The overarching theme of the thesis was to investigate the association between smart device use and computer vision syndrome. The initial study designed and developed the Open Field Tear film Analyser (OFTA) enabling a continuous, real-time assessment of the tear film and blink characteristics during smart device use. The monocular OFTA prototype was validated and showed good intra- and inter-observer repeatability relative to the Oculus Keratograph 5M and Bausch and Lomb one position keratometer. Subsequently, tear osmolarity following engagement with reading and gaming tasks on smart device and paper platforms was investigated. Discrete measures of osmolarity pre- and post-engagement with the tasks were obtained with the TearLab osmometer; osmolarity values differed between platforms when participants were engaged in a gaming task but no such difference was observed with the reading task. In addition, the influence of repeated measurements on tear osmolarity was also explored. To simulate the habitual binocular viewing conditions normally associated with smart device use, the binocular OFTA was developed. The device was used to assess the tear film and blink characteristics whilst engaging with reading and gaming tasks on smart device and paper platforms. The results revealed differences in blink characteristics and non-invasive tear break up time between the different platforms and tasks assessed. In addition, the thesis also reports on an investigation examining the real-time accommodative response to various targets displayed on smart devices using an open-field autorefractor with a Badal lens system adaptation. The results showed that accommodative latency, accommodative lag, mean velocity of accommodation, speed of disaccommodation and mean velocity of disaccommodation varied across the different platforms. Through the use of validated subjective questionnaires and smartphone apps, the relationship between duration of smartphone use and symptoms of dry eye were examined. The findings of this study demonstrated that longer duration of smartphone and personal computer use were associated with higher risk of dry eyes as indicated by subjective questionnaire outcomes.

A obtenção e a reconstrução da geometria tridimensional (3D) de objetos e ambientes têm importância crescente em áreas como visão computacional e computação gráfica. As formas atuais de obtenção e reconstrução 3D necessitam de equipamentos e montagens sofisticadas que, por conseqüência, têm custos elevados e aplicação limitada. Este trabalho apresenta criticamente os principais algoritmos para a reconstrução 3D a partir de par de imagens estéreo e identifica os mais viáveis para utilização com equipamentos convencionais. Por meio da implementação de alguns destes algoritmos, da comparação dos resultados obtidos em sua execução e também pela comparação com os resultados encontrados na literatura, são identificadas as principais deficiências. São propostas adequações aos algoritmos existentes, em particular, é apresentada a proposta da técnica das faixas que proporciona a redução drástica no consumo de memória para o processamento da geometria 3D e que possui desempenho computacional melhor em relação às técnicas tradicionais. Foi implementado um protótipo de sistema de reconstrução 3D que permite a reconstrução pelas diferentes técnicas estudadas e propostas, bem como permite visualizar o cenário reconstruído sob diferentes pontos de vista de forma interativa. / The acquisition and reconstruction of three-dimensional (3D) geometry of objects and environments have their importance growing in areas such as Computer Vision and Computer Graphics. The current methods to acquire and reconstruct three-dimensional data need sophisticated equipments and assemblies, which have expensive costs and limited applications. This work presents the main algorithms for 3D reconstruction using a pair of stereo images and identifies which are viable to use with conventional equipments. Through the implementation of some of these algorithms, by comparing the results obtained and comparing with the results presented in the literature, the main limitations were identified. This work proposes adjustments in the existing algorithms, in particular it proposes the stripping technique, which provides a huge memory usage reduction for 3D geometry processing and better computing performance if compared with traditional approaches. A prototype system for 3D reconstruction was implemented, which allows the reconstruction using the different researched and proposed techniques and allows interactive visualization of the reconstructed scene in different angles.

The observation or measurement of eye movement can aid in the detection and localization of vestibular pathology due to the relationship between the function of the vestibular sensory receptors in the inner ear and the eye movements produced by the vestibulo-ocular reflex (VOR). The majority of bedside and laboratory tests of vestibular function involve the observation or measurement of horizontal eye movements (i.e., horizontal VOR) produced by stimuli that activate the horizontal semicircular canals (SCCs) and the superior vestibular nerve. The video head impulse test (vHIT) is a new clinical test of dynamic SCC function that uses a high-speed digital video camera embedded in light-weight goggles to record head and eye movement during passive head rotations. An important precursor to the clinical use of a new diagnostic test is the evaluation of test reproducibility. If test reproducibility is poor, then the test is unlikely to be clinically useful. Currently, there are no published data concerning both inter- and intra-examiner reliability of the vHIT. The purpose of this study was to assess the test-retest reliability of the horizontal SCC vHIT in young healthy adult participants using the Otometrics Impulse vHIT device using a prospective repeated measures design. Forty-four young adults with normal hearing, normal caloric test results, and a negative history of vestibular disorder, neurological disease, open or closed head injury, or cervical spine injury participated in the study. Each examiner underwent one hour of training on the vHIT device prior to the initiation of the study. The vHIT was administered to each participant by each of two different examiners on two different days. Inter-session interval ranged from 1 to 10 days and examiner order was randomized. Each examiner manually rotated each participant’s head in leftward and rightward directions, and VOR gain (eye velocity/head velocity) was calculated for the left and right horizontal SCCs. The effects of examiner, session, and SCC (left horizontal versus right horizontal) on the magnitude of VOR gain were assessed using repeated measures analysis of variance. The intra-class correlation (ICC) coefficient was used to assess intra- and inter-examiner reliability. Preliminary findings obtained in 30 participants indicated that the main effects of examiner, session, and SCC on VOR gain were not significant. The ICCs for both inter-examiner (.847) and intra-examiner reliability (.813 for Examiner 1 and .845 for Examiner 2) were good. Testing was well-tolerated and completed in most participants in ~5 minutes. The vHIT has some important advantages relative to more established laboratory tests of horizontal SCC function including the ability to assess the vertical SCCs, lower cost, shorter test time, greater portability, minimal space requirements, and increased patient comfort. Additional data should be obtained from older participants with normal vestibular function and from patients with vestibular disorders. Within-subject comparisons between the results of the vHIT and the traditional tests of horizontal SCC function (caloric and rotary chair tests) will be important in determining the role of the vHIT in the vestibular test battery.

The angular vestibulo-ocular reflex (VOR) ensures gaze stability during head rotations by generating eye movements that are equal and opposite to head rotation. The gain of the VOR (eye velocity/head velocity) for natural head movements, therefore, approaches unity in healthy individuals. The VOR has four main anatomic components: the semicircular canals (SCCs) and vestibular nerve in the peripheral vestibular system, the vestibular and ocular motor nuclei in the brainstem, and the extraocular muscles. The SCCs are positioned in three nearly orthogonal planes within the head thereby allowing for the detection of head rotation about any axis in space. The SCCs function as angular accelerometers in a push-pull fashion with two coplanar canals on each side of the head working together, i.e., left and right horizontal SCCs, the right anterior and left posterior SCCs or RALP, and the left anterior and right posterior SCCs or LARP. The observation or measurement of eye movement can aid in the detection and localization of vestibular pathology due to the relationship between the function of the vestibular sensory receptors in the inner ear and the eye movements produced by the VOR. The video head impulse test (vHIT) is a relatively new clinical test of dynamic SCC function that uses a high-speed digital video camera embedded in light-weight goggles to record head and eye movement during passive head rotations in the horizontal and vertical planes. An important precursor to the clinical use of a new diagnostic test is the evaluation of test reproducibility. If test reproducibility is poor, then the test is unlikely to be clinically useful. There are no published data concerning both inter- and intra-examiner reliability of the vHIT. The purpose of this study was to establish normal reference intervals and assess the test-retest reliability of the vHIT in young healthy adult participants using the Micromedical vHIT device, two examiners, and a prospective repeated measures design. Each examiner underwent five hours of training on the vHIT device prior to the initiation of the study. The vHIT was administered to each participant (n = 35) by each examiner on two different days. Inter-session interval ranged from 1 to 30 days and examiner order was alternated for successive subjects; canal-plane order was randomized. At each session, participants underwent head impulse testing in each plane resulting in the stimulation of each of the six SCCs. The dependent variable was VOR gain (eye velocity/head velocity) and the effects of examiner, session, eye, and SCC on the magnitude of VOR gain were assessed using repeated measures analysis of variance. The intra-class correlation (ICC) coefficient was used to assess intra- and inter-examiner reliability. The cut-offs (5th percentiles) for normal VOR gain were 0.76 (right and left horizontal SCCs), 0.68 (right anterior SCC), 0.70 (left anterior SCC), 0.69 (right posterior SCC), and 0.75 (left posterior SCC). There was no significant effect of examiner on VOR gain and the ICCs indicated fair-to-good inter- and intra-examiner reliability with better reliability for the horizontal SCCs than for the posterior and anterior SCCs

The measurement of eye movement can aid in the detection and localization of vestibular pathology due to the relationship between the function of the vestibular sensory receptors in the inner ear and the eye movements produced by the vestibulo-ocular reflex (VOR). The majority of tests of vestibular function involve the measurement of horizontal eye movements produced by stimuli that activates the horizontal semicirculuar canals (hSCCs). The video head impulse test (vHIT) is a new clinical test of dynamic SCC function that uses a high-speed digital video camera embedded in light-weight goggles to record head and eye movement during passive head rotations. There are no published data concerning the examiner reliability of the vHIT. A prospective repeated measures design was used to assess test-retest reliability of the hSCC vHIT in young healthy adult participants (n=44). The vHIT was administered to each participant by each of two different examiners on two different days. A repeated measures analysis of variance was used to determine the effects of examiner, session, and hSCC on the magnitude of VOR gain (eye velocity/head velocity). The intra-class correlation coeffecient and the coefficient of repeatability were used to assess intra- and inter-examiner reliability.

Chez les animaux à vision binoculaire, la vision tridimensionnelle permet la perception de la profondeur grâce à l'intégration de l'information visuelle en provenance des deux yeux. La première étape de cette intégration est rendue possible anatomiquement par la ségrégation des axones controlatéraux et ipsilatéraux des cellules ganglionnaires de la rétine (CGR) au niveau du chiasma optique. Les axones controlatéraux croisent la ligne médiane au chiasma en route du nerf optique vers le cerveau. À l’inverse, les axones ipsilatéraux s'écartent du chiasma et continuent dans le tractus optique ipsilatéral, en évitant la ligne médiane vers leurs cibles cérébrales. Les mécanismes moléculaires à la base de ce phénomène ne sont pas complètement compris. Les études présentées dans cette thèse montrent que Boc, le récepteur de Sonic Hedgehog (Shh) dans le guidage axonal, est enrichi dans les CGRs ipsilatérales de la rétine en développement. La présence de Shh sur la ligne médiane, et le mode d'expression complémentaire du récepteur nous ont conduit à émettre l'hypothèse que Shh pourrait repousser les axones ipsilatéraux au niveau du chiasma en activant le récepteur Boc. Conformément à cette hypothèse, nous avons constaté que seulement les CGR exprimant Boc se rétractent in vitro en réponse à Shh et que cette réponse est perdue dans les CGR mutantes pour Boc. In vivo, nous démontrons que Boc est requis pour la ségrégation normale des axones ipsilatéraux au niveau du chiasma optique et, inversement, que l'expression ectopique de Boc dans les CGR contralatérales empêche leurs axones de traverser le chiasma optique. Dans l’ensemble, ces résultats suggèrent que Shh repousse les axones ipsilatéraux au niveau du chiasma optique par son récepteur Boc. Cette première partie de notre travail identifie un nouveau couple ligand-récepteur requis pour la ségrégation des axones au niveau du chiasma optique. Une interaction moléculaire impliquée dans cette ségrégation implique l’éphrine-B2 et ses récepteurs EphB (EphB1). Dans la deuxième partie de notre travail, nous montrons, in vivo, en utilisant des souris doubles et quadruples mutantes pour les récepteurs Boc, EphB1 ou les trois récepteurs EphB, que l’abrogation des deux voies de signalisation Shh et éphrine-B2 conduit à l'absence de projections ipsilatérales. Ceci indique que les deux signalisations agissent de façon indépendante dans des voies parallèles. De manière intéressante, ces souris mutantes ont été utilisées comme modèle génétique pour démontrer des défauts dans la perception de la profondeur de champs chez des animaux dépourvus de projections visuelles ipsilatérales. Ainsi, les travaux présentés dans cette thèse démontrent pour la première fois que la formation des projections rétiniennes ipsilatérales est essentielle à l’établissement de la vision binoculaire et dépend des voies induites par les récepteurs d’éphrine-B2 et Shh. / In animals with binocular vision, three dimensional vision allows perception of depth through the integration of visual information from both eyes. The first step of this integration is possible anatomically with the segregation of contralateral and ipsilateral axons at the optic chiasm. Contralateral axons cross the chiasm midline as they progress from the optic nerve to the optic tract. In contrast, ipsilateral axons deviate from the chiasm and continue in the ipsilateral optic tract. The molecular mechanism underlying this phenomenon is not completely understood. The studies presented in this thesis show that the Sonic Hedgehog (Shh) receptor Boc is enriched in ipsilateral RGCs of the developing retina. Together with the presence of Shh at the midline, this complementary expression pattern led us to hypothesize that Shh might repel ipsilateral RGC axons at the chiasm. Consistent with this hypothesis, we found that only Boc positive RGC axons retract in vitro in response to Shh and that this response is lost in Boc mutant RGCs. In vivo, we show that Boc is required for the normal segregation of ipsilateral axons at the optic chiasm and, conversely, that Boc expression in contralateral RGCs prevents their axons from crossing the optic chiasm. Taken together, these results suggest that Shh repels ipsilateral RGC axons at the optic chiasm via its receptor Boc. This first part of this thesis identifies a novel receptor required for the segregation of axons at the optic chiasm. The other couple ligand-receptor involved in this segregation is the Ephrin-B2/EphB signalling. In the second part of this thesis, I show that in vivo, the abrogation of both signalling pathways using quadruple knockout mice of the receptor Boc and three EphB receptors led to the absence of ipsilateral projections, indicating that Shh and ephrinB2 signalling act independently in two parallel pathways. More importantly, these animals, used as a new genetic model to perform visual tests, had a diminished ability to perceive depth. Thus, this thesis demonstrates for the first time that the establishment of ipsilateral retinal projections, essential for accurate binocular vision and perception of depth, is made possible by the combination of EphB and Shh signalling.

Abstract Introduction: H.J.-Haase developed a systematic set of tests for evaluating binocular vision called the Pola Test. The Pola Test measures associated phoria and stereoacuity at distance and near using a variety of different targets for each. This testing method and interpretation is referred to as MKH-Haase (Measuring and Correcting Methodology after H.J.Haase ???the MKH) method. The MKH method is more commonly used in Germany and other European countries than English speaking countries. The MKH-Haase method has been considered a reliable method for prescribing prisms to symptomatic binocular vision patients. Purpose: To investigate the test-retest reliability of binocular vision measurements using the MKH-Haase series of tests that comprise the Pola Test. In addition, I will compare the Pola results with other associated phoria and stereoacuity tests used in North America. Methods: Thirty-four symptomatic and 40 asymptomatic subjects (based on a symptoms questionnaire) participated in this study. Associated phoria and stereoacuity with different tests, including the Pola Test at distance and near, were measured for those subjects on two different sessions. Not all of subjects were tested with all tests. Only 30 subjects in each group completed all of tests. The Pola Test protocol requires the associated phoria and stereoacuity to be measured twice within a session; once with the Polariods oriented with their axes at 45o and 135o and again with the axes switched. Results: Within and between-sessions repeatability of MKH-Haase associated phoria and stereoacuity tests results revealed that most of MKH-Haase associated phoria and stereoacuity tests showed good repeatability within and between-sessions at both distance and near. However, there were a few exceptions to this general finding. Distance horizontal associated phoria values for the Cross Test and Pointer Test at the first session, and the distance Double Pointer Test values at the second session showed some differences between the two views. Between-sessions repeatability of the associated phoria tests did not show any significant differences. For the stereoacuity tests, the differences between the two disparities were statistically significant at the first session for the symptomatic group Line Test and asymptomatic group Step Test. For the second session at distance, the differences were significant with Step Test for both groups. The differences between sessions for both disparities were not significant for most of tests. The symptomatic group???s Step Test for crossed disparity and asymptomatic group's Step Test for uncrossed disparity were exceptions. A repeated measures ANOVA test was conducted to compare different associated phoria tests. Horizontal associated phoria tests without central fusion lock were significantly different from those with central fusion lock at distance and near. Comparison of different stereoacuity tests was conducted by comparing the number of subjects who could identify specific stereothreshold values. Results showed that at both distance and near, there were no significant differences between contour and global stereoacuity tests based on number of subjects who could attain 60 sec of arc or better. Discussion and Conclusion: Most of MKH-Haase associated phoria and stereoacuity charts have reasonable within and between-sessions repeatability. However, some associated phoria tests showed some differences especially with subjects who had higher values. Although there was a significant difference between various horizontal associated phoria tests at distance and near, most of the values differed by around 0.50 ???. The exception was the difference between the Wesson Card and Disparometer. The Wesson card was more exo by 1.50 ??? than the Disparometer. Vertical associated phoria tests did not show any significant differences. Although MKH-Haase chart can measure local stereothreshold down to 10 sec of arc at distance, the AO Slide is easier to perceive. Random dot stereoacuity can be measured with MKH-Haase charts at distance down to 30 sec of arc. All of the contour stereoacuity tests are comparable at near. However, the MKH-Haase chart was easier to perceive. The Random Dot Randot test would be more useful for fast screening purposes. Random dot MKH-Haase test would be easier than TNO Test to measure random dot stereothreshold at near.

PURPOSE. Gait during obstacle negotiation is adapted in visually normal subjects whose vision is temporarily and unilaterally blurred or occluded. This study was conducted to examine whether gait parameters in individuals with long-standing deficient stereopsis are similarly adapted. METHODS. Twelve visually normal subjects and 16 individuals with deficient stereopsis due to amblyopia and/or its associated conditions negotiated floor-based obstacles of different heights (7-22 cm). Trials were conducted during binocular viewing and monocular occlusion. Analyses focused on foot placement before the obstacle and toe clearance over it. RESULTS. Across all viewing conditions, there were significant group-by-obstacle height interactions for toe clearance (P < 0.001), walking velocity (P = 0.003), and penultimate step length (P = 0.022). Toe clearance decreased (similar to 0.7 cm) with increasing obstacle height in visually normal subjects, but it increased (similar to 1.5 cm) with increasing obstacle height in the stereo-deficient group. Walking velocity and penultimate step length decreased with increasing obstacle height in both groups, but the reduction was more pronounced in stereo-deficient individuals. Post hoc analyses indicated group differences in toe clearance and penultimate step length when negotiating the highest obstacle (P < 0.05). CONCLUSIONS. Occlusion of either eye caused significant and similar gait changes in both groups, suggesting that in stereo-deficient individuals, as in visually normal subjects, both eyes contribute usefully to the execution of adaptive gait. Under monocular and binocular viewing, obstacle-crossing performance in stereo-deficient individuals was more cautious when compared with that of visually normal subjects, but this difference became evident only when the subjects were negotiating higher obstacles; suggesting that such individuals may be at greater risk of tripping or falling during everyday locomotion. / RCUK (Research Councils, UK)

In binocular rivalry, paradigms have been proposed for unobtrusive moment-by-moment readout of observers' perceptual experience (“no-report paradigms”). Here, we take a first step to extend this concept to auditory multistability. Observers continuously reported which of two concurrent tone sequences they perceived in the foreground: high-pitch (1008 Hz) or low-pitch (400 Hz) tones. Interstimulus intervals were either fixed per sequence (Experiments 1 and 2) or random with tones alternating (Experiment 3). A horizontally drifting grating was presented to each eye; to induce binocular rivalry, gratings had distinct colors and motion directions. To associate each grating with one tone sequence, a pattern on the grating jumped vertically whenever the respective tone occurred. We found that the direction of the optokinetic nystagmus (OKN)—induced by the visually dominant grating—could be used to decode the tone (high/low) that was perceived in the foreground well above chance. This OKN-based readout improved after observers had gained experience with the auditory task (Experiments 1 and 2) and for simpler auditory tasks (Experiment 3). We found no evidence that the visual stimulus affected auditory multistability. Although decoding performance is still far from perfect, our paradigm may eventually provide a continuous estimate of the currently dominant percept in auditory multistability.

Conformal geometric algebra is defined in the thesis. Representations of geometric objects and possibilities of their geometric transformations are presented. Conformal geometric algebra is applied to the calculation of forward kinematics of a robotic manipulator UR10 from Universal Robots. It is also applied to determine the position of the machine based on the location and rotation of two cameras. Then it is used in an inverse task, where based on records from the two cameras, dimensions of the UR10 manipulator and possibilities of its movement, the mutual position of these cameras is determined. And consequently the possibilities of their location in space. Finally, the derived procedures are implemented in a custom program created in the CluCalc environment, using which a sample example verifying the correctness of these procedures is calculated.