La stéréopsie est souvent présente, bien qu’altérée, chez les sujets microstrabiques. Cependant, leur seuil de stéréopsie serait différent selon que le test utilisé contient (stéréopsie locale) ou non (stéréopsie globale) des contours définis. Peu d’études ont évalué empiriquement la différence de performance selon le type de tests utilisé. Le premier article est une étude rétrospective de 26 enfants microstrabiques. La majorité des enfants (73 %) possédaient un seuil de stéréopsie locale normal ou légèrement inférieur à la normale. Une absence de stéréopsie locale a été observée chez les 7 autres enfants (27 %). Aucune stéréopsie globale n’était mesurable chez 25 des 26 enfants étudiés. La stéréopsie locale est donc présente chez les enfants microstrabiques, mais ceux-ci montrent généralement une absence de stéréoperception globale. La seconde étude avait pour objectif d'étudier le rôle du scotome de suppression dans la perception stéréoscopique de sujets microstrabiques. Trois tâches psychophysiques de stéréopsie locale et globale ont été effectuées chez 9 enfants microstrabiques et 9 enfants contrôles appariés, en utilisant deux grandeurs de cible (4° et 12°). Aucune amélioration des performances n’a été notée chez les sujets microstrabiques pour la tâche de stéréopsie locale, mais les seuils de stéréopsie globale étaient inférieurs avec la cible de 12°. La zone de suppression semble jouer un rôle dans le déficit de stéréopsie globale des sujets microstrabiques. Le scotome de suppression pourrait être partiellement responsable du déficit stéréoscopique puisque même avec l’augmentation de la taille angulaire des stimuli stéréoscopiques, la stéréoperception des microstrabiques demeurent inférieure à celle des sujets normaux. / Stereopsis is often present, although decreased, in subjects with microstrabismus. However, their threshold would differ depending on whether the test contains (local stereopsis) or not (global stereopsis) defined contours. Few studies have evaluated empirically the performance difference depending on the type of tests used. The first article is a retrospective study of 26 microstrabismic children. Majority of the children (73 %) had a normal local stereopsis threshold or slightly lower than normal. An absence of local stereopsis was observed in the 7 other children (27 %). No global stereopsis was measured on 25 of the 26 children. Local stereopsis is present, although reduced, among microstrabismic children, but they generally show a lack of global stereoperception. The objective of the second study was to examine the potential role of the suppression in the stereoscopic perception. Three psychophysical tasks of local and global stereopsis were performed on 9 microstrabismic children and 9 matched controls children using two size of stimulus (4° and 12°). No performance improvement has been noted in microstrabismic subjects for the local stereopsis task, but their global stereopsis thresholds were lower with the target of 12°. The suppression scotoma seems to play a role in global stereopsis deficits noted in subjects with microstrabismus. The area of suppression might be partly responsible for the stereoscopic deficits present in microstrabismic subjects since even with the increase of the angular size of the stereoscopic stimuli, the stereoperception of microstrabimic subjects remain lower than in normal subjects.

La stéréopsie est souvent présente, bien qu’altérée, chez les sujets microstrabiques. Cependant, leur seuil de stéréopsie serait différent selon que le test utilisé contient (stéréopsie locale) ou non (stéréopsie globale) des contours définis. Peu d’études ont évalué empiriquement la différence de performance selon le type de tests utilisé. Le premier article est une étude rétrospective de 26 enfants microstrabiques. La majorité des enfants (73 %) possédaient un seuil de stéréopsie locale normal ou légèrement inférieur à la normale. Une absence de stéréopsie locale a été observée chez les 7 autres enfants (27 %). Aucune stéréopsie globale n’était mesurable chez 25 des 26 enfants étudiés. La stéréopsie locale est donc présente chez les enfants microstrabiques, mais ceux-ci montrent généralement une absence de stéréoperception globale. La seconde étude avait pour objectif d'étudier le rôle du scotome de suppression dans la perception stéréoscopique de sujets microstrabiques. Trois tâches psychophysiques de stéréopsie locale et globale ont été effectuées chez 9 enfants microstrabiques et 9 enfants contrôles appariés, en utilisant deux grandeurs de cible (4° et 12°). Aucune amélioration des performances n’a été notée chez les sujets microstrabiques pour la tâche de stéréopsie locale, mais les seuils de stéréopsie globale étaient inférieurs avec la cible de 12°. La zone de suppression semble jouer un rôle dans le déficit de stéréopsie globale des sujets microstrabiques. Le scotome de suppression pourrait être partiellement responsable du déficit stéréoscopique puisque même avec l’augmentation de la taille angulaire des stimuli stéréoscopiques, la stéréoperception des microstrabiques demeurent inférieure à celle des sujets normaux. / Stereopsis is often present, although decreased, in subjects with microstrabismus. However, their threshold would differ depending on whether the test contains (local stereopsis) or not (global stereopsis) defined contours. Few studies have evaluated empirically the performance difference depending on the type of tests used. The first article is a retrospective study of 26 microstrabismic children. Majority of the children (73 %) had a normal local stereopsis threshold or slightly lower than normal. An absence of local stereopsis was observed in the 7 other children (27 %). No global stereopsis was measured on 25 of the 26 children. Local stereopsis is present, although reduced, among microstrabismic children, but they generally show a lack of global stereoperception. The objective of the second study was to examine the potential role of the suppression in the stereoscopic perception. Three psychophysical tasks of local and global stereopsis were performed on 9 microstrabismic children and 9 matched controls children using two size of stimulus (4° and 12°). No performance improvement has been noted in microstrabismic subjects for the local stereopsis task, but their global stereopsis thresholds were lower with the target of 12°. The suppression scotoma seems to play a role in global stereopsis deficits noted in subjects with microstrabismus. The area of suppression might be partly responsible for the stereoscopic deficits present in microstrabismic subjects since even with the increase of the angular size of the stereoscopic stimuli, the stereoperception of microstrabimic subjects remain lower than in normal subjects.

Le terme stéréopsie renvoie à la sensation de profondeur qui est perçue lorsqu’une scène est vue de manière binoculaire. Le système visuel s’appuie sur les disparités horizontales entre les images projetées sur les yeux gauche et droit pour calculer une carte des différentes profondeurs présentes dans la scène visuelle. Il est communément admis que le système stéréoscopique est encapsulé et fortement contraint par les connexions neuronales qui s’étendent des aires visuelles primaires (V1/V2) aux aires intégratives des voies dorsales et ventrales (V3, cortex temporal inférieur, MT). A travers quatre projets expérimentaux, nous avons étudié comment le système visuel utilise la disparité binoculaire pour calculer la profondeur des objets. Nous avons montré que le traitement de la disparité binoculaire peut être fortement influencé par d’autres sources d’information telles que l’occlusion binoculaire ou le son. Plus précisément, nos résultats expérimentaux suggèrent que : (1) La stéréo de da Vinci est résolue par un mécanisme qui intègre des processus de stéréo classiques (double fusion), des contraintes géométriques (les objets monoculaires sont nécessairement cachés à un œil, par conséquent ils sont situés derrière le plan de l’objet caché) et des connaissances à priori (une préférence pour les faibles disparités). (2) Le traitement du mouvement en profondeur peut être influencé par une information auditive : un son temporellement corrélé avec une cible définie par le mouvement stéréo peut améliorer significativement la recherche visuelle. Les détecteurs de mouvement stéréo sont optimalement adaptés pour détecter le mouvement 3D mais peu adaptés pour traiter le mouvement 2D. (3) Grouper la disparité binoculaire avec un signal auditif dans une dimension orthogonale (hauteur tonale) peut améliorer l’acuité stéréo d’approximativement 30% / Stereopsis refers the perception of depth that arises when a scene is viewed binocularly. The visual system relies on the horizontal disparities between the images from the left and right eyes to compute a map of the different depth values present in the scene. It is usually thought that the stereoscopic system is encapsulated and highly constrained by the wiring of neurons from the primary visual areas (V1/V2) to higher integrative areas in the ventral and dorsal streams (V3, inferior temporal cortex, MT). Throughout four distinct experimental projects, we investigated how the visual system makes use of binocular disparity to compute the depth of objects. In summary, we show that the processing of binocular disparity can be substantially influenced by other types of information such as binocular occlusion or sound. In more details, our experimental results suggest that: (1) da Vinci stereopsis is solved by a mechanism that integrates classic stereoscopic processes (double fusion), geometrical constraints (monocular objects are necessarily hidden to one eye, therefore they are located behind the plane of the occluder) and prior information (a preference for small disparities). (2) The processing of motion-in-depth can be influenced by auditory information: a sound that is temporally correlated with a stereomotion defined target can substantially improve visual search. Stereomotion detectors are optimally suited to track 3D motion but poorly suited to process 2D motion. (3) Grouping binocular disparity with an orthogonal auditory signal (pitch) can increase stereoacuity by approximately 30%

When seen through a stereoscope, a Gabor pattern (a Gaussian enveloped sinusoid) that is masked by visual noise is more readily detectable when it appears in front of or behind the noise than when it is embedded in the noise itself. The enhanced visibility brought about by stereo cues is referred to as binocular unmasking. In this work, we investigated whether binocular unmasking may also occur with visual objects more complex than simple Gabor patterns, and with tasks more demanding than detection. Specifically, we examined the effects of binocular unmasking in the detection, categorization, and identification of noise masked images of natural objects. We observed the occurrence of binocular unmasking in all three tasks. However, the size of this effect was greater for detection performance than for categorization or identification performance; the latter two benefited to the same extent by the availability of stereoscopic cues. We argue that these results suggest that low level stereoscopic depth cues may play a helpful role, not only in simple detection tasks with psychophysical stimuli, but also in the perception of complex stimuli depicting natural objects.

When seen through a stereoscope, a Gabor pattern (a Gaussian enveloped sinusoid) that is masked by visual noise is more readily detectable when it appears in front of or behind the noise than when it is embedded in the noise itself. The enhanced visibility brought about by stereo cues is referred to as binocular unmasking. In this work, we investigated whether binocular unmasking may also occur with visual objects more complex than simple Gabor patterns, and with tasks more demanding than detection. Specifically, we examined the effects of binocular unmasking in the detection, categorization, and identification of noise masked images of natural objects. We observed the occurrence of binocular unmasking in all three tasks. However, the size of this effect was greater for detection performance than for categorization or identification performance; the latter two benefited to the same extent by the availability of stereoscopic cues. We argue that these results suggest that low level stereoscopic depth cues may play a helpful role, not only in simple detection tasks with psychophysical stimuli, but also in the perception of complex stimuli depicting natural objects.

A graphical user interface program was created along with shape models, which allow persons with disabilities to set up a stereovision system with off-the-shelf hardware and detect objects of interest, which can be picked up using a sensor assisted telerobotic manipulator. A Hitachi KP-D50 CCD camera and an Imaging Source CCD camera were used along with two Imaging Source DFG/LC1 frame grabbers to set up a stereovision system. In order to use the stereovision system, the two main problems of correspondence and reconstruction are solved using subroutines of the program created for this work.The user interface allows the user to easily perform the intrinsic and extrinsic camera calibration required for stereovision, by following a few basic steps incorporated into the user interface program, which are described in this thesis. A calibration table required for these tasks can also be easily created using the program. In order to detect the object of interest, shape models, created by the user interface program, are used to solve the correspondence problem of stereovision. The correspondence problem is that of locating corresponding points in the left eye and the right eye, which are necessary to perform the calculations to obtain the location of the object of interest with respect to the end-effector. The shape models created for some commonly available items such as a doorknob and a door handle are included in the program and used to test the stereovision system. As expected, the error of detection decreases as the stereo system is moved closer to the object of interest in the x-, y- and z-position.

Background/Aims: In an investigation of the functional impact of amblyopia on children, the fine motor skills, perceived self-esteem and eye movements of amblyopic children were compared with that of age-matched controls. The influence of amblyogenic condition or treatment factors that might predict any decrement in outcome measures was investigated. The relationship between indirect measures of eye movements that are used clinically and eye movement characteristics recorded during reading was examined and the relevance of proficiency in fine motor skills to performance on standardised educational tests was explored in a sub-group of the control children. Methods: Children with amblyopia (n=82; age 8.2 ± 1.3 years) from differing causes (infantile esotropia n=17, acquired strabismus n=28, anisometropia n=15, mixed n=13 and deprivation n=9), and a control group of children (n=106; age 9.5 ± 1.2 years) participated in this study. Measures of visual function included monocular logMAR visual acuity (VA) and stereopsis assessed with the Randot Preschool Stereoacuity test, while fine motor skills were measured using the Visual-Motor Control (VMC) and Upper Limb Speed and Dexterity (ULSD) subtests of the Brunicks-Oseretsky Test of Motor Proficiency. Perceived self esteem was assessed for those children from grade 3 school level with the Harter Self Perception Profile for Children and for those in younger grades (preschool to grade 2) with the Pictorial Scale of Perceived Competence and Acceptance for Young Children. A clinical measure of eye movements was made with the Developmental Eye Movement (DEM) test for those children aged eight years and above. For appropriate case-control comparison of data, the results from amblyopic children were compared with age-matched sub-samples drawn from the group of children with normal vision who completed the tests. Eye movements during reading for comprehension were recorded by the Visagraph infra-red recording system and results of standardised tests of educational performance were also obtained for a sub-set of the control group. Results Amblyopic children (n=82; age 8.2 ± 1.7 years) performed significantly poorer than age-matched control children (n=37; age 8.3 ± 1.3 years) on 9 of 16 fine motor skills sub-items and for the overall age-standardised scores for both VMC and ULSD items (p<0.05); differences were most evident on timed manual dexterity tasks. The underlying aetiology of amblyopia and level of stereoacuity significantly affected fine motor skill performance on both items. However, when examined in a multiple regression model that took into account the inter-correlation between visual characteristics, poorer fine motor skills performance was only associated with strabismus (F1,75 = 5.428; p =0. 022), and not with the level of stereoacuity, refractive error or visual acuity in either eye. Amblyopic children from grade 3 school level and above (n=47; age 9.2 ± 1.3 years), particularly those with acquired strabismus, had significantly lower social acceptance scores than age-matched control children (n=52; age 9.4 ± 0.5 years) (F(5,93) = 3.14; p = 0.012). However, the scores of the amblyopic children were not significantly different to controls for other areas related to self-esteem, including scholastic competence, physical appearance, athletic competence, behavioural conduct and global self worth. A lower social acceptance score was independently associated with a history of treatment with patching but not with a history of strabismus or wearing glasses. Amblyopic children from pre-school to grade 2 school level (n=29; age = 6.6 ± 0.6 years) had similar self-perception scores to their age-matched peers (n=20; age = 6.4 ± 0.5 years). There were no significant differences between the amblyopic (n=39; age 9.1 ± 0.9 years) and age-matched control (n = 42; age = 9.3 ± 0.38 years) groups for any of the DEM outcome measures (Vertical Time, Horizontal Time, Number of Errors and Ratio (Horizontal time/Vertical time)). Performance on the DEM did not significantly relate to measures of VA in either eye, level of binocular function, history of strabismus or refractive error. Developmental Eye Movement test outcome measures Horizontal Time and Vertical Time were significantly correlated with reading rates measured by the Visagraph for both reading for comprehension and naming numbers (r>0.5). Some moderate correlations were also seen between the DEM Ratio and word reading rates as recorded by Visagraph (r=0.37). In children with normal vision, academic scores in mathematics, spelling and reading were associated with measures of fine motor skills. Strongest effect sizes were seen with the timed manual dexterity domain, Upper Limb Speed and Dexterity. Conclusions Amblyopia may have a negative impact on a child’s fine motor skills and an older child’s sense of acceptance by their peers may be influenced by treatment that includes eye patching. Clinical measures of eye movements were not affected in amblyopic children. A number of the outcome measures of the DEM are associated with objective recordings of reading rates, supporting its clinical use for identification of children with slower reading rates. In children with normal vision, proficiency on clinical measures of fine motor skill are associated with outcomes on standardised measures of educational performance. Scores on timed manual dexterity tasks had the strongest association with educational performance. Collectively, the results of this study indicate that, in addition to the reduction in visual acuity and binocular function that define the condition, amblyopes have functional impairment in childhood development skills that underlie proficiency in everyday activities. The study provides support for strategies aimed at early identification and remediation of amblyopia and the co-morbidities that arise from abnormal visual neurodevelopment.

Purpose: It is unknown whether individuals with two balanced eyes show quicker response and lower threshold in fine stereoscopic detection. Previous methods to measure ocular dominance were primarily qualitative, which do not quantify the degree of dominance and show limitation in identifying the dominant eye. In this study, we aimed at quantifying the difference of ocular strength between the two eyes with ocular dominance index (ODI) and studying the association of ocular balance between the two eyes with stereoscopic detection. Methods: Stereoscopic threshold was measured in thirty-three subjects. Stereopsis was measured with random dot stimuli. The minimal detectable disparity (Dmin) and the minimal time needed to acquire the best stereoacuity (Tmin) were quantified. Ocular dominance was measured by a continuous flashing technique with the tested eye viewing a titled Gabor patch increasing in contrast and the fellow non-tested eye viewing a Mondrian noise decreasing in contrast. The log ratio of Mondrian to Gabor’s contrasts was recorded when a subject just detected the tilting direction of the Gabor during each trial. The t-value derived from a t-test of the 50 values obtained in each eye was used to determine a subject’s ODI (ocular dominance index) to quantify the degree of ocular dominance. A subject with ODI ≥ 2 (p < 0.05) was defined to have clear dominance and the eye with larger mean ratio was the dominant eye. Results: The Dmin (55.40 arcsec) in subjects with two balanced eyes were not significantly different from the Dmin (43.29 arcsec) in subjects with clear ocular dominance (p = 0.87). Subjects with two balanced eyes had significantly (p = 0.01) shorter reaction times on average (Tmin = 138.28 msec) compared to subjects with clear dominance (Tmin = 1229.02 msec). Tmin values were highly correlated with ocular dominance (p = 0.0004). Conclusion: Subjects with two relatively balanced eyes take shorter reaction time to achieve optimal level of stereoacuity. Keywords: Ocular Dominance, Local Stereopsis, Binocular, Balanced Eyes, Anisometropia

Syfte: Syftet med denna pilotstudie var att jämföra en center distance-design mot en center near-design på asfäriska multifokala kontaktlinser och se dess påverkan på den funktionella synen hos presbyoper.  Metod: Totalt deltog 11 deltagare i åldrarna 45-55 år och genomgick mätningar av  synskärpa avstånd och nära, stereoseende avstånd och nära, kontrastkänslighet samt läshastighet. Testerna utfördes tre gånger, en gång med deltagarens refraktiva korrektion, en gång med center distance kontaktlinser och en gång med center near kontaktlinser i en randomiserad ordning. För testerna med normalfördelad data utfördes repeated measures ANOVA, och gällande testerna med icke normalfördelad data användes Friedmans non parametric ANOVA. Resultat: Ingen statistisk skillnad kunde hittas mellan linsdesignerna i något av testerna. Varken vid testerna för den funktionella synen, eller vid tester för synskärpa. En statistisk signifikant skillnad (p&lt;0,05)  hittades mellan linser och glasögonkorrektion vid tester för synskärpa, både vid avstånd och på nära håll, där en glasögonkorrektion gav bättre resultat.  Slutsats: Denna studie kunde ej påvisa någon skillnad mellan en center distance-design och en center near-design på asfäriska multifokala kontaktlinser vid tester gällande den funktionella synen för presbyoper. / Aim: This pilot study aimed to compare a center distance design against a center near design for aspheric multifocal contact lenses and their performance regarding visual function in presbyopes Method: 11 participants, between the age of 45-55, completed measurements in visual acuity for distance and near, stereoacuity for distance and near, contrast sensitivity and reading speed. These tests were performed three times, one time with spectacle correction, one time with a center distance contact lens design and a one time with a center near contact lens design in a randomized order. Regarding the tests with normally distributed data, a repeated measures ANOVA was conducted, and for the non-normally distributed data, a Friedman non parametric ANOVA was used. Results: No statistical difference was found between the two lens designs in any of the tests regarding visual function or regarding visual acuity. A statistically significant difference was found (p&lt;0,05) between spectacle correction and the two contact lenses regarding visual acuity for both distance and near, where a spectacle correction performed better.   Conclusion: This study did not find any difference in the visual function in presbyopes between a center distance design and a center near design for aspheric multifocal contact lenses.

Syfte: Syftet med denna studie är att undersöka om stereoseendet på nära håll påverkas genom att skapa en vertikal imbalans inducerad av 1 prismadioptri och således om det kan ge information som kan ligga till grund för glasval vid exempelvis anisometropi i vertikalled. Metod: 30 deltagare mellan 20-31 år, med medelålder 22,9 + 2,12, som uppfyllde inklusionskriterierna undersöktes. Subjektiv refraktion utfördes och en korrektion togs fram för deltagarna. Därefter undersöktes stereoseendet med TNO-test, först med 1 prd inducerad framför det dominanta ögat, därefter med 1 prd inducerad framför det icke-dominanta ögat, och sist med endast full korrektion. Därefter sammanställdes och analyserades resultatet. Resultat: Det hittades inget signifikant förhållande mellan 1 prd inducerad i vertikalled och stereoseende på nära håll, oavsett framför vilket öga vertikalprisma placerades (p&gt;0,05). När två outliers togs bort blev medianen för 1 prd framför dominant öga 90”, med 1 prd framför det icke-dominanta ögat 60” och med full korrektion 60”. Medianvärden och medelrankning visar en trend där stereopsis försämras med 1 prd inducerad i vertikalled, jämfört med full korrektion och störst försämring gavs med 1 prd inducerat framför det dominanta ögat. Slutsats: Studien visar att stereopsis på nära håll inte påverkas av att inducera 1 prd i vertikalled. Däremot kan studien påvisa en trend där stereoseendet påverkas negativt oavsett om vertikalprisma induceras framför det dominanta ögat eller icke-dominanta ögat. Störst försämring på stereopsis gavs när vertikalprisma placerades framför det dominanta ögat. / Purpose: The aim of this study was to investigate whether near-stereopsis is affected by creating a vertical imbalance induced by 1 prism dioptre and whether it can provide information considering glass selection, for example in case of anisometropia in the vertical direction. Method: 30 participants between ages of 20-31, with mean age 22,9 + 2,12, who met the inclusion criteria were examined. Subjective refraction was performed and a correction was produced for the participants. Stereovision was examined with TNO test, first with 1 prd induced in front of the dominant eye, then with 1 prd induced in front of the non-dominant eye, and lastly with only full correction. The results were compiled and analyzed. Result: No significant relationship was found between 1 prd induced in the vertical direction and near stereo vision, regardless of which eye the vertical prism was placed in front of (p&gt;0,05). When two outliers were removed, the median stereopsis for 1 prd in front of the dominant eye was 90”, with 1 prd in front of the non-dominant eye 60” and with full correction 60”. Median values and mean ranking show a trend where stereopsis worsens with 1 prd induced in the vertical direction, compared to full correction, and the greatest deterioration was given with 1 prd induced in front of the dominant eye. Conclusion: The study shows that stereopsis at near is not statistically significantly affected by inducing 1 prd in the vertical direction. However, this study can demonstrate a trend where stereopsis is negatively affected regardless of whether vertical prism is induced in front of the dominant eye or the non-dominant eye. The greatest deterioration in stereopsis occurred when the vertical prism was placed in front of the dominant eye.