els resultats del primer estudi demostren que les configuracions d’il·luminaciĂł dels eye-trackers que formen les reflexions corneals a la zona inferior de la còrnia sĂłn mĂ©s precises. La precisiĂł vertical Ă©s lleugerament millor amb mĂ©s fonts de llum. Tot i això, els mètodes de normalitzaciĂł proposats milloren considerablement la precisiĂł vertical i contraresten la tendència de mĂ©s precisiĂł amb mĂ©s fonts de llum. D’aquesta manera, si les fonts de llum no interfereixen amb les parpelles i s’apliquen els mètodes de normalitzaciĂł, no cal que els eye-trackers tinguin mĂ©s de dues fonts de llum. En el segon estudi s’ha proposat un mètode automĂ tic i objectiu per mesurar la fòria. Aquest mètode Ă©s significativament mĂ©s repetitiu que dos altres mètodes clĂnics. Tot i això, els resultats amb els tres mètodes no sĂłn intercanviables. Aquest estudi posa de manifest avantatges que podrien tenir els eye-trackers a la prĂ ctica clĂnica optomètrica. En el tercer estudi s’analitzen les caracterĂstiques dels moviments sacĂ dics que es produeixen durant la prova del punt proper de convergència. Els resultats demostren que l’amplitud dels sacĂ dics augmenta i la freqüència disminueix a mesura que s’escurça la distĂ ncia. Aquests canvis poden ser deguts a que la demanda de vergència canvia mĂ©s rĂ pid a distĂ ncies properes que llunyanes, i a l’increment de la mida angular de l’objecte de fixaciĂł. En general, els sacĂ dics contribueixen a corregir els errors de vergència i els errors de fixaciĂł de l’ull dominant. Finalment, el quart estudi se centra en els efectes de la predictibilitat de l’estĂmul 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 mĂ©s curts quan l’estĂmul es predictible que quan Ă©s aleatori. La latència dels moviments de convergència i divergència estĂ influenciada per la direcciĂł de la fòria. Altres factors com el grau d’atenciĂł 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·laciĂł de vergència, encara que es necessiten mĂ©s investigacions per especificar l'impacte en la prova clĂnica
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, promociĂł 2018-2019. Ă€mbit 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 funciĂł visual no Ă©s sinònim exclusivament de bona agudesa visual. Cal que altres sistemes com l’acomodatiu o la visiĂł binocular siguin eficaços. La visiĂł binocular Ă©s la capacitat del sistema visual per coordinar i integrar la informaciĂł que reben els dos ulls en una Ăşnica percepciĂł. Anomalies en el sistema de visiĂł binocular poden donar lloc a disfuncions associades a sĂmptomes com astenopia, o visiĂł doble. La disfunciĂł no estrĂ bica de la visiĂł binocular mĂ©s prevalent Ă©s la insuficiència de convergència. Els tests que normalment es fan per avaluar la visiĂł binocular es basen en estimular moviments oculars i demanar als pacients que indiquin quan veuen doble i quan fusionen. A la prĂ ctica clĂnica convencional, aquests tests solen ser subjectius. No obstant, hi ha instruments que serveixen per determinar objectivament la posiciĂł 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 aplicaciĂł directa dels eye-trackers podria ser en l’avaluaciĂł de la visiĂł binocular, els sistemes de seguiment de mirada gairebĂ© no s’utilitzen en la prĂ ctica clĂnica optomètrica. En aquest context, l’objectiu principal d’aquesta tesi Ă©s desenvolupar noves metodologies per a l’avaluaciĂł clĂnica, objectiva i automatitzada de la funciĂł visual basades en l’anĂ lisi dels moviments oculars. La tesi estĂ estructurada en 4 estudis. En el primer, es proposen nous mètodes per a un eye-tracker basat en mĂşltiples reflexos corneals. Els altres 3 estudis tenen com a objectiu analitzar els moviments oculars en situacions d’interès clĂnic per avaluar objectiva i automĂ ticament la visiĂł binocular. Els resultats del primer estudi demostren que les configuracions d’il·luminaciĂł dels eye-trackers que formen les reflexions corneals a la zona inferior de la còrnia sĂłn mĂ©s precises. La precisiĂł vertical Ă©s lleugerament millor amb mĂ©s fonts de llum. Tot i això, els mètodes de normalitzaciĂł proposats milloren considerablement la precisiĂł vertical i contraresten la tendència de mĂ©s precisiĂł amb mĂ©s fonts de llum. D’aquesta manera, si les fonts de llum no interfereixen amb les parpelles i s’apliquen els mètodes de normalitzaciĂł, no cal que els eye-trackers tinguin mĂ©s de dues fonts de llum. En el segon estudi s’ha proposat un mètode automĂ tic i objectiu per mesurar la fòria. Aquest mètode Ă©s significativament mĂ©s repetitiu que dos altres mètodes clĂnics. Tot i això, els resultats amb els tres mètodes no sĂłn intercanviables. Aquest estudi posa de manifest avantatges que podrien tenir els eye-trackers a la prĂ ctica clĂnica optomètrica. En el tercer estudi s’analitzen les caracterĂstiques dels moviments sacĂ dics que es produeixen durant la prova del punt proper de convergència. Els resultats demostren que l’amplitud dels sacĂ dics augmenta i la freqüència disminueix a mesura que s’escurça la distĂ ncia. Aquests canvis poden ser deguts a que la demanda de vergència canvia mĂ©s rĂ pid a distĂ ncies properes que llunyanes, i a l’increment de la mida angular de l’objecte de fixaciĂł. En general, els sacĂ dics contribueixen a corregir els errors de vergència i els errors de fixaciĂł de l’ull dominant. Finalment, el quart estudi se centra en els efectes de la predictibilitat de l’estĂmul 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 mĂ©s curts quan l’estĂmul es predictible que quan Ă©s aleatori. La latència dels moviments de convergència i divergència estĂ influenciada per la direcciĂł de la fòria. Altres factors com el grau d’atenciĂł 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·laciĂł de vergència, encara que es necessiten mĂ©s investigacions per especificar l'impacte en la prova clĂnica.Award-winningPostprint (published version
A multimodal investigation in eye movements
While functional magnetic resonance imaging (fMRI) has identified which regions of interest (ROIs) are functionally active during a vergence movement (inward or outward eye rotation), task-modulated coactivation between ROIs is less understood. This study tests the following hypotheses: (1) significant task-modulated coactivation would be observed between the frontal eye fields (FEFs), the posterior parietal cortex (PPC), and the cerebellar vermis (CV); (2) significantly more functional activity and task-modulated coactivation would be observed in binocularly normal controls (BNCs) compared with convergence insufficiency (CI) subjects; and (3) after vergence training, the functional activity and task-modulated coactivation would increase in CIs compared with their baseline measurements. A block design of sustained fixation versus vergence eye movements stimulates activity in the FEFs, PPC, and CV. fMRI data from four CI subjects before and after vergence training are compared with seven BNCs. Functional activity is assessed using the blood oxygenation level dependent (BOLD) percent signal change. Task-modulated coactivation is assessed using an ROI-based task modulated coactivation analysis that reveals significant correlation between ROIs
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3D motion : encoding and perception
The visual system supports perception and inferences about events in a dynamic, three-dimensional (3D) world. While remarkable progress has been made in the study of visual information processing, the existing paradigms for examining visual perception and its relation to neural activity often fail to generalize to perception in the real world which has complex dynamics and 3D spatial structure. This thesis focuses on the case of 3D motion, developing dynamic tasks for studying visual perception and constructing a neural coding framework to relate neural activity to perception in a 3D environment.
First, I introduce target-tracking as a psychophysical method and develop an analysis framework based on state space models and the Kalman filter. I demonstrate that target-tracking in conjunction with a Kalman filter analysis framework produce estimates of visual sensitivity that are comparable to those obtained with a traditional forced-choice task and a signal detection theory analysis. Next, I use the target-tracking paradigm in a series of experiments examining 3D motion perception, specifically comparing the perception of frontoparallel motion with the perception of motion-through-depth. I find that continuous tracking of motion-through-depth is selectively impaired due to the relatively small retinal projections resulting from motion-through-depth and the slower processing of binocular disparities.
The thesis then turns the neural representation of 3D motion and how that underlies perception. First I introduce a theoretical framework that extends the standard neural coding approach, incorporating the environment-to-retina transformation. Neural coding typically treats the visuals stimulus as a direct proxy for the pattern of stimulation that falls on the retina. Incorporating the environment-to-retina transformation results in a neural representation fundamentally shaped by the projective geometry of the world onto the retina. This model explains substantial anomalies in existing neurophysiological recordings in primate visual cortical neurons during presentations of 3D motion and in psychophysical studies of human perception. In a series of psychophysical experiments, I systematically examine the predictions of the model for human perception by observing how perceptual performance changes as a function of viewing distance and eccentricity. Performance in these experiments suggests a reliance on a neural representation similar to the one described by the model.
Taken together, the experimental and theoretical findings reported here advance the understanding of the neural representation and perception of the dynamic 3D world, and adds to the behavioral tools available to vision scientists.Neuroscienc
Methods for reducing visual discomfort in stereoscopic 3D: A review
This work was supported by the EPSRC Grant EP/M01469X/1, “Geometric Evaluation of Stereoscopic Video”
Naturalistic depth perception and binocular vision
Humans continuously move both their eyes to redirect their foveae to objects at new depths. To correctly execute these complex combinations of saccades, vergence eye movements and accommodation changes, the visual system makes use of multiple sources of depth information, including binocular disparity and defocus. Furthermore, during development, both fine-tuning of oculomotor control as well as correct eye growth are likely driven by complex interactions between eye movements, accommodation, and the distributions of defocus and depth information across the retina. I have employed photographs of natural scenes taken with a commercial plenoptic camera to examine depth perception while varying perspective, blur and binocular disparity. Using a gaze contingent display with these natural images, I have shown that disparity and peripheral blur interact to modify eye movements and facilitate binocular fusion. By decoupling visual feedback for each eye, I have found it possible to induces both conjugate and disconjugate changes in saccadic adaptation, which helps us understand to what degree the eyes can be individually controlled. To understand the aetiology of myopia, I have developed geometric models of emmetropic and myopic eye shape, from which I have derived psychophysically testable predictions about visual function. I have then tested the myopic against the emmetropic visual system and have found that some aspects of visual function decrease in the periphery at a faster rate in best-corrected myopic observers than in emmetropes. To study the effects of different depth cues on visual development, I have investigated accommodation response and sensitivity to blur in normal and myopic subjects. This body of work furthers our understanding of oculomotor control and 3D perception, has applied implications regarding discomfort in the use of virtual reality, and provides clinically relevant insights regarding the development of refractive error and potential approaches to prevent incorrect emmetropization
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