Right Visual Field Advantage in Parafoveal Processing: Evidence from Eye-Fixation-Related Potentials

Science.gov (United States)

Simola, Jaana; Holmqvist, Kenneth; Lindgren, Magnus

2009-01-01

Readers acquire information outside the current eye fixation. Previous research indicates that having only the fixated word available slows reading, but when the next word is visible, reading is almost as fast as when the whole line is seen. Parafoveal-on-foveal effects are interpreted to reflect that the characteristics of a parafoveal word can…

Eye movement identification based on accumulated time feature

Science.gov (United States)

Guo, Baobao; Wu, Qiang; Sun, Jiande; Yan, Hua

2017-06-01

Eye movement is a new kind of feature for biometrical recognition, it has many advantages compared with other features such as fingerprint, face, and iris. It is not only a sort of static characteristics, but also a combination of brain activity and muscle behavior, which makes it effective to prevent spoofing attack. In addition, eye movements can be incorporated with faces, iris and other features recorded from the face region into multimode systems. In this paper, we do an exploring study on eye movement identification based on the eye movement datasets provided by Komogortsev et al. in 2011 with different classification methods. The time of saccade and fixation are extracted from the eye movement data as the eye movement features. Furthermore, the performance analysis was conducted on different classification methods such as the BP, RBF, ELMAN and SVM in order to provide a reference to the future research in this field.

Assessment of a new hydrophilic acrylic supplementary IOL for sulcus fixation in pseudophakic cadaver eyes

Science.gov (United States)

Reiter, N; Werner, L; Guan, J; Li, J; Tsaousis, K T; Mamalis, N; Srinivasan, S

2017-01-01

Purpose Management of refractive errors after cataract surgery includes spectacles or contact lens, secondary laser vision correction, intraocular lens (IOL) exchange, or piggyback lens implantation. We evaluated for the first time a single-piece hydrophilic acrylic IOL designed for supplementary sulcus fixation in postmortem pseudophakic human eyes. Methods Pseudophakic human cadaver eyes were imaged by anterior segment optical coherence tomography (AS-OCT) to assess position of the primary IOL. Eyes were prepared as per the Miyake-Apple technique. The supplementary IOL (Medicontur A4 Addon IOL family) was then inserted into the ciliary sulcus. AS-OCT and photographs from anterior and posterior views were used to assess IOL centration, tilt, and interlenticular distance from the primary IOL. Results Data were obtained from 12 eyes having primary IOLs of varying materials and designs in the bag and representing different sizes of eyes and severity of Soemmering's ring formation. The A4 Addon IOL was successfully inserted into the ciliary sulcus and was well centered in all cases. Four cases of tilt were observed on AS-OCT: three with mild tilt due to pre-existing zonular dehiscence, and one due to a localized area of Soemmering's ring formation. Interlenticular distance ranged from 0.34 to 1.24 mm and was not dependent on severity of Soemmering's ring or type of primary IOL. Conclusions The A4 Addon IOL was designed for sulcus fixation as a supplementary lens, with a large diameter, a square-shaped optic, four smooth loop haptics, and a convex–concave optical surface. It exhibited appropriate centration and interlenticular distance with different primary in-the-bag IOLs. PMID:28106890

Fixation distance and fixation duration to vertical road signs.

Science.gov (United States)

Costa, Marco; Simone, Andrea; Vignali, Valeria; Lantieri, Claudio; Palena, Nicola

2018-05-01

The distance of first-fixation to vertical road signs was assessed in 22 participants while driving a route of 8.34 km. Fixations to road signs were recorded by a mobile eye-movement-tracking device synchronized to GPS and kinematic data. The route included 75 road signs. First-fixation distance and fixation duration distributions were positively skewed. Median distance of first-fixation was 51 m. Median fixation duration was 137 ms with a modal value of 66 ms. First-fixation distance was linearly related to speed and fixation duration. Road signs were gazed at a much closer distance than their visibility distance. In a second study a staircase procedure was used to test the presentation-time threshold that lead to a 75% accuracy in road sign identification. The threshold was 35 ms, showing that short fixations to a road signs could lead to a correct identification. Copyright © 2018 Elsevier Ltd. All rights reserved.

How do children deal with inconsistencies in text? An eye fixation and self-paced reading study in primary school children.

NARCIS (Netherlands)

van der Schoot, M.; Reijntjes, A.H.A.; van Lieshout, E.C.D.M.

2012-01-01

In two experiments, we investigated comprehension monitoring in 10-12 years old children differing in reading comprehension skill. The children's self-paced reading times (Experiment 1) and eye fixations and regressions (Experiment 2) were measured as they read narrative texts in which an action of

EEG Negativity in Fixations Used for Gaze-Based Control: Toward Converting Intentions into Actions with an Eye-Brain-Computer Interface

Science.gov (United States)

Shishkin, Sergei L.; Nuzhdin, Yuri O.; Svirin, Evgeny P.; Trofimov, Alexander G.; Fedorova, Anastasia A.; Kozyrskiy, Bogdan L.; Velichkovsky, Boris M.

2016-01-01

We usually look at an object when we are going to manipulate it. Thus, eye tracking can be used to communicate intended actions. An effective human-machine interface, however, should be able to differentiate intentional and spontaneous eye movements. We report an electroencephalogram (EEG) marker that differentiates gaze fixations used for control from spontaneous fixations involved in visual exploration. Eight healthy participants played a game with their eye movements only. Their gaze-synchronized EEG data (fixation-related potentials, FRPs) were collected during game's control-on and control-off conditions. A slow negative wave with a maximum in the parietooccipital region was present in each participant's averaged FRPs in the control-on conditions and was absent or had much lower amplitude in the control-off condition. This wave was similar but not identical to stimulus-preceding negativity, a slow negative wave that can be observed during feedback expectation. Classification of intentional vs. spontaneous fixations was based on amplitude features from 13 EEG channels using 300 ms length segments free from electrooculogram contamination (200–500 ms relative to the fixation onset). For the first fixations in the fixation triplets required to make moves in the game, classified against control-off data, a committee of greedy classifiers provided 0.90 ± 0.07 specificity and 0.38 ± 0.14 sensitivity. Similar (slightly lower) results were obtained for the shrinkage Linear Discriminate Analysis (LDA) classifier. The second and third fixations in the triplets were classified at lower rate. We expect that, with improved feature sets and classifiers, a hybrid dwell-based Eye-Brain-Computer Interface (EBCI) can be built using the FRP difference between the intended and spontaneous fixations. If this direction of BCI development will be successful, such a multimodal interface may improve the fluency of interaction and can possibly become the basis for a new input device

EEG Negativity in Fixations Used for Gaze-Based Control: Toward Converting Intentions into Actions with an Eye-Brain-Computer Interface

Directory of Open Access Journals (Sweden)

Sergei L. Shishkin

2016-11-01

Full Text Available We usually look at an object when we are going to manipulate it. Thus, eye tracking can be used to communicate intended actions. An effective human-machine interface, however, should be able to differentiate intentional and spontaneous eye movements. We report an electroencephalogram (EEG marker that differentiates gaze fixations used for control from spontaneous fixations involved in visual exploration. Eight healthy participants played a game with their eye movements only. Their gaze-synchronized EEG data (fixation-related potentials, FRPs were collected during game’s control-on and control-off conditions. A slow negative wave with a maximum in the parietooccipital region was present in each participant’s averaged FRPs in the control-on conditions and was absent or had much lower amplitude in the control-off condition. This wave was similar but not identical to stimulus-preceding negativity, a slow negative wave that can be observed during feedback expectation. Classification of intentional vs. spontaneous fixations was based on amplitude features from 13 EEG channels using 300 ms length segments free from electrooculogram contamination (200..500 ms relative to the fixation onset. For the first fixations in the fixation triplets required to make moves in the game, classified against control-off data, a committee of greedy classifiers provided 0.90 ± 0.07 specificity and 0.38 ± 0.14 sensitivity. Similar (slightly lower results were obtained for the shrinkage LDA classifier. The second and third fixations in the triplets were classified at lower rate. We expect that, with improved feature sets and classifiers, a hybrid dwell-based Eye-Brain-Computer Interface (EBCI can be built using the FRP difference between the intended and spontaneous fixations. If this direction of BCI development will be successful, such a multimodal interface may improve the fluency of interaction and can possibly become the basis for a new input device for

Transient improvements in fixational stability in strabismic amblyopes following bifoveal fixation and reduced interocular suppression.

Science.gov (United States)

Raveendran, Rajkumar Nallour; Babu, Raiju J; Hess, Robert F; Bobier, William R

2014-03-01

To test the hypothesis that fixational stability of the amblyopic eye in strabismics will improve when viewing provides both bifoveal fixation and reduced inter-ocular suppression by reducing the contrast to the fellow eye. Seven strabismic amblyopes (Age: 29.2 ± 9 years; five esotropes and two exotropes) showing clinical characteristics of central suppression were recruited. Interocular suppression was measured by a global motion task. For each participant, a balance point was determined which defined contrast levels for each eye where binocular combination was optimal (interocular suppression minimal). When the balance point could not be determined, this participant was excluded. Bifoveal fixation was established by ocular alignment using a haploscope. Participants dichoptically viewed similar targets (a cross of 2.3° surrounded by a square of 11.3°) at 40 cm. Target contrasts presented to each eye were either high contrast (100% to both eyes) or balanced contrast (attenuated contrast in the fellow fixing eye). Fixation stability was measured over a 5 min period and quantified using bivariate contour ellipse areas in four different binocular conditions; unaligned/high contrast, unaligned/balance point, aligned/high contrast and aligned/balance point. Fixation stability was also measured in six control subjects (Age: 25.3 ± 4 years). Bifoveal fixation in the strabismics was transient (58.15 ± 15.7 s). Accordingly, fixational stability was analysed over the first 30 s using repeated measures anova. Post hoc analysis revealed that for the amblyopic subjects, the fixational stability of the amblyopic eye was significantly improved in aligned/high contrast (p = 0.01) and aligned/balance point (p suppression. However, once initiated, bifoveal fixation is transient with the strabismic eye drifting away from foveal alignment, thereby increasing the angle of strabismus. © 2014 The Authors Ophthalmic & Physiological Optics © 2014 The College of Optometrists.

How strongly do word reading times and lexical decision times correlate? Combining data from eye movement corpora and megastudies.

Science.gov (United States)

Kuperman, Victor; Drieghe, Denis; Keuleers, Emmanuel; Brysbaert, Marc

2013-01-01

We assess the amount of shared variance between three measures of visual word recognition latencies: eye movement latencies, lexical decision times, and naming times. After partialling out the effects of word frequency and word length, two well-documented predictors of word recognition latencies, we see that 7-44% of the variance is uniquely shared between lexical decision times and naming times, depending on the frequency range of the words used. A similar analysis of eye movement latencies shows that the percentage of variance they uniquely share either with lexical decision times or with naming times is much lower. It is 5-17% for gaze durations and lexical decision times in studies with target words presented in neutral sentences, but drops to 0.2% for corpus studies in which eye movements to all words are analysed. Correlations between gaze durations and naming latencies are lower still. These findings suggest that processing times in isolated word processing and continuous text reading are affected by specific task demands and presentation format, and that lexical decision times and naming times are not very informative in predicting eye movement latencies in text reading once the effect of word frequency and word length are taken into account. The difference between controlled experiments and natural reading suggests that reading strategies and stimulus materials may determine the degree to which the immediacy-of-processing assumption and the eye-mind assumption apply. Fixation times are more likely to exclusively reflect the lexical processing of the currently fixated word in controlled studies with unpredictable target words rather than in natural reading of sentences or texts.

Decision-making in information seeking on texts: an eye-fixation-related potentials investigation.

Science.gov (United States)

Frey, Aline; Ionescu, Gelu; Lemaire, Benoit; López-Orozco, Francisco; Baccino, Thierry; Guérin-Dugué, Anne

2013-01-01

Reading on a web page is known to be not linear and people need to make fast decisions about whether they have to stop or not reading. In such context, reading, and decision-making processes are intertwined and this experiment attempts to separate them through electrophysiological patterns provided by the Eye-Fixation-Related Potentials technique (EFRPs). We conducted an experiment in which EFRPs were recorded while participants read blocks of text that were semantically highly related, moderately related, and unrelated to a given goal. Participants had to decide as fast as possible whether the text was related or not to the semantic goal given at a prior stage. Decision making (stopping information search) may occur when the paragraph is highly related to the goal (positive decision) or when it is unrelated to the goal (negative decision). EFRPs were analyzed on and around typical eye fixations: either on words belonging to the goal (target), subjected to a high rate of positive decisions, or on low frequency unrelated words (incongruent), subjected to a high rate of negative decisions. In both cases, we found EFRPs specific patterns (amplitude peaking between 51 to 120 ms after fixation onset) spreading out on the next words following the goal word and the second fixation after an incongruent word, in parietal and occipital areas. We interpreted these results as delayed late components (P3b and N400), reflecting the decision to stop information searching. Indeed, we show a clear spill-over effect showing that the effect on word N spread out on word N + 1 and N + 2.

Decision-making in information seeking on texts: an eye-fixation-related potentials investigation

Science.gov (United States)

Frey, Aline; Ionescu, Gelu; Lemaire, Benoit; López-Orozco, Francisco; Baccino, Thierry; Guérin-Dugué, Anne

2013-01-01

Reading on a web page is known to be not linear and people need to make fast decisions about whether they have to stop or not reading. In such context, reading, and decision-making processes are intertwined and this experiment attempts to separate them through electrophysiological patterns provided by the Eye-Fixation-Related Potentials technique (EFRPs). We conducted an experiment in which EFRPs were recorded while participants read blocks of text that were semantically highly related, moderately related, and unrelated to a given goal. Participants had to decide as fast as possible whether the text was related or not to the semantic goal given at a prior stage. Decision making (stopping information search) may occur when the paragraph is highly related to the goal (positive decision) or when it is unrelated to the goal (negative decision). EFRPs were analyzed on and around typical eye fixations: either on words belonging to the goal (target), subjected to a high rate of positive decisions, or on low frequency unrelated words (incongruent), subjected to a high rate of negative decisions. In both cases, we found EFRPs specific patterns (amplitude peaking between 51 to 120 ms after fixation onset) spreading out on the next words following the goal word and the second fixation after an incongruent word, in parietal and occipital areas. We interpreted these results as delayed late components (P3b and N400), reflecting the decision to stop information searching. Indeed, we show a clear spill-over effect showing that the effect on word N spread out on word N + 1 and N + 2. PMID:23966913

Start Position Strongly Influences Fixation Patterns during Face Processing: Difficulties with Eye Movements as a Measure of Information Use

Science.gov (United States)

Arizpe, Joseph; Kravitz, Dwight J.; Yovel, Galit; Baker, Chris I.

2012-01-01

Fixation patterns are thought to reflect cognitive processing and, thus, index the most informative stimulus features for task performance. During face recognition, initial fixations to the center of the nose have been taken to indicate this location is optimal for information extraction. However, the use of fixations as a marker for information use rests on the assumption that fixation patterns are predominantly determined by stimulus and task, despite the fact that fixations are also influenced by visuo-motor factors. Here, we tested the effect of starting position on fixation patterns during a face recognition task with upright and inverted faces. While we observed differences in fixations between upright and inverted faces, likely reflecting differences in cognitive processing, there was also a strong effect of start position. Over the first five saccades, fixation patterns across start positions were only coarsely similar, with most fixations around the eyes. Importantly, however, the precise fixation pattern was highly dependent on start position with a strong tendency toward facial features furthest from the start position. For example, the often-reported tendency toward the left over right eye was reversed for the left starting position. Further, delayed initial saccades for central versus peripheral start positions suggest greater information processing prior to the initial saccade, highlighting the experimental bias introduced by the commonly used center start position. Finally, the precise effect of face inversion on fixation patterns was also dependent on start position. These results demonstrate the importance of a non-stimulus, non-task factor in determining fixation patterns. The patterns observed likely reflect a complex combination of visuo-motor effects and simple sampling strategies as well as cognitive factors. These different factors are very difficult to tease apart and therefore great caution must be applied when interpreting absolute

Fixation Time for Evolutionary Graphs

Science.gov (United States)

Nie, Pu-Yan; Zhang, Pei-Ai

Evolutionary graph theory (EGT) is recently proposed by Lieberman et al. in 2005. EGT is successful for explaining biological evolution and some social phenomena. It is extremely important to consider the time of fixation for EGT in many practical problems, including evolutionary theory and the evolution of cooperation. This study characterizes the time to asymptotically reach fixation.

Simulation of airbag impact on eyes with different axial lengths after transsclerally fixated posterior chamber intraocular lens by using finite element analysis

Directory of Open Access Journals (Sweden)

Huang J

2015-02-01

Full Text Available Jane Huang,1 Eiichi Uchio,1 Satoru Goto2 1Department of Ophthalmology, Fukuoka University School of Medicine, Fukuoka, 2Nihon ESI KK Technical Division, Tokyo, Japan Purpose: To determine the biomechanical response of an impacting airbag on eyes with different axial lengths with transsclerally fixated posterior chamber intraocular lens (PC IOL.Materials and methods: Simulations in a model human eye were performed with a computer using a finite element analysis program created by Nihon, ESI Group. The airbag was set to be deployed at five different velocities and to impact on eyes with three different axial lengths. These eyes were set to have transsclerally fixated PC IOL by a 10-0 polypropylene possessing a tensile force limit of 0.16 N according to the United States Pharmacopeia XXII.Results: The corneoscleral opening was observed at a speed of 40 m/second or more in all model eyes. Eyes with the longest axial length of 25.85 mm had the greatest extent of deformity at any given impact velocity. The impact force exceeded the tensile force of 10-0 polypropylene at an impact velocity of 60 m/second in all eyes, causing breakage of the suture. Conclusion: Eyes with transsclerally fixated PC IOL could rupture from airbag impact at high velocities. Eyes with long axial lengths experienced a greater deformity upon airbag impact due to a thinner eye wall. Further basic research on the biomechanical response for assessing eye injuries could help in developing a better airbag and in the further understanding of ocular traumas. Keywords: airbag, ocular trauma, computer simulation, transsclerally fixated posterior chamber intraocular lens, finite element analysis

The eye-voice span during reading aloud

Directory of Open Access Journals (Sweden)

Jochen eLaubrock

2015-09-01

Full Text Available Although eye movements during reading are modulated by cognitive processing demands, they also reflect visual sampling of the input, and possibly preparation of output for speech or the inner voice. By simultaneously recording eye movements and the voice during reading aloud, we obtained an output measure that constrains the length of time spent on cognitive processing. Here we investigate the dynamics of the eye-voice span (EVS, the distance between eye and voice. We show that the EVS is regulated immediately during fixation of a word by either increasing fixation duration or programming a regressive eye movement against the reading direction. EVS size at the beginning of a fixation was positively correlated with the likelihood of regressions and refixations. Regression probability was further increased if the EVS was still large at the end of a fixation: if adjustment of fixation duration did not sufficiently reduce the EVS during a fixation, then a regression rather than a refixation followed with high probability. We further show that the EVS can help understand cognitive influences on fixation duration during reading: in mixed model analyses, the EVS was a stronger predictor of fixation durations than either word frequency or word length. The EVS modulated the influence of several other predictors on single fixation durations. For example, word-N frequency effects were larger with a large EVS, especially when word N-1 frequency was low. Finally, a comparison of single fixation durations during oral and silent reading showed that reading is governed by similar principles in both reading modes, although EVS maintenance and articulatory processing also cause some differences. In summary, the eye-voice span is regulated by adjusting fixation duration and/or by programming a regressive eye movement when the eye-voice span gets too large. Overall, the EVS appears to be directly related to updating of the working memory buffer during reading.

The ticking time bomb: Using eye-tracking methodology to capture attentional processing during gradual time constraints.

Science.gov (United States)

Franco-Watkins, Ana M; Davis, Matthew E; Johnson, Joseph G

2016-11-01

Many decisions are made under suboptimal circumstances, such as time constraints. We examined how different experiences of time constraints affected decision strategies on a probabilistic inference task and whether individual differences in working memory accounted for complex strategy use across different levels of time. To examine information search and attentional processing, we used an interactive eye-tracking paradigm where task information was occluded and only revealed by an eye fixation to a given cell. Our results indicate that although participants change search strategies during the most restricted times, the occurrence of the shift in strategies depends both on how the constraints are applied as well as individual differences in working memory. This suggests that, in situations that require making decisions under time constraints, one can influence performance by being sensitive to working memory and, potentially, by acclimating people to the task time gradually.

Intrascleral IOL Fixation.

Science.gov (United States)

Jacob, Soosan

2017-01-01

Intrascleral sutureless intraocular lens (IOL) fixation utilizes direct haptic fixation within the sclera in eyes with deficient capsular support. This has advantages of long-term stability, good control of tilt and decentration, and lesser pseudophakodonesis. This review summarizes various techniques for intrascleral haptic fixation, results, complications, adaptations in special situations, modifications of the technique, combination surgeries, and intrascleral capsular bag fixation techniques (glued capsular hook). Copyright 2017 Asia-Pacific Academy of Ophthalmology.

Evaluating camouflage design using eye movement data.

Science.gov (United States)

Lin, Chiuhsiang Joe; Chang, Chi-Chan; Lee, Yung-Hui

2014-05-01

This study investigates the characteristics of eye movements during a camouflaged target search task. Camouflaged targets were randomly presented on two natural landscapes. The performance of each camouflage design was assessed by target detection hit rate, detection time, number of fixations on display, first saccade amplitude to target, number of fixations on target, fixation duration on target, and subjective ratings of search task difficulty. The results showed that the camouflage patterns could significantly affect the eye-movement behavior, especially first saccade amplitude and fixation duration, and the findings could be used to increase the sensitivity of the camouflage assessment. We hypothesized that the assessment could be made with regard to the differences in detectability and discriminability of the camouflage patterns. These could explain less efficient search behavior in eye movements. Overall, data obtained from eye movements can be used to significantly enhance the interpretation of the effects of different camouflage design. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Eye movements discriminate fatigue due to chronotypical factors and time spent on task--a double dissociation.

Directory of Open Access Journals (Sweden)

Dario Cazzoli

Full Text Available Systematic differences in circadian rhythmicity are thought to be a substantial factor determining inter-individual differences in fatigue and cognitive performance. The synchronicity effect (when time of testing coincides with the respective circadian peak period seems to play an important role. Eye movements have been shown to be a reliable indicator of fatigue due to sleep deprivation or time spent on cognitive tasks. However, eye movements have not been used so far to investigate the circadian synchronicity effect and the resulting differences in fatigue. The aim of the present study was to assess how different oculomotor parameters in a free visual exploration task are influenced by: a fatigue due to chronotypical factors (being a 'morning type' or an 'evening type'; b fatigue due to the time spent on task. Eighteen healthy participants performed a free visual exploration task of naturalistic pictures while their eye movements were recorded. The task was performed twice, once at their optimal and once at their non-optimal time of the day. Moreover, participants rated their subjective fatigue. The non-optimal time of the day triggered a significant and stable increase in the mean visual fixation duration during the free visual exploration task for both chronotypes. The increase in the mean visual fixation duration correlated with the difference in subjectively perceived fatigue at optimal and non-optimal times of the day. Conversely, the mean saccadic speed significantly and progressively decreased throughout the duration of the task, but was not influenced by the optimal or non-optimal time of the day for both chronotypes. The results suggest that different oculomotor parameters are discriminative for fatigue due to different sources. A decrease in saccadic speed seems to reflect fatigue due to time spent on task, whereas an increase in mean fixation duration a lack of synchronicity between chronotype and time of the day.

Retropupillary Fixation of Iris-Claw Intraocular Lens for Aphakic Eyes in Children.

Directory of Open Access Journals (Sweden)

Martina Brandner

Full Text Available To report outcome, complications and safety of retropupillary fixated iris-claw intraocular lenses in a pediatric population.Retrospective study.Ten consecutive pediatric patients (15 eyes underwent placement of retropupillary fixated iris-claw intraocular lenses between October 2007 and July 2013 at the Department of Ophthalmology, Medical University Graz and General Hospital Klagenfurt, Austria. Postoperative visual acuity and complications were analyzed.Median final best-corrected visual acuity improved by 0.12 logMAR from preoperative baseline. Mean postoperative spherical equivalent was -0.05 ± 1.76 D. No serious complications were observed intra- or postoperatively during the entire follow-up period of up to 40 months. One patient experienced a haptic disenclavation with IOL subluxation immediately after a car accident.Our study demonstrates that iris-claw intraocular lens implantation behind the iris is safe in children with lack of capsular support and yields excellent visual outcome with low complication rate.

Retropupillary Fixation of Iris-Claw Intraocular Lens for Aphakic Eyes in Children

Science.gov (United States)

Brandner, Martina; Thaler-Saliba, Sarah; Plainer, Sophie; Vidic, Bertram; El-Shabrawi, Yosuf; Ardjomand, Navid

2015-01-01

Purpose To report outcome, complications and safety of retropupillary fixated iris-claw intraocular lenses in a pediatric population. Design Retrospective study. Patients and Methods Ten consecutive pediatric patients (15 eyes) underwent placement of retropupillary fixated iris-claw intraocular lenses between October 2007 and July 2013 at the Department of Ophthalmology, Medical University Graz and General Hospital Klagenfurt, Austria. Postoperative visual acuity and complications were analyzed. Results Median final best-corrected visual acuity improved by 0.12 logMAR from preoperative baseline. Mean postoperative spherical equivalent was -0.05 ± 1.76 D. No serious complications were observed intra- or postoperatively during the entire follow-up period of up to 40 months. One patient experienced a haptic disenclavation with IOL subluxation immediately after a car accident. Conclusion Our study demonstrates that iris-claw intraocular lens implantation behind the iris is safe in children with lack of capsular support and yields excellent visual outcome with low complication rate. PMID:26110864

Eye Movement Indices in the Study of Depressive Disorder.

Science.gov (United States)

Li, Yu; Xu, Yangyang; Xia, Mengqing; Zhang, Tianhong; Wang, Junjie; Liu, Xu; He, Yongguang; Wang, Jijun

2016-12-25

Impaired cognition is one of the most common core symptoms of depressive disorder. Eye movement testing mainly reflects patients' cognitive functions, such as cognition, memory, attention, recognition, and recall. This type of testing has great potential to improve theories related to cognitive functioning in depressive episodes as well as potential in its clinical application. This study investigated whether eye movement indices of patients with unmedicated depressive disorder were abnormal or not, as well as the relationship between these indices and mental symptoms. Sixty patients with depressive disorder and sixty healthy controls (who were matched by gender, age and years of education) were recruited, and completed eye movement tests including three tasks: fixation task, saccade task and free-view task. The EyeLink desktop eye tracking system was employed to collect eye movement information, and analyze the eye movement indices of the three tasks between the two groups. (1) In the fixation task, compared to healthy controls, patients with depressive disorder showed more fixations, shorter fixation durations, more saccades and longer saccadic lengths; (2) In the saccade task, patients with depressive disorder showed longer anti-saccade latencies and smaller anti-saccade peak velocities; (3) In the free-view task, patients with depressive disorder showed fewer saccades and longer mean fixation durations; (4) Correlation analysis showed that there was a negative correlation between the pro-saccade amplitude and anxiety symptoms, and a positive correlation between the anti-saccade latency and anxiety symptoms. The depression symptoms were negatively correlated with fixation times, saccades, and saccadic paths respectively in the free-view task; while the mean fixation duration and depression symptoms showed a positive correlation. Compared to healthy controls, patients with depressive disorder showed significantly abnormal eye movement indices. In addition

Measuring vigilance decrement using computer vision assisted eye tracking in dynamic naturalistic environments.

Science.gov (United States)

Bodala, Indu P; Abbasi, Nida I; Yu Sun; Bezerianos, Anastasios; Al-Nashash, Hasan; Thakor, Nitish V

2017-07-01

Eye tracking offers a practical solution for monitoring cognitive performance in real world tasks. However, eye tracking in dynamic environments is difficult due to high spatial and temporal variation of stimuli, needing further and thorough investigation. In this paper, we study the possibility of developing a novel computer vision assisted eye tracking analysis by using fixations. Eye movement data is obtained from a long duration naturalistic driving experiment. Source invariant feature transform (SIFT) algorithm was implemented using VLFeat toolbox to identify multiple areas of interest (AOIs). A new measure called `fixation score' was defined to understand the dynamics of fixation position between the target AOI and the non target AOIs. Fixation score is maximum when the subjects focus on the target AOI and diminishes when they gaze at the non-target AOIs. Statistically significant negative correlation was found between fixation score and reaction time data (r =-0.2253 and pdecrement, the fixation score decreases due to visual attention shifting away from the target objects resulting in an increase in the reaction time.

Biometric recognition via fixation density maps

Science.gov (United States)

Rigas, Ioannis; Komogortsev, Oleg V.

2014-05-01

This work introduces and evaluates a novel eye movement-driven biometric approach that employs eye fixation density maps for person identification. The proposed feature offers a dynamic representation of the biometric identity, storing rich information regarding the behavioral and physical eye movement characteristics of the individuals. The innate ability of fixation density maps to capture the spatial layout of the eye movements in conjunction with their probabilistic nature makes them a particularly suitable option as an eye movement biometrical trait in cases when free-viewing stimuli is presented. In order to demonstrate the effectiveness of the proposed approach, the method is evaluated on three different datasets containing a wide gamut of stimuli types, such as static images, video and text segments. The obtained results indicate a minimum EER (Equal Error Rate) of 18.3 %, revealing the perspectives on the utilization of fixation density maps as an enhancing biometrical cue during identification scenarios in dynamic visual environments.

Eying the future: Eye movement in past and future thinking.

Science.gov (United States)

El Haj, Mohamad; Lenoble, Quentin

2017-06-07

We investigated eye movement during past and future thinking. Participants were invited to retrieve past events and to imagine future events while their scan path was recorded by an eye-tracker. Past thinking triggered more fixation (p thinking. Past and future thinking triggered a similar duration of fixations and saccades, as well as a similar amplitude of saccades. Interestingly, participants rated past thinking as more vivid than future thinking (p thinking seems to be accompanied by an increased number of fixations and saccades. Fixations and saccades in past thinking can be interpreted as an attempt by the visual system to find (through saccades) and activate (through fixations) stored memory representations. The same interpretation can be applied to future thinking as this ability requires activation of past experiences. However, future thinking triggers fewer fixations and saccades than past thinking: this may be due to its decreased demand on visual imagery, but could also be related to a potentially deleterious effect of eye movements on spatial imagery required for future thinking. Copyright © 2017 Elsevier Ltd. All rights reserved.

The effect of hubs and shortcuts on fixation time in evolutionary graphs

Science.gov (United States)

Askari, Marziyeh; Moradi Miraghaei, Zeinab; Aghababaei Samani, Keivan

2017-07-01

How can a new species (like a gene, an idea, or a strategy) take over the whole of a population? This process, which is called fixation, is considerably affected by the structure of the population. There are two key quantities to quantify the fixation process, namely fixation probability and fixation time. Fixation probability has been vastly studied in recent years, but fixation time has not been completely explored, yet. This is because the discovery of a relationship between fixation time and network structure is quite challenging. In this paper we investigate this relationship for a number of well-known complex networks. We show that the existence of a few high-degree nodes (hubs) in the network results in a longer fixation time, while the existence of a few short-cuts decreases the fixation time. Furthermore we investigate the effect of network parameters, such as connection probability, on fixation time. We show that by increasing the density of edges, fixation time decreases for all types of studied networks. Finally, we survey the effect of rewiring probability in a Watts-Strogatz network on fixation time.

Effect of phenylephrine/ketorolac on iris fixation ring use and surgical times in patients at risk of intraoperative miosis

Directory of Open Access Journals (Sweden)

Visco D

2018-02-01

Full Text Available Denise Visco Eyes of York Cataract & Laser Center, York, PA, USA Purpose: To evaluate the effect of intracameral phenylephrine/ketorolac (1%/0.3% during cataract surgery on the use of iris fixation ring and surgical time in patients with poor pupil dilation (≤5.0 mm or intraoperative floppy iris syndrome (IFIS. Setting: Private practice outpatient surgical center. Design: This retrospective analysis was conducted from January 1, 2014 to October 7, 2015. Materials and methods: The use of iris fixation rings was evaluated in a retrospective analysis of 46 patients who underwent cataract surgery from January 1, 2014, to October 7, 2015, and who were identified before surgery to be at risk for intraoperative miosis. The qualifying factors were presurgical examination of pupil dilation ≤5.0 mm after being administered topical tropicamide 1% and phenylephrine 2.5% or history of IFIS during surgery in the fellow eye. All patients received a 2-day preoperative course of topical nonsteroidal anti-inflammatory drugs (NSAIDs and day-of-surgery preoperative dilation using topical cyclopentolate 1%, tropicamide 1%, and phenylephrine 10%. Phenylephrine/ketorolac 1%/0.3% (Omidria® or epinephrine 1:1,000 with sulfites was added to the ophthalmic irrigation solution and delivered intracamerally at the start of the procedure and throughout surgery. The use of iris fixation rings and surgical time for each patient were captured for each group. Results: Eighteen (50% of the patients in the epinephrine group and no patients in the phenylephrine/ketorolac group required iris fixation ring insertion to maintain pupil dilation or to control IFIS (p=0.0034. Mean surgical time was significantly shorter in the group of patients who received phenylephrine/ketorolac (p=0.0068. Conclusion: In this retrospective cohort analysis of patients with poorly dilated pupils and/or IFIS, the use of intracameral phenylephrine/ketorolac in patients at risk for intraoperative

Smaller Fixation Target Size Is Associated with More Stable Fixation and Less Variance in Threshold Sensitivity.

Directory of Open Access Journals (Sweden)

Kazunori Hirasawa

Full Text Available The aims of this randomized observational case control study were to quantify fixation behavior during standard automated perimetry (SAP with different fixation targets and to evaluate the relationship between fixation behavior and threshold variability at each test point in healthy young participants experienced with perimetry. SAP was performed on the right eyes of 29 participants using the Octopus 900 perimeter, program 32, dynamic strategy. The fixation targets of Point, Cross, and Ring were used for SAP. Fixation behavior was recorded using a wearable eye-tracking glass. All participants underwent SAP twice with each fixation target in a random fashion. Fixation behavior was quantified by calculating the bivariate contour ellipse area (BCEA and the frequency of deviation from the fixation target. The BCEAs (deg2 of Point, Cross, and Ring targets were 1.11, 1.46, and 2.02, respectively. In all cases, BCEA increased significantly with increasing fixation target size (p < 0.05. The logarithmic value of BCEA demonstrated the same tendency (p < 0.05. A positive correlation was identified between fixation behavior and threshold variability for the Point and Cross targets (ρ = 0.413-0.534, p < 0.05. Fixation behavior increased with increasing fixation target size. Moreover, a larger fixation behavior tended to be associated with a higher threshold variability. A small fixation target is recommended during the visual field test.

Eye tracking to explore attendance in health-state descriptions.

Directory of Open Access Journals (Sweden)

Anna Selivanova

Full Text Available A crucial assumption in health valuation methods is that respondents pay equal attention to all information components presented in the response task. So far, there is no solid evidence that respondents are fulfilling this condition. The aim of our study is to explore the attendance to various information cues presented in the discrete choice (DC response tasks.Eye tracking was used to study the eye movements and fixations on specific information areas. This was done for seven DC response tasks comprising health-state descriptions. A sample of 10 respondents participated in the study. Videos of their eye movements were recorded and are presented graphically. Frequencies were computed for length of fixation and number of fixations, so differences in attendance were demonstrated for particular attributes in the tasks.All respondents completed the survey. Respondents were fixating on the left-sided health-state descriptions slightly longer than on the right-sided. Fatigue was not observed, as the time spent did not decrease in the final response tasks. The time spent on the tasks depended on the difficulty of the task and the amount of information presented.Eye tracking proved to be a feasible method to study the process of paying attention and fixating on health-state descriptions in the DC response tasks. Eye tracking facilitates the investigation of whether respondents fully read the information in health descriptions or whether they ignore particular elements.

Fixation and escape times in stochastic game learning

International Nuclear Information System (INIS)

Realpe-Gomez, John; Szczesny, Bartosz; Galla, Tobias; Dall’Asta, Luca

2012-01-01

Evolutionary dynamics in finite populations is known to fixate eventually in the absence of mutation. We here show that a similar phenomenon can be found in stochastic game dynamical batch learning, and investigate fixation in learning processes in a simple 2×2 game, for two-player games with cyclic interaction, and in the context of the best-shot network game. The analogues of finite populations in evolution are here finite batches of observations between strategy updates. We study when and how such fixation can occur, and present results on the average time-to-fixation from numerical simulations. Simple cases are also amenable to analytical approaches and we provide estimates of the behaviour of so-called escape times as a function of the batch size. The differences and similarities with escape and fixation in evolutionary dynamics are discussed. (paper)

Real-time recording and classification of eye movements in an immersive virtual environment.

Science.gov (United States)

Diaz, Gabriel; Cooper, Joseph; Kit, Dmitry; Hayhoe, Mary

2013-10-10

Despite the growing popularity of virtual reality environments, few laboratories are equipped to investigate eye movements within these environments. This primer is intended to reduce the time and effort required to incorporate eye-tracking equipment into a virtual reality environment. We discuss issues related to the initial startup and provide algorithms necessary for basic analysis. Algorithms are provided for the calculation of gaze angle within a virtual world using a monocular eye-tracker in a three-dimensional environment. In addition, we provide algorithms for the calculation of the angular distance between the gaze and a relevant virtual object and for the identification of fixations, saccades, and pursuit eye movements. Finally, we provide tools that temporally synchronize gaze data and the visual stimulus and enable real-time assembly of a video-based record of the experiment using the Quicktime MOV format, available at http://sourceforge.net/p/utdvrlibraries/. This record contains the visual stimulus, the gaze cursor, and associated numerical data and can be used for data exportation, visual inspection, and validation of calculated gaze movements.

Immaturity of Visual Fixations in Dyslexic Children.

Directory of Open Access Journals (Sweden)

TIADI eBi Kuyami Guy Aimé

2016-02-01

Full Text Available To our knowledge, behavioral studies recording visual fixations abilities in dyslexic children are scarce. The object of this paper is to explore further the visual fixation ability in dyslexics compared to chronological age-matched and reading age-matched non-dyslexic children. Fifty-five dyslexic children from 7 to 14 years old, fifty-five chronological age-matched non-dyslexic children and fifty-five reading age-matched non-dyslexic children participated to this study. Eye movements from both eyes were recorded horizontally and vertically by a video-oculography system (EyeBrain® T2. The fixation task consisted in fixating a white-filled circle appearing in the centre of the screen for 30 seconds. Results showed that dyslexic children produced a significantly higher number of unwanted saccades than both groups of non-dyslexic children. Moreover, the number of unwanted saccades significantly decreased with age in both groups of non-dyslexic children, but not in dyslexics. Furthermore, dyslexics made more saccades during the last 15 sec of fixation period with respect to both groups of non-dyslexic children. Such poor visual fixation capability in dyslexic children could be due to impaired attention abilities, as well as to an immaturity of the cortical areas controlling the fixation system.

Induced Gamma-Band Activity and Fixational Eye Movements are Differentially Influenced by Low-and High-Level Factors in a Visual Object Classification Task

Directory of Open Access Journals (Sweden)

J Martinovic

2011-04-01

Full Text Available Until recently induced high frequency oscillatory activity (gamma-band activity; >30 Hz was considered a neural marker of cortical object representation. However, Yuval-Greenberg et al (2008; Neuron demonstrated that induced gamma-band activity (GBA in the elecetroencephalogram (EEG is susceptible to artifacts caused by miniature eye movements, which account for the major part of the signal in the crucial time window of 200-400 ms after stimulus onset. Is there an underlying cortical-induced gamma-band response that is obscured by ocular artifacts but can still be recorded with EEG? Furthermore, if object-specific modulations of induced GBA in previous studies were caused by ocular artifacts, should we instead study fixational eye movements as a response that can reflect higher-level representational processes in vision? In order to investigate this, we conducted an eye tracking experiment and an EEG experiment using the same design. Participants were asked to classify line drawings of objects or non-objects. To introduce low-level differences, their contours were defined along different directions in cardinal colour space: 1 S-cone-isolating (S, or 2 intermediate isoluminant (S and L-M, or 3 a full-colour stimulus, containing an additional achromatic component (S; L-M; L+M+S. In both experiments, behavioural performance was optimal for full-colour stimuli. In the eye tracking experiment, fixational eye movement rates 200-400 ms after stimulus onset depended on low-level factors, with no difference between objects and non-objects. In the EEG experiment, miniature eye movements were identified and removed using the saccadic filter approach. The artifact-free induced GBA exhibited a lateralised distribution, with enhancements at left and right posterior sites. Activity was higher for full-colour objects on the left, with the opposite effect observed on the right. We conclude that induced GBA can be observed in the EEG. While it showed high

Modeling fixation locations using spatial point processes.

Science.gov (United States)

Barthelmé, Simon; Trukenbrod, Hans; Engbert, Ralf; Wichmann, Felix

2013-10-01

Whenever eye movements are measured, a central part of the analysis has to do with where subjects fixate and why they fixated where they fixated. To a first approximation, a set of fixations can be viewed as a set of points in space; this implies that fixations are spatial data and that the analysis of fixation locations can be beneficially thought of as a spatial statistics problem. We argue that thinking of fixation locations as arising from point processes is a very fruitful framework for eye-movement data, helping turn qualitative questions into quantitative ones. We provide a tutorial introduction to some of the main ideas of the field of spatial statistics, focusing especially on spatial Poisson processes. We show how point processes help relate image properties to fixation locations. In particular we show how point processes naturally express the idea that image features' predictability for fixations may vary from one image to another. We review other methods of analysis used in the literature, show how they relate to point process theory, and argue that thinking in terms of point processes substantially extends the range of analyses that can be performed and clarify their interpretation.

Eye movements characteristics of Chinese dyslexic children in picture searching.

Science.gov (United States)

Huang, Xu; Jing, Jin; Zou, Xiao-Bing; Wang, Meng-Long; Li, Xiu-Hong; Lin, Ai-Hua

2008-09-05

Reading Chinese, a kind of ideogram, relies more on visual cognition. The visuospatial cognitive deficit of Chinese dyslexia is an interesting topic that has received much attention. The purpose of current research was to explore the visuopatial cognitive characteristics of Chinese dyslexic children by studying their eye movements via a picture searching test. According to the diagnostic criteria defined by ICD-10, twenty-eight dyslexic children (mean age (10.12 +/- 1.42) years) were enrolled from the Clinic of Children Behavioral Disorder in the third affiliated hospital of Sun Yat-sen University. And 28 normally reading children (mean age (10.06 +/- 1.29) years), 1:1 matched by age, sex, grade and family condition were chosen from an elementary school in Guangzhou as a control group. Four groups of pictures (cock, accident, canyon, meditate) from Picture Vocabulary Test were chosen as eye movement experiment targets. All the subjects carried out the picture searching task and their eye movement data were recorded by an Eyelink II High-Speed Eye Tracker. The duration time, average fixation duration, average saccade amplitude, fixation counts and saccade counts were compared between the two groups of children. The dyslexic children had longer total fixation duration and average fixation duration (F = 7.711, P < 0.01; F = 4.520, P < 0.05), more fixation counts and saccade counts (F = 7.498, P < 0.01; F = 11.040, P < 0.01), and a smaller average saccade amplitude (F = 29.743, P < 0.01) compared with controls. But their performance in the picture vocabulary test was the same as those of the control group. The eye movement indexes were affected by the difficulty of the pictures and words, all eye movement indexes, except saccade amplitude, had a significant difference within groups (P < 0.05). Chinese dyslexic children have abnormal eye movements in picture searching, applying slow fixations, more fixations and small and frequent saccades. Their abnormal eye movement

In vivo retinal imaging for fixational eye motion detection using a high-speed digital micromirror device (DMD)-based ophthalmoscope.

Science.gov (United States)

Vienola, Kari V; Damodaran, Mathi; Braaf, Boy; Vermeer, Koenraad A; de Boer, Johannes F

2018-02-01

Retinal motion detection with an accuracy of 0.77 arcmin corresponding to 3.7 µm on the retina is demonstrated with a novel digital micromirror device based ophthalmoscope. By generating a confocal image as a reference, eye motion could be measured from consecutively measured subsampled frames. The subsampled frames provide 7.7 millisecond snapshots of the retina without motion artifacts between the image points of the subsampled frame, distributed over the full field of view. An ophthalmoscope pattern projection speed of 130 Hz enabled a motion detection bandwidth of 65 Hz. A model eye with a scanning mirror was built to test the performance of the motion detection algorithm. Furthermore, an in vivo motion trace was obtained from a healthy volunteer. The obtained eye motion trace clearly shows the three main types of fixational eye movements. Lastly, the obtained eye motion trace was used to correct for the eye motion in consecutively obtained subsampled frames to produce an averaged confocal image correct for motion artefacts.

An information maximization model of eye movements

Science.gov (United States)

Renninger, Laura Walker; Coughlan, James; Verghese, Preeti; Malik, Jitendra

2005-01-01

We propose a sequential information maximization model as a general strategy for programming eye movements. The model reconstructs high-resolution visual information from a sequence of fixations, taking into account the fall-off in resolution from the fovea to the periphery. From this framework we get a simple rule for predicting fixation sequences: after each fixation, fixate next at the location that minimizes uncertainty (maximizes information) about the stimulus. By comparing our model performance to human eye movement data and to predictions from a saliency and random model, we demonstrate that our model is best at predicting fixation locations. Modeling additional biological constraints will improve the prediction of fixation sequences. Our results suggest that information maximization is a useful principle for programming eye movements.

Using support vector machines to identify literacy skills: Evidence from eye movements.

Science.gov (United States)

Lou, Ya; Liu, Yanping; Kaakinen, Johanna K; Li, Xingshan

2017-06-01

Is inferring readers' literacy skills possible by analyzing their eye movements during text reading? This study used Support Vector Machines (SVM) to analyze eye movement data from 61 undergraduate students who read a multiple-paragraph, multiple-topic expository text. Forward fixation time, first-pass rereading time, second-pass fixation time, and regression path reading time on different regions of the text were provided as features. The SVM classification algorithm assisted in distinguishing high-literacy-skilled readers from low-literacy-skilled readers with 80.3 % accuracy. Results demonstrate the effectiveness of combining eye tracking and machine learning techniques to detect readers with low literacy skills, and suggest that such approaches can be potentially used in predicting other cognitive abilities.

Perception and eye movements in simulated traffic situations.

Science.gov (United States)

Luoma, J

1984-01-01

In an experiment to simulate the perception task of a driver, subjects were shown uninterrupted series of colour slides of different kinds of highway scenes. The dependent variables were eye fixations, fixation times and conscious perceptions for the part of the traffic signs and roadside advertisements. Perceptions were achieved mostly as a result of fixation, but partly also by using peripheral vision. On the other hand fixation did not always cause perception. The lengthening of fixation time increased the number of correct perceptions. When the traffic sign and the roadside advertisement were in the same slide, the advertisement disturbed the perception of the sign, but in the daylight conditions this effect was not noticed as an alteration of the fixation of the sign, but as prevention of further information processing. The disturbing influence of the advertisement was increased by its bad information ergonomics which caused a long fixation time.

Single-suture scleral fixation of subluxated foldable intraocular lenses.

Science.gov (United States)

Yarangumeli, Alper; Alp, Mehmet Numan; Kural, Gulcan

2012-01-01

To evaluate the results of single-suture scleral fixation of subluxated foldable intraocular lenses (IOL) in eyes with sufficient residual capsular support. The results of IOL repositioning by single-suture scleral fixation in 6 eyes of 6 patients with IOL subluxation were included. All subluxated IOLs were single-piece hydrophilic acrylic. Subluxation resulted from posterior capsule tears in 3 eyes, zonular dialyses in 2 eyes, and zonular dialysis with a capsulorhexis tear in 1 eye. A similar technique was used in all eyes in which one haptic was externalized through a superior clear corneal incision and tied with a Pair-PAK 10-0 polypropylene suture, and was finally retracted and fixated behind the iris close to the ciliary sulcus at the 12:00 meridian. All patients were followed up for at least 6 months. Best-corrected visual acuities ranged between finger counting and 20/70 (mean logMAR 1.02±0.64) preoperatively, and between 20/100 and 20/20 (mean logMAR 0.22±0.26) at the final postoperative visit. All IOLs remained centered and no significant postoperative complications were encountered except for an IOL tilt which resulted in a considerable oblique astigmatism in one eye. Subluxated foldable IOLs may safely be repositioned and secured with a single scleral fixation suture in selected cases with adequate amount of capsular remnants.

The Effects of Body Action and Attentive Anticipation on Oculomotor Fixation Stability

Directory of Open Access Journals (Sweden)

Hyosun Choi

2011-10-01

Full Text Available Tiny eye movements, such as micro-saccades, ocular tremor, and drifts, occur involuntarily during fixation. We found evidence that involvement of body action and anticipation of visual stimuli modulates them. While eye movements were monitored, subjects performed the working memory task with a touch-screen display in two different conditions. In the passive condition, each number was shown for 400-ms and spaced in time by 500-ms automatically. In the active condition, touching action was required to trigger the appearance of each number. The delay between the touch and stimulus onset was constant within a block as 200, 500, or 800-ms. Subjects were prompted to type in the number sequence after five numbers were shown. As a measure of fixation instability, deviation of eye position was analyzed by comparing eye positions with those during the reference interval (0∼50ms time period after the number onset. We observed two results: first, the deviation was smaller in pre-reference time than in post-reference time. Second, the deviation was smaller in the active condition. These results show that micro eye movements are influenced by attentive anticipation of upcoming events, which becomes more pronounced with bodily interactions. These findings suggest a cross-modal interaction among visual, motor, and oculomotor systems.

Fixation Characteristics of Severe Amblyopia Subtypes: Which One is Worse?

Science.gov (United States)

Koylu, Mehmet Talay; Ozge, Gokhan; Kucukevcilioglu, Murat; Mutlu, Fatih Mehmet; Ceylan, Osman Melih; Akıncıoglu, Dorukcan; Ayyıldız, Onder

2017-01-01

To determine differences in macular sensitivity and fixation patterns in different subtypes of severe amblyopia. This case-control study enrolled a total of 73 male adults, including 18 with pure strabismic severe amblyopia, 19 with pure anisometropic severe amblyopia, 18 with mixed (strabismic plus anizometropic) severe amblyopia, and 18 healthy controls. MP-1 microperimetry was used to evaluate macular sensitivity, location of fixation, and stability of fixation. Mean macular sensitivity, stability of fixation, and location of fixation were significantly worse in all amblyopia subtypes when compared with healthy controls. Intergroup comparisons between amblyopia subtypes revealed that mean macular sensitivity, stability of fixation, and location of fixation were significantly worse in pure strabismic and mixed amblyopic eyes when compared with pure anisometropic amblyopic eyes. Strabismus seems to be a worse prognostic factor in severe amblyopia than anisometropia in terms of fixation characteristics and retinal sensitivity.

Calculation of the time fixation accuracy for Si(Li)-detectors

International Nuclear Information System (INIS)

Kondrat'ev, V.P.; Krasnov, L.V.

1981-01-01

An accuracy of time fixation to pulses of changing shape for li-frifted si detectors with thickness over 1 mm is evaluated. The method of the comparison of main and converted signal shapes is the most universal method of time fixation. The idea of the method consists in shaping a bipolar pulse using a single-polar input Rulse and recording the point of the bipolar signal intersection with the zero level. The combination of an analytical method with numerical computer calculations is used for evaluating the time fixation fluctuations. Analysis of the results obtained shows that the value of delay p=tausub(d)/tausub(n) (where tausub(d) is delay time for the main part of a signal, tausub(n) is the maximum time of electron collection) affects most strongly the time shift. The parameter K=tausub(i)/tausub(n) (tausub(i) is a constant of integrating circuit) affects slightly the maximum value of time shift. For the li-drifted si detector 2 mm thick with dispattacement vottage of 400 V the moment of the time fixation will be equal to 47 is in the case of K--1, p=0.4 and x=0.25 (x=R/i, where R is a particle range in the detector, l is the thickness of the detector depleted area. The fluctuations in time fixation don't exceed 2.3 ns for the whole particle energy range

Eye movement perimetry in glaucoma.

Science.gov (United States)

Trope, G E; Eizenman, M; Coyle, E

1989-08-01

Present-day computerized perimetry is often inaccurate and unreliable owing to the need to maintain central fixation over long periods while repressing the normal response to presentation of peripheral stimuli. We tested a new method of perimetry that does not require prolonged central fixation. During this test eye movements were encouraged on presentation of a peripheral target. Twenty-three eyes were studied with an Octopus perimeter, with a technician monitoring eye movements. The sensitivity was 100% and the specificity 23%. The low specificity was due to the technician's inability to accurately monitor small eye movements in the central 6 degrees field. If small eye movements are monitored accurately with an eye tracker, eye movement perimetry could become an alternative method to standard perimetry.

Keep your eyes on the ball: smooth pursuit eye movements enhance prediction of visual motion.

Science.gov (United States)

Spering, Miriam; Schütz, Alexander C; Braun, Doris I; Gegenfurtner, Karl R

2011-04-01

Success of motor behavior often depends on the ability to predict the path of moving objects. Here we asked whether tracking a visual object with smooth pursuit eye movements helps to predict its motion direction. We developed a paradigm, "eye soccer," in which observers had to either track or fixate a visual target (ball) and judge whether it would have hit or missed a stationary vertical line segment (goal). Ball and goal were presented briefly for 100-500 ms and disappeared from the screen together before the perceptual judgment was prompted. In pursuit conditions, the ball moved towards the goal; in fixation conditions, the goal moved towards the stationary ball, resulting in similar retinal stimulation during pursuit and fixation. We also tested the condition in which the goal was fixated and the ball moved. Motion direction prediction was significantly better in pursuit than in fixation trials, regardless of whether ball or goal served as fixation target. In both fixation and pursuit trials, prediction performance was better when eye movements were accurate. Performance also increased with shorter ball-goal distance and longer presentation duration. A longer trajectory did not affect performance. During pursuit, an efference copy signal might provide additional motion information, leading to the advantage in motion prediction.

Emotion Words Affect Eye Fixations during Reading

Science.gov (United States)

Scott, Graham G.; O'Donnell, Patrick J.; Sereno, Sara C.

2012-01-01

Emotion words are generally characterized as possessing high arousal and extreme valence and have typically been investigated in paradigms in which they are presented and measured as single words. This study examined whether a word's emotional qualities influenced the time spent viewing that word in the context of normal reading. Eye movements…

When the mean is not enough: Calculating fixation time distributions in birth-death processes.

Science.gov (United States)

Ashcroft, Peter; Traulsen, Arne; Galla, Tobias

2015-10-01

Studies of fixation dynamics in Markov processes predominantly focus on the mean time to absorption. This may be inadequate if the distribution is broad and skewed. We compute the distribution of fixation times in one-step birth-death processes with two absorbing states. These are expressed in terms of the spectrum of the process, and we provide different representations as forward-only processes in eigenspace. These allow efficient sampling of fixation time distributions. As an application we study evolutionary game dynamics, where invading mutants can reach fixation or go extinct. We also highlight the median fixation time as a possible analog of mixing times in systems with small mutation rates and no absorbing states, whereas the mean fixation time has no such interpretation.

Eye Movements in Darkness Modulate Self-Motion Perception.

Science.gov (United States)

Clemens, Ivar Adrianus H; Selen, Luc P J; Pomante, Antonella; MacNeilage, Paul R; Medendorp, W Pieter

2017-01-01

During self-motion, humans typically move the eyes to maintain fixation on the stationary environment around them. These eye movements could in principle be used to estimate self-motion, but their impact on perception is unknown. We had participants judge self-motion during different eye-movement conditions in the absence of full-field optic flow. In a two-alternative forced choice task, participants indicated whether the second of two successive passive lateral whole-body translations was longer or shorter than the first. This task was used in two experiments. In the first ( n = 8), eye movements were constrained differently in the two translation intervals by presenting either a world-fixed or body-fixed fixation point or no fixation point at all (allowing free gaze). Results show that perceived translations were shorter with a body-fixed than a world-fixed fixation point. A linear model indicated that eye-movement signals received a weight of ∼25% for the self-motion percept. This model was independently validated in the trials without a fixation point (free gaze). In the second experiment ( n = 10), gaze was free during both translation intervals. Results show that the translation with the larger eye-movement excursion was judged more often to be larger than chance, based on an oculomotor choice probability analysis. We conclude that eye-movement signals influence self-motion perception, even in the absence of visual stimulation.

Visual and linguistic determinants of the eyes' initial fixation position in reading development.

Science.gov (United States)

Ducrot, Stéphanie; Pynte, Joël; Ghio, Alain; Lété, Bernard

2013-03-01

Two eye-movement experiments with one hundred and seven first- through fifth-grade children were conducted to examine the effects of visuomotor and linguistic factors on the recognition of words and pseudowords presented in central vision (using a variable-viewing-position technique) and in parafoveal vision (shifted to the left or right of a central fixation point). For all groups of children, we found a strong effect of stimulus location, in both central and parafoveal vision. This effect corresponds to the children's apparent tendency, for peripherally located targets, to reach a position located halfway between the middle and the left edge of the stimulus (preferred viewing location, PVL), whether saccading to the right or left. For centrally presented targets, refixation probability and lexical-decision time were the lowest near the word's center, suggesting an optimal viewing position (OVP). The viewing-position effects found here were modulated (1) by print exposure, both in central and parafoveal vision; and (2) by the intrinsic qualities of the stimulus (lexicality and word frequency) for targets in central vision but not for parafoveally presented targets. Copyright © 2013 Elsevier B.V. All rights reserved.

Eye movement during retrieval of emotional autobiographical memories.

Science.gov (United States)

El Haj, Mohamad; Nandrino, Jean-Louis; Antoine, Pascal; Boucart, Muriel; Lenoble, Quentin

2017-03-01

This study assessed whether specific eye movement patterns are observed during emotional autobiographical retrieval. Participants were asked to retrieve positive, negative and neutral memories while their scan path was recorded by an eye-tracker. Results showed that positive and negative emotional memories triggered more fixations and saccades but shorter fixation duration than neutral memories. No significant differences were observed between emotional and neutral memories for duration and amplitude of saccades. Positive and negative retrieval triggered similar eye movement (i.e., similar number of fixations and saccades, fixation duration, duration of saccades, and amplitude of saccades). Interestingly, the participants reported higher visual imagery for emotional memories than for neutral memories. The findings demonstrate similarities and differences in eye movement during retrieval of neutral and emotional memories. Eye movement during autobiographical retrieval seems to be triggered by the creation of visual mental images as the latter are indexed by autobiographical reconstruction. Copyright © 2016. Published by Elsevier B.V.

On the relationship between optical variability, visual saliency, and eye fixations: a computational approach.

Science.gov (United States)

Garcia-Diaz, Antón; Leborán, Víctor; Fdez-Vidal, Xosé R; Pardo, Xosé M

2012-06-12

A hierarchical definition of optical variability is proposed that links physical magnitudes to visual saliency and yields a more reductionist interpretation than previous approaches. This definition is shown to be grounded on the classical efficient coding hypothesis. Moreover, we propose that a major goal of contextual adaptation mechanisms is to ensure the invariance of the behavior that the contribution of an image point to optical variability elicits in the visual system. This hypothesis and the necessary assumptions are tested through the comparison with human fixations and state-of-the-art approaches to saliency in three open access eye-tracking datasets, including one devoted to images with faces, as well as in a novel experiment using hyperspectral representations of surface reflectance. The results on faces yield a significant reduction of the potential strength of semantic influences compared to previous works. The results on hyperspectral images support the assumptions to estimate optical variability. As well, the proposed approach explains quantitative results related to a visual illusion observed for images of corners, which does not involve eye movements.

Eye movements during object recognition in visual agnosia.

Science.gov (United States)

Charles Leek, E; Patterson, Candy; Paul, Matthew A; Rafal, Robert; Cristino, Filipe

2012-07-01

This paper reports the first ever detailed study about eye movement patterns during single object recognition in visual agnosia. Eye movements were recorded in a patient with an integrative agnosic deficit during two recognition tasks: common object naming and novel object recognition memory. The patient showed normal directional biases in saccades and fixation dwell times in both tasks and was as likely as controls to fixate within object bounding contour regardless of recognition accuracy. In contrast, following initial saccades of similar amplitude to controls, the patient showed a bias for short saccades. In object naming, but not in recognition memory, the similarity of the spatial distributions of patient and control fixations was modulated by recognition accuracy. The study provides new evidence about how eye movements can be used to elucidate the functional impairments underlying object recognition deficits. We argue that the results reflect a breakdown in normal functional processes involved in the integration of shape information across object structure during the visual perception of shape. Copyright © 2012 Elsevier Ltd. All rights reserved.

Time Savings and Surgery Task Load Reduction in Open Intraperitoneal Onlay Mesh Fixation Procedure

Directory of Open Access Journals (Sweden)

Sanjoy Roy

2015-01-01

Full Text Available Background. This study assessed the reduction in surgeon stress associated with savings in procedure time for mechanical fixation of an intraperitoneal onlay mesh (IPOM compared to a traditional suture fixation in open ventral hernia repair. Study Design. Nine general surgeons performed 36 open IPOM fixation procedures in porcine model. Each surgeon conducted two mechanical (using ETHICON SECURESTRAPTM Open and two suture fixation procedures. Fixation time was measured using a stopwatch, and related surgeon stress was assessed using the validated SURG-TLX questionnaire. T-tests were used to compare between-group differences, and a two-sided 95% confidence interval for the difference in stress levels was established using nonparametric methodology. Results. The mechanical fixation group demonstrated an 89.1% mean reduction in fixation time, as compared to the suture group (p<0.00001. Surgeon stress scores measured using SURG-TLX were 55.5% lower in the mechanical compared to the suture fixation group (p<0.001. Scores in five of the six sources of stress were significantly lower for mechanical fixation. Conclusions. Mechanical fixation with ETHICON SECURESTRAPTM Open demonstrated a significant reduction in fixation time and surgeon stress, which may translate into improved operating efficiency, improved performance, improved surgeon quality of life, and reduced overall costs of the procedure.

Time Savings and Surgery Task Load Reduction in Open Intraperitoneal Onlay Mesh Fixation Procedure

Science.gov (United States)

Roy, Sanjoy; Hammond, Jeffrey; Panish, Jessica; Shnoda, Pullen; Savidge, Sandy; Wilson, Mark

2015-01-01

Background. This study assessed the reduction in surgeon stress associated with savings in procedure time for mechanical fixation of an intraperitoneal onlay mesh (IPOM) compared to a traditional suture fixation in open ventral hernia repair. Study Design. Nine general surgeons performed 36 open IPOM fixation procedures in porcine model. Each surgeon conducted two mechanical (using ETHICON SECURESTRAPTM Open) and two suture fixation procedures. Fixation time was measured using a stopwatch, and related surgeon stress was assessed using the validated SURG-TLX questionnaire. T-tests were used to compare between-group differences, and a two-sided 95% confidence interval for the difference in stress levels was established using nonparametric methodology. Results. The mechanical fixation group demonstrated an 89.1% mean reduction in fixation time, as compared to the suture group (p Open demonstrated a significant reduction in fixation time and surgeon stress, which may translate into improved operating efficiency, improved performance, improved surgeon quality of life, and reduced overall costs of the procedure. PMID:26240834

Mean-field approximations of fixation time distributions of evolutionary game dynamics on graphs

Science.gov (United States)

Ying, Li-Min; Zhou, Jie; Tang, Ming; Guan, Shu-Guang; Zou, Yong

2018-02-01

The mean fixation time is often not accurate for describing the timescales of fixation probabilities of evolutionary games taking place on complex networks. We simulate the game dynamics on top of complex network topologies and approximate the fixation time distributions using a mean-field approach. We assume that there are two absorbing states. Numerically, we show that the mean fixation time is sufficient in characterizing the evolutionary timescales when network structures are close to the well-mixing condition. In contrast, the mean fixation time shows large inaccuracies when networks become sparse. The approximation accuracy is determined by the network structure, and hence by the suitability of the mean-field approach. The numerical results show good agreement with the theoretical predictions.

Eye-hand coupling during closed-loop drawing: evidence of shared motor planning?

Science.gov (United States)

Reina, G Anthony; Schwartz, Andrew B

2003-04-01

Previous paradigms have used reaching movements to study coupling of eye-hand kinematics. In the present study, we investigated eye-hand kinematics as curved trajectories were drawn at normal speeds. Eye and hand movements were tracked as a monkey traced ellipses and circles with the hand in free space while viewing the hand's position on a computer monitor. The results demonstrate that the movement of the hand was smooth and obeyed the 2/3 power law. Eye position, however, was restricted to 2-3 clusters along the hand's trajectory and fixed approximately 80% of the time in one of these clusters. The eye remained stationary as the hand moved away from the fixation for up to 200 ms and saccaded ahead of the hand position to the next fixation along the trajectory. The movement from one fixation cluster to another consistently occurred just after the tangential hand velocity had reached a local minimum, but before the next segment of the hand's trajectory began. The next fixation point was close to an area of high curvature along the hand's trajectory even though the hand had not reached that point along the path. A visuo-motor illusion of hand movement demonstrated that the eye movement was influenced by hand movement and not simply by visual input. During the task, neural activity of pre-motor cortex (area F4) was recorded using extracellular electrodes and used to construct a population vector of the hand's trajectory. The results suggest that the saccade onset is correlated in time with maximum curvature in the population vector trajectory for the hand movement. We hypothesize that eye and arm movements may have common, or shared, information in forming their motor plans.

EyeFrame: Real-time memory aid improves human multitasking via domain-general eye tracking procedures

Directory of Open Access Journals (Sweden)

P. eTaylor

2015-09-01

Full Text Available OBJECTIVE: We developed an extensively general closed-loop system to improve human interaction in various multitasking scenarios, with semi-autonomous agents, processes, and robots. BACKGROUND: Much technology is converging toward semi-independent processes with intermittent human supervision distributed over multiple computerized agents. Human operators multitask notoriously poorly, in part due to cognitive load and limited working memory. To multitask optimally, users must remember task order, e.g., the most neglected task, since longer times not monitoring an element indicates greater probability of need for user input. The secondary task of monitoring attention history over multiple spatial tasks requires similar cognitive resources as primary tasks themselves. Humans can not reliably make more than ~2 decisions/s. METHODS: Participants managed a range of 4-10 semi-autonomous agents performing rescue tasks. To optimize monitoring and controlling multiple agents, we created an automated short term memory aid, providing visual cues from users' gaze history. Cues indicated when and where to look next, and were derived from an inverse of eye fixation recency. RESULTS: Contingent eye tracking algorithms drastically improved operator performance, increasing multitasking capacity. The gaze aid reduced biases, and reduced cognitive load, measured by smaller pupil dilation. CONCLUSIONS: Our eye aid likely helped by delegating short-term memory to the computer, and by reducing decision making load. Past studies used eye position for gaze-aware control and interactive updating of displays in application-specific scenarios, but ours is the first to successfully implement domain-general algorithms. Procedures should generalize well to: process control, factory operations, robot control, surveillance, aviation, air traffic control, driving, military, mobile search and rescue, and many tasks where probability of utility is predicted by duration since last

Sutureless intrascleral intraocular lens fixation with lamellar dissection of scleral tunnel

Directory of Open Access Journals (Sweden)

Kawaji T

2016-01-01

Full Text Available Takahiro Kawaji,1,2 Tomoki Sato,2 Hidenobu Tanihara11Department of Ophthalmology, Faculty of Life Sciences, Kumamoto University, Chuo-ku, 2Sato Eye & Internal Medicine Clinic, Kumamoto, JapanPurpose: To report the results of sutureless scleral fixation of a posterior chamber intraocular lens (IOL by using our developed simple technique.Methods: We retrospectively reviewed the medical records of 48 eyes of 47 patients who underwent sutureless intrascleral IOL fixation by using our modified technique. A 25-gauge microvitreoretinal knife was used to perform sclerotomies and create limbus-parallel scleral tunnels with lamellar dissection in which the haptics were fixed.Results: The IOLs were fixed and centered well. The mean follow-up period was 26.7 months. Postoperative complications included smooth vitreous hemorrhage in four eyes (8.3%, cystoid macular edema in two eyes (4.2%, and iris capture of the IOL in two eyes (4.2%. No other complications, such as breakage of the IOL, spontaneous IOL dislocation, or retinal detachment, were detected during the follow-up period.Conclusion: The lamellar dissection of the limbus-parallel scleral tunnel can simplify the forceps-assisted introduction of the haptics into the scleral tunnel, and this technique seemed to be safe.Keywords: intraocular lenses, ophthalmologic surgical procedures, intrascleral fixation, sutureless fixation

Late dislocation of in-the-bag intraocular lenses in uveitic eyes: An analysis of management and complications

Directory of Open Access Journals (Sweden)

Sudha K Ganesh

2017-01-01

Full Text Available Aim: An analysis of late in-the-bag dislocation of intraocular lenses (IOL, in uveitic eyes. Setting: Referral uveitis clinic. Design: Retrospective case series. Materials and Methods: All case records of eyes with chronic uveitis that had phacoemulsification with IOL implantation, at a referral uveitis clinic between February 1997 and January 2015 were retrieved and analyzed. Only those eyes with no documented intraoperative complication and no predisposing risks to IOL dislocation, such as pseudoexfoliation, high myopia, trauma, and prior VR surgery were included in this study. Results: A total of 581 eyes with chronic uveitis underwent phacoemulsification with IOL implantation under steroid cover from February 1997 to December 2015. Out of these 581 eyes, 10 patients (11 eyes had experienced late in-the-bag IOL dislocation (1.89%. All 11 eyes had chronic intermediate uveitis. The mean duration from the time of cataract surgery to IOL dislocation was 11.24 years. 5 out of 11 eyes had pars plana vitrectomy (PPV with IOL removal with 4-point sutured scleral fixated IOL. Two out of 11 eyes had PPV with in-the-bag IOL re-fixation. Out of 11, 2 eyes had PPV with IOL removal only. Remaining 2 eyes of 2 patients did not opt for surgery. Out of 11, 8 eyes had improved vision at last follow-up. Conclusions: In-the-bag dislocation of IOL is a rare late complication in uveitic eyes. With tight perioperative inflammatory control, scleral-fixated posterior chamber intraocular lens or IOL re-fixation are good options of restoring vision in these high-risk eyes.

Fixation to features and neural processing of facial expressions in a gender discrimination task.

Science.gov (United States)

Neath, Karly N; Itier, Roxane J

2015-10-01

Early face encoding, as reflected by the N170 ERP component, is sensitive to fixation to the eyes. Whether this sensitivity varies with facial expressions of emotion and can also be seen on other ERP components such as P1 and EPN, was investigated. Using eye-tracking to manipulate fixation on facial features, we found the N170 to be the only eye-sensitive component and this was true for fearful, happy and neutral faces. A different effect of fixation to features was seen for the earlier P1 that likely reflected general sensitivity to face position. An early effect of emotion (∼120 ms) for happy faces was seen at occipital sites and was sustained until ∼350 ms post-stimulus. For fearful faces, an early effect was seen around 80 ms followed by a later effect appearing at ∼150 ms until ∼300 ms at lateral posterior sites. Results suggests that in this emotion-irrelevant gender discrimination task, processing of fearful and happy expressions occurred early and largely independently of the eye-sensitivity indexed by the N170. Processing of the two emotions involved different underlying brain networks active at different times. Copyright © 2015 Elsevier Inc. All rights reserved.

Experience with compound words influences their processing: An eye movement investigation with English compound words.

Science.gov (United States)

Juhasz, Barbara J

2016-11-14

Recording eye movements provides information on the time-course of word recognition during reading. Juhasz and Rayner [Juhasz, B. J., & Rayner, K. (2003). Investigating the effects of a set of intercorrelated variables on eye fixation durations in reading. Journal of Experimental Psychology: Learning, Memory and Cognition, 29, 1312-1318] examined the impact of five word recognition variables, including familiarity and age-of-acquisition (AoA), on fixation durations. All variables impacted fixation durations, but the time-course differed. However, the study focused on relatively short, morphologically simple words. Eye movements are also informative for examining the processing of morphologically complex words such as compound words. The present study further examined the time-course of lexical and semantic variables during morphological processing. A total of 120 English compound words that varied in familiarity, AoA, semantic transparency, lexeme meaning dominance, sensory experience rating (SER), and imageability were selected. The impact of these variables on fixation durations was examined when length, word frequency, and lexeme frequencies were controlled in a regression model. The most robust effects were found for familiarity and AoA, indicating that a reader's experience with compound words significantly impacts compound recognition. These results provide insight into semantic processing of morphologically complex words during reading.

Prediction of Human Eye Fixations using Symmetry

OpenAIRE

Kootstra, Gert; Schomaker, Lambert R. B.

2009-01-01

Humans are very sensitive to symmetry in visual patterns. Reaction time experiments show that symmetry is detected and recognized very rapidly. This suggests that symmetry is a highly salient feature. Existing computational models of saliency, however, have mainly focused on contrast as a measure of saliency. In this paper, we discuss local symmetry as a measure of saliency. We propose a number of symmetry models and perform an eye-tracking study with human participants viewing photographic i...

Eye gaze during comprehension of American Sign Language by native and beginning signers.

Science.gov (United States)

Emmorey, Karen; Thompson, Robin; Colvin, Rachael

2009-01-01

An eye-tracking experiment investigated where deaf native signers (N = 9) and hearing beginning signers (N = 10) look while comprehending a short narrative and a spatial description in American Sign Language produced live by a fluent signer. Both groups fixated primarily on the signer's face (more than 80% of the time) but differed with respect to fixation location. Beginning signers fixated on or near the signer's mouth, perhaps to better perceive English mouthing, whereas native signers tended to fixate on or near the eyes. Beginning signers shifted gaze away from the signer's face more frequently than native signers, but the pattern of gaze shifts was similar for both groups. When a shift in gaze occurred, the sign narrator was almost always looking at his or her hands and was most often producing a classifier construction. We conclude that joint visual attention and attention to mouthing (for beginning signers), rather than linguistic complexity or processing load, affect gaze fixation patterns during sign language comprehension.

Evaluation of pars plana sclera fixation of posterior chamber intraocular lens

Directory of Open Access Journals (Sweden)

Fangju Han

2014-01-01

Full Text Available Purpose: The purpose of this study was to evaluate the clinical efficacy and safety of modified posterior chamber intraocular lens (PCIOL implantation with transscleral fixation. Design and Setting: This is a study, which is conducted at Department of Ophthalmology, Jinan Eye Hospital, Jinan Second People′s Hospital. Materials and Methods: A total of 82 patients who were scheduled for sutured PCIOL were divided randomly into modified and conventional groups. The former underwent PCIOL through pars plana fixation with knot buried and without scleral flap and the latter underwent transscleral fixation of PCIOL in the ciliary sulcus. The main outcome measures included operative time, postoperative visual acuity, and postoperative complications. Results: The mean operative time of the modified group was 39.95 ± 5.87 min, which was significantly less than that of the conventional group (45.77 ± 5.21 min; P < 0.05. No difference was found in postoperative visual acuity between the two groups. There were no significant postoperative complications, including knot exposure, endophthalmitis, and retinal detachment in either group. The optical clamping of PCIOL was prone to occur in the conventional group. Conclusion: Modified sutured PCIOL implantation is a safe, effective, and feasible technique for the correction of aphakia in eyes without adequate posterior capsular support.

Flanged Intrascleral Intraocular Lens Fixation with Double-Needle Technique.

Science.gov (United States)

Yamane, Shin; Sato, Shimpei; Maruyama-Inoue, Maiko; Kadonosono, Kazuaki

2017-08-01

To report the clinical outcomes of a new technique for transconjunctival intrascleral fixation of an intraocular lens (IOL). Prospective, noncomparative, interventional case series. One hundred eyes of 97 consecutive patients with aphakia, dislocated IOL, or subluxated crystalline lens who underwent posterior chamber sutureless implantation of an IOL were studied. Two angled incisions parallel to the limbus were made by 30-gauge thin-wall needles. Haptics of an IOL were externalized with the needles and cauterized to make a flange of the haptics. The flange of the haptics were pushed back and fixed into the scleral tunnels. Best-corrected visual acuity (VA), corneal endothelial cell density, IOL tilt, and complications were determined. The IOLs were fixed with exact centration and axial stability. The mean preoperative best-corrected VA was 0.25 logarithm of the minimum angle of resolution (logMAR) units; after surgery, it improved significantly to 0.11 logMAR, 0.09 logMAR, 0.12 logMAR, and 0.04 logMAR at 6, 12, 24, and 36 months, respectively (P IOL tilt was 3.4°±2.5°. The postoperative complications included iris capture by the IOL in 8 eyes (8%), vitreous hemorrhage in 5 eyes (5%), and cystoid macular edema in 1 eye (1%). There were no incidents of postoperative retinal detachment, endophthalmitis, or IOL dislocation. We have developed a new technique for intrascleral IOL fixation. The flanged IOL fixation technique is a simple and minimally invasive method for achieving good IOL fixation with firm haptic fixation. Copyright © 2017 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Influence of social presence on eye movements in visual search tasks.

Science.gov (United States)

Liu, Na; Yu, Ruifeng

2017-12-01

This study employed an eye-tracking technique to investigate the influence of social presence on eye movements in visual search tasks. A total of 20 male subjects performed visual search tasks in a 2 (target presence: present vs. absent) × 2 (task complexity: complex vs. simple) × 2 (social presence: alone vs. a human audience) within-subject experiment. Results indicated that the presence of an audience could evoke a social facilitation effect on response time in visual search tasks. Compared with working alone, the participants made fewer and shorter fixations, larger saccades and shorter scan path in simple search tasks and more and longer fixations, smaller saccades and longer scan path in complex search tasks when working with an audience. The saccade velocity and pupil diameter in the audience-present condition were larger than those in the working-alone condition. No significant change in target fixation number was observed between two social presence conditions. Practitioner Summary: This study employed an eye-tracking technique to examine the influence of social presence on eye movements in visual search tasks. Results clarified the variation mechanism and characteristics of oculomotor scanning induced by social presence in visual search.

Eye Tracker Accuracy: Quantitative Evaluation of the Invisible Eye Center Location

OpenAIRE

Wyder, Stephan; Cattin, Philippe C.

2017-01-01

Purpose. We present a new method to evaluate the accuracy of an eye tracker based eye localization system. Measuring the accuracy of an eye tracker's primary intention, the estimated point of gaze, is usually done with volunteers and a set of fixation points used as ground truth. However, verifying the accuracy of the location estimate of a volunteer's eye center in 3D space is not easily possible. This is because the eye center is an intangible point hidden by the iris. Methods. We evaluate ...

Adolescents' attention to responsibility messages in magazine alcohol advertisements: an eye-tracking approach.

Science.gov (United States)

Thomsen, Steven R; Fulton, Kristi

2007-07-01

To investigate whether adolescent readers attend to responsibility or moderation messages (e.g., "drink responsibly") included in magazine advertisements for alcoholic beverages and to assess the association between attention and the ability to accurately recall the content of these messages. An integrated head-eye tracking system (ASL Eye-TRAC 6000) was used to measure the eye movements, including fixations and fixation duration, of a group of 63 adolescents (ages 12-14 years) as they viewed six print advertisements for alcoholic beverages. Immediately after the eye-tracking sessions, participants completed a masked-recall exercise. Overall, the responsibility or moderation messages were the least frequently viewed textual or visual areas of the advertisements. Participants spent an average of only .35 seconds, or 7% of the total viewing time, fixating on each responsibility message. Beverage bottles, product logos, and cartoon illustrations were the most frequently viewed elements of the advertisements. Among those participants who fixated at least once on an advertisement's warning message, only a relatively small percentage were able to recall its general concept or restate it verbatim in the masked recall test. Voluntary responsibility or moderation messages failed to capture the attention of teenagers who participated in this study and need to be typographically modified to be more effective.

The saccadic flow baseline: Accounting for image-independent biases in fixation behavior.

Science.gov (United States)

Clarke, Alasdair D F; Stainer, Matthew J; Tatler, Benjamin W; Hunt, Amelia R

2017-09-01

Much effort has been made to explain eye guidance during natural scene viewing. However, a substantial component of fixation placement appears to be a set of consistent biases in eye movement behavior. We introduce the concept of saccadic flow, a generalization of the central bias that describes the image-independent conditional probability of making a saccade to (xi+1, yi+1), given a fixation at (xi, yi). We suggest that saccadic flow can be a useful prior when carrying out analyses of fixation locations, and can be used as a submodule in models of eye movements during scene viewing. We demonstrate the utility of this idea by presenting bias-weighted gaze landscapes, and show that there is a link between the likelihood of a saccade under the flow model, and the salience of the following fixation. We also present a minor improvement to our central bias model (based on using a multivariate truncated Gaussian), and investigate the leftwards and coarse-to-fine biases in scene viewing.

From Covert Processes to Overt Outcomes of Refutation Text Reading: The Interplay of Science Text Structure and Working Memory Capacity through Eye Fixations

Science.gov (United States)

Ariasi, Nicola; Mason, Lucia

2014-01-01

This study extends current research on the refutation text effect by investigating it in learners with different levels of working memory capacity. The purpose is to outline the link between online processes (revealed by eye fixation indices) and off-line outcomes in these learners. In science education, unlike a standard text, a refutation text…

Legibility difference between e-books and paper books by using an eye tracker.

Science.gov (United States)

Kim, Jung-Yong; Min, Seung-Nam; Subramaniyam, Murali; Cho, Young-Jin

2014-01-01

The aim of the study was to evaluate the difference in legibility between e-books and paper books by using an eye tracker. Eight male and eight female subjects free of eye disease participated in the experiment. The experiment was conducted using a 2 × 3 within-subject design. The book type (e-book, paper book) and font size (8 pt, 10 pt, 12 pt) were independent variables, and fixation duration time, saccade length, blink rate and subjective discomfort were dependent variables. In the results, all dependent variables showed that reading paper books provided a better experience than reading e-books did. These results indicate that the legibility of e-books needs further improvement, considering fixation duration time, saccade movement, eye fatigue, device and so on. This study evaluated the legibility difference between e-books and paper books from the viewpoint of readability, eye fatigue and subjective discomfort by using an eye tracker. The results showed that paper books provided a better experience than e-books. This indicates that the readability of e-books needs further improvement in relation to paper books.

Capsule-Fixated Intraocular Lens Implantation in Small Pupil Cases.

Science.gov (United States)

Schojai, Merita; Schultz, Tim; Burkhard Dick, H

2017-08-01

To describe a new technique for implantation of capsule-fixated intraocular lenses (IOLs) (FEMTIS; Oculentis, Berlin, Germany) in patients with small pupils. In 4 eyes with small pupils, an anterior capsule-fixated IOL was implanted into the capsular bag after femtosecond laser treatment. The two large and two small flaps of the IOL were elevated to the front of the iris and the anterior capsule. Finally, the iris was flipped over the flaps to ensure a fixation of the capsule inside of the capsulotomy. In all cases, the implantation of anterior capsule-fixated IOLs was possible. No complications occurred during surgery or within the first months after surgery. With the described technique, capsulefixated IOLs can be implanted in eyes with small pupil easily and safely. This type of IOL has great potential to improve the refractive outcome by better prediction of the postoperative IOL position and eliminating IOL rotation after cataract surgery. [J Refract Surg. 2017;33(8):568-570.]. Copyright 2017, SLACK Incorporated.

Intraocular lens iris fixation. Clinical and macular OCT outcomes

Science.gov (United States)

2012-01-01

Background To assess the efficacy, clinical outcomes, visual acuity (VA), incidence of adverse effects, and complications of peripheral iris fixation of 3-piece acrylic IOLs in eyes lacking capsular support. Thirteen patients who underwent implantation and peripheral iris fixation of a 3-piece foldable acrylic PC IOL for aphakia in the absence of capsular support were followed after surgery. Clinical outcomes and macular SD-OCT (Cirrus OCT; Carl Zeiss Meditec, Germany) were analyzed. Findings The final CDVA was 20/40 or better in 8 eyes (62%), 20/60 or better in 12 eyes (92%), and one case of 20/80 due to corneal astigmatism and mild persistent edema. No intraoperative complications were reported. There were seven cases of medically controlled ocular hypertension after surgery due to the presence of viscoelastic in the AC. There were no cases of cystoid macular edema, chronic iridocyclitis, IOL subluxation, pigment dispersion, or glaucoma. Macular edema did not develop in any case by means of SD-OCT. Conclusions We think that this technique for iris suture fixation provides safe and effective results. Patients had substantial improvements in UDVA and CDVA. This surgical strategy may be individualized however; age, cornea status, angle structures, iris anatomy, and glaucoma are important considerations in selecting candidates for an appropriate IOL fixation method. PMID:23050659

A MATLAB-based eye tracking control system using non-invasive helmet head restraint in the macaque.

Science.gov (United States)

De Luna, Paolo; Mohamed Mustafar, Mohamed Faiz Bin; Rainer, Gregor

2014-09-30

Tracking eye position is vital for behavioral and neurophysiological investigations in systems and cognitive neuroscience. Infrared camera systems which are now available can be used for eye tracking without the need to surgically implant magnetic search coils. These systems are generally employed using rigid head fixation in monkeys, which maintains the eye in a constant position and facilitates eye tracking. We investigate the use of non-rigid head fixation using a helmet that constrains only general head orientation and allows some freedom of movement. We present a MATLAB software solution to gather and process eye position data, present visual stimuli, interact with various devices, provide experimenter feedback and store data for offline analysis. Our software solution achieves excellent timing performance due to the use of data streaming, instead of the traditionally employed data storage mode for processing analog eye position data. We present behavioral data from two monkeys, demonstrating that adequate performance levels can be achieved on a simple fixation paradigm and show how performance depends on parameters such as fixation window size. Our findings suggest that non-rigid head restraint can be employed for behavioral training and testing on a variety of gaze-dependent visual paradigms, reducing the need for rigid head restraint systems for some applications. While developed for macaque monkey, our system of course can work equally well for applications in human eye tracking where head constraint is undesirable. Copyright © 2014. Published by Elsevier B.V.

Through the Eyes of the Beholder: Simulated Eye-movement Experience ("SEE") Modulates Valence Bias in Response to Emotional Ambiguity.

Science.gov (United States)

Neta, Maital; Dodd, Michael D

2018-02-01

Although some facial expressions provide clear information about people's emotions and intentions (happy, angry), others (surprise) are ambiguous because they can signal both positive (e.g., surprise party) and negative outcomes (e.g., witnessing an accident). Without a clarifying context, surprise is interpreted as positive by some and negative by others, and this valence bias is stable across time. When compared to fearful expressions, which are consistently rated as negative, surprise and fear share similar morphological features (e.g., widened eyes) primarily in the upper part of the face. Recently, we demonstrated that the valence bias was associated with a specific pattern of eye movements (positive bias associated with faster fixation to the lower part of the face). In this follow-up, we identified two participants from our previous study who had the most positive and most negative valence bias. We used their eye movements to create a moving window such that new participants viewed faces through the eyes of one our previous participants (subjects saw only the areas of the face that were directly fixated by the original participants in the exact order they were fixated; i.e., Simulated Eye-movement Experience). The input provided by these windows modulated the valence ratings of surprise, but not fear faces. These findings suggest there are meaningful individual differences in how people process faces, and that these differences impact our emotional perceptions. Furthermore, this study is unique in its approach to examining individual differences in emotion by creating a new methodology adapted from those used primarily in the vision/attention domain. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Sutureless glueless intrascleral fixation of posterior chamber intraocular lens: Boon for aphakic

Directory of Open Access Journals (Sweden)

Nagendra Shekhawat

2017-01-01

Full Text Available Purpose: To report results of intrascleral fixation of 3-piece IOL without the help of suture and glue. Methods: Study included intrascleral fixation of haptic in 50 eyes by T-fixation technique. Preoperative and postoperative visual acuity, slit lamp and fundus examination, applanation tonometry, keratometry, biometry, optical coherence tomography, Scheimpflug imaging were done for extensive evaluation. Qualitative and quantitative data were summarized in the form of proportion and mean and standard deviation, respectively. The significance of difference was measured by Chi-square test or unpaired t-test or ANOVA whichever is appropriate. P < 0.05 was considered as statistically significant. Results: There was one case in which haptic broke during handshake maneuver and another IOL was required. Postoperative complications included corneal edema (4%, increased intraocular pressure (6%, cystoid macular edema (2%, decentration (4%, and dislocation (2%, which were all managed to the level of good visual recovery. There was no significant change in corneal astigmatism. There was significant change found in best-corrected visual acuity and uncorrected visual acuity after surgery. Conclusion: This modified technique seems to be a good alternative in IOL implantation in eyes with deficient capsules in view of the decrease in the learning time and surgical time and risk for complications.

Toward FRP-Based Brain-Machine Interfaces-Single-Trial Classification of Fixation-Related Potentials.

Directory of Open Access Journals (Sweden)

Andrea Finke

Full Text Available The co-registration of eye tracking and electroencephalography provides a holistic measure of ongoing cognitive processes. Recently, fixation-related potentials have been introduced to quantify the neural activity in such bi-modal recordings. Fixation-related potentials are time-locked to fixation onsets, just like event-related potentials are locked to stimulus onsets. Compared to existing electroencephalography-based brain-machine interfaces that depend on visual stimuli, fixation-related potentials have the advantages that they can be used in free, unconstrained viewing conditions and can also be classified on a single-trial level. Thus, fixation-related potentials have the potential to allow for conceptually different brain-machine interfaces that directly interpret cortical activity related to the visual processing of specific objects. However, existing research has investigated fixation-related potentials only with very restricted and highly unnatural stimuli in simple search tasks while participant's body movements were restricted. We present a study where we relieved many of these restrictions while retaining some control by using a gaze-contingent visual search task. In our study, participants had to find a target object out of 12 complex and everyday objects presented on a screen while the electrical activity of the brain and eye movements were recorded simultaneously. Our results show that our proposed method for the classification of fixation-related potentials can clearly discriminate between fixations on relevant, non-relevant and background areas. Furthermore, we show that our classification approach generalizes not only to different test sets from the same participant, but also across participants. These results promise to open novel avenues for exploiting fixation-related potentials in electroencephalography-based brain-machine interfaces and thus providing a novel means for intuitive human-machine interaction.

Intraocular lens iris fixation. Clinical and macular OCT outcomes

Directory of Open Access Journals (Sweden)

Garcia-Rojas Leonardo

2012-10-01

Full Text Available Abstract Background To assess the efficacy, clinical outcomes, visual acuity (VA, incidence of adverse effects, and complications of peripheral iris fixation of 3-piece acrylic IOLs in eyes lacking capsular support. Thirteen patients who underwent implantation and peripheral iris fixation of a 3-piece foldable acrylic PC IOL for aphakia in the absence of capsular support were followed after surgery. Clinical outcomes and macular SD-OCT (Cirrus OCT; Carl Zeiss Meditec, Germany were analyzed. Findings The final CDVA was 20/40 or better in 8 eyes (62%, 20/60 or better in 12 eyes (92%, and one case of 20/80 due to corneal astigmatism and mild persistent edema. No intraoperative complications were reported. There were seven cases of medically controlled ocular hypertension after surgery due to the presence of viscoelastic in the AC. There were no cases of cystoid macular edema, chronic iridocyclitis, IOL subluxation, pigment dispersion, or glaucoma. Macular edema did not develop in any case by means of SD-OCT. Conclusions We think that this technique for iris suture fixation provides safe and effective results. Patients had substantial improvements in UDVA and CDVA. This surgical strategy may be individualized however; age, cornea status, angle structures, iris anatomy, and glaucoma are important considerations in selecting candidates for an appropriate IOL fixation method.

Eye fixations indicate men's preference for female breasts or buttocks.

Science.gov (United States)

Dagnino, Bruno; Navajas, Joaquin; Sigman, Mariano

2012-08-01

Evolutionary psychologists have been interested in male preferences for particular female traits that are thought to signal health and reproductive potential. While the majority of studies have focused on what makes specific body traits attractive-such as the waist-to-hip ratio, the body mass index, and breasts shape and size-there is little empirical research that has examined individual differences in male preferences for specific traits (e.g., favoring breasts over buttocks). The current study begins to fill this empirical gap. In the first experiment (Study 1), 184 male participants were asked to report their preference between breasts and buttocks on a continuous scale. We found that (1) the distribution of preference was bimodal, indicating that Argentinean males tended to define themselves as favoring breasts or buttocks but rarely thinking that these traits contributed equally to their choice and (2) the distribution was biased towards buttocks. In a second experiment (Study 2), 19 male participants were asked to rate pictures of female breasts and buttocks. This study was necessary to generate three categories of pictures with statistically different ratings (high, medium, and low). In a third experiment (Study 3), we recorded eye-movements of 25 male participants while they chose the more attractive between two women, only seeing their breasts and buttock. We found that the first and last fixations were systematically directed towards the self-reported preferred trait.

Brief report: eye-movement patterns during an embedded figures test in children with ASD.

Science.gov (United States)

Keehn, Brandon; Brenner, Laurie A; Ramos, Aurora I; Lincoln, Alan J; Marshall, Sandra P; Müller, Ralph-Axel

2009-02-01

The present study examined fixation frequency and duration during an Embedded Figures Test (EFT) in an effort to better understand the attentional and perceptual processes by which individuals with autism spectrum disorder (ASD) achieve accelerated EFT performance. In particular, we aimed to elucidate differences in the patterns of eye-movement in ASD and typically developing (TD) children, thus providing evidence relevant to the competing theories of weak central coherence (WCC) and enhanced perceptual functioning. Consistent with prior EFT studies, we found accelerated response time (RT) in children with ASD. No group differences were seen for fixation frequency, but the ASD group made significantly shorter fixations compared to the TD group. Eye-movement results indicate that RT advantage in ASD is related to both WCC and enhanced perceptual functioning.

Does consolidation of visuospatial sequence knowledge depend on eye movements?

Directory of Open Access Journals (Sweden)

Daphné Coomans

Full Text Available In the current study, we assessed whether visuospatial sequence knowledge is retained over 24 hours and whether this retention is dependent on the occurrence of eye movements. Participants performed two sessions of a serial reaction time (SRT task in which they had to manually react to the identity of a target letter pair presented in one of four locations around a fixation cross. When the letter pair 'XO' was presented, a left response had to be given, when the letter pair 'OX' was presented, a right response was required. In the Eye Movements (EM condition, eye movements were necessary to perform the task since the fixation cross and the target were separated by at least 9° visual angle. In the No Eye Movements (NEM condition, on the other hand, eye movements were minimized by keeping the distance from the fixation cross to the target below 1° visual angle and by limiting the stimulus presentation to 100 ms. Since the target identity changed randomly in both conditions, no manual response sequence was present in the task. However, target location was structured according to a deterministic sequence in both the EM and NEM condition. Learning of the target location sequence was determined at the end of the first session and 24 hours after initial learning. Results indicated that the sequence learning effect in the SRT task diminished, yet remained significant, over the 24 hour interval in both conditions. Importantly, the difference in eye movements had no impact on the transfer of sequence knowledge. These results suggest that the retention of visuospatial sequence knowledge occurs alike, irrespective of whether this knowledge is supported by eye movements or not.

The oculomotor system of decapod cephalopods: eye muscles, eye muscle nerves, and the oculomotor neurons in the central nervous system.

Science.gov (United States)

Budelmann, B U; Young, J Z

1993-04-29

Fourteen extraocular eye muscles are described in the decapods Loligo and Sepioteuthis, and thirteen in Sepia; they are supplied by four eye muscle nerves. The main action of most of the muscles is a linear movement of the eyeball, only three muscles produce strong rotations. The arrangement, innervation and action of the decapod eye muscles are compared with those of the seven eye muscles and seven eye muscle nerves in Octopus. The extra muscles in decapods are attached to the anterior and superior faces of the eyes. At least, the anterior muscles, and presumably also the superior muscles, are concerned with convergent eye movements for binocular vision during fixation and capture of prey by the tentacles. The remaining muscles are rather similar in the two cephalopod groups. In decapods, the anterior muscles include conjunctive muscles; these cross the midline and each presumably moves both eyes at the same time during fixation. In the squids Loligo and Sepioteuthis there is an additional superior conjunctive muscle of perhaps similar function. Some of the anterior muscles are associated with a narrow moveable plate, the trochlear cartilage; it is attached to the eyeball by trochlear membranes. Centripetal cobalt fillings showed that all four eye muscle nerves have fibres that originate from somata in the ipsilateral anterior lateral pedal lobe, which is the oculomotor centre. The somata of the individual nerves show different but overlapping distributions. Bundles of small presumably afferent fibres were seen in two of the four nerves. They do not enter the anterior lateral pedal lobe but run to the ventral magnocellular lobe; some afferent fibres enter the brachio-palliovisceral connective and run perhaps as far as the palliovisceral lobe.

Methods of fixation of intraocular lenses according to the anatomical structures in trauma eyes.

Science.gov (United States)

Fiorentzis, Miltiadis; Viestenz, Anja; Heichel, Jens; Seitz, Berthold; Hammer, Thomas; Viestenz, Arne

2018-01-01

Ocular trauma can lead to severe visual impairment and morbidity, depending on the anatomical structures affected. The main causes of ocular trauma include foreign bodies, impact by an object, falls, and chemicals. Most ocular traumas occur in children or young male adults. A meticulous slit lamp examination is crucial for assessing all anatomical structures. Trauma to the crystalline lens can result in dislocation, an intralenticular foreign body, cataract, fragmentation, and capsular breach. An intraocular lens (IOL) can endure subluxation or luxation under the conjunctiva, into the anterior chamber or the vitreous, or can be extruded. The surgical approach depends on the condition and morphology of the lens and the anatomical structures surrounding it. If there is capsular bag support, a secondary IOL can be placed in the sulcus using remnants of the damaged capsule. If there is no capsular bag support, a secondary IOL can be fixated to the anterior chamber angle, to the iris, or to the sclera. A detailed history of injury cannot always be obtained in trauma settings. Proper education, supervision, and certified safety eye protectors could prevent up to 90% of ocular injuries. Lens trauma can be treated with various surgical procedures and fixation techniques, which nevertheless require advanced surgical skills owing to the fine anatomical structure of the anterior segment. A careful surgical strategy should be established for a globe reconstruction after trauma with secondary lens implantation. Clin. Anat. 31:6-15, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

The socialization effect on decision making in the Prisoner's Dilemma game: An eye-tracking study.

Directory of Open Access Journals (Sweden)

Anastasia G Peshkovskaya

Full Text Available We used a mobile eye-tracking system (in the form of glasses to study the characteristics of visual perception in decision making in the Prisoner's Dilemma game. In each experiment, one of the 12 participants was equipped with eye-tracking glasses. The experiment was conducted in three stages: an anonymous Individual Game stage against a randomly chosen partner (one of the 12 other participants of the experiment; a Socialization stage, in which the participants were divided into two groups; and a Group Game stage, in which the participants played with partners in the groups. After each round, the respondent received information about his or her personal score in the last round and the overall winner of the game at the moment. The study proves that eye-tracking systems can be used for studying the process of decision making and forecasting. The total viewing time and the time of fixation on areas corresponding to noncooperative decisions is related to the participants' overall level of cooperation. The increase in the total viewing time and the time of fixation on the areas of noncooperative choice is due to a preference for noncooperative decisions and a decrease in the overall level of cooperation. The number of fixations on the group attributes is associated with group identity, but does not necessarily lead to cooperative behavior.

The Relationship Between Problem Size and Fixation Patterns During Addition, Subtraction, Multiplication, and Division

Directory of Open Access Journals (Sweden)

Evan T. Curtis

2016-08-01

Full Text Available Eye-tracking methods have only rarely been used to examine the online cognitive processing that occurs during mental arithmetic on simple arithmetic problems, that is, addition and multiplication problems with single-digit operands (e.g., operands 2 through 9; 2 + 3, 6 x 8 and the inverse subtraction and division problems (e.g., 5 – 3; 48 ÷ 6. Participants (N = 109 solved arithmetic problems from one of the four operations while their eye movements were recorded. We found three unique fixation patterns. During addition and multiplication, participants allocated half of their fixations to the operator and one-quarter to each operand, independent of problem size. The pattern was similar on small subtraction and division problems. However, on large subtraction problems, fixations were distributed approximately evenly across the three stimulus components. On large division problems, over half of the fixations occurred on the left operand, with the rest distributed between the operation sign and the right operand. We discuss the relations between these eye tracking patterns and other research on the differences in processing across arithmetic operations.

Vertical eye position-dependence of the human vestibuloocular reflex during passive and active yaw head rotations.

Science.gov (United States)

Thurtell, M J; Black, R A; Halmagyi, G M; Curthoys, I S; Aw, S T

1999-05-01

Vertical eye position-dependence of the human vestibuloocular reflex during passive and active yaw head rotations. The effect of vertical eye-in-head position on the compensatory eye rotation response to passive and active high acceleration yaw head rotations was examined in eight normal human subjects. The stimuli consisted of brief, low amplitude (15-25 degrees ), high acceleration (4,000-6,000 degrees /s2) yaw head rotations with respect to the trunk (peak velocity was 150-350 degrees /s). Eye and head rotations were recorded in three-dimensional space using the magnetic search coil technique. The input-output kinematics of the three-dimensional vestibuloocular reflex (VOR) were assessed by finding the difference between the inverted eye velocity vector and the head velocity vector (both referenced to a head-fixed coordinate system) as a time series. During passive head impulses, the head and eye velocity axes aligned well with each other for the first 47 ms after the onset of the stimulus, regardless of vertical eye-in-head position. After the initial 47-ms period, the degree of alignment of the eye and head velocity axes was modulated by vertical eye-in-head position. When fixation was on a target 20 degrees up, the eye and head velocity axes remained well aligned with each other. However, when fixation was on targets at 0 and 20 degrees down, the eye velocity axis tilted forward relative to the head velocity axis. During active head impulses, the axis tilt became apparent within 5 ms of the onset of the stimulus. When fixation was on a target at 0 degrees, the velocity axes remained well aligned with each other. When fixation was on a target 20 degrees up, the eye velocity axis tilted backward, when fixation was on a target 20 degrees down, the eye velocity axis tilted forward. The findings show that the VOR compensates very well for head motion in the early part of the response to unpredictable high acceleration stimuli-the eye position- dependence of the

Computing eye gaze metrics for the automatic assessment of radiographer performance during X-ray image interpretation.

Science.gov (United States)

McLaughlin, Laura; Bond, Raymond; Hughes, Ciara; McConnell, Jonathan; McFadden, Sonyia

2017-09-01

To investigate image interpretation performance by diagnostic radiography students, diagnostic radiographers and reporting radiographers by computing eye gaze metrics using eye tracking technology. Three groups of participants were studied during their interpretation of 8 digital radiographic images including the axial and appendicular skeleton, and chest (prevalence of normal images was 12.5%). A total of 464 image interpretations were collected. Participants consisted of 21 radiography students, 19 qualified radiographers and 18 qualified reporting radiographers who were further qualified to report on the musculoskeletal (MSK) system. Eye tracking data was collected using the Tobii X60 eye tracker and subsequently eye gaze metrics were computed. Voice recordings, confidence levels and diagnoses provided a clear demonstration of the image interpretation and the cognitive processes undertaken by each participant. A questionnaire afforded the participants an opportunity to offer information on their experience in image interpretation and their opinion on the eye tracking technology. Reporting radiographers demonstrated a 15% greater accuracy rate (p≤0.001), were more confident (p≤0.001) and took a mean of 2.4s longer to clinically decide on all features compared to students. Reporting radiographers also had a 15% greater accuracy rate (p≤0.001), were more confident (p≤0.001) and took longer to clinically decide on an image diagnosis (p=0.02) than radiographers. Reporting radiographers had a greater mean fixation duration (p=0.01), mean fixation count (p=0.04) and mean visit count (p=0.04) within the areas of pathology compared to students. Eye tracking patterns, presented within heat maps, were a good reflection of group expertise and search strategies. Eye gaze metrics such as time to first fixate, fixation count, fixation duration and visit count within the areas of pathology were indicative of the radiographer's competency. The accuracy and confidence of

Comparative study of fixation density maps

NARCIS (Netherlands)

Engelke, U.; Liu, H.; Wang, Junle; Callet, Le P.; Heynderickx, I.E.J.; Zepernick, H.-J.; Maeder, A.

2013-01-01

Fixation density maps (FDM) created from eye tracking experiments are widely used in image processing applications. The FDM are assumed to be reliable ground truths of human visual attention and as such, one expects a high similarity between FDM created in different laboratories. So far, no studies

Detection of differential viewing patterns to erotic and non-erotic stimuli using eye-tracking methodology.

Science.gov (United States)

Lykins, Amy D; Meana, Marta; Kambe, Gretchen

2006-10-01

As a first step in the investigation of the role of visual attention in the processing of erotic stimuli, eye-tracking methodology was employed to measure eye movements during erotic scene presentation. Because eye-tracking is a novel methodology in sexuality research, we attempted to determine whether the eye-tracker could detect differences (should they exist) in visual attention to erotic and non-erotic scenes. A total of 20 men and 20 women were presented with a series of erotic and non-erotic images and tracked their eye movements during image presentation. Comparisons between erotic and non-erotic image groups showed significant differences on two of three dependent measures of visual attention (number of fixations and total time) in both men and women. As hypothesized, there was a significant Stimulus x Scene Region interaction, indicating that participants visually attended to the body more in the erotic stimuli than in the non-erotic stimuli, as evidenced by a greater number of fixations and longer total time devoted to that region. These findings provide support for the application of eye-tracking methodology as a measure of visual attentional capture in sexuality research. Future applications of this methodology to expand our knowledge of the role of cognition in sexuality are suggested.

Effect of driving experience on anticipatory look-ahead fixations in real curve driving.

Science.gov (United States)

Lehtonen, Esko; Lappi, Otto; Koirikivi, Iivo; Summala, Heikki

2014-09-01

Anticipatory skills are a potential factor for novice drivers' curve accidents. Behavioural data show that steering and speed regulation are affected by forward planning of the trajectory. When approaching a curve, the relevant visual information for online steering control and for planning is located at different eccentricities, creating a need to disengage the gaze from the guidance of steering to anticipatory look-ahead fixations over curves. With experience, peripheral vision can be increasingly used in the visual guidance of steering. This could leave experienced drivers more gaze time to invest on look-ahead fixations over curves, facilitating the trajectory planning. Eighteen drivers (nine novices, nine experienced) drove an instrumented vehicle on a rural road four times in both directions. Their eye movements were analyzed in six curves. The trajectory of the car was modelled and divided to approach, entry and exit phases. Experienced drivers spent less time on the road-ahead and more time on the look-ahead fixations over the curves. Look-ahead fixations were also more common in the approach than in the entry phase of the curve. The results suggest that with experience drivers allocate greater part of their visual attention to trajectory planning. Copyright © 2014 Elsevier Ltd. All rights reserved.

Psychopathic traits are associated with reduced attention to the eyes of emotional faces among adult male non-offenders

Directory of Open Access Journals (Sweden)

Steven Mark Gillespie

2015-10-01

Full Text Available Psychopathic traits are linked with impairments in emotional facial expression recognition. These impairments may, in part, reflect reduced attention to the eyes of emotional faces. Although reduced attention to the eyes has been noted among children with conduct problems and callous-unemotional traits, similar findings are yet to be found in relation to psychopathic traits among adult male participants. Here we investigated the relationship of primary (selfish, uncaring and secondary (impulsive, antisocial psychopathic traits with attention to the eyes among adult male non-offenders during an emotion recognition task. We measured the number of fixations, and overall dwell time, on the eyes and the mouth of male and female faces showing the six basic emotions at varying levels of intensity. We found no relationship of primary or secondary psychopathic traits with recognition accuracy. However, primary psychopathic traits were associated with a reduced number of fixations, and lower overall dwell time, on the eyes relative to the mouth across expressions, intensity, and sex. Furthermore, the relationship of primary psychopathic traits with attention to the eyes of angry and fearful faces was influenced by the sex and intensity of the expression. We also showed that a greater number of fixations on the eyes, relative to the mouth, was associated with increased accuracy for angry and fearful expression recognition. These results are the first to show effects of psychopathic traits on attention to the eyes of emotional faces in an adult male sample, and may support amygdala based accounts of psychopathy. These findings may also have methodological implications for clinical studies of emotion recognition.

Automatic real-time surveillance of eye position and gating for stereotactic radiotherapy of uveal melanoma

International Nuclear Information System (INIS)

Petersch, Bernhard; Bogner, Joachim; Dieckmann, Karin; Poetter, Richard; Georg, Dietmar

2004-01-01

A new prototype (hardware and software) for monitoring eye movements using a noninvasive technique for gated linac-based stereotactic radiotherapy (SRT) of uveal melanoma was developed. The prototype was tested within the scope of a study for 11 patients. Eye immobilization was achieved by having the patient fixate a light source integrated into the system. The system is used in conjunction with a Head and Neck mask system for immobilization, and uses infrared tracking technology for positioning (both BrainLAB AG Heimstetten/Germany). It was used during CT and MR image acquisition as well as during all of five treatment fractions (6 MeV, 5x12 Gy to 80% isodose) to guarantee identical patient setup and eye rotational state during treatment planning and treatment delivery. Maximum temporal and angular deviations tolerated during treatment delivery can be chosen by the physician, the radiation then being interrupted automatically and instantaneously if those criteria are being exceeded during irradiation. A graphical user interface displays life video images of the treated eye and information about the current and previous rotational deviation of the eye from its reference treatment position. The physician thus has online access to data directly linked to the success of the treatment and possible side effects. Mean angular deviations during CT/MR scans and treatment deliveries ranged from 1.61 deg. to 3.64 deg. (standard deviations 0.87 deg. to 2.09 deg.) which is in accordance with precision requirements for SRT. Typical situations when preset deviation criteria were exceeded are slow drifts (fatigue), sudden large eye movements (irritation), or if patients closed their eyes (fatigue). In these cases radiation was reliably interrupted by the gating system. In our clinical setup the novel system for computer-controlled eye movement gated treatments was well tolerated by all patients. The system yields quantitative real-time information about the eye's rotational state

Rett syndrome: basic features of visual processing-a pilot study of eye-tracking.

Science.gov (United States)

Djukic, Aleksandra; Valicenti McDermott, Maria; Mavrommatis, Kathleen; Martins, Cristina L

2012-07-01

Consistently observed "strong eye gaze" has not been validated as a means of communication in girls with Rett syndrome, ubiquitously affected by apraxia, unable to reply either verbally or manually to questions during formal psychologic assessment. We examined nonverbal cognitive abilities and basic features of visual processing (visual discrimination attention/memory) by analyzing patterns of visual fixation in 44 girls with Rett syndrome, compared with typical control subjects. To determine features of visual fixation patterns, multiple pictures (with the location of the salient and presence/absence of novel stimuli as variables) were presented on the screen of a TS120 eye-tracker. Of the 44, 35 (80%) calibrated and exhibited meaningful patterns of visual fixation. They looked longer at salient stimuli (cartoon, 2.8 ± 2 seconds S.D., vs shape, 0.9 ± 1.2 seconds S.D.; P = 0.02), regardless of their position on the screen. They recognized novel stimuli, decreasing the fixation time on the central image when another image appeared on the periphery of the slide (2.7 ± 1 seconds S.D. vs 1.8 ± 1 seconds S.D., P = 0.002). Eye-tracking provides a feasible method for cognitive assessment and new insights into the "hidden" abilities of individuals with Rett syndrome. Copyright © 2012 Elsevier Inc. All rights reserved.

Eye Tracking in the Cockpit: a Review of the Relationships between Eye Movements and the Aviators Cognitive State

Science.gov (United States)

2014-12-01

proportional dwell time OTW in order to assess the impact of novel cockpit instruments on situational awareness in nearby airspace (Cote, Krueger, & Simmons...frequency. In particular, Spady (1978) examined eye movements during simulated landing approach under instrument flight rules ( IFR ). Simulated turbulence...al. (2007) found that NNI varied across phases of simulated IFR flight, showing the least random (most clustered) distribution of fixations during

Predictors of Time to Union After Operative Fixation of Closed Ankle Fractures.

Science.gov (United States)

Matson, Andrew P; Hamid, Kamran S; Adams, Samuel B

2017-08-01

Ankle fractures are common and represent a significant burden to society. We aim to report the rate of union as determined by clinical and radiographic data, and to identify factors that predict time to union. A cohort of 112 consecutive patients with isolated, closed, operative malleolar ankle fractures treated with open reduction and internal fixation was retrospectively reviewed for time to clinical union. Clinical union was defined based on radiographic and clinical parameters, and delayed union was defined by time to union >12 weeks. Injury characteristics, patient factors and treatment variables were recorded, and statistical techniques employed included the Chi-square test, the Student's T-test, and multivariate linear regression modeling. Forty-two (37.5%) of patients who achieved union did so in less than 12 weeks, and 69 (61.6%) of these patients demonstrated delayed union at a mean of 16.7 weeks (range, 12.1-26.7 weeks), and the remaining patient required revision surgery. Factors associated with higher rates of delayed union or increased time to union included tobacco use, bimalleolar fixation, and high energy mechanism (all punion were BMI, dislocation of the tibiotalar joint, external fixation for initial stabilization and delay of definitive management (all punion following open reduction and internal fixation of closed ankle fractures. These findings should assist with patient counseling, and help guide the provider when considering adjunctive therapies that promote bone healing. Prognostic, Level IV: Case series.

Fixation and its role in the causation, laterality and location of pterygium: a study in amblyopes and non-amblyopes.

Science.gov (United States)

Sudhalkar, A

2012-03-01

To evaluate the role of fixation in causing pterygium and determining its laterality and location. This is a prospective, observational, case-control study. Cases were defined as patients with primary pterygium who had unilateral amblyopia with eccentric fixation. Controls were age-matched patients with primary pterygium, but without amblyopia and eccentric fixation. All patients underwent complete ocular, orthoptic, and systemic examination and a detailed risk-factor assessment (latitude of residence, exposure to sunlight, sand, and a high-reflectance environment). The role of fixation in the causation, laterality and location of pterygium was evaluated. Fisher's exact test, the unpaired t-test, and odds ratio (OR) were carried out to determine the significance of the observations. The mean age of subjects was 47.1±5.25 years in cases (n=107) and 48.2±4.75 years in controls (n=310; P=0.78). As far as known risk factors were concerned, both groups were evenly matched. Among the cases, 88 (82.2%) patients demonstrated suppression of the amblyopic eye and 19 (17.8%) patients had abnormal retinal correspondence (ARC). Patients with suppression had a unilateral pterygium in the better (fixating) eye, whereas those with ARC had bilateral pterygia. Among the controls, 192 (61.9%) eyes had bilateral pterygia and 118 (38.1%) eyes had unilateral pterygium. In controls, the dominant eye had a higher prevalence of pterygium. All patients in both groups had a nasal pterygium. Pterygium and fixation were strongly associated (P=0.007; Fisher's exact test; OR -15.98; P=0.008). Fixation appears to have an important role in causing pterygium and determining its location and laterality.

Bilateral spontaneous subluxation of scleral-fixated intraocular lenses.

Science.gov (United States)

Assia, Ehud I; Nemet, Arie; Sachs, Dani

2002-12-01

Two young men with primary ectopic lenses had intracapsular cataract extraction and scleral fixation of posterior chamber intraocular lenses (PC IOLs) using 10-0 polypropylene sutures tied to the IOL eyelets. Three to 9 years after implantation, spontaneous IOL vertical subluxation occurred in all 4 eyes (5 IOL loops), probably because of suture breakage. Late subluxation of a sutured IOL may occur several years after implantation. Double fixation and thicker sutures should be considered, especially in young patients.

Fixation and saliency during search of natural scenes: the case of visual agnosia.

Science.gov (United States)

Foulsham, Tom; Barton, Jason J S; Kingstone, Alan; Dewhurst, Richard; Underwood, Geoffrey

2009-07-01

Models of eye movement control in natural scenes often distinguish between stimulus-driven processes (which guide the eyes to visually salient regions) and those based on task and object knowledge (which depend on expectations or identification of objects and scene gist). In the present investigation, the eye movements of a patient with visual agnosia were recorded while she searched for objects within photographs of natural scenes and compared to those made by students and age-matched controls. Agnosia is assumed to disrupt the top-down knowledge available in this task, and so may increase the reliance on bottom-up cues. The patient's deficit in object recognition was seen in poor search performance and inefficient scanning. The low-level saliency of target objects had an effect on responses in visual agnosia, and the most salient region in the scene was more likely to be fixated by the patient than by controls. An analysis of model-predicted saliency at fixation locations indicated a closer match between fixations and low-level saliency in agnosia than in controls. These findings are discussed in relation to saliency-map models and the balance between high and low-level factors in eye guidance.

Neurons in the monkey amygdala detect eye-contact during naturalistic social interactions

Science.gov (United States)

Mosher, Clayton P.; Zimmerman, Prisca E.; Gothard, Katalin M.

2014-01-01

Summary Primates explore the visual world through eye-movement sequences. Saccades bring details of interest into the fovea while fixations stabilize the image [1]. During natural vision, social primates direct their gaze at the eyes of others to communicate their own emotions and intentions and to gather information about the mental states of others [2]. Direct gaze is an integral part of facial expressions that signals cooperation or conflict over resources and social status [3-6]. Despite the great importance of making and breaking eye contact in the behavioral repertoire of primates, little is known about the neural substrates that support these behaviors. Here we show that the monkey amygdala contains neurons that respond selectively to fixations at the eyes of others and to eye contact. These “eye cells” share several features with the canonical, visually responsive neurons in the monkey amygdala, however, they respond to the eyes only when they fall within the fovea of the viewer, either as a result of a deliberate saccade, or as eyes move into the fovea of the viewer during a fixation intended to explore a different feature. The presence of eyes in peripheral vision fails to activate the eye cells. These findings link the primate amygdala to eye-movements involved in the exploration and selection of details in visual scenes that contain socially and emotionally salient features. PMID:25283782

Neurons in the monkey amygdala detect eye contact during naturalistic social interactions.

Science.gov (United States)

Mosher, Clayton P; Zimmerman, Prisca E; Gothard, Katalin M

2014-10-20

Primates explore the visual world through eye-movement sequences. Saccades bring details of interest into the fovea, while fixations stabilize the image. During natural vision, social primates direct their gaze at the eyes of others to communicate their own emotions and intentions and to gather information about the mental states of others. Direct gaze is an integral part of facial expressions that signals cooperation or conflict over resources and social status. Despite the great importance of making and breaking eye contact in the behavioral repertoire of primates, little is known about the neural substrates that support these behaviors. Here we show that the monkey amygdala contains neurons that respond selectively to fixations on the eyes of others and to eye contact. These "eye cells" share several features with the canonical, visually responsive neurons in the monkey amygdala; however, they respond to the eyes only when they fall within the fovea of the viewer, either as a result of a deliberate saccade or as eyes move into the fovea of the viewer during a fixation intended to explore a different feature. The presence of eyes in peripheral vision fails to activate the eye cells. These findings link the primate amygdala to eye movements involved in the exploration and selection of details in visual scenes that contain socially and emotionally salient features. Copyright © 2014 Elsevier Ltd. All rights reserved.

Observing eye movements and the influence of cognition during a symbol search task: a comparison across three age groups.

Science.gov (United States)

Perrin, Maxine; Robillard, Manon; Roy-Charland, Annie

2017-12-01

This study examined eye movements during a visual search task as well as cognitive abilities within three age groups. The aim was to explore scanning patterns across symbol grids and to better understand the impact of symbol location in AAC displays on speed and accuracy of symbol selection. For the study, 60 students were asked to locate a series of symbols on 16 cell grids. The EyeLink 1000 was used to measure eye movements, accuracy, and response time. Accuracy was high across all cells. Participants had faster response times, longer fixations, and more frequent fixations on symbols located in the middle of the grid. Group comparisons revealed significant differences for accuracy and reaction times. The Leiter-R was used to evaluate cognitive abilities. Sustained attention and cognitive flexibility scores predicted the participants' reaction time and accuracy in symbol selection. Findings suggest that symbol location within AAC devices and individuals' cognitive abilities influence the speed and accuracy of retrieving symbols.

Retinal image registration for eye movement estimation.

Science.gov (United States)

Kolar, Radim; Tornow, Ralf P; Odstrcilik, Jan

2015-01-01

This paper describes a novel methodology for eye fixation measurement using a unique videoophthalmoscope setup and advanced image registration approach. The representation of the eye movements via Poincare plot is also introduced. The properties, limitations and perspective of this methodology are finally discussed.

Where do neurologists look when viewing brain CT images? An eye-tracking study involving stroke cases.

Directory of Open Access Journals (Sweden)

Hideyuki Matsumoto

Full Text Available The aim of this study was to investigate where neurologists look when they view brain computed tomography (CT images and to evaluate how they deploy their visual attention by comparing their gaze distribution with saliency maps. Brain CT images showing cerebrovascular accidents were presented to 12 neurologists and 12 control subjects. The subjects' ocular fixation positions were recorded using an eye-tracking device (Eyelink 1000. Heat maps were created based on the eye-fixation patterns of each group and compared between the two groups. The heat maps revealed that the areas on which control subjects frequently fixated often coincided with areas identified as outstanding in saliency maps, while the areas on which neurologists frequently fixated often did not. Dwell time in regions of interest (ROI was likewise compared between the two groups, revealing that, although dwell time on large lesions was not different between the two groups, dwell time in clinically important areas with low salience was longer in neurologists than in controls. Therefore it appears that neurologists intentionally scan clinically important areas when reading brain CT images showing cerebrovascular accidents. Both neurologists and control subjects used the "bottom-up salience" form of visual attention, although the neurologists more effectively used the "top-down instruction" form.

Keeping Your Eye on the Rail: Gaze Behaviour of Horse Riders Approaching a Jump

Science.gov (United States)

Hall, Carol; Varley, Ian; Kay, Rachel; Crundall, David

2014-01-01

The gaze behaviour of riders during their approach to a jump was investigated using a mobile eye tracking device (ASL Mobile Eye). The timing, frequency and duration of fixations on the jump and the percentage of time when their point of gaze (POG) was located elsewhere were assessed. Fixations were identified when the POG remained on the jump for 100 ms or longer. The jumping skill of experienced but non-elite riders (n = 10) was assessed by means of a questionnaire. Their gaze behaviour was recorded as they completed a course of three identical jumps five times. The speed and timing of the approach was calculated. Gaze behaviour throughout the overall approach and during the last five strides before take-off was assessed following frame-by-frame analyses. Differences in relation to both round and jump number were found. Significantly longer was spent fixated on the jump during round 2, both during the overall approach and during the last five strides (pJump 1 was fixated on significantly earlier and more frequently than jump 2 or 3 (pjump 3 than with jump 1 (p = 0.01) but there was no difference in errors made between rounds. Although no significant correlations between gaze behaviour and skill scores were found, the riders who scored higher for jumping skill tended to fixate on the jump earlier (p = 0.07), when the horse was further from the jump (p = 0.09) and their first fixation on the jump was of a longer duration (p = 0.06). Trials with elite riders are now needed to further identify sport-specific visual skills and their relationship with performance. Visual training should be included in preparation for equestrian sports participation, the positive impact of which has been clearly demonstrated in other sports. PMID:24846055

Long-term follow-up after scleral lens fixation in patients with Marfan syndrome.

Science.gov (United States)

Luebke, Jan; Reinhard, Thomas; Agostini, Hansjuergen; Boehringer, Daniel; Eberwein, Philipp

2017-12-06

The dislocation of the crystalline lens is a common finding in patients with Marfan syndrome (MFS). Scleral intraocular lens (IOL) fixation is an accepted treatment method of this complication. To now, no long-term data on scleral IOL fixation in MFS exist. We present a retrospective study of 27 eyes of 17 MFS patients that underwent scleral lens fixation at our clinic between 1999 and 2012. These patients are compared to an age- and surgeon-matched group of 31 eyes of 27 patients who underwent the same procedure for reasons other than MFS. The median age in the MFS group was 35.4 years versus 35.6 years in the non-MFS group. The median follow-up was 4 years for MFS and 3 years for non-MFS. In the MFS group, significantly more IOL-dislocations occurred than compared to the non-MFS group (30% vs. 6.5%, p = 0.02). Retinal detachment occurred in four MFS-eyes compared to three eyes in the non-MFS group. Biometry prediction error was 1.11 diopters (D) for MFS and 1.33 D for non-MFS (p = 0.11). Median BCVA (best-corrected visual acuity, logMAR) was 0.1 in the MFS group versus 0.3 in non-MFS patients. Scleral lens fixation in MFS patients achieves satisfying visual and refractive outcomes. Our data shows a significantly higher rate of IOL dislocations in patients with MFS. We therefore recommend addressing this complication preoperatively.

Eye-tracking study of inanimate objects

Directory of Open Access Journals (Sweden)

Ković Vanja

2009-01-01

Full Text Available Unlike the animate objects, where participants were consistent in their looking patterns, for inanimates it was difficult to identify both consistent areas of fixations and a consistent order of fixations. Furthermore, in comparison to animate objects, in animates received significantly shorter total looking time, shorter longest looks and a smaller number of overall fixations. However, as with animates, looking patterns did not systematically differ between the naming and non-naming conditions. These results suggested that animacy, but not labelling, impacts on looking behavior in this paradigm. In the light of feature-based accounts of semantic memory organization, one could interpret these findings as suggesting that processing of the animate objects is based on the saliency/diagnosticity of their visual features (which is then reflected through participants eye-movements towards those features, whereas processing of the inanimate objects is based more on functional features (which cannot be easily captured by looking behavior in such a paradigm.

Improved fixation quality provided by a Bessel beacon in an adaptive optics system.

Science.gov (United States)

Lambert, Andrew J; Daly, Elizabeth M; Dainty, Christopher J

2013-07-01

We investigate whether a structured probe beam that creates the beacon for use in a retinal imaging adaptive optics system can provide useful side effects. In particular we investigate whether a Bessel beam that is seen by the subject as a set of concentric rings has a dampening effect on fixation variations of the subject under observation. This calming effect would allow longer periods of observation, particularly for patients with abnormal fixation. An experimental adaptive optics system developed for retinal imaging is used to monitor the fluctuations in aberrations for artificial and human subjects. The probe beam is alternated between a traditional beacon and one provided by a Bessel beam created by SLM. Time-frequency analysis is used to indicate the differences in power and time variation during fixation depending on whether the Bessel beam or the traditional beacon is employed. Comparison is made with the response for an artificial eye to discount systemic variations. Significant evidence is accrued to indicate the reduced fluctuations in fixation when the Bessel beam is employed to create the beacon. © 2013 The Authors Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Eye and hand movements during reconstruction of spatial memory.

Science.gov (United States)

Burke, Melanie R; Allen, Richard J; Gonzalez, Claudia

2012-01-01

Recent behavioural and biological evidence indicates common mechanisms serving working memory and attention (e.g., Awh et al, 2006 Neuroscience 139 201-208). This study explored the role of spatial attention and visual search in an adapted Corsi spatial memory task. Eye movements and touch responses were recorded from participants who recalled locations (signalled by colour or shape change) from an array presented either simultaneously or sequentially. The time delay between target presentation and recall (0, 5, or 10 s) and the number of locations to be remembered (2-5) were also manipulated. Analysis of the response phase revealed subjects were less accurate (touch data) and fixated longer (eye data) when responding to sequentially presented targets suggesting higher cognitive effort. Fixation duration on target at recall was also influenced by whether spatial location was initially signalled by colour or shape change. Finally, we found that the sequence tasks encouraged longer fixations on the signalled targets than simultaneous viewing during encoding, but no difference was observed during recall. We conclude that the attentional manipulations (colour/shape) mainly affected the eye movement parameters, whereas the memory manipulation (sequential versus simultaneous, number of items) mainly affected the performance of the hand during recall, and thus the latter is more important for ascertaining if an item is remembered or forgotten. In summary, the nature of the stimuli that is used and how it is presented play key roles in determining subject performance and behaviour during spatial memory tasks.

Development of Text Reading in Japanese: An Eye Movement Study

Science.gov (United States)

Jincho, Nobuyuki; Feng, Gary; Mazuka, Reiko

2014-01-01

This study examined age-group differences in eye movements among third-grade, fifth-grade, and adult Japanese readers. In Experiment 1, Japanese children, but not adults, showed a longer fixation time on logographic kanji words than on phonologically transparent hiragana words. Further, an age-group difference was found in the first fixation…

[Effectiveness comparison of suspension fixation plus hinged external fixator and double plate internal fixation in treatment of type C humeral intercondylar fractures].

Science.gov (United States)

Zhang, Jian; Lin, Xu; Zhong, Zeli; Wu, Chao; Tan, Lun

2017-07-01

To compare the effectiveness of suspension fixation plus hinged external fixator with double plate internal fixation in the treatment of type C humeral intercondylar fractures. Between January 2014 and April 2016, 30 patients with type C (Association for the Study of Internal Fixation, AO/ASIF) humeral intercondylar fractures were treated. Kirschner wire suspension fixation plus hinged external fixator was used in 14 cases (group A), and double plate internal fixation in 16 cases (group B). There was no significant difference in gender, age, injury cause, disease duration, injury side, and type of fracture between 2 groups ( P >0.05). There was no significant difference in operation time and hospitalization stay between 2 groups ( P >0.05). But the intraoperative blood loss in group A was significantly less than that in group B ( P internal fixation removal, the intraoperative blood loss, and VAS score at 1 day and 3 days after operation in group A were significant better than those in group B ( P external fixator and double plate internal fixation for the treatment of type C humeral intercondylar fractures have ideal outcome in elbow function. But the suspension fixation plus hinged external fixator is better than double plate internal fixation in intraoperative blood loss, postoperative VAS score, and time of internal fixation removal.

Functional magnetic resonance imaging of the frontal eye fields during saccadic eye movements

International Nuclear Information System (INIS)

Miki, Atsushi; Takagi, Mineo; Abe, Haruki; Nakajima, Takashi; Miyauchi, Satoru.

1996-01-01

We evaluated activity-induced signal intensity changes in the human cerebral cortex during horizontal saccadic eye movements using functional magnetic resonance imaging (fMRI) based on the blood-oxygenation-level-dependent (BOLD) contrast method. Compared with central fixation, significant signal increases were observed bilaterally in the middle frontal gyrus (Brodmann area 8) during saccadic conditions. The location of the activated area was consistent with that of previously reported frontal eye fields (FEF). These results suggest that fMRI has potential merit for the study of cortical control of eye movements in humans. (author)

SR and LR Union Suture for the Treatment of Myopic Strabismus Fixus: Is Scleral Fixation Necessary?

Directory of Open Access Journals (Sweden)

Carol P. S. Lam

2015-01-01

Full Text Available Purpose. To evaluate and compare the effectiveness of scleral fixation SR and LR union suture and nonscleral fixation union suture for the treatment of myopic strabismus fixus. Methods. Retrospective review of 32 eyes of 22 patients with myopic strabismus fixus who had undergone union suture of superior rectus (SR and lateral rectus (LR with or without scleral fixation, and follow-up longer than 6 months at Hong Kong Eye Hospital from 2006 to 2013. Surgical techniques and outcomes in terms of ocular alignment are analyzed. Results. There is significant overall improvement both in postoperative angle of esodeviation (P0.05. Conclusions. Union suture of SR and LR is an effective procedure in correcting myopic strabismus fixus. Fixation of the union suture to the sclera does not improve surgical outcome.

Kinetic study of time-dependent fixation of U{sup VI} on biochar

Energy Technology Data Exchange (ETDEWEB)

Ashry, A. [Division of Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD (United Kingdom); Radiation Protection Department, Nuclear Research Centre, Egyptian Atomic Energy Authority, Cairo (Egypt); Bailey, E.H., E-mail: liz.bailey@nottingham.ac.uk [Division of Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD (United Kingdom); Chenery, S.R.N. [British Geological Survey, Nicker Hill, Keyworth, Nottingham NG12 5GG (United Kingdom); Young, S.D. [Division of Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD (United Kingdom)

2016-12-15

Biochar, a by-product from the production of biofuel and syngas by gasification, was tested as a material for adsorption and fixation of U{sup VI} from aqueous solutions. A batch experiment was conducted to study the factors that influence the adsorption and time-dependent fixation on biochar at 20 °C, including pH, initial concentration of U{sup VI} and contact time. Uranium (U{sup VI}) adsorption was highly dependent on pH but adsorption on biochar was high over a wide range of pH values, from 4.5 to 9.0, and adsorption strength was time-dependent over several days. The experimental data for pH > 7 were most effectively modelled using a Freundlich adsorption isotherm coupled to a reversible first order kinetic equation to describe the time-dependent fixation of U{sup VI} within the biochar structure. Desorption experiments showed that U{sup VI} was only sparingly desorbable from the biochar with time and isotopic dilution with {sup 233}U{sup VI} confirmed the low, or time-dependent, lability of adsorbed {sup 238}U{sup VI}. Below pH 7 the adsorption isotherm trend suggested precipitation, rather than true adsorption, may occur. However, across all pH values (4.5-9) measured saturation indices suggested precipitation was possible: autunite below pH 6.5 and either swartzite, liebigite or bayleyite above pH 6.5.

The role of eye movement driven attention in functional strabismic amblyopia.

Science.gov (United States)

Wang, Hao; Crewther, Sheila Gillard; Yin, Zheng Qin

2015-01-01

Strabismic amblyopia "blunt vision" is a developmental anomaly that affects binocular vision and results in lowered visual acuity. Strabismus is a term for a misalignment of the visual axes and is usually characterized by impaired ability of the strabismic eye to take up fixation. Such impaired fixation is usually a function of the temporally and spatially impaired binocular eye movements that normally underlie binocular shifts in visual attention. In this review, we discuss how abnormal eye movement function in children with misaligned eyes influences the development of normal binocular visual attention and results in deficits in visual function such as depth perception. We also discuss how eye movement function deficits in adult amblyopia patients can also lead to other abnormalities in visual perception. Finally, we examine how the nonamblyopic eye of an amblyope is also affected in strabismic amblyopia.

The Role of Eye Movement Driven Attention in Functional Strabismic Amblyopia

Directory of Open Access Journals (Sweden)

Hao Wang

2015-01-01

Full Text Available Strabismic amblyopia “blunt vision” is a developmental anomaly that affects binocular vision and results in lowered visual acuity. Strabismus is a term for a misalignment of the visual axes and is usually characterized by impaired ability of the strabismic eye to take up fixation. Such impaired fixation is usually a function of the temporally and spatially impaired binocular eye movements that normally underlie binocular shifts in visual attention. In this review, we discuss how abnormal eye movement function in children with misaligned eyes influences the development of normal binocular visual attention and results in deficits in visual function such as depth perception. We also discuss how eye movement function deficits in adult amblyopia patients can also lead to other abnormalities in visual perception. Finally, we examine how the nonamblyopic eye of an amblyope is also affected in strabismic amblyopia.

An analysis of the suitability of a low-cost eye tracker for assessing the cognitive load of drivers.

Science.gov (United States)

Čegovnik, Tomaž; Stojmenova, Kristina; Jakus, Grega; Sodnik, Jaka

2018-04-01

This paper presents a driving simulator study in which we investigated whether the Eye Tribe eye tracker (ET) is capable of assessing changes in the cognitive load of drivers through oculography and pupillometry. In the study, participants were asked to drive a simulated vehicle and simultaneously perform a set of secondary tasks with different cognitive complexity levels. We measured changes in eye properties, such as the pupil size, blink rate and fixation time. We also performed a measurement with a Detection Response Task (DRT) to validate the results and to prove a steady increase of cognitive load with increasing secondary task difficulty. The results showed that the ET precisely recognizes an increasing pupil diameter with increasing secondary task difficulty. In addition, the ET shows increasing blink rates, decreasing fixation time and narrowing of the attention field with increasing secondary task difficulty. The results were validated with the DRT method and the secondary task performance. We conclude that the Eye Tribe ET is a suitable device for assessing a driver's cognitive load. Copyright © 2017 Elsevier Ltd. All rights reserved.

Perceptual switching, eye movements, and the bus paradox

NARCIS (Netherlands)

Ito, J.; Nikolaev, A.R.; Luman, M.; Aukes, M.F.; Nakatani, C.; Leeuwen, C.

2003-01-01

According to a widely cited finding by Ellis and Stark (1978 Perception 7 575-581), the duration of eye fixations is longer at the instant of perceptual reversal of an ambiguous figure than before or after the reversal. However, long fixations are more likely to include samples of an independent

Does conspicuity enhance distraction? Saliency and eye landing position when searching for objects.

Science.gov (United States)

Foulsham, Tom; Underwood, Geoffrey

2009-06-01

While visual saliency may sometimes capture attention, the guidance of eye movements in search is often dominated by knowledge of the target. How is the search for an object influenced by the saliency of an adjacent distractor? Participants searched for a target amongst an array of objects, with distractor saliency having an effect on response time and on the speed at which targets were found. Saliency did not predict the order in which objects in target-absent trials were fixated. The within-target landing position was distributed around a modal position close to the centre of the object. Saliency did not affect this position, the latency of the initial saccade, or the likelihood of the distractor being fixated, suggesting that saliency affects the allocation of covert attention and not just eye movements.

Kinetic study of time-dependent fixation of U"V"I on biochar

International Nuclear Information System (INIS)

Ashry, A.; Bailey, E.H.; Chenery, S.R.N.; Young, S.D.

2016-01-01

Biochar, a by-product from the production of biofuel and syngas by gasification, was tested as a material for adsorption and fixation of U"V"I from aqueous solutions. A batch experiment was conducted to study the factors that influence the adsorption and time-dependent fixation on biochar at 20 °C, including pH, initial concentration of U"V"I and contact time. Uranium (U"V"I) adsorption was highly dependent on pH but adsorption on biochar was high over a wide range of pH values, from 4.5 to 9.0, and adsorption strength was time-dependent over several days. The experimental data for pH > 7 were most effectively modelled using a Freundlich adsorption isotherm coupled to a reversible first order kinetic equation to describe the time-dependent fixation of U"V"I within the biochar structure. Desorption experiments showed that U"V"I was only sparingly desorbable from the biochar with time and isotopic dilution with "2"3"3U"V"I confirmed the low, or time-dependent, lability of adsorbed "2"3"8U"V"I. Below pH 7 the adsorption isotherm trend suggested precipitation, rather than true adsorption, may occur. However, across all pH values (4.5-9) measured saturation indices suggested precipitation was possible: autunite below pH 6.5 and either swartzite, liebigite or bayleyite above pH 6.5.

Magnifying visual target information and the role of eye movements in motor sequence learning.

Science.gov (United States)

Massing, Matthias; Blandin, Yannick; Panzer, Stefan

2016-01-01

An experiment investigated the influence of eye movements on learning a simple motor sequence task when the visual display was magnified. The task was to reproduce a 1300 ms spatial-temporal pattern of elbow flexions and extensions. The spatial-temporal pattern was displayed in front of the participants. Participants were randomly assigned to four groups differing on eye movements (free to use their eyes/instructed to fixate) and the visual display (small/magnified). All participants had to perform a pre-test, an acquisition phase, a delayed retention test, and a transfer test. The results indicated that participants in each practice condition increased their performance during acquisition. The participants who were permitted to use their eyes in the magnified visual display outperformed those who were instructed to fixate on the magnified visual display. When a small visual display was used, the instruction to fixate induced no performance decrements compared to participants who were permitted to use their eyes during acquisition. The findings demonstrated that a spatial-temporal pattern can be learned without eye movements, but being permitting to use eye movements facilitates the response production when the visual angle is increased. Copyright © 2015 Elsevier B.V. All rights reserved.

The subject-fixated coaxially sighted corneal light reflex: a clinical marker for centration of refractive treatments and devices.

Science.gov (United States)

Chang, Daniel H; Waring, George O

2014-11-01

To describe the inconsistencies in definition, application, and usage of the ocular reference axes (optical axis, visual axis, line of sight, pupillary axis, and topographic axis) and angles (angle kappa, lambda, and alpha) and to propose a precise, reproducible, clinically defined reference marker and axis for centration of refractive treatments and devices. Perspective. Literature review of papers dealing with ocular reference axes, angles, and centration. The inconsistent definitions and usage of the current ocular axes, as derived from eye models, limit their clinical utility. With a clear understanding of Purkinje images and a defined alignment of the observer, light source/fixation target, and subject eye, the subject-fixated coaxially sighted corneal light reflex can be a clinically useful reference marker. The axis formed by connecting the subject-fixated coaxially sighted corneal light reflex and the fixation point, the subject-fixated coaxially sighted corneal light reflex axis, is independent of pupillary dilation and phakic status of the eye. The relationship of the subject-fixated coaxially sighted corneal light reflex axis to a refined definition of the visual axis without reference to nodal points, the foveal-fixation axis, is discussed. The displacement between the subject-fixated coaxially sighted corneal light reflex and pupil center is described not by an angle, but by a chord, here termed chord mu. The application of the subject-fixated coaxially sighted corneal light reflex to the surgical centration of refractive treatments and devices is discussed. As a clinically defined reference marker, the subject-fixated coaxially sighted corneal light reflex avoids the shortcomings of current ocular axes for clinical application and may contribute to better consensus in the literature and improved patient outcomes. Copyright © 2014 Elsevier Inc. All rights reserved.

Attention and Recall of Point-of-sale Tobacco Marketing: A Mobile Eye-Tracking Pilot Study

Directory of Open Access Journals (Sweden)

Maansi Bansal-Travers

2016-01-01

Full Text Available  Introduction: As tobacco advertising restrictions have increased, the retail ‘power wall’ behind the counter is increasingly invaluable for marketing tobacco products. Objective: The primary objectives of this pilot study were 3-fold: (1 evaluate the attention paid/fixations on the area behind the cash register where tobacco advertising is concentrated and tobacco products are displayed in a real-world setting, (2 evaluate the duration (dwell-time of these fixations, and (3 evaluate the recall of advertising displayed on the tobacco power wall. Methods: Data from 13 Smokers (S and 12 Susceptible or non-daily Smokers (SS aged 180–30 from a mobile eye-tracking study. Mobile-eye tracking technology records the orientation (fixation and duration (dwell-time of visual attention. Participants were randomized to one of three purchase tasks at a convenience store: Candy bar Only (CO; N = 10, Candy bar + Specified cigarette Brand (CSB; N = 6, and Candy bar + cigarette Brand of their Choice (CBC; N = 9. A post-session survey evaluated recall of tobacco marketing. Key outcomes were fixations and dwell-time on the cigarette displays at the point-of-sale. Results: Participants spent a median time of 44 seconds during the standardized time evaluated and nearly three-quarters (72% fixated on the power wall during their purchase, regardless of smoking status (S: 77%, SS: 67% or purchase task (CO: 44%, CSB: 71%, CBC: 100%. In the post session survey, nearly all participants (96% indicated they noticed a cigarette brand and 64% were able to describe a specific part of the tobacco wall or recall a promotional offer. Conclusions: Consumers are exposed to point-of-sale tobacco marketing, regardless of smoking status. FDA should consider regulations that limit exposure to point-of-sale tobacco marketing among consumers.

Attention and Recall of Point-of-sale Tobacco Marketing: A Mobile Eye-Tracking Pilot Study.

Science.gov (United States)

Bansal-Travers, Maansi; Adkison, Sarah E; O'Connor, Richard J; Thrasher, James F

2016-01-01

As tobacco advertising restrictions have increased, the retail 'power wall' behind the counter is increasingly invaluable for marketing tobacco products. The primary objectives of this pilot study were 3-fold: (1) evaluate the attention paid/fixations on the area behind the cash register where tobacco advertising is concentrated and tobacco products are displayed in a real-world setting, (2) evaluate the duration (dwell-time) of these fixations, and (3) evaluate the recall of advertising displayed on the tobacco power wall. Data from 13 Smokers (S) and 12 Susceptible or non-daily Smokers (SS) aged 180-30 from a mobile eye-tracking study. Mobile-eye tracking technology records the orientation (fixation) and duration (dwell-time) of visual attention. Participants were randomized to one of three purchase tasks at a convenience store: Candy bar Only (CO; N = 10), Candy bar + Specified cigarette Brand (CSB; N = 6), and Candy bar + cigarette Brand of their Choice (CBC; N = 9). A post-session survey evaluated recall of tobacco marketing. Key outcomes were fixations and dwell-time on the cigarette displays at the point-of-sale. Participants spent a median time of 44 seconds during the standardized time evaluated and nearly three-quarters (72%) fixated on the power wall during their purchase, regardless of smoking status (S: 77%, SS: 67%) or purchase task (CO: 44%, CSB: 71%, CBC: 100%). In the post session survey, nearly all participants (96%) indicated they noticed a cigarette brand and 64% were able to describe a specific part of the tobacco wall or recall a promotional offer. Consumers are exposed to point-of-sale tobacco marketing, regardless of smoking status. FDA should consider regulations that limit exposure to point-of-sale tobacco marketing among consumers.

Eye Movement Training and Suggested Gaze Strategies in Tunnel Vision - A Randomized and Controlled Pilot Study.

Directory of Open Access Journals (Sweden)

Iliya V Ivanov

Full Text Available Degenerative retinal diseases, especially retinitis pigmentosa (RP, lead to severe peripheral visual field loss (tunnel vision, which impairs mobility. The lack of peripheral information leads to fewer horizontal eye movements and, thus, diminished scanning in RP patients in a natural environment walking task. This randomized controlled study aimed to improve mobility and the dynamic visual field by applying a compensatory Exploratory Saccadic Training (EST.Oculomotor responses during walking and avoiding obstacles in a controlled environment were studied before and after saccade or reading training in 25 RP patients. Eye movements were recorded using a mobile infrared eye tracker (Tobii glasses that measured a range of spatial and temporal variables. Patients were randomly assigned to two training conditions: Saccade (experimental and reading (control training. All subjects who first performed reading training underwent experimental training later (waiting list control group. To assess the effect of training on subjects, we measured performance in the training task and the following outcome variables related to daily life: Response Time (RT during exploratory saccade training, Percent Preferred Walking Speed (PPWS, the number of collisions with obstacles, eye position variability, fixation duration, and the total number of fixations including the ones in the subjects' blind area of the visual field.In the saccade training group, RTs on average decreased, while the PPWS significantly increased. The improvement persisted, as tested 6 weeks after the end of the training. On average, the eye movement range of RP patients before and after training was similar to that of healthy observers. In both, the experimental and reading training groups, we found many fixations outside the subjects' seeing visual field before and after training. The average fixation duration was significantly shorter after the training, but only in the experimental training

Eye Movement Training and Suggested Gaze Strategies in Tunnel Vision - A Randomized and Controlled Pilot Study.

Science.gov (United States)

Ivanov, Iliya V; Mackeben, Manfred; Vollmer, Annika; Martus, Peter; Nguyen, Nhung X; Trauzettel-Klosinski, Susanne

2016-01-01

Degenerative retinal diseases, especially retinitis pigmentosa (RP), lead to severe peripheral visual field loss (tunnel vision), which impairs mobility. The lack of peripheral information leads to fewer horizontal eye movements and, thus, diminished scanning in RP patients in a natural environment walking task. This randomized controlled study aimed to improve mobility and the dynamic visual field by applying a compensatory Exploratory Saccadic Training (EST). Oculomotor responses during walking and avoiding obstacles in a controlled environment were studied before and after saccade or reading training in 25 RP patients. Eye movements were recorded using a mobile infrared eye tracker (Tobii glasses) that measured a range of spatial and temporal variables. Patients were randomly assigned to two training conditions: Saccade (experimental) and reading (control) training. All subjects who first performed reading training underwent experimental training later (waiting list control group). To assess the effect of training on subjects, we measured performance in the training task and the following outcome variables related to daily life: Response Time (RT) during exploratory saccade training, Percent Preferred Walking Speed (PPWS), the number of collisions with obstacles, eye position variability, fixation duration, and the total number of fixations including the ones in the subjects' blind area of the visual field. In the saccade training group, RTs on average decreased, while the PPWS significantly increased. The improvement persisted, as tested 6 weeks after the end of the training. On average, the eye movement range of RP patients before and after training was similar to that of healthy observers. In both, the experimental and reading training groups, we found many fixations outside the subjects' seeing visual field before and after training. The average fixation duration was significantly shorter after the training, but only in the experimental training condition

Eye movements during the handwriting of words: Individually and within sentences.

Science.gov (United States)

Sita, Jodi C; Taylor, Katelyn A

2015-10-01

Handwriting, a complex motor process involves the coordination of both the upper limb and visual system. The gaze behavior that occurs during the handwriting process is an area that has been little studied. This study investigated the eye-movements of adults during writing and reading tasks. Eye and handwriting movements were recorded for six different words over three different tasks. The results compared reading and handwriting the same words, a between condition comparison and a comparison between the two handwriting tasks. Compared to reading, participants produced more fixations during handwriting tasks and the average fixation durations were longer. When reading fixations were found to be mostly around the center of word, whereas fixations when writing appear to be made for each letter in a written word and were located around the base of letters and flowed in a left to right direction. Between the two writing tasks more fixations were made when words were written individually compared to within sentences, yet fixation durations were no different. Correlation of the number of fixations made to kinematic variables revealed that horizontal size and road length held a strong correlation with the number of fixations made by participants. Copyright © 2015 Elsevier B.V. All rights reserved.

Abnormalities of fixation, saccade and pursuit in posterior cortical atrophy.

Science.gov (United States)

Shakespeare, Timothy J; Kaski, Diego; Yong, Keir X X; Paterson, Ross W; Slattery, Catherine F; Ryan, Natalie S; Schott, Jonathan M; Crutch, Sebastian J

2015-07-01

The clinico-neuroradiological syndrome posterior cortical atrophy is the cardinal 'visual dementia' and most common atypical Alzheimer's disease phenotype, offering insights into mechanisms underlying clinical heterogeneity, pathological propagation and basic visual phenomena (e.g. visual crowding). Given the extensive attention paid to patients' (higher order) perceptual function, it is surprising that there have been no systematic analyses of basic oculomotor function in this population. Here 20 patients with posterior cortical atrophy, 17 patients with typical Alzheimer's disease and 22 healthy controls completed tests of fixation, saccade (including fixation/target gap and overlap conditions) and smooth pursuit eye movements using an infrared pupil-tracking system. Participants underwent detailed neuropsychological and neurological examinations, with a proportion also undertaking brain imaging and analysis of molecular pathology. In contrast to informal clinical evaluations of oculomotor dysfunction frequency (previous studies: 38%, current clinical examination: 33%), detailed eyetracking investigations revealed eye movement abnormalities in 80% of patients with posterior cortical atrophy (compared to 17% typical Alzheimer's disease, 5% controls). The greatest differences between posterior cortical atrophy and typical Alzheimer's disease were seen in saccadic performance. Patients with posterior cortical atrophy made significantly shorter saccades especially for distant targets. They also exhibited a significant exacerbation of the normal gap/overlap effect, consistent with 'sticky fixation'. Time to reach saccadic targets was significantly associated with parietal and occipital cortical thickness measures. On fixation stability tasks, patients with typical Alzheimer's disease showed more square wave jerks whose frequency was associated with lower cerebellar grey matter volume, while patients with posterior cortical atrophy showed large saccadic intrusions

Evaluation of the Tobii EyeX Eye tracking controller and Matlab toolkit for research.

Science.gov (United States)

Gibaldi, Agostino; Vanegas, Mauricio; Bex, Peter J; Maiello, Guido

2017-06-01

The Tobii Eyex Controller is a new low-cost binocular eye tracker marketed for integration in gaming and consumer applications. The manufacturers claim that the system was conceived for natural eye gaze interaction, does not require continuous recalibration, and allows moderate head movements. The Controller is provided with a SDK to foster the development of new eye tracking applications. We review the characteristics of the device for its possible use in scientific research. We develop and evaluate an open source Matlab Toolkit that can be employed to interface with the EyeX device for gaze recording in behavioral experiments. The Toolkit provides calibration procedures tailored to both binocular and monocular experiments, as well as procedures to evaluate other eye tracking devices. The observed performance of the EyeX (i.e. accuracy < 0.6°, precision < 0.25°, latency < 50 ms and sampling frequency ≈55 Hz), is sufficient for some classes of research application. The device can be successfully employed to measure fixation parameters, saccadic, smooth pursuit and vergence eye movements. However, the relatively low sampling rate and moderate precision limit the suitability of the EyeX for monitoring micro-saccadic eye movements or for real-time gaze-contingent stimulus control. For these applications, research grade, high-cost eye tracking technology may still be necessary. Therefore, despite its limitations with respect to high-end devices, the EyeX has the potential to further the dissemination of eye tracking technology to a broad audience, and could be a valuable asset in consumer and gaming applications as well as a subset of basic and clinical research settings.

Population growth enhances the mean fixation time of neutral mutations and the persistence of neutral variation.

Science.gov (United States)

Waxman, D

2012-06-01

A fundamental result of population genetics states that a new mutation, at an unlinked neutral locus in a randomly mating diploid population, has a mean time of fixation of ∼4N(e) generations, where N(e) is the effective population size. This result is based on an assumption of fixed population size, which does not universally hold in natural populations. Here, we analyze such neutral fixations in populations of changing size within the framework of the diffusion approximation. General expressions are derived for the mean and variance of the fixation time in changing populations. Some explicit results are given for two cases: (i) the effective population size undergoes a sudden change, representing a sudden population expansion or a sudden bottleneck; (ii) the effective population changes linearly for a limited period of time and then remains constant. Additionally, a lower bound for the mean time of fixation is obtained for an effective population size that increases with time, and this is applied to exponentially growing populations. The results obtained in this work show, among other things, that for populations that increase in size, the mean time of fixation can be enhanced, sometimes substantially so, over 4N(e,0) generations, where N(e,0) is the effective population size at the time the mutation arises. Such an enhancement is associated with (i) an increased probability of neutral polymorphism in a population and (ii) an enhanced persistence of high-frequency neutral variation, which is the variation most likely to be observed.

How successful are mutants in multiplayer games with fluctuating environments? Sojourn times, fixation and optimal switching

Science.gov (United States)

Baron, Joseph W.; Galla, Tobias

2018-03-01

Using a stochastic model, we investigate the probability of fixation, and the average time taken to achieve fixation, of a mutant in a population of wild-types. We do this in a context where the environment in which the competition takes place is subject to stochastic change. Our model takes into account interactions which can involve multiple participants. That is, the participants take part in multiplayer games. We find that under certain circumstances, there are environmental switching dynamics which minimize the time that it takes for the mutants to fixate. To analyse the dynamics more closely, we develop a method by which to calculate the sojourn times for general birth-death processes in fluctuating environments.

Understanding eye movements in face recognition using hidden Markov models.

Science.gov (United States)

Chuk, Tim; Chan, Antoni B; Hsiao, Janet H

2014-09-16

We use a hidden Markov model (HMM) based approach to analyze eye movement data in face recognition. HMMs are statistical models that are specialized in handling time-series data. We conducted a face recognition task with Asian participants, and model each participant's eye movement pattern with an HMM, which summarized the participant's scan paths in face recognition with both regions of interest and the transition probabilities among them. By clustering these HMMs, we showed that participants' eye movements could be categorized into holistic or analytic patterns, demonstrating significant individual differences even within the same culture. Participants with the analytic pattern had longer response times, but did not differ significantly in recognition accuracy from those with the holistic pattern. We also found that correct and wrong recognitions were associated with distinctive eye movement patterns; the difference between the two patterns lies in the transitions rather than locations of the fixations alone. © 2014 ARVO.

Comparing eye tracking with electrooculography for measuring individual sentence comprehension duration

DEFF Research Database (Denmark)

Müller, Jana Annina; Wendt, Dorothea; Kollmeier, Birger

2016-01-01

The aim of this study was to validate a procedure for performing the audio-visual paradigm introduced by Wendt et al. (2015) with reduced practical challenges. The original paradigm records eye fixations using an eye tracker and calculates the duration of sentence comprehension based on a bootstrap...... procedure. In order to reduce practical challenges, we first reduced the measurement time by evaluating a smaller measurement set with fewer trials. The results of 16 listeners showed effects comparable to those obtained when testing the original full measurement set on a different collective of listeners...

Pigment dispersion glaucoma induced by the chafing effect of intraocular lens haptics in Asian eyes.

Science.gov (United States)

Hong, Ying; Sun, Yan-Xiu; Qi, Hong; Zhou, Ji-Chao; Hao, Yan-Sheng

2013-03-01

To study the possible mechanism and treatment for pigment dispersion glaucoma (PDG) caused by single-piece acrylic (SPA) intraocular lens (IOL) ciliary sulcus fixation in Asian eyes. Patients referred for PDG caused by SPA IOL ciliary sulcus fixation to our hospital from April 2005 to June 2011 were included. The patients' general information, IOL type, interval between initial surgery and PDG occurrence, examination findings, antiglaucoma medicine regimen and surgical interventions were recorded. In total, six eyes from five Chinese patients were included in this study. The intraocular pressure (IOP) increased 19-30 days after cataract surgery and was not satisfactorily controlled with antiglaucoma medication. Dense pigmentation was deposited on the IOLs and on the anterior chamber angle. IOL haptic chafing was noted on the rear iris surface. IOL repositioning in the capsular bag was performed in three eyes and was combined with trabeculectomy in two eyes with progressive glaucoma. An IOL exchange with three-piece IOL ciliary sulcus fixation was performed in the other three eyes. Scanning electron microscopy of the explanted IOLs demonstrated a rough edge on the IOL haptics. SPA IOLs were not suitable for ciliary sulcus fixation. The chafing effect of the IOL haptics on the posterior iris pigment epithelium could induce PDG in Asian eyes. IOLs should be positioned in the capsular bag or a three-piece IOL should be used instead.

Impaired eye region search accuracy in children with autistic spectrum disorders.

Directory of Open Access Journals (Sweden)

John R Pruett

Full Text Available To explore mechanisms underlying reduced fixation of eyes in autism, children with autistic spectrum disorders (ASD and typically developing children were tested in five visual search experiments: simple color feature; color-shape conjunction; face in non-face objects; mouth region; and eye region. No group differences were found for reaction time profile shapes in any of the five experiments, suggesting intact basic search mechanics in children with ASD. Contrary to early reports in the literature, but consistent with other more recent findings, we observed no superiority for conjunction search in children with ASD. Importantly, children with ASD did show reduced accuracy for eye region search (p = .005, suggesting that eyes contribute less to high-level face representations in ASD or that there is an eye region-specific disruption to attentional processes engaged by search in ASD.

Impaired eye region search accuracy in children with autistic spectrum disorders.

Science.gov (United States)

Pruett, John R; Hoertel, Sarah; Constantino, John N; Moll, Angela LaMacchia; McVey, Kelly; Squire, Emma; Feczko, Eric; Povinelli, Daniel J; Petersen, Steven E

2013-01-01

To explore mechanisms underlying reduced fixation of eyes in autism, children with autistic spectrum disorders (ASD) and typically developing children were tested in five visual search experiments: simple color feature; color-shape conjunction; face in non-face objects; mouth region; and eye region. No group differences were found for reaction time profile shapes in any of the five experiments, suggesting intact basic search mechanics in children with ASD. Contrary to early reports in the literature, but consistent with other more recent findings, we observed no superiority for conjunction search in children with ASD. Importantly, children with ASD did show reduced accuracy for eye region search (p = .005), suggesting that eyes contribute less to high-level face representations in ASD or that there is an eye region-specific disruption to attentional processes engaged by search in ASD.

Isolating Discriminant Neural Activity in the Presence of Eye Movements and Concurrent Task Demands

Directory of Open Access Journals (Sweden)

Jon Touryan

2017-07-01

Full Text Available A growing number of studies use the combination of eye-tracking and electroencephalographic (EEG measures to explore the neural processes that underlie visual perception. In these studies, fixation-related potentials (FRPs are commonly used to quantify early and late stages of visual processing that follow the onset of each fixation. However, FRPs reflect a mixture of bottom-up (sensory-driven and top-down (goal-directed processes, in addition to eye movement artifacts and unrelated neural activity. At present there is little consensus on how to separate this evoked response into its constituent elements. In this study we sought to isolate the neural sources of target detection in the presence of eye movements and over a range of concurrent task demands. Here, participants were asked to identify visual targets (Ts amongst a grid of distractor stimuli (Ls, while simultaneously performing an auditory N-back task. To identify the discriminant activity, we used independent components analysis (ICA for the separation of EEG into neural and non-neural sources. We then further separated the neural sources, using a modified measure-projection approach, into six regions of interest (ROIs: occipital, fusiform, temporal, parietal, cingulate, and frontal cortices. Using activity from these ROIs, we identified target from non-target fixations in all participants at a level similar to other state-of-the-art classification techniques. Importantly, we isolated the time course and spectral features of this discriminant activity in each ROI. In addition, we were able to quantify the effect of cognitive load on both fixation-locked potential and classification performance across regions. Together, our results show the utility of a measure-projection approach for separating task-relevant neural activity into meaningful ROIs within more complex contexts that include eye movements.

Dry eye signs and symptoms in night-time workers

OpenAIRE

Ali Makateb; Hamed Torabifard

2017-01-01

Purpose: To determine the effect of night-time working on dry eye signs and symptoms. Methods: A total of 50 healthy subjects completed a dry eye questionnaire and underwent clinical examinations including basic Schirmer's test and tear breakup time (TBUT) test on two consecutive days, before and after the night shift (12-hrs night-shift). Results: All dry eye symptoms were aggravated significantly after the night shift (P 

One visual search, many memory searches: An eye-tracking investigation of hybrid search.

Science.gov (United States)

Drew, Trafton; Boettcher, Sage E P; Wolfe, Jeremy M

2017-09-01

Suppose you go to the supermarket with a shopping list of 10 items held in memory. Your shopping expedition can be seen as a combination of visual search and memory search. This is known as "hybrid search." There is a growing interest in understanding how hybrid search tasks are accomplished. We used eye tracking to examine how manipulating the number of possible targets (the memory set size [MSS]) changes how observers (Os) search. We found that dwell time on each distractor increased with MSS, suggesting a memory search was being executed each time a new distractor was fixated. Meanwhile, although the rate of refixation increased with MSS, it was not nearly enough to suggest a strategy that involves repeatedly searching visual space for subgroups of the target set. These data provide a clear demonstration that hybrid search tasks are carried out via a "one visual search, many memory searches" heuristic in which Os examine items in the visual array once with a very low rate of refixations. For each item selected, Os activate a memory search that produces logarithmic response time increases with increased MSS. Furthermore, the percentage of distractors fixated was strongly modulated by the MSS: More items in the MSS led to a higher percentage of fixated distractors. Searching for more potential targets appears to significantly alter how Os approach the task, ultimately resulting in more eye movements and longer response times.

Eye movement analysis of reading from computer displays, eReaders and printed books.

Science.gov (United States)

Zambarbieri, Daniela; Carniglia, Elena

2012-09-01

To compare eye movements during silent reading of three eBooks and a printed book. The three different eReading tools were a desktop PC, iPad tablet and Kindle eReader. Video-oculographic technology was used for recording eye movements. In the case of reading from the computer display the recordings were made by a video camera placed below the computer screen, whereas for reading from the iPad tablet, eReader and printed book the recording system was worn by the subject and had two cameras: one for recording the movement of the eyes and the other for recording the scene in front of the subject. Data analysis provided quantitative information in terms of number of fixations, their duration, and the direction of the movement, the latter to distinguish between fixations and regressions. Mean fixation duration was different only in reading from the computer display, and was similar for the Tablet, eReader and printed book. The percentage of regressions with respect to the total amount of fixations was comparable for eReading tools and the printed book. The analysis of eye movements during reading an eBook from different eReading tools suggests that subjects' reading behaviour is similar to reading from a printed book. © 2012 The College of Optometrists.

Searching for Chaos Evidence in Eye Movement Signals

Directory of Open Access Journals (Sweden)

Katarzyna Harezlak

2018-01-01

Full Text Available Most naturally-occurring physical phenomena are examples of nonlinear dynamic systems, the functioning of which attracts many researchers seeking to unveil their nature. The research presented in this paper is aimed at exploring eye movement dynamic features in terms of the existence of chaotic nature. Nonlinear time series analysis methods were used for this purpose. Two time series features were studied: fractal dimension and entropy, by utilising the embedding theory. The methods were applied to the data collected during the experiment with “jumping point” stimulus. Eye movements were registered by means of the Jazz-novo eye tracker. One thousand three hundred and ninety two (1392 time series were defined, based on the horizontal velocity of eye movements registered during imposed, prolonged fixations. In order to conduct detailed analysis of the signal and identify differences contributing to the observed patterns of behaviour in time scale, fractal dimension and entropy were evaluated in various time series intervals. The influence of the noise contained in the data and the impact of the utilized filter on the obtained results were also studied. The low pass filter was used for the purpose of noise reduction with a 50 Hz cut-off frequency, estimated by means of the Fourier transform and all concerned methods were applied to time series before and after noise reduction. These studies provided some premises, which allow perceiving eye movements as observed chaotic data: characteristic of a space-time separation plot, low and non-integer time series dimension, and the time series entropy characteristic for chaotic systems.

Quiet eye training improves surgical knot tying more than traditional technical training: a randomized controlled study.

Science.gov (United States)

Causer, Joe; Harvey, Adrian; Snelgrove, Ryan; Arsenault, Gina; Vickers, Joan N

2014-08-01

We examined the effectiveness of technical training (TT) and quiet eye training (QE) on the performance of one-handed square knot tying in surgical residents. Twenty surgical residents were randomly assigned to the 2 groups and completed pretest, training, retention, and transfer tests. Participants wore a mobile eye tracker that simultaneously recorded their gaze and hand movements. Dependent variables were knot tying performance (%), QE duration (%), number of fixations, total movement time (s), and hand movement phase time (s). The QE training group had significantly higher performance scores, a longer QE duration, fewer fixations, faster total knot tying times, and faster movement phase times compared with the TT group. The QE group maintained performance in the transfer test, whereas the TT group significantly decreased performance from retention to transfer. QE training significantly improved learning, retention, and transfer of surgical knot tying compared with a traditional technical approach. Both performance effectiveness (performance outcome) and movement efficiency (hand movement times) were improved using QE modeling, instruction, and feedback. Copyright © 2014 Elsevier Inc. All rights reserved.

External fixation combined with delayed internal fixation in treatment of tibial plateau fractures with dislocation.

Science.gov (United States)

Tao, Xingguang; Chen, Nong; Pan, Fugen; Cheng, Biao

2017-10-01

The aim of this study was to evaluate the clinical efficacy of external fixation, delayed open reduction, and internal fixation in treating tibial plateau fracture with dislocation.Clinical data of 34 patients diagnosed with tibial plateau fracture complicated with dislocation between January 2009 and May 2015 were retrospectively analyzed. Fifteen patients in group A underwent early calcaneus traction combined with open reduction and internal fixation and 19 in group B received early external fixation combined with delayed open reduction and internal fixation. Operation time, postoperative complication, bone healing time, knee joint range of motion, initial weight-bearing time, Rasmussen tibial plateau score, and knee function score (HSS) were statistically compared between 2 groups.The mean follow-up time was 18.6 months (range: 5-24 months). The mean operation time in group A was 96 minutes, significantly longer than 71 minutes in group B (P  .05). In group A, initial weight-bearing time in group A was (14.0 ± 3.6) weeks, significantly differing from (12.9 ± 2.8) weeks in group B (P  0.05). Rasmussen tibial plateau score in group A was slightly lower than that in group B (P > .05). The excellent rate of knee joint function in group A was 80% and 84.21% in group B (P > .05).External fixation combined with delayed open reduction and internal fixation is a safer and more efficacious therapy of tibial plateau fracture complicated with dislocation compared with early calcaneus traction and open reduction and internal fixation.

Combined 23-gauge transconjunctival vitrectomy and scleral fixation of intraocular lens without conjunctival dissection in managing lens complications.

Science.gov (United States)

Yeung, Ling; Wang, Nan-Kai; Wu, Wei-Chi; Chen, Kuan-Jen

2018-04-23

To evaluate the safety and efficacy of combined 23-gauge transconjunctival pars plana vitrectomy and scleral fixation of intraocular lens (IOL) without conjunctival dissection. A retrospective study in Chang Gung Memorial Hospital, Keelung and Taoyuan, Taiwan. Patients receiving combined 23-gauge transconjunctival pars plana vitrectomy and scleral fixation of IOL without conjunctival dissection were enrolled. The ocular findings, causes of lens complication, surgical procedures, type of IOL used, and complications were documented. We included 40 eyes from 39 patients (27 male, 12 female) with a mean age of 59.5 [standard deviation (±) 14.8] years old. The mean follow-up duration was 6.8 ± 5.4 months. The cause of lens complications was ocular trauma in 24 (60%) eyes, cataract surgery complications in 11 (28%) eyes, and spontaneous subluxation of crystalline lens in 5 (13%) eyes. The overall best corrected visual acuity (BCVA) (logMAR) improved from 1.359 ± 0.735 to 0.514 ± 0.582 (p IOL decentration was found in 3 (8%) eyes and 1 (3%) eye respectively. Combined 23-gauge transconjunctival vitrectomy and scleral fixation of IOL without conjunctival dissection is effective and safe in managing a wide variety of lens complications, with good postoperative comfort and visual recovery. Retrospective study, not applicable.

"Gaze Leading": Initiating Simulated Joint Attention Influences Eye Movements and Choice Behavior

Science.gov (United States)

Bayliss, Andrew P.; Murphy, Emily; Naughtin, Claire K.; Kritikos, Ada; Schilbach, Leonhard; Becker, Stefanie I.

2013-01-01

Recent research in adults has made great use of the gaze cuing paradigm to understand the behavior of the follower in joint attention episodes. We implemented a gaze leading task to investigate the initiator--the other person in these triadic interactions. In a series of gaze-contingent eye-tracking studies, we show that fixation dwell time upon…

What interests them in the pictures?--differences in eye-tracking between rhesus monkeys and humans.

Science.gov (United States)

Hu, Ying-Zhou; Jiang, Hui-Hui; Liu, Ci-Rong; Wang, Jian-Hong; Yu, Cheng-Yang; Carlson, Synnöve; Yang, Shang-Chuan; Saarinen, Veli-Matti; Rizak, Joshua D; Tian, Xiao-Guang; Tan, Hen; Chen, Zhu-Yue; Ma, Yuan-Ye; Hu, Xin-Tian

2013-10-01

Studies estimating eye movements have demonstrated that non-human primates have fixation patterns similar to humans at the first sight of a picture. In the current study, three sets of pictures containing monkeys, humans or both were presented to rhesus monkeys and humans. The eye movements on these pictures by the two species were recorded using a Tobii eye-tracking system. We found that monkeys paid more attention to the head and body in pictures containing monkeys, whereas both monkeys and humans paid more attention to the head in pictures containing humans. The humans always concentrated on the eyes and head in all the pictures, indicating the social role of facial cues in society. Although humans paid more attention to the hands than monkeys, both monkeys and humans were interested in the hands and what was being done with them in the pictures. This may suggest the importance and necessity of hands for survival. Finally, monkeys scored lower in eye-tracking when fixating on the pictures, as if they were less interested in looking at the screen than humans. The locations of fixation in monkeys may provide insight into the role of eye movements in an evolutionary context.

Neural processing of fearful and happy facial expressions during emotion-relevant and emotion-irrelevant tasks: a fixation-to-feature approach

Science.gov (United States)

Neath-Tavares, Karly N.; Itier, Roxane J.

2017-01-01

Research suggests an important role of the eyes and mouth for discriminating facial expressions of emotion. A gaze-contingent procedure was used to test the impact of fixation to facial features on the neural response to fearful, happy and neutral facial expressions in an emotion discrimination (Exp.1) and an oddball detection (Exp.2) task. The N170 was the only eye-sensitive ERP component, and this sensitivity did not vary across facial expressions. In both tasks, compared to neutral faces, responses to happy expressions were seen as early as 100–120ms occipitally, while responses to fearful expressions started around 150ms, on or after the N170, at both occipital and lateral-posterior sites. Analyses of scalp topographies revealed different distributions of these two emotion effects across most of the epoch. Emotion processing interacted with fixation location at different times between tasks. Results suggest a role of both the eyes and mouth in the neural processing of fearful expressions and of the mouth in the processing of happy expressions, before 350ms. PMID:27430934

Exploratory eye movements to pictures in childhood-onset schizophrenia and attention-deficit/hyperactivity disorder (ADHD).

Science.gov (United States)

Karatekin, C; Asarnow, R F

1999-02-01

We investigated exploratory eye movements to thematic pictures in schizophrenic, attention-deficit/hyperactivity disorder (ADHD), and normal children. For each picture, children were asked three questions varying in amount of structure. We tested if schizophrenic children would stare or scan extensively and if their scan patterns were differentially affected by the question. Time spent viewing relevant and irrelevant regions, fixation duration (an estimate of processing rate), and distance between fixations (an estimate of breadth of attention) were measured. ADHD children showed a trend toward shorter fixations than normals on the question requiring the most detailed analysis. Schizophrenic children looked at fewer relevant, but not more irrelevant, regions than normals. They showed a tendency to stare more when asked to decide what was happening but not when asked to attend to specific regions. Thus, lower levels of visual attention (e.g., basic control of eye movements) were intact in schizophrenic children. In contrast, they had difficulty with top-down control of selective attention in the service of self-guided behavior.

Differences in Sequential Eye Movement Behavior between Taiwanese and American Viewers

Directory of Open Access Journals (Sweden)

Yen Ju eLee

2016-05-01

Full Text Available Knowledge of how information is sought in the visual world is useful for predicting and simulating human behavior. Taiwanese participants and American participants were instructed to judge the facial expression of a focal face that was flanked horizontally by other faces while their eye movements were monitored. The Taiwanese participants distributed their eye fixations more widely than American participants, started to look away from the focal face earlier than American participants, and spent a higher percentage of time looking at the flanking faces. Eye movement transition matrices also provided evidence that Taiwanese participants continually, and systematically shifted gaze between focal and flanking faces. Eye movement patterns were less systematic and less prevalent in American participants. This suggests that both cultures utilized different attention allocation strategies. The results highlight the importance of determining sequential eye movement statistics in cross-cultural research on the utilization of visual context.

Eye tracking and the translation process

DEFF Research Database (Denmark)

Hvelplund, Kristian Tangsgaard

2014-01-01

Eye tracking has become increasingly popular as a quantitative research method in translation research. This paper discusses some of the major methodological issues involved in the use of eye tracking in translation research. It focuses specifically on challenges in the analysis and interpretation...... of eye-tracking data as reflections of cognitive processes during translation. Four types of methodological issues are discussed in the paper. The first part discusses the preparatory steps that precede the actual recording of eye-tracking data. The second part examines critically the general assumptions...... linking eye movements to cognitive processing in the context of translation research. The third part of the paper discusses two popular eye-tracking measures often used in translation research, fixations and pupil size, while the fourth part proposes a method to evaluate the quality of eye-tracking data....

Using eye tracking technology to compare the effectiveness of malignant hyperthermia cognitive aid design.

Science.gov (United States)

King, Roderick; Hanhan, Jaber; Harrison, T Kyle; Kou, Alex; Howard, Steven K; Borg, Lindsay K; Shum, Cynthia; Udani, Ankeet D; Mariano, Edward R

2018-05-15

Malignant hyperthermia is a rare but potentially fatal complication of anesthesia, and several different cognitive aids designed to facilitate a timely and accurate response to this crisis currently exist. Eye tracking technology can measure voluntary and involuntary eye movements, gaze fixation within an area of interest, and speed of visual response and has been used to a limited extent in anesthesiology. With eye tracking technology, we compared the accessibility of five malignant hyperthermia cognitive aids by collecting gaze data from twelve volunteer participants. Recordings were reviewed and annotated to measure the time required for participants to locate objects on the cognitive aid to provide an answer; cumulative time to answer was the primary outcome. For the primary outcome, there were differences detected between cumulative time to answer survival curves (P typescript with minimal use of single color blocking.

Visual scan-path analysis with feature space transient fixation moments

Science.gov (United States)

Dempere-Marco, Laura; Hu, Xiao-Peng; Yang, Guang-Zhong

2003-05-01

The study of eye movements provides useful insight into the cognitive processes underlying visual search tasks. The analysis of the dynamics of eye movements has often been approached from a purely spatial perspective. In many cases, however, it may not be possible to define meaningful or consistent dynamics without considering the features underlying the scan paths. In this paper, the definition of the feature space has been attempted through the concept of visual similarity and non-linear low dimensional embedding, which defines a mapping from the image space into a low dimensional feature manifold that preserves the intrinsic similarity of image patterns. This has enabled the definition of perceptually meaningful features without the use of domain specific knowledge. Based on this, this paper introduces a new concept called Feature Space Transient Fixation Moments (TFM). The approach presented tackles the problem of feature space representation of visual search through the use of TFM. We demonstrate the practical values of this concept for characterizing the dynamics of eye movements in goal directed visual search tasks. We also illustrate how this model can be used to elucidate the fundamental steps involved in skilled search tasks through the evolution of transient fixation moments.

Origins of superior dynamic visual acuity in baseball players: superior eye movements or superior image processing.

Directory of Open Access Journals (Sweden)

Yusuke Uchida

Full Text Available Dynamic visual acuity (DVA is defined as the ability to discriminate the fine parts of a moving object. DVA is generally better in athletes than in non-athletes, and the better DVA of athletes has been attributed to a better ability to track moving objects. In the present study, we hypothesized that the better DVA of athletes is partly derived from better perception of moving images on the retina through some kind of perceptual learning. To test this hypothesis, we quantitatively measured DVA in baseball players and non-athletes using moving Landolt rings in two conditions. In the first experiment, the participants were allowed to move their eyes (free-eye-movement conditions, whereas in the second they were required to fixate on a fixation target (fixation conditions. The athletes displayed significantly better DVA than the non-athletes in the free-eye-movement conditions. However, there was no significant difference between the groups in the fixation conditions. These results suggest that the better DVA of athletes is primarily due to an improved ability to track moving targets with their eyes, rather than to improved perception of moving images on the retina.

Origins of superior dynamic visual acuity in baseball players: superior eye movements or superior image processing.

Science.gov (United States)

Uchida, Yusuke; Kudoh, Daisuke; Murakami, Akira; Honda, Masaaki; Kitazawa, Shigeru

2012-01-01

Dynamic visual acuity (DVA) is defined as the ability to discriminate the fine parts of a moving object. DVA is generally better in athletes than in non-athletes, and the better DVA of athletes has been attributed to a better ability to track moving objects. In the present study, we hypothesized that the better DVA of athletes is partly derived from better perception of moving images on the retina through some kind of perceptual learning. To test this hypothesis, we quantitatively measured DVA in baseball players and non-athletes using moving Landolt rings in two conditions. In the first experiment, the participants were allowed to move their eyes (free-eye-movement conditions), whereas in the second they were required to fixate on a fixation target (fixation conditions). The athletes displayed significantly better DVA than the non-athletes in the free-eye-movement conditions. However, there was no significant difference between the groups in the fixation conditions. These results suggest that the better DVA of athletes is primarily due to an improved ability to track moving targets with their eyes, rather than to improved perception of moving images on the retina.

Fixation times in evolutionary games under weak selection

International Nuclear Information System (INIS)

Altrock, Philipp M; Traulsen, Arne

2009-01-01

In evolutionary game dynamics, reproductive success increases with the performance in an evolutionary game. If strategy A performs better than strategy B, strategy A will spread in the population. Under stochastic dynamics, a single mutant will sooner or later take over the entire population or go extinct. We analyze the mean exit times (or average fixation times) associated with this process. We show analytically that these times depend on the payoff matrix of the game in an amazingly simple way under weak selection, i.e. strong stochasticity: the payoff difference Δπ is a linear function of the number of A individuals i, Δπ=u i+v. The unconditional mean exit time depends only on the constant term v. Given that a single A mutant takes over the population, the corresponding conditional mean exit time depends only on the density dependent term u. We demonstrate this finding for two commonly applied microscopic evolutionary processes.

Preliminary Experience Using Eye-Tracking Technology to Differentiate Novice and Expert Image Interpretation for Ultrasound-Guided Regional Anesthesia.

Science.gov (United States)

Borg, Lindsay K; Harrison, T Kyle; Kou, Alex; Mariano, Edward R; Udani, Ankeet D; Kim, T Edward; Shum, Cynthia; Howard, Steven K

2018-02-01

Objective measures are needed to guide the novice's pathway to expertise. Within and outside medicine, eye tracking has been used for both training and assessment. We designed this study to test the hypothesis that eye tracking may differentiate novices from experts in static image interpretation for ultrasound (US)-guided regional anesthesia. We recruited novice anesthesiology residents and regional anesthesiology experts. Participants wore eye-tracking glasses, were shown 5 sonograms of US-guided regional anesthesia, and were asked a series of anatomy-based questions related to each image while their eye movements were recorded. The answer to each question was a location on the sonogram, defined as the area of interest (AOI). The primary outcome was the total gaze time in the AOI (seconds). Secondary outcomes were the total gaze time outside the AOI (seconds), total time to answer (seconds), and time to first fixation on the AOI (seconds). Five novices and 5 experts completed the study. Although the gaze time (mean ± SD) in the AOI was not different between groups (7 ± 4 seconds for novices and 7 ± 3 seconds for experts; P = .150), the gaze time outside the AOI was greater for novices (75 ± 18 versus 44 ± 4 seconds for experts; P = .005). The total time to answer and total time to first fixation in the AOI were both shorter for experts. Experts in US-guided regional anesthesia take less time to identify sonoanatomy and spend less unfocused time away from a target compared to novices. Eye tracking is a potentially useful tool to differentiate novices from experts in the domain of US image interpretation. © 2017 by the American Institute of Ultrasound in Medicine.

An eye movement based reading intervention in lexical and segmental readers with acquired dyslexia.

Science.gov (United States)

Ablinger, Irene; von Heyden, Kerstin; Vorstius, Christian; Halm, Katja; Huber, Walter; Radach, Ralph

2014-01-01

Due to their brain damage, aphasic patients with acquired dyslexia often rely to a greater extent on lexical or segmental reading procedures. Thus, therapy intervention is mostly targeted on the more impaired reading strategy. In the present work we introduce a novel therapy approach based on real-time measurement of patients' eye movements as they attempt to read words. More specifically, an eye movement contingent technique of stepwise letter de-masking was used to support sequential reading, whereas fixation-dependent initial masking of non-central letters stimulated a lexical (parallel) reading strategy. Four lexical and four segmental readers with acquired central dyslexia received our intensive reading intervention. All participants showed remarkable improvements as evident in reduced total reading time, a reduced number of fixations per word and improved reading accuracy. Both types of intervention led to item-specific training effects in all subjects. A generalisation to untrained items was only found in segmental readers after the lexical training. Eye movement analyses were also used to compare word processing before and after therapy, indicating that all patients, with one exclusion, maintained their preferred reading strategy. However, in several cases the balance between sequential and lexical processing became less extreme, indicating a more effective individual interplay of both word processing routes.

Which Eye Tracker is Right for Your Research Performance Evaluation of Several Cost Variant Eye Trackers

Science.gov (United States)

2016-09-19

utilized to study a diverse number of topics such as the patterns of fixations and saccades while reading text (e.g., Rayner, 1998), the workload of...of their accessibility to our laboratory and because they represent a diverse set of relative price points, from low (Eye Tribe Tracker, Tobii EyeX...see Figure 1 for the layout of those systems). At both workstations, task stimuli were presented to observers on 48.26 cm Samsung SyncMaster 940Bx

Ab-interno scleral suture loop fixation with cow-hitch knot in posterior chamber intraocular lens decentration

Directory of Open Access Journals (Sweden)

Ertugrul Can

2016-01-01

Full Text Available Aim of Study: To describe a simplified ab-interno cow-hitch suture fixation technique for repositioning decentered posterior chamber intraocular lens (PC IOL. Materials and Methods: Two cases are presented with the surgical correction of decentered and subluxated IOL. Ab-interno scleral suture fixation technique with hitch-cow knot in the eye was performed with a ciliary sulcus guide instrument and 1 year follow-up was completed. Results: Both of the patients had well centered lenses postoperatively. Corrected distant and near visual acuities of the patients were improved. There was no significant postoperative complication. In the follow-up period of 1 year, no evidence of suture erosion was found. Conclusions: Ab-interno scleral suture loop fixation with hitch-cow knot in the eye was effective in repositioning decentered or subluxated PC IOLs with excellent postoperative centered lenses and visual outcomes.

Real time eye tracking using Kalman extended spatio-temporal context learning

Science.gov (United States)

Munir, Farzeen; Minhas, Fayyaz ul Amir Asfar; Jalil, Abdul; Jeon, Moongu

2017-06-01

Real time eye tracking has numerous applications in human computer interaction such as a mouse cursor control in a computer system. It is useful for persons with muscular or motion impairments. However, tracking the movement of the eye is complicated by occlusion due to blinking, head movement, screen glare, rapid eye movements, etc. In this work, we present the algorithmic and construction details of a real time eye tracking system. Our proposed system is an extension of Spatio-Temporal context learning through Kalman Filtering. Spatio-Temporal Context Learning offers state of the art accuracy in general object tracking but its performance suffers due to object occlusion. Addition of the Kalman filter allows the proposed method to model the dynamics of the motion of the eye and provide robust eye tracking in cases of occlusion. We demonstrate the effectiveness of this tracking technique by controlling the computer cursor in real time by eye movements.

Both lexical and non-lexical characters are processed during saccadic eye movements.

Directory of Open Access Journals (Sweden)

Hao Zhang

Full Text Available On average our eyes make 3-5 saccadic movements per second when we read, although their neural mechanism is still unclear. It is generally thought that saccades help redirect the retinal fovea to specific characters and words but that actual discrimination of information only occurs during periods of fixation. Indeed, it has been proposed that there is active and selective suppression of information processing during saccades to avoid experience of blurring due to the high-speed movement. Here, using a paradigm where a string of either lexical (Chinese or non-lexical (alphabetic characters are triggered by saccadic eye movements, we show that subjects can discriminate both while making saccadic eye movement. Moreover, discrimination accuracy is significantly better for characters scanned during the saccadic movement to a fixation point than those not scanned beyond it. Our results showed that character information can be processed during the saccade, therefore saccades during reading not only function to redirect the fovea to fixate the next character or word but allow pre-processing of information from the ones adjacent to the fixation locations to help target the next most salient one. In this way saccades can not only promote continuity in reading words but also actively facilitate reading comprehension.

Measures and limits of models of fixation selection.

Directory of Open Access Journals (Sweden)

Niklas Wilming

Full Text Available Models of fixation selection are a central tool in the quest to understand how the human mind selects relevant information. Using this tool in the evaluation of competing claims often requires comparing different models' relative performance in predicting eye movements. However, studies use a wide variety of performance measures with markedly different properties, which makes a comparison difficult. We make three main contributions to this line of research: First we argue for a set of desirable properties, review commonly used measures, and conclude that no single measure unites all desirable properties. However the area under the ROC curve (a classification measure and the KL-divergence (a distance measure of probability distributions combine many desirable properties and allow a meaningful comparison of critical model performance. We give an analytical proof of the linearity of the ROC measure with respect to averaging over subjects and demonstrate an appropriate correction of entropy-based measures like KL-divergence for small sample sizes in the context of eye-tracking data. Second, we provide a lower bound and an upper bound of these measures, based on image-independent properties of fixation data and between subject consistency respectively. Based on these bounds it is possible to give a reference frame to judge the predictive power of a model of fixation selection. We provide open-source python code to compute the reference frame. Third, we show that the upper, between subject consistency bound holds only for models that predict averages of subject populations. Departing from this we show that incorporating subject-specific viewing behavior can generate predictions which surpass that upper bound. Taken together, these findings lay out the required information that allow a well-founded judgment of the quality of any model of fixation selection and should therefore be reported when a new model is introduced.

The right look for the job: decoding cognitive processes involved in the task from spatial eye-movement patterns.

Science.gov (United States)

Król, Magdalena Ewa; Król, Michał

2018-02-20

The aim of the study was not only to demonstrate whether eye-movement-based task decoding was possible but also to investigate whether eye-movement patterns can be used to identify cognitive processes behind the tasks. We compared eye-movement patterns elicited under different task conditions, with tasks differing systematically with regard to the types of cognitive processes involved in solving them. We used four tasks, differing along two dimensions: spatial (global vs. local) processing (Navon, Cognit Psychol, 9(3):353-383 1977) and semantic (deep vs. shallow) processing (Craik and Lockhart, J Verbal Learn Verbal Behav, 11(6):671-684 1972). We used eye-movement patterns obtained from two time periods: fixation cross preceding the target stimulus and the target stimulus. We found significant effects of both spatial and semantic processing, but in case of the latter, the effect might be an artefact of insufficient task control. We found above chance task classification accuracy for both time periods: 51.4% for the period of stimulus presentation and 34.8% for the period of fixation cross presentation. Therefore, we show that task can be to some extent decoded from the preparatory eye-movements before the stimulus is displayed. This suggests that anticipatory eye-movements reflect the visual scanning strategy employed for the task at hand. Finally, this study also demonstrates that decoding is possible even from very scant eye-movement data similar to Coco and Keller, J Vis 14(3):11-11 (2014). This means that task decoding is not limited to tasks that naturally take longer to perform and yield multi-second eye-movement recordings.

Eye and Hand Movements during Reconstruction of Spatial Memory

Directory of Open Access Journals (Sweden)

Melanie Rose Burke

2012-05-01

Full Text Available Recent behavioural and biological evidence indicates common mechanisms serving working memory and attention (eg, Awh et al 2006, Trends in Cognitive Sciences 10, 124–130. This study explored the role of spatial attention and visual search in an adapted Corsi spatial memory task. Eye movements and touch responses were recorded from participants who recalled locations (signalled by colour or shape change from an array presented either simultaneously or sequentially. The time delay between target presentation and recall (0, 5, or 10s and the number of locations to be remembered (2–5 were also manipulated. Analysis of the response phase revealed subjects were less accurate (touch data and fixated longer (eye data when responding to sequentially presented targets. Fixation duration was also influenced by whether spatial location was initially signalled by colour or shape change. We conclude that attention and temporal delays during retention of a target play a minor role in motor behaviour during a corsi spatial memory task. In contrast, the type of memory required (ie, location and/or memory and number of items plays a key role on subject performance and behaviour.

REVISION ANKLE SYNDESMOSIS FIXATION - FUNCTIONAL OUTCOME AFTER TIGHTROPE ® FIXATION

Directory of Open Access Journals (Sweden)

Sendhilvelan Rajagopalan

2016-07-01

Full Text Available BACKGROUND Syndesmotic disruptions are often seen in ankle fractures. Malreduction of these fractures can result in arthritis and instability. A proportion of these patients with malreduction require revision fixation. This study presents the results of revision fixation in such patients, using the Ankle TightRope ® (Arthrex system. METHODS Between January 2000 to December 2009, 124 patients who underwent ankle fracture fixations with syndesmotic stabilisation were analysed. Out of 124 patients, 8 patients were diagnosed with failure of primary stabilisation (based on radiological and clinical criteria and subjected to revision fixation using the Ankle TightRope ® (Arthrex system. Followup was done at periodic time intervals of 3, 6 and 12 months. Both clinical and radiological assessment was performed. Complications and duration of hospital stay was recorded. Functional evaluation was performed using the American Orthopaedic Foot and Ankle Society (AOFAS scoring system. RESULTS Five patients had good results, one satisfactory and two had poor outcomes. CONCLUSIONS Ankle TightRope ® fixation is an alternative method of stabilisation in patients who require revision syndesmosis fixation. Further studies are required to evaluate this method of revision stabilisation as compared to screws.

De-warping of images and improved eye tracking for the scanning laser ophthalmoscope.

Directory of Open Access Journals (Sweden)

Phillip Bedggood

Full Text Available A limitation of scanning laser ophthalmoscopy (SLO is that eye movements during the capture of each frame distort the retinal image. Various sophisticated strategies have been devised to ensure that each acquired frame can be mapped quickly and accurately onto a chosen reference frame, but such methods are blind to distortions in the reference frame itself. Here we explore a method to address this limitation in software, and demonstrate its accuracy. We used high-speed (200 fps, high-resolution (~1 μm, flood-based imaging of the human retina with adaptive optics to obtain "ground truth" information on the retinal image and motion of the eye. This information was used to simulate SLO video sequences at 20 fps, allowing us to compare various methods for eye-motion recovery and subsequent minimization of intra-frame distortion. We show that a a single frame can be near-perfectly recovered with perfect knowledge of intra-frame eye motion; b eye motion at a given time point within a frame can be accurately recovered by tracking the same strip of tissue across many frames, due to the stochastic symmetry of fixational eye movements. This approach is similar to, and easily adapted from, previously suggested strip-registration approaches; c quality of frame recovery decreases with amplitude of eye movements, however, the proposed method is affected less by this than other state-of-the-art methods and so offers even greater advantages when fixation is poor. The new method could easily be integrated into existing image processing software, and we provide an example implementation written in Matlab.

Influence of Vehicle Speed on the Characteristics of Driver's Eye Movement at a Highway Tunnel Entrance during Day and Night Conditions: A Pilot Study.

Science.gov (United States)

Qin, Li; Dong, Li-Li; Xu, Wen-Hai; Zhang, Li-Dong; Leon, Arturo S

2018-04-02

The aim of this study was to investigate how vehicle speed influences the characteristics of driver's eye movement at highway tunnel entrances during day and night. In this study, six drivers' eye movement data (from 200 m before tunnel entrance to 200 m inside tunnel entrance) under five predetermined vehicle speeds (40, 50, 60, 70 and 80 km/h) in the daytime and three predetermined vehicle speeds (40, 60 and 80 km/h) in the nighttime were recorded using the non-intrusive Dikablis Professional eye-tracking system. Pupil size, the average fixation duration time and the average number of fixation were analyzed and then the influence of the vehicle speed on these parameters was evaluated by means of IBM SPSS Statistics 20.0. The results for pupil size in daytime increased when approaching the tunnel entrance, while as for nighttime, pupil size decreased when approaching the tunnel entrance and then increased after entering the tunnel. The pupil size in daytime has a significant negative correlation with vehicle speed, while the pupil size in nighttime did not show a significant association with vehicle speed. Furthermore, the average fixation duration in daytime increased when entering the tunnel, and had a significant negative correlation with vehicle speed. Also, the average number of fixations in daytime decreased when entering the tunnel and has a significant negative correlation with vehicle speed. However, the average fixation duration and the average number of fixations in nighttime did not show any significant association with vehicle speed. Moreover, limitations and future directions of the study are discussed for the further investigation.

Scleral Fixation of Posteriorly Dislocated Intraocular Lenses by 23-Gauge Vitrectomy without Anterior Segment Approach

Directory of Open Access Journals (Sweden)

Jeroni Nadal

2015-01-01

Full Text Available Background. To evaluate visual outcomes, corneal changes, intraocular lens (IOL stability, and complications after repositioning posteriorly dislocated IOLs and sulcus fixation with polyester sutures. Design. Prospective consecutive case series. Setting. Institut Universitari Barraquer. Participants. 25 eyes of 25 patients with posteriorly dislocated IOL. Methods. The patients underwent 23-gauge vitrectomy via the sulcus to rescue dislocated IOLs and fix them to the scleral wall with a previously looped nonabsorbable polyester suture. Main Outcome Measures. Best corrected visual acuity (BCVA LogMAR, corneal astigmatism, endothelial cell count, IOL stability, and postoperative complications. Results. Mean follow-up time was 18.8 ± 10.9 months. Mean surgery time was 33 ± 2 minutes. Mean BCVA improved from 0.30 ± 0.48 before surgery to 0.18 ± 0.60 (p=0.015 at 1 month, which persisted to 12 months (0.18 ± 0.60. Neither corneal astigmatism nor endothelial cell count showed alterations 1 year after surgery. Complications included IOL subluxation in 1 eye (4%, vitreous hemorrhage in 2 eyes (8%, transient hypotony in 2 eyes (8%, and cystic macular edema in 1 eye (4%. No patients presented retinal detachment. Conclusion. This surgical technique proved successful in the management of dislocated IOL. Functional results were good and the complications were easily resolved.

Scleral Fixation of Posteriorly Dislocated Intraocular Lenses by 23-Gauge Vitrectomy without Anterior Segment Approach.

Science.gov (United States)

Nadal, Jeroni; Kudsieh, Bachar; Casaroli-Marano, Ricardo P

2015-01-01

Background. To evaluate visual outcomes, corneal changes, intraocular lens (IOL) stability, and complications after repositioning posteriorly dislocated IOLs and sulcus fixation with polyester sutures. Design. Prospective consecutive case series. Setting. Institut Universitari Barraquer. Participants. 25 eyes of 25 patients with posteriorly dislocated IOL. Methods. The patients underwent 23-gauge vitrectomy via the sulcus to rescue dislocated IOLs and fix them to the scleral wall with a previously looped nonabsorbable polyester suture. Main Outcome Measures. Best corrected visual acuity (BCVA) LogMAR, corneal astigmatism, endothelial cell count, IOL stability, and postoperative complications. Results. Mean follow-up time was 18.8 ± 10.9 months. Mean surgery time was 33 ± 2 minutes. Mean BCVA improved from 0.30 ± 0.48 before surgery to 0.18 ± 0.60 (p = 0.015) at 1 month, which persisted to 12 months (0.18 ± 0.60). Neither corneal astigmatism nor endothelial cell count showed alterations 1 year after surgery. Complications included IOL subluxation in 1 eye (4%), vitreous hemorrhage in 2 eyes (8%), transient hypotony in 2 eyes (8%), and cystic macular edema in 1 eye (4%). No patients presented retinal detachment. Conclusion. This surgical technique proved successful in the management of dislocated IOL. Functional results were good and the complications were easily resolved.

[Reduction of decentration after LASIK using a modified eye tracker ring for the MEL-70 excimer laser].

Science.gov (United States)

Schulze, S; Nietgen, G; Sekundo, W

2004-07-01

The aim of this study was to determine and compare the rate of eccentric laser ablation after LASIK depending on the eye tracker ring used. All LASIK treatments were carried out using the MEL-70 flying spot excimer laser (Zeiss-Meditec, Jena). The flap was produced using a Corneal Shaper trade mark or Hansatome trade mark Microkeratome (B and L Surgical, Heidelberg). Initially we used an 11 mm eye tracker ring without hinge protector. At the end of February 2001 this ring was replaced by a 10 mm and a 9.5 mm ring with built-in hinge protector. An additional modification was introduced by us: at 1 mm separations little teeth-like spikes were engraved into the eyeward side of the ring, thus stabilising the position of the ring on the globe and allowing free liquid to flow through the spaces between each spike. The built-in calibration system of the corneal topography (TMS 3, Tomey, Erlangen) from patients with a follow-up of one month or longer was used to determine the distance between the centre of the ablation zone from the fixation point. In group I patients (old ring) 42 eyes were treated. In 4 eyes ablation was perfect, in 21 eyes the ablation centre was located 0.1 to 0.49 mm from the fixation point, in 11 eyes 0.51 to 0.99 mm and in 5 eyes 1.1 to 1.49 mm whereas one eye showed a decentred ablation of 1.53 mm. In group II (new ring) 42 eyes were investigated also. In 11 eyes ablation was perfect, in 20 eyes the ablation centre was located 0.1 to 0.49 mm from the fixation point, in 10 eyes 0.5 to 0.99 mm and one eye had an eccentric ablation of 1.28 mm from the fixation point. The further development of our eye tracker ring for the MEL-70 laser considerably reduced the rate of decentred ablations. An enhanced grip of the ring onto the globe reduces a slow slide during the laser procedure.

Children’s Empathy and Their Perception and Evaluation of Facial Pain Expression: An Eye Tracking Study

Directory of Open Access Journals (Sweden)

Zhiqiang Yan

2017-12-01

Full Text Available The function of empathic concern to process pain is a product of evolutionary adaptation. Focusing on 5- to 6-year old children, the current study employed eye-tracking in an odd-one-out task (searching for the emotional facial expression among neutral expressions, N = 47 and a pain evaluation task (evaluating the pain intensity of a facial expression, N = 42 to investigate the relationship between children’s empathy and their behavioral and perceptual response to facial pain expression. We found children detected painful expression faster than others (angry, sad, and happy, children high in empathy performed better on searching facial expression of pain, and gave higher evaluation of pain intensity; and rating for pain in painful expressions was best predicted by a self-reported empathy score. As for eye-tracking in pain detection, children fixated on pain more quickly, less frequently and for shorter times. Of facial clues, children fixated on eyes and mouth more quickly, more frequently and for longer times. These results implied that painful facial expression was different from others in a cognitive sense, and children’s empathy might facilitate their search and make them perceive the intensity of observed pain on the higher side.

Online webcam-based eye tracking in cognitive science: A first look.

Science.gov (United States)

Semmelmann, Kilian; Weigelt, Sarah

2018-04-01

Online experimentation is emerging in many areas of cognitive psychology as a viable alternative or supplement to classical in-lab experimentation. While performance- and reaction-time-based paradigms are covered in recent studies, one instrument of cognitive psychology has not received much attention up to now: eye tracking. In this study, we used JavaScript-based eye tracking algorithms recently made available by Papoutsaki et al. (International Joint Conference on Artificial Intelligence, 2016) together with consumer-grade webcams to investigate the potential of online eye tracking to benefit from the common advantages of online data conduction. We compared three in-lab conducted tasks (fixation, pursuit, and free viewing) with online-acquired data to analyze the spatial precision in the first two, and replicability of well-known gazing patterns in the third task. Our results indicate that in-lab data exhibit an offset of about 172 px (15% of screen size, 3.94° visual angle) in the fixation task, while online data is slightly less accurate (18% of screen size, 207 px), and shows higher variance. The same results were found for the pursuit task with a constant offset during the stimulus movement (211 px in-lab, 216 px online). In the free-viewing task, we were able to replicate the high attention attribution to eyes (28.25%) compared to other key regions like the nose (9.71%) and mouth (4.00%). Overall, we found web technology-based eye tracking to be suitable for all three tasks and are confident that the required hard- and software will be improved continuously for even more sophisticated experimental paradigms in all of cognitive psychology.

Relationship between abstract thinking and eye gaze pattern in patients with schizophrenia

Science.gov (United States)

2014-01-01

Background Effective integration of visual information is necessary to utilize abstract thinking, but patients with schizophrenia have slow eye movement and usually explore limited visual information. This study examines the relationship between abstract thinking ability and the pattern of eye gaze in patients with schizophrenia using a novel theme identification task. Methods Twenty patients with schizophrenia and 22 healthy controls completed the theme identification task, in which subjects selected which word, out of a set of provided words, best described the theme of a picture. Eye gaze while performing the task was recorded by the eye tracker. Results Patients exhibited a significantly lower correct rate for theme identification and lesser fixation and saccade counts than controls. The correct rate was significantly correlated with the fixation count in patients, but not in controls. Conclusions Patients with schizophrenia showed impaired abstract thinking and decreased quality of gaze, which were positively associated with each other. Theme identification and eye gaze appear to be useful as tools for the objective measurement of abstract thinking in patients with schizophrenia. PMID:24739356

Usability Analysis of Online Bank Login Interface Based on Eye Tracking Experiment

Directory of Open Access Journals (Sweden)

Xiaofang YUAN

2014-02-01

Full Text Available With the rapid development of information technology and rapid popularization of online banking, it is used by the more and more consumers. Studying on the usability of online banking interface, improving the user-friendliness of web interface, and enhancing attraction of bank website, which have gradually become the basic network marketing strategy of the banks. Therefore, this study took three banks as an example to record subjects’’ eye tracking data of time to first fixation, fixation duration and blink count and so on by using Tobii T60XL Eye Tracking equipment, while they login online banking web interface, and analyzed that the factors of webpage layout, colors, the amount of information presentation which impacts on the usability of online banking login interface. The results shows that the login entry, account login information and other key control buttons should be placed in the upper left corner to quickly lock the target, and the interface should have a moderate amount of information presentation, the appropriate proportion, reasonable font size settings, harmonious, simple, and warmth design style.

Influence of age, spatial memory, and ocular fixation on localization of auditory, visual, and bimodal targets by human subjects.

Science.gov (United States)

Dobreva, Marina S; O'Neill, William E; Paige, Gary D

2012-12-01

A common complaint of the elderly is difficulty identifying and localizing auditory and visual sources, particularly in competing background noise. Spatial errors in the elderly may pose challenges and even threats to self and others during everyday activities, such as localizing sounds in a crowded room or driving in traffic. In this study, we investigated the influence of aging, spatial memory, and ocular fixation on the localization of auditory, visual, and combined auditory-visual (bimodal) targets. Head-restrained young and elderly subjects localized targets in a dark, echo-attenuated room using a manual laser pointer. Localization accuracy and precision (repeatability) were quantified for both ongoing and transient (remembered) targets at response delays up to 10 s. Because eye movements bias auditory spatial perception, localization was assessed under target fixation (eyes free, pointer guided by foveal vision) and central fixation (eyes fixed straight ahead, pointer guided by peripheral vision) conditions. Spatial localization across the frontal field in young adults demonstrated (1) horizontal overshoot and vertical undershoot for ongoing auditory targets under target fixation conditions, but near-ideal horizontal localization with central fixation; (2) accurate and precise localization of ongoing visual targets guided by foveal vision under target fixation that degraded when guided by peripheral vision during central fixation; (3) overestimation in horizontal central space (±10°) of remembered auditory, visual, and bimodal targets with increasing response delay. In comparison with young adults, elderly subjects showed (1) worse precision in most paradigms, especially when localizing with peripheral vision under central fixation; (2) greatly impaired vertical localization of auditory and bimodal targets; (3) increased horizontal overshoot in the central field for remembered visual and bimodal targets across response delays; (4) greater vulnerability to

Scanning mid-IR laser apparatus with eye tracking for refractive surgery

Science.gov (United States)

Telfair, William B.; Yoder, Paul R., Jr.; Bekker, Carsten; Hoffman, Hanna J.; Jensen, Eric F.

1999-06-01

A robust, real-time, dynamic eye tracker has been integrated with the short pulse mid-infrared laser scanning delivery system previously described. This system employs a Q- switched Nd:YAG laser pumped optical parametric oscillator operating at 2.94 micrometers. Previous ablation studies on human cadaver eyes and in-vivo cat eyes demonstrated very smooth ablations with extremely low damage levels similar to results with an excimer. A 4-month healing study with cats indicated no adverse healing effects. In order to treat human eyes, the tracker is required because the eyes move during the procedure due to both voluntary and involuntary motions such as breathing, heartbeat, drift, loss of fixation, saccades and microsaccades. Eye tracking techniques from the literature were compared. A limbus tracking system was best for this application. Temporal and spectral filtering techniques were implemented to reduce tracking errors, reject stray light, and increase signal to noise ratio. The expanded-capability system (IRVision AccuScan 2000 Laser System) has been tested in the lab on simulated eye targets, glass eyes, cadaver eyes, and live human subjects. Circular targets ranging from 10-mm to 14-mm diameter were successfully tracked. The tracker performed beyond expectations while the system performed myopic photorefractive keratectomy procedures on several legally blind human subjects.

[Effectiveness comparison of flexible fixation and rigid fixation in treatment of ankle pronation-external rotation fractures with distal tibiofibular syndesmosis].

Science.gov (United States)

Li, Yuewei; Zhang, Minghui; Li, Xiaorong; Chen, Xiaoyong; Deng, Jianlong

2017-07-01

To compare the effectiveness of flexible fixation and rigid fixation in the treatment of ankle pronation-external rotation fractures with distal tibiofibular syndesmosis. A retrospective analysis was made on the clinical data of 50 patients with ankle pronation-external rotation fractures and distal tibiofibular syndesmosis treated between January 2013 and December 2015. Suture-button fixation was used in 23 patients (flexible fixation group) and cortical screw fixation in 27 patients (rigid fixation group). There was no significant difference in age, gender, weight, side, fracture type, and time from trauma to surgery between 2 groups ( P >0.05). The operation time, medial clear space (MCS), tibiofibular clear space (TFCS), tibiofibular overlap (TFO), American Orthopaedic Foot and Ankle Society (AOFAS) score, and Foot and Ankle Disability Index (FADI) score were compared between 2 groups. The operation time was (83.0±9.1) minutes in the flexible fixation group and was (79.6±13.1) minutes in the rigid fixation group, showing no significant difference ( t =1.052, P =0.265). All patients achieved healing of incision by first intention. The patients were followed up 12-20 months (mean, 14 months). The X-ray films showed good healing of fracture in 2 groups. There was no screw fracture, delayed union or nounion. The fracture healing time was (12.1±2.5) months in the flexible fixation group and was (11.3±3.2) months in the rigid fixation group, showing no significant difference between 2 groups ( t =1.024, P =0.192). Reduction loss occurred after removal of screw in 2 cases of the rigid fixation group. At last follow-up, there was no significant difference in MCS, TFCS, TFO, AOFAS score and FADI score between 2 groups ( P >0.05). Suture-button fixation has similar effectiveness to screw fixation in ankle function and imaging findings, and flexible fixation has lower risk of reduction loss of distal tibiofibular syndesmosis than rigid fixation.

Electronic eye occluder with time-counting and reflection control

Science.gov (United States)

Karitans, V.; Ozolinsh, M.; Kuprisha, G.

2008-09-01

In pediatric ophthalmology 2 - 3 % of all the children are impacted by a visual pathology - amblyopia. It develops if a clear image isn't presented to the retina during an early stage of the development of the visual system. A common way of treating this pathology is to cover the better-seeing eye to force the "lazy" eye to learn seeing. However, children are often reluctant to wear such an occluder because they are ashamed or simply because they find it inconvenient. This fact requires to find a way how to track the regime of occlusion because results of occlusion is a hint that the actual regime of occlusion isn't that what the optometrist has recommended. We design an electronic eye occluder that allows to track the regime of eye occlusion. We employ real-time clock DS1302 providing time information from seconds to years. Data is stored in the internal memory of the CPU (EEPROM). The MCU (PIC16F676) switches on only if a mechanical switch is closed and temperature has reached a satisfactory level. The occlusion is registered between time moments when the infrared signal appeared and disappeared.

A dual visual-local feedback model of the vergence eye movement system

NARCIS (Netherlands)

Erkelens, C.J.

2011-01-01

Pure vergence movements are the eye movements that we make when we change our binocular fixation between targets differing in distance but not in direction relative to the head. Pure vergence is slow and controlled by visual feedback. Saccades are the rapid eye movements that we make between targets

Glued intrascleral fixation of posterior chamber intraocular lens in children.

Science.gov (United States)

Kumar, Dhivya Ashok; Agarwal, Amar; Prakash, Dimple; Prakash, Gaurav; Jacob, Soosan; Agarwal, Athiya

2012-04-01

To evaluate the short-term results of glued intrascleral fixation of posterior chamber intraocular lens (glued IOL) in children without adequate capsular support. Noncomparative retrospective observational case series. Institutional practice. Forty-one eyes of 33 children who underwent glued IOL implantation were retrospectively evaluated. The indications were postsurgical aphakia, subluxated cataract, ectopia lentis, traumatic subluxation, and decentered IOL. Visual acuity (VA), endothelial cell changes, intraoperative and postoperative complications. The mean age at the time of glued IOL was 10.7±3.6 years (range 5-15). The mean duration of follow-up after surgery was 17.5±8.5 months (range 12-36). The mean postoperative best spectacle-corrected visual acuity (BCVA in decimal equivalent) was 0.43±0.33 and there was significant change noted (P20/60 BCVA was obtained in 17.1% and 46.3% of eyes respectively. BCVA improvement more than 1 line was seen in 22 eyes (53.6%). The mean postoperative refraction was myopic (-1.19±0.7 diopters [D]) in 19 eyes and hyperopic (+1.02±0.7 D) in 22 eyes. The mean endothelial loss was 4.13% (range 1.3%-5.94%). The 3 causes of reduced BCVA were the preexisting corneal, retinal pathology, and amblyopia. Postoperative complications included optic capture in 1 eye (2.4%), macular edema in 2 eyes (4.8%), and clinical decentration in 2 eyes (4.8%). There was no postoperative retinal detachment, IOL dislocation, endophthalmitis, or glaucoma. Short-term results in children after glued IOL were favorable, with a low rate of complications. However, regular follow-ups are required since long-term risks are unknown. Copyright © 2012 Elsevier Inc. All rights reserved.

The effect of beat frequency on eye movements during free viewing.

Science.gov (United States)

Maróti, Emese; Knakker, Balázs; Vidnyánszky, Zoltán; Weiss, Béla

2017-02-01

External periodic stimuli entrain brain oscillations and affect perception and attention. It has been shown that background music can change oculomotor behavior and facilitate detection of visual objects occurring on the musical beat. However, whether musical beats in different tempi modulate information sampling differently during natural viewing remains to be explored. Here we addressed this question by investigating how listening to naturalistic drum grooves in two different tempi affects eye movements of participants viewing natural scenes on a computer screen. We found that the beat frequency of the drum grooves modulated the rate of eye movements: fixation durations were increased at the lower beat frequency (1.7Hz) as compared to the higher beat frequency (2.4Hz) and no music conditions. Correspondingly, estimated visual sampling frequency decreased as fixation durations increased with lower beat frequency. These results imply that slow musical beats can retard sampling of visual information during natural viewing by increasing fixation durations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Determination of the lowest concentrations of aldehyde fixatives for completely fixing various cellular structures by real-time imaging and quantification.

Science.gov (United States)

Zeng, Fangfa; Yang, Wen; Huang, Jie; Chen, Yuan; Chen, Yong

2013-05-01

The effectiveness of fixatives for fixing biological specimens has long been widely investigated. However, the lowest concentrations of fixatives needed to completely fix whole cells or various cellular structures remain unclear. Using real-time imaging and quantification, we determined the lowest concentrations of glutaraldehyde (0.001-0.005, ~0.005, 0.01-005, 0.01-005, and 0.01-0.1 %) and formaldehyde/paraformaldehyde (0.01-0.05, ~0.05, 0.5-1, 1-1.5, and 0.5-1 %) required to completely fix focal adhesions, cell-surface particles, stress fibers, the cell cortex, and the inner structures of human umbilical vein endothelial cells within 20 min. With prolonged fixation times (>20 min), the concentration of fixative required to completely fix these structures will shift to even lower values. These data may help us understand and optimize fixation protocols and understand the potential effects of the small quantities of endogenously generated aldehydes in human cells. We also determined the lowest concentration of glutaraldehyde (0.5 %) and formaldehyde/paraformaldehyde (2 %) required to induce cell blebbing. We found that the average number and size of the fixation-induced blebs per cell were dependent on both fixative concentration and cell spread area, but were independent of temperature. These data provide important information for understanding cell blebbing, and may help optimize the vesiculation-based technique used to isolate plasma membrane by suggesting ways of controlling the number or size of fixation-induced cell blebs.

Blink patterns and lid-contact times in dry-eye and normal subjects

Directory of Open Access Journals (Sweden)

Ousler GW 3rd

2014-05-01

Full Text Available George W Ousler 3rd,1 Mark B Abelson,1,2 Patrick R Johnston,1 John Rodriguez,1 Keith Lane,1 Lisa M Smith11Ora, Andover, MA, USA; 2Department of Ophthalmology, Harvard Medical School, Boston, MA, USAPurpose: To classify blinks in dry eye and normal subjects into six subtypes, and to define the blink rate and duration within each type of blink, as well as the total lid-contact time/minute.Materials and methods: This was a single-centered, prospective, double-blind study of eleven dry-eye and ten normal subjects. Predefined subjects watched a video while blinks were recorded for 10 minutes. Partial blinks were classified by percentage closure of maximal palpebral fissure opening: 25%, 50%, 75%. Complete blinks were characterized as full (>0 seconds, extended (>0.1 seconds, or superextended (>0.5 seconds. The mean duration of each type of blink was determined and standardized per minute as total lid-contact time.Results: Total blinks observed were 4,990 (1,414 normal, 3,756 dry eye: 1,809 (50.59% partial and 1,767 (49.41% complete blinks among dry-eye subjects versus 741 (52.90% partial and 673 (47.60% complete blinks among normal subjects. Only superextended blinks of ≥0.5-second duration were significantly more frequent in dry-eye subjects than normals (2.3% versus 0.2%, respectively; P=0.023. Total contact time was seven times higher in dry-eye subjects than normals (0.565 versus 0.080 seconds, respectively; P<0.001. Isolating only extended blinks (>0.1 second, the average contact time (seconds was four times longer in dry-eye versus normal subjects (2.459 in dry eye, 0.575 in normals; P=0.003. Isolating only superextended blinks (>0.5 seconds, average contact time was also significantly different (7.134 in dry eye, 1.589 in normals; P<0.001. The contact rate for all full closures was 6.4 times longer in dry-eye (0.045 versus 0.007, P<0.001 than normal subjects.Conclusion: Dry-eye subjects spent 4.5% of a

A geometric method for computing ocular kinematics and classifying gaze events using monocular remote eye tracking in a robotic environment.

Science.gov (United States)

Singh, Tarkeshwar; Perry, Christopher M; Herter, Troy M

2016-01-26

Robotic and virtual-reality systems offer tremendous potential for improving assessment and rehabilitation of neurological disorders affecting the upper extremity. A key feature of these systems is that visual stimuli are often presented within the same workspace as the hands (i.e., peripersonal space). Integrating video-based remote eye tracking with robotic and virtual-reality systems can provide an additional tool for investigating how cognitive processes influence visuomotor learning and rehabilitation of the upper extremity. However, remote eye tracking systems typically compute ocular kinematics by assuming eye movements are made in a plane with constant depth (e.g. frontal plane). When visual stimuli are presented at variable depths (e.g. transverse plane), eye movements have a vergence component that may influence reliable detection of gaze events (fixations, smooth pursuits and saccades). To our knowledge, there are no available methods to classify gaze events in the transverse plane for monocular remote eye tracking systems. Here we present a geometrical method to compute ocular kinematics from a monocular remote eye tracking system when visual stimuli are presented in the transverse plane. We then use the obtained kinematics to compute velocity-based thresholds that allow us to accurately identify onsets and offsets of fixations, saccades and smooth pursuits. Finally, we validate our algorithm by comparing the gaze events computed by the algorithm with those obtained from the eye-tracking software and manual digitization. Within the transverse plane, our algorithm reliably differentiates saccades from fixations (static visual stimuli) and smooth pursuits from saccades and fixations when visual stimuli are dynamic. The proposed methods provide advancements for examining eye movements in robotic and virtual-reality systems. Our methods can also be used with other video-based or tablet-based systems in which eye movements are performed in a peripersonal

Eye Movements Affect Postural Control in Young and Older Females.

Science.gov (United States)

Thomas, Neil M; Bampouras, Theodoros M; Donovan, Tim; Dewhurst, Susan

2016-01-01

Visual information is used for postural stabilization in humans. However, little is known about how eye movements prevalent in everyday life interact with the postural control system in older individuals. Therefore, the present study assessed the effects of stationary gaze fixations, smooth pursuits, and saccadic eye movements, with combinations of absent, fixed and oscillating large-field visual backgrounds to generate different forms of retinal flow, on postural control in healthy young and older females. Participants were presented with computer generated visual stimuli, whilst postural sway and gaze fixations were simultaneously assessed with a force platform and eye tracking equipment, respectively. The results showed that fixed backgrounds and stationary gaze fixations attenuated postural sway. In contrast, oscillating backgrounds and smooth pursuits increased postural sway. There were no differences regarding saccades. There were also no differences in postural sway or gaze errors between age groups in any visual condition. The stabilizing effect of the fixed visual stimuli show how retinal flow and extraocular factors guide postural adjustments. The destabilizing effect of oscillating visual backgrounds and smooth pursuits may be related to more challenging conditions for determining body shifts from retinal flow, and more complex extraocular signals, respectively. Because the older participants matched the young group's performance in all conditions, decreases of posture and gaze control during stance may not be a direct consequence of healthy aging. Further research examining extraocular and retinal mechanisms of balance control and the effects of eye movements, during locomotion, is needed to better inform fall prevention interventions.

"Far from the heart far from the eye": evidence from the Capgras delusion.

Science.gov (United States)

Brighetti, Gianni; Bonifacci, Paola; Borlimi, Rosita; Ottaviani, Cristina

2007-05-01

Capgras syndrome is characterised by the belief that a significant other has been replaced by an identical-looking impostor. These patients have no difficulties with visual recognition but fail to show a skin conductance response (SCR) to the objects of the delusion. A case of Capgras delusion (YY), specifically characterised by the absence of brain lesions, constituted a good opportunity to test the relationship between SCR hyporesponsiveness and eye movement patterns to familiar and unfamiliar faces. Visual scan path and SCR were recorded for YY and 8 controls during the presentation of family members' photographs matched with unfamiliar faces of the same sex, age, and physical likeness. Eye movement patterns were explored by selecting three specific areas of interest (AOI) involving the eyes, the mouth, and the face regions. In contrast with controls, YY showed a reduction in number and sum of fixation durations to the eyes (p.05) to familiar vs. nonfamiliar faces. SCR and fixation duration to family members' eyes were significantly correlated (r=.77) in both YY and controls. Eye region exploration seems to be related to the autonomic reactivity elicited by the affective valence of familiar faces.

Eye-Head Coordination in 31 Space Shuttle Astronauts during Visual Target Acquisition.

Science.gov (United States)

Reschke, Millard F; Kolev, Ognyan I; Clément, Gilles

2017-10-27

Between 1989 and 1995, NASA evaluated how increases in flight duration of up to 17 days affected the health and performance of Space Shuttle astronauts. Thirty-one Space Shuttle pilots participating in 17 space missions were tested at 3 different times before flight and 3 different times after flight, starting within a few hours of return to Earth. The astronauts moved their head and eyes as quickly as possible from the central fixation point to a specified target located 20°, 30°, or 60° off center. Eye movements were measured with electro-oculography (EOG). Head movements were measured with a triaxial rate sensor system mounted on a headband. The mean time to visually acquire the targets immediately after landing was 7-10% (30-34 ms) slower than mean preflight values, but results returned to baseline after 48 hours. This increase in gaze latency was due to a decrease in velocity and amplitude of both the eye saccade and head movement toward the target. Results were similar after all space missions, regardless of length.

What checkers actually check: an eye tracking study of inhibitory control and working memory.

Directory of Open Access Journals (Sweden)

Ben Harkin

Full Text Available Not only is compulsive checking the most common symptom in Obsessive Compulsive Disorder (OCD with an estimated prevalence of 50-80% in patients, but approximately ∼15% of the general population reveal subclinical checking tendencies that impact negatively on their performance in daily activities. Therefore, it is critical to understand how checking affects attention and memory in clinical as well as subclinical checkers. Eye fixations are commonly used as indicators for the distribution of attention but research in OCD has revealed mixed results at best.Here we report atypical eye movement patterns in subclinical checkers during an ecologically valid working memory (WM manipulation. Our key manipulation was to present an intermediate probe during the delay period of the memory task, explicitly asking for the location of a letter, which, however, had not been part of the encoding set (i.e., misleading participants. Using eye movement measures we now provide evidence that high checkers' inhibitory impairments for misleading information results in them checking the contents of WM in an atypical manner. Checkers fixate more often and for longer when misleading information is presented than non-checkers. Specifically, checkers spend more time checking stimulus locations as well as locations that had actually been empty during encoding.We conclude that these atypical eye movement patterns directly reflect internal checking of memory contents and we discuss the implications of our findings for the interpretation of behavioural and neuropsychological data. In addition our results highlight the importance of ecologically valid methodology for revealing the impact of detrimental attention and memory checking on eye movement patterns.

EEG and Eye Tracking Signatures of Target Encoding during Structured Visual Search

Directory of Open Access Journals (Sweden)

Anne-Marie Brouwer

2017-05-01

Full Text Available EEG and eye tracking variables are potential sources of information about the underlying processes of target detection and storage during visual search. Fixation duration, pupil size and event related potentials (ERPs locked to the onset of fixation or saccade (saccade-related potentials, SRPs have been reported to differ dependent on whether a target or a non-target is currently fixated. Here we focus on the question of whether these variables also differ between targets that are subsequently reported (hits and targets that are not (misses. Observers were asked to scan 15 locations that were consecutively highlighted for 1 s in pseudo-random order. Highlighted locations displayed either a target or a non-target stimulus with two, three or four targets per trial. After scanning, participants indicated which locations had displayed a target. To induce memory encoding failures, participants concurrently performed an aurally presented math task (high load condition. In a low load condition, participants ignored the math task. As expected, more targets were missed in the high compared with the low load condition. For both conditions, eye tracking features distinguished better between hits and misses than between targets and non-targets (with larger pupil size and shorter fixations for missed compared with correctly encoded targets. In contrast, SRP features distinguished better between targets and non-targets than between hits and misses (with average SRPs showing larger P300 waveforms for targets than for non-targets. Single trial classification results were consistent with these averages. This work suggests complementary contributions of eye and EEG measures in potential applications to support search and detect tasks. SRPs may be useful to monitor what objects are relevant to an observer, and eye variables may indicate whether the observer should be reminded of them later.

Loneliness and hypervigilance to social cues in females: an eye-tracking study.

Directory of Open Access Journals (Sweden)

Gerine M A Lodder

Full Text Available The goal of the present study was to examine whether lonely individuals differ from nonlonely individuals in their overt visual attention to social cues. Previous studies showed that loneliness was related to biased post-attentive processing of social cues (e.g., negative interpretation bias, but research on whether lonely and nonlonely individuals also show differences in an earlier information processing stage (gazing behavior is very limited. A sample of 25 lonely and 25 nonlonely students took part in an eye-tracking study consisting of four tasks. We measured gazing (duration, number of fixations and first fixation at the eyes, nose and mouth region of faces expressing emotions (Task 1, at emotion quadrants (anger, fear, happiness and neutral expression (Task 2, at quadrants with positive and negative social and nonsocial images (Task 3, and at the facial area of actors in video clips with positive and negative content (Task 4. In general, participants tended to gaze most often and longest at areas that conveyed most social information, such as the eye region of the face (T1, and social images (T3. Participants gazed most often and longest at happy faces (T2 in still images, and more often and longer at the facial area in negative than in positive video clips (T4. No differences occurred between lonely and nonlonely participants in their gazing times and frequencies, nor at first fixations at social cues in the four different tasks. Based on this study, we found no evidence that overt visual attention to social cues differs between lonely and nonlonely individuals. This implies that biases in social information processing of lonely individuals may be limited to other phases of social information processing. Alternatively, biased overt attention to social cues may only occur under specific conditions, for specific stimuli or for specific lonely individuals.

Revisiting the time until fixation of a neutral mutant in a finite population - A coalescent theory approach.

Science.gov (United States)

Greenbaum, Gili

2015-09-07

Evaluation of the time scale of the fixation of neutral mutations is crucial to the theoretical understanding of the role of neutral mutations in evolution. Diffusion approximations of the Wright-Fisher model are most often used to derive analytic formulations of genetic drift, as well as for the time scales of the fixation of neutral mutations. These approximations require a set of assumptions, most notably that genetic drift is a stochastic process in a continuous allele-frequency space, an assumption appropriate for large populations. Here equivalent approximations are derived using a coalescent theory approach which relies on a different set of assumptions than the diffusion approach, and adopts a discrete allele-frequency space. Solutions for the mean and variance of the time to fixation of a neutral mutation derived from the two approaches converge for large populations but slightly differ for small populations. A Markov chain analysis of the Wright-Fisher model for small populations is used to evaluate the solutions obtained, showing that both the mean and the variance are better approximated by the coalescent approach. The coalescence approximation represents a tighter upper-bound for the mean time to fixation than the diffusion approximation, while the diffusion approximation and coalescence approximation form an upper and lower bound, respectively, for the variance. The converging solutions and the small deviations of the two approaches strongly validate the use of diffusion approximations, but suggest that coalescent theory can provide more accurate approximations for small populations. Copyright © 2015 Elsevier Ltd. All rights reserved.

Long-term outcomes of ciliary sulcus versus capsular bag fixation of intraocular lenses in children: An ultrasound biomicroscopy study.

Directory of Open Access Journals (Sweden)

Yun-E Zhao

Full Text Available To evaluate the long-term outcomes of ciliary sulcus versus capsular bag fixation of intraocular lenses (IOLs in children after pediatric cataract surgery.IOL was implanted in the ciliary sulcus in 21 eyes of 14 children, and in the capsular bag in 19 eyes of 12 children for the treatment of pediatric cataract in an institutional setting. Ultrasound biomicroscopy (UBM was performed. Main outcome measures included IOL decentration, IOL tilt, anterior chamber depth (ACD, angle-opening distance at 500 μm (AOD500, trabecular-iris angle (TIA, best-corrected visual acuity (BCVA, intraocular pressure (IOP, and incidence of postoperative complications.The mean follow-up period was 6.81 ± 1.82 years. Comparing to the capsular bag fixation group, the ciliary sulcus fixation group had higher vertical IOL decentration, horizontal IOL tilt, and vertical IOL tilt (p = 0.02, 0.01,0.01, respectively, higher incidence of iris-IOL contact and peripheral anterior synechia (p = 0.001, 0.03, respectively, smaller ACD, AOD500, and TIA (p = 0.02, 0.03, 0.04, respectively, higher mean IOP (17.10 ±6.06 mmHg vs.14.15± 4.74 mmHg, p = 0.01, and higher incidence of secondary glaucoma (28.57% vs. 10.53%, p = 0.007.There was no significant difference between the two groups with regard to the BCVA, refractive errors, incidence of myopic shift, nystagmus, strabismus, and visual axis opacity.Ciliary sulcus fixation of IOLs in pediatric eyes may increase IOL malposition and crowding of the anterior segment, and may associate with a higher risk of secondary glaucoma compared to capsular bag fixation of IOLs.

Altered brain rhythms and functional network disruptions involved in patients with generalized fixation-off epilepsy

OpenAIRE

Solana Sánchez, Ana Beatriz; Hernández Tamames, J.A.; Molina, E.; Martínez, K.; Pineda Pardo, José Ángel; Bruña Fernandez, Ricardo; Toledano, Rafael; San Antonio-Arce, Victoria; Garcia Morales, Irene; Gil Nagel, Antonio; Alfayate, E.; Álvarez Linera, Juan; Pozo Guerrero, Francisco del

2012-01-01

Fixation-off sensitivity (FOS) denotes the forms of epilepsy elicited by elimination of fixation. FOS-IGE patients are rare cases [1]. In a previous work [2] we showed that two FOS-IGE patients had different altered EEG rhythms when closing eyes; only beta band was altered in patient 1 while theta, alpha and beta were altered in patient 2. In the present work, we explain the relationship between the altered brain rhythms in these patients and the disruption in functional brain net...

Reading strategies in mild to moderate strabismic amblyopia: an eye movement investigation.

Science.gov (United States)

Kanonidou, Evgenia; Proudlock, Frank A; Gottlob, Irene

2010-07-01

PURPOSE. To investigate oculomotor strategies in strabismic amblyopia and evaluate abnormalities during monocular and binocular reading. METHODS. Eye movements were recorded with a head-mounted infrared video eye-tracker (250 Hz, amblyopia, reading is impaired, not only during monocular viewing with the amblyopic eye, but also with the nonamblyopic eye and binocularly, even though normal visual acuity pertains to the latter two conditions. The impaired reading performance is associated with differences in both the saccadic and fixational patterns, most likely as adaptation strategies to abnormal sensory experiences such as crowding and suppression.

Differences of accommodative responses between two eyes under binocular viewing condition mediated by polarizing glasses

Directory of Open Access Journals (Sweden)

Rui-Qing Wang

2016-04-01

Full Text Available AIM:To study the differences of accommodative responses between the two eyes under 3 different polarized viewing conditions. METHODS:Fifteen volunteers with emmetrope were recruited into this study(aged 18～38, 6 males and 9 females. Three different viewing conditions were set up by using polarizing glasses and liquid crystal display:(1right eye could see the visual target on the screen, but left eye cannot see it;(2left eye could see the visual target on the screen, but right eye cannot see it;(3both eyes could see the target. Accommodative responses were measured by infrared auto-refractor when fixating at the target at 5, 2, 1, 0.5 and 0.33m under the above 3 viewing conditions. The differences of accommodative responses under different viewing conditions were compared by using variance analysis of repeated measuring and t test. RESULTS:Significant differences of accommodative responses between the two eyes were found under condition(1and(2at all the fixating distance. The accommodative responses in used eyes which can see the visual target were higher than in non-used eyes which cannot see the visual target(PP>0.05. CONCLUSION:Ciliary muscles in the used eyes were more relatively tonic than non-used eyes under binocular open viewing condition. The imbalance of accommodative responses between two eyes may be one of the risk factors resulting into the occurrence of myopia.

Designs and Algorithms to Map Eye Tracking Data with Dynamic Multielement Moving Objects

Directory of Open Access Journals (Sweden)

Ziho Kang

2016-01-01

Full Text Available Design concepts and algorithms were developed to address the eye tracking analysis issues that arise when (1 participants interrogate dynamic multielement objects that can overlap on the display and (2 visual angle error of the eye trackers is incapable of providing exact eye fixation coordinates. These issues were addressed by (1 developing dynamic areas of interests (AOIs in the form of either convex or rectangular shapes to represent the moving and shape-changing multielement objects, (2 introducing the concept of AOI gap tolerance (AGT that controls the size of the AOIs to address the overlapping and visual angle error issues, and (3 finding a near optimal AGT value. The approach was tested in the context of air traffic control (ATC operations where air traffic controller specialists (ATCSs interrogated multiple moving aircraft on a radar display to detect and control the aircraft for the purpose of maintaining safe and expeditious air transportation. In addition, we show how eye tracking analysis results can differ based on how we define dynamic AOIs to determine eye fixations on moving objects. The results serve as a framework to more accurately analyze eye tracking data and to better support the analysis of human performance.

Eye tracking measures of uncertainty during perceptual decision making.

Science.gov (United States)

Brunyé, Tad T; Gardony, Aaron L

2017-10-01

Perceptual decision making involves gathering and interpreting sensory information to effectively categorize the world and inform behavior. For instance, a radiologist distinguishing the presence versus absence of a tumor, or a luggage screener categorizing objects as threatening or non-threatening. In many cases, sensory information is not sufficient to reliably disambiguate the nature of a stimulus, and resulting decisions are done under conditions of uncertainty. The present study asked whether several oculomotor metrics might prove sensitive to transient states of uncertainty during perceptual decision making. Participants viewed images with varying visual clarity and were asked to categorize them as faces or houses, and rate the certainty of their decisions, while we used eye tracking to monitor fixations, saccades, blinks, and pupil diameter. Results demonstrated that decision certainty influenced several oculomotor variables, including fixation frequency and duration, the frequency, peak velocity, and amplitude of saccades, and phasic pupil diameter. Whereas most measures tended to change linearly along with decision certainty, pupil diameter revealed more nuanced and dynamic information about the time course of perceptual decision making. Together, results demonstrate robust alterations in eye movement behavior as a function of decision certainty and attention demands, and suggest that monitoring oculomotor variables during applied task performance may prove valuable for identifying and remediating transient states of uncertainty. Published by Elsevier B.V.

Signalling properties of identified deep cerebellar nuclear neurons related to eye and head movements in the alert cat.

Science.gov (United States)

Gruart, A; Delgado-García, J M

1994-07-01

1. The spike activity of deep cerebellar nuclear neurons was recorded in the alert cat during spontaneous and during vestibularly and visually induced eye movements. 2. Neurons were classified according to their location in the nuclei, their antidromic activation from projection sites, their sensitivity to eye position and velocity during spontaneous eye movements, and their responses to vestibular and optokinetic stimuli. 3. Type I EPV (eye position and velocity) neurons were located mainly in the posterior part of the fastigial nucleus and activated antidromically almost exclusively from the medial longitudinal fasciculus close to the oculomotor complex. These neurons, reported here for the first time, increased their firing rate during saccades and eye fixations towards the contralateral hemifield. Their position sensitivity to eye fixations in the horizontal plane was 5.3 +/- 2.6 spikes s-1 deg-1 (mean +/- S.D.). Eye velocity sensitivity during horizontal saccades was 0.71 +/- 0.52 spikes s-1 deg-1 s-1. Variability of their firing rate during a given eye fixation was higher than that shown by abducens motoneurons. 4. Type I EPV neurons increased their firing rate during ipsilateral head rotations at 0.5 Hz with a mean phase lead over eye position of 95.3 +/- 9.5 deg. They were also activated by contralateral optokinetic stimulation at 30 deg s-1. Their sensitivity to eye position and velocity in the horizontal plane during vestibular and optokinetic stimuli yielded values similar to those obtained for spontaneous eye movements. 5. Type II neurons were located in both fastigial and dentate nuclei and were activated antidromically from the restiform body, the medial longitudinal fasciculus close to the oculomotor complex, the red nucleus and the pontine nuclei. Type II neurons were not related to spontaneous eye movements. These neurons increased their firing rate in response to contralateral head rotation and during ipsilateral optokinetic stimulation, and

EEG Eye State Identification Using Incremental Attribute Learning with Time-Series Classification

Directory of Open Access Journals (Sweden)

Ting Wang

2014-01-01

Full Text Available Eye state identification is a kind of common time-series classification problem which is also a hot spot in recent research. Electroencephalography (EEG is widely used in eye state classification to detect human's cognition state. Previous research has validated the feasibility of machine learning and statistical approaches for EEG eye state classification. This paper aims to propose a novel approach for EEG eye state identification using incremental attribute learning (IAL based on neural networks. IAL is a novel machine learning strategy which gradually imports and trains features one by one. Previous studies have verified that such an approach is applicable for solving a number of pattern recognition problems. However, in these previous works, little research on IAL focused on its application to time-series problems. Therefore, it is still unknown whether IAL can be employed to cope with time-series problems like EEG eye state classification. Experimental results in this study demonstrates that, with proper feature extraction and feature ordering, IAL can not only efficiently cope with time-series classification problems, but also exhibit better classification performance in terms of classification error rates in comparison with conventional and some other approaches.

Saccadic Eye Movement Improves Plantar Sensation and Postural Balance in Elderly Women.

Science.gov (United States)

Bae, Youngsook

2016-06-01

Vision, proprioception and plantar sensation contribute to the control of postural balance (PB). Reduced plantar sensation alters postural response and is at an increased risk of fall, and eye movements reduce the postural sway. Therefore, the aim of this study was to study the improvement of plantar sensation and PB after saccadic eye movement (SEM) and pursuit eye movement (PEM) in community-dwelling elderly women. Participants (104 females; 75.11 ± 6.25 years) were randomly allocated into the SEM group (n = 52) and PEM groups (n = 52). The SEM group performed eye fixation and SEM for 5 minutes, and the PEM group performed eye fixation and PEM for 5 minutes. The plantar sensation was measured according to the plantar surface area of the feet in contact with the floor surface before and after the intervention. Before and after SEM and PEM with the eyes open and closed, PB was measured as the area (mm(2)), length (cm), and velocity (cm/s) of the fluctuation of the center of pressure (COP). The plantar sensation of both feet improved in both groups (p eye open and close in both groups (p < 0.01). The length and velocity of the COP significantly decreased in the SEM group compared to the PEM group (p < 0.05). In conclusion, SEM and PEM are effective interventions for improving plantar sensation and PB in elderly women, with greater PB improvement after SEM.

Comparison of skeletal stability after sagittal split ramus osteotomy among mono-cortical plate fixation, bi-cortical plate fixation, and hybrid fixation using absorbable plates and screws.

Science.gov (United States)

Ueki, Koichiro; Moroi, Akinori; Yoshizawa, Kunio; Hotta, Asami; Tsutsui, Takamitsu; Fukaya, Kenichi; Hiraide, Ryota; Takayama, Akihiro; Tsunoda, Tatsuta; Saito, Yuki

2017-02-01

The purpose of this study was to examine skeletal stability and plate breakage after sagittal split ramus osteotomy (SSRO) with the mono-cortical plate fixation, bi-cortical plate fixation, and hybrid fixation techniques using absorbable plates and screws. A total of 76 Japanese patients diagnosed with mandibular prognathism with and without maxillary deformity were divided into 3 groups randomly. A total of 28 patients underwent SSRO with mono-cortical plate fixation, 23 underwent SSRO with bi-cortical plate fixation, and 25 underwent SSRO with hybrid fixation. Skeletal stability and horizontal condylar angle were analyzed by axial, frontal, and lateral cephalograms from before the operation to 1 year postoperatively. Breakage of the plate and screws was observed by 3-dimensional computed tomography (3DCT) immediately after surgery and after 1 year. Although there was a significant difference between the mono-cortical plate fixation group and hybrid fixation group regarding right MeAg in T1 (P = 0.0488) and occlusal plane in T1 (P = 0.0346), there were no significant differences between the groups for the other measurements in each time interval. In 2 cases, namely, 6 sides in the mono-cortical plate fixation group, breakage of the absorbable plate was found by 3DCT. However, there was no breakage in the bi-cortical plate fixation group and hybrid fixation group. This study results suggested that there were no significant differences in the postoperative skeletal stability among the 3 groups, and bi-cortical fixation as well as hybrid fixation was a reliable and useful method to prevent plate breakage even if an absorbable material was used. Copyright © 2016 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Complications are reduced with a protocol to standardize timing of fixation based on response to resuscitation.

Science.gov (United States)

Vallier, Heather A; Moore, Timothy A; Como, John J; Wilczewski, Patricia A; Steinmetz, Michael P; Wagner, Karl G; Smith, Charles E; Wang, Xiao-Feng; Dolenc, Andrea J

2015-10-01

Our group developed a protocol, entitled Early Appropriate Care (EAC), to determine timing of definitive fracture fixation based on presence and severity of metabolic acidosis. We hypothesized that utilization of EAC would result in fewer complications than a historical cohort and that EAC patients with definitive fixation within 36 h would have fewer complications than those treated at a later time. Three hundred thirty-five patients with mean age 39.2 years and mean Injury Severity Score (ISS) 26.9 and 380 fractures of the femur (n = 173), pelvic ring (n = 71), acetabulum (n = 57), and/or spine (n = 79) were prospectively evaluated. The EAC protocol recommended definitive fixation within 36 h if lactate <4.0 mmol/L, pH ≥7.25, or base excess (BE) ≥-5.5 mmol/L. Complications including infections, sepsis, DVT, organ failure, pneumonia, acute respiratory distress syndrome (ARDS), and pulmonary embolism (PE) were identified and compared for early and delayed patients and with a historical cohort. All 335 patients achieved the desired level of resuscitation within 36 h of injury. Two hundred sixty-nine (80%) were treated within 36 h, and 66 had protocol violations, treated on a delayed basis, due to surgeon choice in 71%. Complications occurred in 16.3% of patients fixed within 36 h and in 33.3% of delayed patients (p = 0.0009). Hospital and ICU stays were shorter in the early group: 9.5 versus 17.3 days and 4.4 versus 11.6 days, respectively, both p < 0.0001. This group of patients when compared with a historical cohort of 1443 similar patients with 1745 fractures had fewer complications (16.3 versus 22.1%, p = 0.017) and shorter length of stay (LOS) (p = 0.018). Our EAC protocol recommends definitive fixation within 36 h in resuscitated patients. Early fixation was associated with fewer complications and shorter LOS. The EAC recommendations are safe and effective for the majority of severely injured patients with mechanically

Graft fixation in cruciate ligament reconstruction.

Science.gov (United States)

Brand, J; Weiler, A; Caborn, D N; Brown, C H; Johnson, D L

2000-01-01

Cruciate ligament reconstruction has progressed dramatically in the last 20 years. Anatomic placement of ligament substitutes has fostered rehabilitation efforts that stress immediate and full range of motion, immediate weightbearing, neuromuscular strength and coordination, and early return to athletic competition (3 months). This has placed extreme importance on secure graft fixation at the time of ligament reconstruction. Current ligament substitutes require a bony or soft tissue component to be fixed within a bone tunnel or on the periosteum at a distance from the normal ligament attachment site. Fixation devices have progressed from metal to biodegradable and from far to near-normal native ligament attachment sites. Ideally, the biomechanical properties of the entire graft construct would approach those of the native ligament and facilitate biologic incorporation of the graft. Fixation should be done at the normal anatomic attachment site of the native ligament (aperture fixation) and, over time, allow the biologic return of the histologic transition zone from ligament to fibrocartilage, to calcified fibrocartilage, to bone. The purpose of this article is to review current fixation devices and techniques in cruciate ligament surgery.

Gaze shifts and fixations dominate gaze behavior of walking cats

Science.gov (United States)

Rivers, Trevor J.; Sirota, Mikhail G.; Guttentag, Andrew I.; Ogorodnikov, Dmitri A.; Shah, Neet A.; Beloozerova, Irina N.

2014-01-01

Vision is important for locomotion in complex environments. How it is used to guide stepping is not well understood. We used an eye search coil technique combined with an active marker-based head recording system to characterize the gaze patterns of cats walking over terrains of different complexity: (1) on a flat surface in the dark when no visual information was available, (2) on the flat surface in light when visual information was available but not required, (3) along the highly structured but regular and familiar surface of a horizontal ladder, a task for which visual guidance of stepping was required, and (4) along a pathway cluttered with many small stones, an irregularly structured surface that was new each day. Three cats walked in a 2.5 m corridor, and 958 passages were analyzed. Gaze activity during the time when the gaze was directed at the walking surface was subdivided into four behaviors based on speed of gaze movement along the surface: gaze shift (fast movement), gaze fixation (no movement), constant gaze (movement at the body’s speed), and slow gaze (the remainder). We found that gaze shifts and fixations dominated the cats’ gaze behavior during all locomotor tasks, jointly occupying 62–84% of the time when the gaze was directed at the surface. As visual complexity of the surface and demand on visual guidance of stepping increased, cats spent more time looking at the surface, looked closer to them, and switched between gaze behaviors more often. During both visually guided locomotor tasks, gaze behaviors predominantly followed a repeated cycle of forward gaze shift followed by fixation. We call this behavior “gaze stepping”. Each gaze shift took gaze to a site approximately 75–80 cm in front of the cat, which the cat reached in 0.7–1.2 s and 1.1–1.6 strides. Constant gaze occupied only 5–21% of the time cats spent looking at the walking surface. PMID:24973656

Analysis of clinical efficacy and complications of titanium mini plate internal fixation and reconstructive surgery for patients with orbital fracture

Directory of Open Access Journals (Sweden)

Yang Liu

2016-07-01

Full Text Available AIM: To analyze the clinical efficacy and complications of titanium mini plate internal fixation and reconstructive surgery for patients with orbital fracture. METHODS: Fifty-seven cases(60 eyeswith orbital fracture from March 2013 to April 2014 in our hospital were researched. According to the random number table method, the patients were divided into observation group(29 cases with 30 eyesand control group(28 cases with 30 eyes. The control group was treated with hydroxyapatite artificial bone plate for internal fixation, and the observation group with titanium mini plate internal fixation and reconstructive surgery. The diplopia grading, grading of ocular movement disorder before and at 1, 3mo after treatment and postoperative complications(prolapse, dislocation, infectionwere compared between the two groups. RESULTS: In both group, all the 60 eyes were healed without scar formation. The rate of diplopia grading as grade 0 1mo postoperatively of observation group and the control groups were 63% and 40%(PPPCONCLUSION: The clinical curative effect of titanium mini plate internal fixation and reconstructive surgery has a good effect for orbital fractures, which can improve the therapeutic effect and reduce the incidence of adverse reactions.

Comparison of Monolateral External Fixation and Internal Fixation for Skeletal Stabilisation in the Management of Small Tibial Bone Defects following Successful Treatment of Chronic Osteomyelitis.

Science.gov (United States)

Wang, Yicun; Jiang, Hui; Deng, Zhantao; Jin, Jiewen; Meng, Jia; Wang, Jun; Zhao, Jianning; Sun, Guojing; Qian, Hongbo

2017-01-01

To compare the salvage rate and complication between internal fixation and external fixation in patients with small bone defects caused by chronic infectious osteomyelitis debridement. 125 patients with chronic infectious osteomyelitis of tibia fracture who underwent multiple irrigation, debridement procedure, and local/systemic antibiotics were enrolled. Bone defects, which were less than 4 cm, were treated with bone grafting using either internal fixation or monolateral external fixation. 12-month follow-up was conducted with an interval of 3 months to evaluate union of bone defect. Patients who underwent monolateral external fixation had higher body mass index and fasting blood glucose, longer time since injury, and larger bone defect compared with internal fixation. No significant difference was observed in incidence of complications (23.5% versus 19.3%), surgery time (156 ± 23 minutes versus 162 ± 21 minutes), and time to union (11.1 ± 3.0 months versus 10.9 ± 3.1 months) between external fixation and internal fixation. Internal fixation had no significant influence on the occurrence of postoperation complications after multivariate adjustment when compared with external fixation. Furthermore, patients who underwent internal fixation experienced higher level of daily living scales and lower level of anxiety. It was relatively safe to use internal fixation for stabilization in osteomyelitis patients whose bone defects were less than 4 cm and infection was well controlled.

The amblyopic eye in subjects with anisometropia show increased saccadic latency in the delayed saccade task

Directory of Open Access Journals (Sweden)

Maciej ePerdziak

2014-10-01

Full Text Available The term amblyopia is used to describe reduced visual function in one eye (or both eyes, though not so often which cannot be fully improved by refractive correction and explained by the organic cause observed during regular eye examination. This developmental disorder of spatial vision affects about 2-5% of the population and is associated with abnormal visual experience (e.g. anisometropia, strabismus during infancy or early childhood. Several studies have shown prolongation of saccadic latency time in amblyopic eye. In our opinion, study of saccadic latency in the context of central vision deficits assessment, should be based on central retina stimulation. For this reason, we proposed saccade delayed task. It requires inhibitory processing for maintaining fixation on the central target until it disappears – what constitutes the GO signal for saccade. The experiment consisted of 100 trials for each eye and was performed under two viewing conditions: monocular amblyopic / non-dominant eye and monocular dominant eye. We examined saccadic latency in 16 subjects (mean age 30±11 years with anisometropic amblyopia (two subjects had also microtropia and in 17 control subjects (mean age 28±8 years. Participants were instructed to look at central (fixation target and when it disappears, to make the saccade toward the periphery (10 deg as fast as possible, either left or the right target. The study results have proved the significant difference in saccadic latency between the amblyopic (mean 262±48 ms and dominant (mean 237±45 ms eye, in anisometropic group. In the control group, the saccadic latency for dominant (mean 226±32ms and non-dominant (mean 230±29 ms eye was not significantly different.By the use of LATER (Linear Approach to the Threshold with Ergodic Rate decision model we interpret our findings as a decrease in accumulation of visual information acquired by means of central (affected retina in subjects with anisometropic amblyopia.

Seeing via miniature eye movements: A dynamic hypothesis for vision

Directory of Open Access Journals (Sweden)

Ehud eAhissar

2012-11-01

Full Text Available During natural viewing, the eyes are never still. Even during fixation, miniature movements of the eyes move the retinal image across tens of foveal photoreceptors. Most theories of vision implicitly assume that the visual system ignores these movements and somehow overcomes the resulting smearing. However, evidence has accumulated to indicate that fixational eye movements cannot be ignored by the visual system if fine spatial details are to be resolved. We argue that the only way the visual system can achieve its high resolution given its fixational movements is by seeing via these movements. Seeing via eye movements also eliminates the instability of the image, which would be induced by them otherwise. Here we present a hypothesis for vision, in which coarse details are spatially-encoded in gaze-related coordinates, and fine spatial details are temporally-encoded in relative retinal coordinates. The temporal encoding presented here achieves its highest resolution by encoding along the elongated axes of simple cell receptive fields and not across these axes as suggested by spatial models of vision. According to our hypothesis, fine details of shape are encoded by inter-receptor temporal phases, texture by instantaneous intra-burst rates of individual receptors, and motion by inter-burst temporal frequencies. We further describe the ability of the visual system to readout the encoded information and recode it internally. We show how reading out of retinal signals can be facilitated by neuronal phase-locked loops (NPLLs, which lock to the retinal jitter; this locking enables recoding of motion information and temporal framing of shape and texture processing. A possible implementation of this locking-and-recoding process by specific thalamocortical loops is suggested. Overall it is suggested that high-acuity vision is based primarily on temporal mechanisms of the sort presented here and low-acuity vision is based primarily on spatial mechanisms.

Eye movements during listening reveal spontaneous grammatical processing.

Science.gov (United States)

Huette, Stephanie; Winter, Bodo; Matlock, Teenie; Ardell, David H; Spivey, Michael

2014-01-01

Recent research using eye-tracking typically relies on constrained visual contexts in particular goal-oriented contexts, viewing a small array of objects on a computer screen and performing some overt decision or identification. Eyetracking paradigms that use pictures as a measure of word or sentence comprehension are sometimes touted as ecologically invalid because pictures and explicit tasks are not always present during language comprehension. This study compared the comprehension of sentences with two different grammatical forms: the past progressive (e.g., was walking), which emphasizes the ongoing nature of actions, and the simple past (e.g., walked), which emphasizes the end-state of an action. The results showed that the distribution and timing of eye movements mirrors the underlying conceptual structure of this linguistic difference in the absence of any visual stimuli or task constraint: Fixations were shorter and saccades were more dispersed across the screen, as if thinking about more dynamic events when listening to the past progressive stories. Thus, eye movement data suggest that visual inputs or an explicit task are unnecessary to solicit analog representations of features such as movement, that could be a key perceptual component to grammatical comprehension.

Eye movements during listening reveal spontaneous grammatical processing

Directory of Open Access Journals (Sweden)

Stephanie eHuette

2014-05-01

Full Text Available Recent research using eye-tracking typically relies on constrained visual contexts in particular goal-oriented contexts, viewing a small array of objects on a computer screen and performing some overt decision or identification. Eyetracking paradigms that use pictures as a measure of word or sentence comprehension are sometimes touted as ecologically invalid because pictures and explicit tasks are not always present during language comprehension. This study compared the comprehension of sentences with two different grammatical forms: the past progressive (e.g., was walking, which emphasizes the ongoing nature of actions, and the simple past (e.g., walked, which emphasizes the end-state of an action. The results showed that the distribution and timing of eye movements mirrors the underlying conceptual structure of this linguistic difference in the absence of any visual stimuli or task constraint: Fixations were shorter and saccades were more dispersed across the screen, as if thinking about more dynamic events when listening to the past progressive stories. Thus, eye movement data suggest that visual inputs or an explicit task are unnecessary to solicit analogue representations of features such as movement, that could be a key perceptual component to grammatical comprehension.

Distinct eye movement patterns enhance dynamic visual acuity

Science.gov (United States)

Palidis, Dimitrios J.; Wyder-Hodge, Pearson A.; Fooken, Jolande; Spering, Miriam

2017-01-01

Dynamic visual acuity (DVA) is the ability to resolve fine spatial detail in dynamic objects during head fixation, or in static objects during head or body rotation. This ability is important for many activities such as ball sports, and a close relation has been shown between DVA and sports expertise. DVA tasks involve eye movements, yet, it is unclear which aspects of eye movements contribute to successful performance. Here we examined the relation between DVA and the kinematics of smooth pursuit and saccadic eye movements in a cohort of 23 varsity baseball players. In a computerized dynamic-object DVA test, observers reported the location of the gap in a small Landolt-C ring moving at various speeds while eye movements were recorded. Smooth pursuit kinematics—eye latency, acceleration, velocity gain, position error—and the direction and amplitude of saccadic eye movements were linked to perceptual performance. Results reveal that distinct eye movement patterns—minimizing eye position error, tracking smoothly, and inhibiting reverse saccades—were related to dynamic visual acuity. The close link between eye movement quality and DVA performance has important implications for the development of perceptual training programs to improve DVA. PMID:28187157

Distinct eye movement patterns enhance dynamic visual acuity.

Science.gov (United States)

Palidis, Dimitrios J; Wyder-Hodge, Pearson A; Fooken, Jolande; Spering, Miriam

2017-01-01

Dynamic visual acuity (DVA) is the ability to resolve fine spatial detail in dynamic objects during head fixation, or in static objects during head or body rotation. This ability is important for many activities such as ball sports, and a close relation has been shown between DVA and sports expertise. DVA tasks involve eye movements, yet, it is unclear which aspects of eye movements contribute to successful performance. Here we examined the relation between DVA and the kinematics of smooth pursuit and saccadic eye movements in a cohort of 23 varsity baseball players. In a computerized dynamic-object DVA test, observers reported the location of the gap in a small Landolt-C ring moving at various speeds while eye movements were recorded. Smooth pursuit kinematics-eye latency, acceleration, velocity gain, position error-and the direction and amplitude of saccadic eye movements were linked to perceptual performance. Results reveal that distinct eye movement patterns-minimizing eye position error, tracking smoothly, and inhibiting reverse saccades-were related to dynamic visual acuity. The close link between eye movement quality and DVA performance has important implications for the development of perceptual training programs to improve DVA.

An eye movement study for identification of suitable font characters for presentation on a computer screen.

Science.gov (United States)

Banerjee, Jayeeta; Majumdar, Dhurjati; Majumdar, Deepti; Pal, Madhu Sudan

2010-06-01

We are experiencing a shifting of media: from the printed paper to the computer screen. This transition is modifying the process of how we read and understand a text. It is very difficult to conclude on suitability of font characters based upon subjective evaluation method only. Present study evaluates the effect of font type on human cognitive workload during perception of individual alphabets on a computer screen. Twenty six young subjects volunteered for this study. Here, subjects have been shown individual characters of different font types and their eye movements have been recorded. A binocular eye movement recorder was used for eye movement recording. The results showed that different eye movement parameters such as pupil diameter, number of fixations, fixation duration were less for font type Verdana. The present study recommends the use of font type Verdana for presentation of individual alphabets on various electronic displays in order to reduce cognitive workload.

Scleral fixation of a single-piece multifocal intraocular lens.

Science.gov (United States)

Can, Ertugrul; Basaran, M Resat; Gül, Adem

2013-01-01

We describe an ab interno technique for injector implantation of a one-piece multifocal intraocular lens (IOL). Transscleral fixation of multifocal posterior chamber IOL implantation using an injector with ab interno technique was performed in an eye of a 9-year-old girl who had undergone pars plana lensectomy 2 years before for bilateral lens subluxation with unknown etiology. No major complications were encountered during a 3-month follow-up of the patient and excellent centration was observed during the follow-up period. Her preoperative best spectacle-corrected distance visual acuity of 20/32 improved to uncorrected distance visual acuity of 20/25. Closed-loop design of IOL served the function of eyelets and position of the IOL was provided using only a 2-point fixation. Intraoperative position adjustment of the IOL provided an excellent centralization of multifocal IOL.

Social exclusion leads to attentional bias to emotional social information: Evidence from eye movement.

Science.gov (United States)

Chen, Zhuohao; Du, Jinchen; Xiang, Min; Zhang, Yan; Zhang, Shuyue

2017-01-01

Social exclusion has many effects on individuals, including the increased need to belong and elevated sensitivity to social information. Using a self-reporting method, and an eye-tracking technique, this study explored people's need to belong and attentional bias towards the socio-emotional information (pictures of positive and negative facial expressions compared to those of emotionally-neutral expressions) after experiencing a brief episode of social exclusion. We found that: (1) socially-excluded individuals reported higher negative emotions, lower positive emotions, and stronger need to belong than those who were not socially excluded; (2) compared to a control condition, social exclusion caused a longer response time to probe dots after viewing positive or negative face images; (3) social exclusion resulted in a higher frequency ratio of first attentional fixation on both positive and negative emotional facial pictures (but not on the neutral pictures) than the control condition; (4) in the social exclusion condition, participants showed shorter first fixation latency and longer first fixation duration to positive pictures than neutral ones but this effect was not observed for negative pictures; (5) participants who experienced social exclusion also showed longer gazing duration on the positive pictures than those who did not; although group differences also existed for the negative pictures, the gaze duration bias from both groups showed no difference from chance. This study demonstrated the emotional response to social exclusion as well as characterising multiple eye-movement indicators of attentional bias after experiencing social exclusion.

Attentional bias to betel quid cues: An eye tracking study.

Science.gov (United States)

Shen, Bin; Chiu, Meng-Chun; Li, Shuo-Heng; Huang, Guo-Joe; Liu, Ling-Jun; Ho, Ming-Chou

2016-09-01

The World Health Organization regards betel quid as a human carcinogen, and DSM-IV and ICD-10 dependence symptoms may develop with heavy use. This study, conducted in central Taiwan, investigated whether betel quid chewers can exhibit overt orienting to selectively respond to the betel quid cues. Twenty-four male chewers' and 23 male nonchewers' eye movements to betel-quid-related pictures and matched pictures were assessed during a visual probe task. The eye movement index showed that betel quid chewers were more likely to initially direct their gaze to the betel quid cues, t(23) = 3.70, p betel quid chewers' attentional bias. The results demonstrated that the betel quid chewers (but not the nonchewers) were more likely to initially direct their gaze to the betel quid cues, and spent more time and were more fixated on them. These findings suggested that when attention is directly measured through the eye tracking technique, this methodology may be more sensitive to detecting attentional biases in betel quid chewers. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Real-time eye lens dose monitoring during cerebral angiography procedures

Energy Technology Data Exchange (ETDEWEB)

Safari, M.J.; Wong, J.H.D.; Kadir, K.A.A.; Ng, K.H. [University of Malaya, Department of Biomedical Imaging, Faculty of Medicine, Kuala Lumpur (Malaysia); University of Malaya, University of Malaya Research Imaging Centre (UMRIC), Faculty of Medicine, Kuala Lumpur (Malaysia); Thorpe, N.K.; Cutajar, D.L.; Petasecca, M.; Lerch, M.L.F.; Rosenfeld, A.B. [University of Wollongong, Centre for Medical Radiation Physics (CMRP), Wollongong, NSW (Australia)

2016-01-15

To develop a real-time dose-monitoring system to measure the patient's eye lens dose during neuro-interventional procedures. Radiation dose received at left outer canthus (LOC) and left eyelid (LE) were measured using Metal-Oxide-Semiconductor Field-Effect Transistor dosimeters on 35 patients who underwent diagnostic or cerebral embolization procedures. The radiation dose received at the LOC region was significantly higher than the dose received by the LE. The maximum eye lens dose of 1492 mGy was measured at LOC region for an AVM case, followed by 907 mGy for an aneurysm case and 665 mGy for a diagnostic angiography procedure. Strong correlations (shown as R{sup 2}) were observed between kerma-area-product and measured eye doses (LOC: 0.78, LE: 0.68). Lateral and frontal air-kerma showed strong correlations with measured dose at LOC (AK{sub L}: 0.93, AK{sub F}: 0.78) and a weak correlation with measured dose at LE. A moderate correlation was observed between fluoroscopic time and dose measured at LE and LOC regions. The MOSkin dose-monitoring system represents a new tool enabling real-time monitoring of eye lens dose during neuro-interventional procedures. This system can provide interventionalists with information needed to adjust the clinical procedure to control the patient's dose. (orig.)

Real-time eye lens dose monitoring during cerebral angiography procedures

International Nuclear Information System (INIS)

Safari, M.J.; Wong, J.H.D.; Kadir, K.A.A.; Ng, K.H.; Thorpe, N.K.; Cutajar, D.L.; Petasecca, M.; Lerch, M.L.F.; Rosenfeld, A.B.

2016-01-01

To develop a real-time dose-monitoring system to measure the patient's eye lens dose during neuro-interventional procedures. Radiation dose received at left outer canthus (LOC) and left eyelid (LE) were measured using Metal-Oxide-Semiconductor Field-Effect Transistor dosimeters on 35 patients who underwent diagnostic or cerebral embolization procedures. The radiation dose received at the LOC region was significantly higher than the dose received by the LE. The maximum eye lens dose of 1492 mGy was measured at LOC region for an AVM case, followed by 907 mGy for an aneurysm case and 665 mGy for a diagnostic angiography procedure. Strong correlations (shown as R 2 ) were observed between kerma-area-product and measured eye doses (LOC: 0.78, LE: 0.68). Lateral and frontal air-kerma showed strong correlations with measured dose at LOC (AK L : 0.93, AK F : 0.78) and a weak correlation with measured dose at LE. A moderate correlation was observed between fluoroscopic time and dose measured at LE and LOC regions. The MOSkin dose-monitoring system represents a new tool enabling real-time monitoring of eye lens dose during neuro-interventional procedures. This system can provide interventionalists with information needed to adjust the clinical procedure to control the patient's dose. (orig.)

[Results of femoral lengthening over an intramedullary nail and external fixator].

Science.gov (United States)

Jasiewicz, Barbara; Kacki, Wojciech; Tesiorowski, Maciej; Potaczek, Tomasz

2008-01-01

Current techniques of operative limb lengthening usually are based on distraction osteogenesis. One of the techniques is limb lengthening over an intramedullary nail. The goal of this study is to evaluate the results of femoral lengthening over an intramedullary nail. Between 1999 and 200619 femoral "over nail" lengthenings were performed. There were 7 males and 12 females. Mean patients' age at surgery was 15.8 years, and mean initial femoral shortening was 5.1 cm. Operative technique consisted of one-stage implantation of intramedullary nail and external fixator. Ilizarov apparatus was used in 9 patients, monolateral fixator in 10 cases--ORTHOFIX in 9 patients, Wagner fixator--in 1 patient. Intramedullary nail was locked proximally with screws or Schanz pins from external fixator. After distraction phase, external fixator was removed and distal locking screws were applied. Evaluation criteria: obtained lengthening, time of external fixator, treatment time, healing index, external fixation index, range of motion in hip and knee joints and complications according to Paley. The mean lengthening was 4.6 cm, and mean distraction time was 66.6 days. Mean time of external fixation was 115.5 days, and external fixation index was 26.2 days for centimeter. Healing index was 36.9 days for centimeter. In cases with monolateral fixator, healing index did not differ with the whole group. During treatment 18 complications occurred, for a rate of 0.9 complication per segment. Lengthening over an intramedullary nail reduces the time of external fixator. Over nail femoral lengthening can prevent axis deviation following regenerate bending. Complication rate is similar to lengthenings with the classic Ilizarov technique. There are no differences in the treatment time in relation to the type of external fixator.

Scene perception in posterior cortical atrophy: categorization, description and fixation patterns.

Science.gov (United States)

Shakespeare, Timothy J; Yong, Keir X X; Frost, Chris; Kim, Lois G; Warrington, Elizabeth K; Crutch, Sebastian J

2013-01-01

Partial or complete Balint's syndrome is a core feature of the clinico-radiological syndrome of posterior cortical atrophy (PCA), in which individuals experience a progressive deterioration of cortical vision. Although multi-object arrays are frequently used to detect simultanagnosia in the clinical assessment and diagnosis of PCA, to date there have been no group studies of scene perception in patients with the syndrome. The current study involved three linked experiments conducted in PCA patients and healthy controls. Experiment 1 evaluated the accuracy and latency of complex scene perception relative to individual faces and objects (color and grayscale) using a categorization paradigm. PCA patients were both less accurate (faces < scenes < objects) and slower (scenes < objects < faces) than controls on all categories, with performance strongly associated with their level of basic visual processing impairment; patients also showed a small advantage for color over grayscale stimuli. Experiment 2 involved free description of real world scenes. PCA patients generated fewer features and more misperceptions than controls, though perceptual errors were always consistent with the patient's global understanding of the scene (whether correct or not). Experiment 3 used eye tracking measures to compare patient and control eye movements over initial and subsequent fixations of scenes. Patients' fixation patterns were significantly different to those of young and age-matched controls, with comparable group differences for both initial and subsequent fixations. Overall, these findings describe the variability in everyday scene perception exhibited by individuals with PCA, and indicate the importance of exposure duration in the perception of complex scenes.

Scene perception in Posterior Cortical Atrophy: categorisation, description and fixation patterns

Directory of Open Access Journals (Sweden)

Timothy J Shakespeare

2013-10-01

Full Text Available Partial or complete Balint’s syndrome is a core feature of the clinico-radiological syndrome of posterior cortical atrophy (PCA, in which individuals experience a progressive deterioration of cortical vision. Although multi-object arrays are frequently used to detect simultanagnosia in the clinical assessment and diagnosis of PCA, to date there have been no group studies of scene perception in patients with the syndrome. The current study involved three linked experiments conducted in PCA patients and healthy controls. Experiment 1 evaluated the accuracy and latency of complex scene perception relative to individual faces and objects (colour and greyscale using a categorisation paradigm. PCA patients were both less accurate (faceseye tracking measures to compare patient and control eye movements over initial and subsequent fixations of scenes. Patients’ fixation patterns were significantly different to those of young and age-matched controls, with comparable group differences for both initial and subsequent fixations. Overall, these findings describe the variability in everyday scene perception exhibited by individuals with PCA, and indicate the importance of exposure duration in the perception of complex scenes.

Individual differences in language ability are related to variation in word recognition, not speech perception: Evidence from eye-movements

Science.gov (United States)

McMurray, Bob; Munson, Cheyenne; Tomblin, J. Bruce

2013-01-01

Purpose This study examined speech perception deficits associated with individual differences in language ability contrasting auditory, phonological or lexical accounts by asking if lexical competition is differentially sensitive to fine-grained acoustic variation. Methods 74 adolescents with a range of language abilities (including 35 impaired) participated in an experiment based on McMurray, Tanenhaus and Aslin (2002). Participants heard tokens from six 9-step Voice Onset Time (VOT) continua spanning two words (beach/peach, beak/peak, etc), while viewing a screen containing pictures of those words and two unrelated objects. Participants selected the referent while eye-movements to each picture were monitored as a measure of lexical activation. Fixations were examined as a function of both VOT and language ability. Results Eye-movements were sensitive to within-category VOT differences: as VOT approached the boundary, listeners made more fixations to the competing word. This did not interact with language ability, suggesting that language impairment is not associated with differential auditory sensitivity or phonetic categorization. Listeners with poorer language skills showed heightened competitors fixations overall, suggesting a deficit in lexical processes. Conclusions Language impairment may be better characterized by a deficit in lexical competition (inability to suppress competing words), rather than differences phonological categorization or auditory abilities. PMID:24687026

Individual differences in language ability are related to variation in word recognition, not speech perception: evidence from eye movements.

Science.gov (United States)

McMurray, Bob; Munson, Cheyenne; Tomblin, J Bruce

2014-08-01

The authors examined speech perception deficits associated with individual differences in language ability, contrasting auditory, phonological, or lexical accounts by asking whether lexical competition is differentially sensitive to fine-grained acoustic variation. Adolescents with a range of language abilities (N = 74, including 35 impaired) participated in an experiment based on McMurray, Tanenhaus, and Aslin (2002). Participants heard tokens from six 9-step voice onset time (VOT) continua spanning 2 words (beach/peach, beak/peak, etc.) while viewing a screen containing pictures of those words and 2 unrelated objects. Participants selected the referent while eye movements to each picture were monitored as a measure of lexical activation. Fixations were examined as a function of both VOT and language ability. Eye movements were sensitive to within-category VOT differences: As VOT approached the boundary, listeners made more fixations to the competing word. This did not interact with language ability, suggesting that language impairment is not associated with differential auditory sensitivity or phonetic categorization. Listeners with poorer language skills showed heightened competitors fixations overall, suggesting a deficit in lexical processes. Language impairment may be better characterized by a deficit in lexical competition (inability to suppress competing words), rather than differences in phonological categorization or auditory abilities.

External fixation of "intertrochanteric" fractures.

Science.gov (United States)

Gani, Naseem Ul; Kangoo, Khursheed Ahmed; Bashir, Arshad; Muzaffer, Rahil; Bhat, Mohammad Farooq; Farooq, Munir; Badoo, Abdul Rashid; Dar, Imtiyaz Hussian; Wani, Mudassir Maqbool

2009-10-10

In developing countries, due to limited availability of modern anesthesia and overcrowding of the hospitals with patients who need surgery, high-risk patients with "intertrochanteric" fractures remain unsuita ble for open reduction and internal fixation.The aim of this study was to analyze the results of external fixation of "intertrochanteric" fractures in high-risk geriatric patients in a developing country.The results of 62 ambulatory high-risk geriatric patients with a mean age of 70 years (range 58-90 years) with "intertrochanteric" fractures, in whom external fixation was performed, are reported.Eight patients died during follow-up due to medical causes unrelated to the surgical procedure. So only 54 patients were available for final assessment. Procedure is simple, performed under local anesthesia, requires less time for surgery and is associated with less blood loss. Good fixation and early ambulation was achieved in most of the patients. Average time to union was 14 weeks. Thirty-one patients developed superficial pin tract infection and 28 patients had average shortening of 15 mm due to impaction and varus angulation. Functional outcome was assessed using Judet's point system. Good to excellent results were achieved in 44 patients.This study demonstrated that external fixation of "intertrochantric" fractures performed under local anesthesia offers significant advantage in ambulatory high-risk geriatric patients especially in a developing country.

Studying the role of vision in cycling : critique on restricting research to fixation behaviour.

NARCIS (Netherlands)

Schepers, J.P. Brinker, B.P.L.M. den Waard, D. de Twisk, D.A.M. Schwab, D.A.M. & Smeets, J.B.J.

2013-01-01

In a recent study published in Accident Analysis & Prevention, Vansteenkiste et al. (2013, http://dx.doi.org/10.1016/j.aap.2012.11.025) – as one of the first in this field – investigated the visual control of bicycle steering. They undertook the interesting task of testing cyclists’ eye fixation

Gaze3DFix: Detecting 3D fixations with an ellipsoidal bounding volume.

Science.gov (United States)

Weber, Sascha; Schubert, Rebekka S; Vogt, Stefan; Velichkovsky, Boris M; Pannasch, Sebastian

2017-10-26

Nowadays, the use of eyetracking to determine 2-D gaze positions is common practice, and several approaches to the detection of 2-D fixations exist, but ready-to-use algorithms to determine eye movements in three dimensions are still missing. Here we present a dispersion-based algorithm with an ellipsoidal bounding volume that estimates 3D fixations. Therefore, 3D gaze points are obtained using a vector-based approach and are further processed with our algorithm. To evaluate the accuracy of our method, we performed experimental studies with real and virtual stimuli. We obtained good congruence between stimulus position and both the 3D gaze points and the 3D fixation locations within the tested range of 200-600 mm. The mean deviation of the 3D fixations from the stimulus positions was 17 mm for the real as well as for the virtual stimuli, with larger variances at increasing stimulus distances. The described algorithms are implemented in two dynamic linked libraries (Gaze3D.dll and Fixation3D.dll), and we provide a graphical user interface (Gaze3DFixGUI.exe) that is designed for importing 2-D binocular eyetracking data and calculating both 3D gaze points and 3D fixations using the libraries. The Gaze3DFix toolkit, including both libraries and the graphical user interface, is available as open-source software at https://github.com/applied-cognition-research/Gaze3DFix .

Time and Space Partitioning the EagleEye Reference Misson

Science.gov (United States)

Bos, Victor; Mendham, Peter; Kauppinen, Panu; Holsti, Niklas; Crespo, Alfons; Masmano, Miguel; de la Puente, Juan A.; Zamorano, Juan

2013-08-01

We discuss experiences gained by porting a Software Validation Facility (SVF) and a satellite Central Software (CSW) to a platform with support for Time and Space Partitioning (TSP). The SVF and CSW are part of the EagleEye Reference mission of the European Space Agency (ESA). As a reference mission, EagleEye is a perfect candidate to evaluate practical aspects of developing satellite CSW for and on TSP platforms. The specific TSP platform we used consists of a simulated LEON3 CPU controlled by the XtratuM separation micro-kernel. On top of this, we run five separate partitions. Each partition runs its own real-time operating system or Ada run-time kernel, which in turn are running the application software of the CSW. We describe issues related to partitioning; inter-partition communication; scheduling; I/O; and fault-detection, isolation, and recovery (FDIR).

Object based implicit contextual learning: a study of eye movements.

Science.gov (United States)

van Asselen, Marieke; Sampaio, Joana; Pina, Ana; Castelo-Branco, Miguel

2011-02-01

Implicit contextual cueing refers to a top-down mechanism in which visual search is facilitated by learned contextual features. In the current study we aimed to investigate the mechanism underlying implicit contextual learning using object information as a contextual cue. Therefore, we measured eye movements during an object-based contextual cueing task. We demonstrated that visual search is facilitated by repeated object information and that this reduction in response times is associated with shorter fixation durations. This indicates that by memorizing associations between objects in our environment we can recognize objects faster, thereby facilitating visual search.

Stereotactic radiotherapy for choroidal melanoma: analysis of eye movement during treatment

Energy Technology Data Exchange (ETDEWEB)

Souza, Felipe Marques Lucas de; Gonçalves, Odair Dias; Cardoso, Simone Coutinho, E-mail: felipemlucas@poli.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Batista, Delano V.S. [Instituto de Radioproteção e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2017-07-01

This study aims to analyze the eye’s movement during radiotherapy treatment for choroidal melanoma, as well as the methodology used in the repositioning of the patient between treatments sessions. For this purpose, the procedures used by the hospital staff were analyzed on site and videos were recorded during the treatments. The methodology for the fixation of the eye is correct in its objective. However, the repositioning needs improvements in its reproducibility. It is recommended the study to fix the eye by the healthy eye and the feasibility study for the development of a software that assists in patient repositioning. (author)

Stereotactic radiotherapy for choroidal melanoma: analysis of eye movement during treatment

International Nuclear Information System (INIS)

Souza, Felipe Marques Lucas de; Gonçalves, Odair Dias; Cardoso, Simone Coutinho; Batista, Delano V.S.

2017-01-01

This study aims to analyze the eye’s movement during radiotherapy treatment for choroidal melanoma, as well as the methodology used in the repositioning of the patient between treatments sessions. For this purpose, the procedures used by the hospital staff were analyzed on site and videos were recorded during the treatments. The methodology for the fixation of the eye is correct in its objective. However, the repositioning needs improvements in its reproducibility. It is recommended the study to fix the eye by the healthy eye and the feasibility study for the development of a software that assists in patient repositioning. (author)

Stereotactic radiotherapy for choroidal melanoma: analysis of eye movement during treatment

Science.gov (United States)

Souza, F. M. L.; Gonçalves, O. D.; Batista, D. V. S.; Cardoso, S. C.

2018-03-01

This study aims to analyse the eye’s movement during radiotherapy treatment for choroidal melanoma, as well as the methodology used in the repositioning of the patient between treatments sessions. For this purpose, the procedures used by the hospital staff were analysed on site and videos were recorded during the treatments. The methodology for the fixation of the eye is correct in its objective. However, the repositioning needs improvements in its reproducibility. It is recommended the study to fix the eye by the healthy eye and the feasibility study for the development of a software that assists in patient repositioning.

Eye movement instructions modulate motion illusion and body sway with Op Art.

Science.gov (United States)

Kapoula, Zoï; Lang, Alexandre; Vernet, Marine; Locher, Paul

2015-01-01

Op Art generates illusory visual motion. It has been proposed that eye movements participate in such illusion. This study examined the effect of eye movement instructions (fixation vs. free exploration) on the sensation of motion as well as the body sway of subjects viewing Op Art paintings. Twenty-eight healthy adults in orthostatic stance were successively exposed to three visual stimuli consisting of one figure representing a cross (baseline condition) and two Op Art paintings providing sense of motion in depth-Bridget Riley's Movements in Squares and Akiyoshi Kitaoka's Rollers. Before their exposure to the Op Art images, participants were instructed either to fixate at the center of the image (fixation condition) or to explore the artwork (free viewing condition). Posture was measured for 30 s per condition using a body fixed sensor (accelerometer). The major finding of this study is that the two Op Art paintings induced a larger antero-posterior body sway both in terms of speed and displacement and an increased motion illusion in the free viewing condition as compared to the fixation condition. For body sway, this effect was significant for the Riley painting, while for motion illusion this effect was significant for Kitaoka's image. These results are attributed to macro-saccades presumably occurring under free viewing instructions, and most likely to the small vergence drifts during fixations following the saccades; such movements in interaction with visual properties of each image would increase either the illusory motion sensation or the antero-posterior body sway.

Motorized injector-assisted intrascleral intraocular lens fixation.

Science.gov (United States)

Hung, Jia-Horung; Wang, Shih-Hao; Teng, Yu-Ti; Hsu, Sheng-Min

2017-03-01

For eyes with deficient capsular support, intraocular lens (IOL) implantation has long been a technical challenge. Recently, intrascleral fixation of the haptics of a three-piece posterior chamber IOL has become a popular option. In this procedure, externalization of the leading haptic during IOL injection is a stressful step. We present a modified technique to improve the ease and safety of this step. Our modified technique involves IOL injection with a motorized injector with several important modifications described here. With these modifications, a surgeon can easily maintain the correct orientation of the IOL in a well-controlled manner during IOL injection. The records of 13 patients who underwent this technique were retrospectively evaluated. Corrected-distance visual acuity improved significantly after surgery (pIOL decentration, or vitreous hemorrhage was noted during the follow-up period. In conclusion, the motorized injector-assisted intrascleral IOL fixation technique is a safe and effective alternative to the conventional procedure. This technique makes the process of leading haptic externalization easier and more controllable. Copyright © 2017. Published by Elsevier Taiwan.

Motorized injector-assisted intrascleral intraocular lens fixation

Directory of Open Access Journals (Sweden)

Jia-Horung Hung

2017-03-01

Full Text Available For eyes with deficient capsular support, intraocular lens (IOL implantation has long been a technical challenge. Recently, intrascleral fixation of the haptics of a three-piece posterior chamber IOL has become a popular option. In this procedure, externalization of the leading haptic during IOL injection is a stressful step. We present a modified technique to improve the ease and safety of this step. Our modified technique involves IOL injection with a motorized injector with several important modifications described here. With these modifications, a surgeon can easily maintain the correct orientation of the IOL in a well-controlled manner during IOL injection. The records of 13 patients who underwent this technique were retrospectively evaluated. Corrected-distance visual acuity improved significantly after surgery (p<0.05. No postoperative retinal detachment, endophthalmitis, IOL decentration, or vitreous hemorrhage was noted during the follow-up period. In conclusion, the motorized injector-assisted intrascleral IOL fixation technique is a safe and effective alternative to the conventional procedure. This technique makes the process of leading haptic externalization easier and more controllable.

The influence of artificial scotomas on eye movements during visual search

NARCIS (Netherlands)

Cornelissen, FW; Bruin, KJ; Kooijman, AC

Purpose. Fixation durations are normally adapted to the difficulty of the foveal analysis task. We examine to what extent artificial central and peripheral visual field defects interfere with this adaptation process. Methods. Subjects performed a visual search task while their eye movements were

An Analysis of the Time Course of Lexical Processing during Reading

Science.gov (United States)

Sheridan, Heather; Reichle, Erik D.

2016-01-01

Reingold, Reichle, Glaholt, and Sheridan (2012) reported a gaze-contingent eye-movement experiment in which survival-curve analyses were used to examine the effects of word frequency, the availability of parafoveal preview, and initial fixation location on the time course of lexical processing. The key results of these analyses suggest that…

Eye movement assessment of selective attentional capture by emotional pictures.

Science.gov (United States)

Nummenmaa, Lauri; Hyönä, Jukka; Calvo, Manuel G

2006-05-01

The eye-tracking method was used to assess attentional orienting to and engagement on emotional visual scenes. In Experiment 1, unpleasant, neutral, or pleasant target pictures were presented simultaneously with neutral control pictures in peripheral vision under instruction to compare pleasantness of the pictures. The probability of first fixating an emotional picture, and the frequency of subsequent fixations, were greater than those for neutral pictures. In Experiment 2, participants were instructed to avoid looking at the emotional pictures, but these were still more likely to be fixated first and gazed longer during the first-pass viewing than neutral pictures. Low-level visual features cannot explain the results. It is concluded that overt visual attention is captured by both unpleasant and pleasant emotional content. 2006 APA, all rights reserved

Biasing moral decisions by exploiting the dynamics of eye gaze.

Science.gov (United States)

Pärnamets, Philip; Johansson, Petter; Hall, Lars; Balkenius, Christian; Spivey, Michael J; Richardson, Daniel C

2015-03-31

Eye gaze is a window onto cognitive processing in tasks such as spatial memory, linguistic processing, and decision making. We present evidence that information derived from eye gaze can be used to change the course of individuals' decisions, even when they are reasoning about high-level, moral issues. Previous studies have shown that when an experimenter actively controls what an individual sees the experimenter can affect simple decisions with alternatives of almost equal valence. Here we show that if an experimenter passively knows when individuals move their eyes the experimenter can change complex moral decisions. This causal effect is achieved by simply adjusting the timing of the decisions. We monitored participants' eye movements during a two-alternative forced-choice task with moral questions. One option was randomly predetermined as a target. At the moment participants had fixated the target option for a set amount of time we terminated their deliberation and prompted them to choose between the two alternatives. Although participants were unaware of this gaze-contingent manipulation, their choices were systematically biased toward the target option. We conclude that even abstract moral cognition is partly constituted by interactions with the immediate environment and is likely supported by gaze-dependent decision processes. By tracking the interplay between individuals, their sensorimotor systems, and the environment, we can influence the outcome of a decision without directly manipulating the content of the information available to them.

Fixations on objects in natural scenes: dissociating importance from salience

Directory of Open Access Journals (Sweden)

Bernard Marius e’t Hart

2013-07-01

Full Text Available The relation of selective attention to understanding of natural scenes has been subject to intense behavioral research and computational modeling, and gaze is often used as a proxy for such attention. The probability of an image region to be fixated typically correlates with its contrast. However, this relation does not imply a causal role of contrast. Rather, contrast may relate to an object’s importance for a scene, which in turn drives attention. Here we operationalize importance by the probability that an observer names the object as characteristic for a scene. We modify luminance contrast of either a frequently named (common/important or a rarely named (rare/unimportant object, track the observers’ eye movements during scene viewing and ask them to provide keywords describing the scene immediately after.When no object is modified relative to the background, important objects draw more fixations than unimportant ones. Increases of contrast make an object more likely to be fixated, irrespective of whether it was important for the original scene, while decreases in contrast have little effect on fixations. Any contrast modification makes originally unimportant objects more important for the scene. Finally, important objects are fixated more centrally than unimportant objects, irrespective of contrast.Our data suggest a dissociation between object importance (relevance for the scene and salience (relevance for attention. If an object obeys natural scene statistics, important objects are also salient. However, when natural scene statistics are violated, importance and salience are differentially affected. Object salience is modulated by the expectation about object properties (e.g., formed by context or gist, and importance by the violation of such expectations. In addition, the dependence of fixated locations within an object on the object’s importance suggests an analogy to the effects of word frequency on landing positions in reading.

Real-time inference of word relevance from electroencephalogram and eye gaze

Science.gov (United States)

Wenzel, M. A.; Bogojeski, M.; Blankertz, B.

2017-10-01

Objective. Brain-computer interfaces can potentially map the subjective relevance of the visual surroundings, based on neural activity and eye movements, in order to infer the interest of a person in real-time. Approach. Readers looked for words belonging to one out of five semantic categories, while a stream of words passed at different locations on the screen. It was estimated in real-time which words and thus which semantic category interested each reader based on the electroencephalogram (EEG) and the eye gaze. Main results. Words that were subjectively relevant could be decoded online from the signals. The estimation resulted in an average rank of 1.62 for the category of interest among the five categories after a hundred words had been read. Significance. It was demonstrated that the interest of a reader can be inferred online from EEG and eye tracking signals, which can potentially be used in novel types of adaptive software, which enrich the interaction by adding implicit information about the interest of the user to the explicit interaction. The study is characterised by the following novelties. Interpretation with respect to the word meaning was necessary in contrast to the usual practice in brain-computer interfacing where stimulus recognition is sufficient. The typical counting task was avoided because it would not be sensible for implicit relevance detection. Several words were displayed at the same time, in contrast to the typical sequences of single stimuli. Neural activity was related with eye tracking to the words, which were scanned without restrictions on the eye movements.

Optical eye tracking system for real-time noninvasive tumor localization in external beam radiotherapy.

Science.gov (United States)

Via, Riccardo; Fassi, Aurora; Fattori, Giovanni; Fontana, Giulia; Pella, Andrea; Tagaste, Barbara; Riboldi, Marco; Ciocca, Mario; Orecchia, Roberto; Baroni, Guido

2015-05-01

External beam radiotherapy currently represents an important therapeutic strategy for the treatment of intraocular tumors. Accurate target localization and efficient compensation of involuntary eye movements are crucial to avoid deviations in dose distribution with respect to the treatment plan. This paper describes an eye tracking system (ETS) based on noninvasive infrared video imaging. The system was designed for capturing the tridimensional (3D) ocular motion and provides an on-line estimation of intraocular lesions position based on a priori knowledge coming from volumetric imaging. Eye tracking is performed by localizing cornea and pupil centers on stereo images captured by two calibrated video cameras, exploiting eye reflections produced by infrared illumination. Additionally, torsional eye movements are detected by template matching in the iris region of eye images. This information allows estimating the 3D position and orientation of the eye by means of an eye local reference system. By combining ETS measurements with volumetric imaging for treatment planning [computed tomography (CT) and magnetic resonance (MR)], one is able to map the position of the lesion to be treated in local eye coordinates, thus enabling real-time tumor referencing during treatment setup and irradiation. Experimental tests on an eye phantom and seven healthy subjects were performed to assess ETS tracking accuracy. Measurements on phantom showed an overall median accuracy within 0.16 mm and 0.40° for translations and rotations, respectively. Torsional movements were affected by 0.28° median uncertainty. On healthy subjects, the gaze direction error ranged between 0.19° and 0.82° at a median working distance of 29 cm. The median processing time of the eye tracking algorithm was 18.60 ms, thus allowing eye monitoring up to 50 Hz. A noninvasive ETS prototype was designed to perform real-time target localization and eye movement monitoring during ocular radiotherapy treatments. The

Fixation-free assessment of the Hirschberg ratio.

Science.gov (United States)

Model, Dmitri; Eizenman, Moshe; Sturm, Veit

2010-08-01

To describe a novel methodology by which to measure the Hirschberg ratio (HR) in infants. The methodology does not require fixation on specific points, and measurements are made while infants look naturally at a display. The HR is calculated automatically from measurements of the direction of the optical axis, the position of the pupil center, and corneal reflexes in video images from an advanced two-camera eye-tracking system. The performance of the novel fixation-free procedure (FFP) was evaluated in 43 adults by measuring the average difference and the 95% limits of agreement with the standard fixation-based procedure (FBP). Repeatability of the HR measurements was evaluated by assessing the 95% limits of agreement between two independent measurements. Performance of the FFP was also evaluated in five infants. In adults, the average HR was 12.89 +/- 1.22 degrees/mm for FFP and 12.81 +/- 1.22 degrees/mm for FBP. FFP and FBP measurements were highly correlated (r = 0.95; P limits of agreement between FFP and FBP were +/-0.86 degrees/mm. The 95% limits of agreement of repeated measurements were +/-0.66 degrees/mm for FFP and +/-0.77 degrees/mm for FBP. In infants, the 95% limits of agreement of repeated measurements by FFP were +/-0.63 degrees/mm. In adults, the FFP provides accurate measurements of the HR that are in excellent agreement with measurements by FBP. In infants, measurements of HR by FFP show the same repeatability and consistency.

Adaptation to vestibular disorientation. VII, Special effects of brief periods of visual fixation on nystagmus and sensations of turning.

Science.gov (United States)

1967-05-01

The influences of (a) disorientation experience and (b) brief periods of visual still-fixation were examined in exposing figure skaters and ordinary subjects to various rates of angular acceleration. Both nystagmic eye movements and sensations of tur...

Nitrogen fixation in denitrified marine waters.

Directory of Open Access Journals (Sweden)

Camila Fernandez

Full Text Available Nitrogen fixation is an essential process that biologically transforms atmospheric dinitrogen gas to ammonia, therefore compensating for nitrogen losses occurring via denitrification and anammox. Currently, inputs and losses of nitrogen to the ocean resulting from these processes are thought to be spatially separated: nitrogen fixation takes place primarily in open ocean environments (mainly through diazotrophic cyanobacteria, whereas nitrogen losses occur in oxygen-depleted intermediate waters and sediments (mostly via denitrifying and anammox bacteria. Here we report on rates of nitrogen fixation obtained during two oceanographic cruises in 2005 and 2007 in the eastern tropical South Pacific (ETSP, a region characterized by the presence of coastal upwelling and a major permanent oxygen minimum zone (OMZ. Our results show significant rates of nitrogen fixation in the water column; however, integrated rates from the surface down to 120 m varied by ∼30 fold between cruises (7.5±4.6 versus 190±82.3 µmol m(-2 d(-1. Moreover, rates were measured down to 400 m depth in 2007, indicating that the contribution to the integrated rates of the subsurface oxygen-deficient layer was ∼5 times higher (574±294 µmol m(-2 d(-1 than the oxic euphotic layer (48±68 µmol m(-2 d(-1. Concurrent molecular measurements detected the dinitrogenase reductase gene nifH in surface and subsurface waters. Phylogenetic analysis of the nifH sequences showed the presence of a diverse diazotrophic community at the time of the highest measured nitrogen fixation rates. Our results thus demonstrate the occurrence of nitrogen fixation in nutrient-rich coastal upwelling systems and, importantly, within the underlying OMZ. They also suggest that nitrogen fixation is a widespread process that can sporadically provide a supplementary source of fixed nitrogen in these regions.

Nitrogen Fixation in Denitrified Marine Waters

Science.gov (United States)

Fernandez, Camila; Farías, Laura; Ulloa, Osvaldo

2011-01-01

Nitrogen fixation is an essential process that biologically transforms atmospheric dinitrogen gas to ammonia, therefore compensating for nitrogen losses occurring via denitrification and anammox. Currently, inputs and losses of nitrogen to the ocean resulting from these processes are thought to be spatially separated: nitrogen fixation takes place primarily in open ocean environments (mainly through diazotrophic cyanobacteria), whereas nitrogen losses occur in oxygen-depleted intermediate waters and sediments (mostly via denitrifying and anammox bacteria). Here we report on rates of nitrogen fixation obtained during two oceanographic cruises in 2005 and 2007 in the eastern tropical South Pacific (ETSP), a region characterized by the presence of coastal upwelling and a major permanent oxygen minimum zone (OMZ). Our results show significant rates of nitrogen fixation in the water column; however, integrated rates from the surface down to 120 m varied by ∼30 fold between cruises (7.5±4.6 versus 190±82.3 µmol m−2 d−1). Moreover, rates were measured down to 400 m depth in 2007, indicating that the contribution to the integrated rates of the subsurface oxygen-deficient layer was ∼5 times higher (574±294 µmol m−2 d−1) than the oxic euphotic layer (48±68 µmol m−2 d−1). Concurrent molecular measurements detected the dinitrogenase reductase gene nifH in surface and subsurface waters. Phylogenetic analysis of the nifH sequences showed the presence of a diverse diazotrophic community at the time of the highest measured nitrogen fixation rates. Our results thus demonstrate the occurrence of nitrogen fixation in nutrient-rich coastal upwelling systems and, importantly, within the underlying OMZ. They also suggest that nitrogen fixation is a widespread process that can sporadically provide a supplementary source of fixed nitrogen in these regions. PMID:21687726

Effect of rectus recession combined with the rear suspension scleral fixation in patients with restrictive strabismus caused by thyroid associated ophthalmopathy

Directory of Open Access Journals (Sweden)

Hai-Hua Qian

2016-04-01

Full Text Available AIM: To investigate the therapeutic effect of rectus recession combined with the rear suspension scleral fixation for patients with restrictive strabismus caused by thyroid associated ophthalmopathy(TAO. METHODS: The clinical data of 48 patients(71 eyeswith severe TAO were retrospective analyzed from January 2013 to January 2015.The patients with severe TAO were divided into the exophthalmos(EMgroup with 25 patients(35 eyes, compressive optic neuropathy(CONgroup with 12 patients(20 eyesand exposure keratopathy(EKgroup with 11 patients(16 eyes.The rectus recession combined with rear suspension scleral fixation treatment was performed in all patients. The visual acuity, clinical activity score(CAS, and diplopia situation of each group were recorded and compared preoperatively and at 6mo postoperatively. RESULTS: The postoperative best corrected visual acuity(BCVAof the three groups were significantly higher than those before operation(PPPPPCONCLUSION: Rectus recession combined with the rear suspension scleral fixation can help improve the restrictive strabismus caused by TAO, visual acuity, eyeballs to roll back, eliminate the diplopia and to improve the life quality of patients.

Eye movements when reading sentences with handwritten words.

Science.gov (United States)

Perea, Manuel; Marcet, Ana; Uixera, Beatriz; Vergara-Martínez, Marta

2016-10-17

The examination of how we read handwritten words (i.e., the original form of writing) has typically been disregarded in the literature on reading. Previous research using word recognition tasks has shown that lexical effects (e.g., the word-frequency effect) are magnified when reading difficult handwritten words. To examine this issue in a more ecological scenario, we registered the participants' eye movements when reading handwritten sentences that varied in the degree of legibility (i.e., sentences composed of words in easy vs. difficult handwritten style). For comparison purposes, we included a condition with printed sentences. Results showed a larger reading cost for sentences with difficult handwritten words than for sentences with easy handwritten words, which in turn showed a reading cost relative to the sentences with printed words. Critically, the effect of word frequency was greater for difficult handwritten words than for easy handwritten words or printed words in the total times on a target word, but not on first-fixation durations or gaze durations. We examine the implications of these findings for models of eye movement control in reading.

External fixation of “intertrochanteric” fractures

Science.gov (United States)

Gani, Naseem ul; Kangoo, Khursheed Ahmed; Bashir, Arshad; Muzaffer, Rahil; Bhat, Mohammad Farooq; Farooq, Munir; Badoo, Abdul Rashid; Dar, Imtiyaz Hussian; Wani, Mudassir Maqbool

2009-01-01

In developing countries, due to limited availability of modern anesthesia and overcrowding of the hospitals with patients who need surgery, high-risk patients with “intertrochanteric” fractures remain unsuita ble for open reduction and internal fixation. The aim of this study was to analyze the results of external fixation of “intertrochanteric” fractures in high-risk geriatric patients in a developing country. The results of 62 ambulatory high-risk geriatric patients with a mean age of 70 years (range 58–90 years) with “intertrochanteric” fractures, in whom external fixation was performed, are reported. Eight patients died during follow-up due to medical causes unrelated to the surgical procedure. So only 54 patients were available for final assessment. Procedure is simple, performed under local anesthesia, requires less time for surgery and is associated with less blood loss. Good fixation and early ambulation was achieved in most of the patients. Average time to union was 14 weeks. Thirty-one patients developed superficial pin tract infection and 28 patients had average shortening of 15 mm due to impaction and varus angulation. Functional outcome was assessed using Judet's point system. Good to excellent results were achieved in 44 patients. This study demonstrated that external fixation of “intertrochantric” fractures performed under local anesthesia offers significant advantage in ambulatory high-risk geriatric patients especially in a developing country. PMID:21808680

External fixation of “intertrochanteric” fractures

Directory of Open Access Journals (Sweden)

Naseem ul Gani

2009-08-01

Full Text Available In developing countries, due to limited availability of modern anesthesia and overcrowding of the hospitals with patients who need surgery, high-risk patients with “intertro-chanteric” fractures remain unsuitable for open reduction and internal fixation. The aim of this study was to analyze the results of external fixation of “intertro-chanteric” fractures in high-risk geriatric patients in a developing country. The results of 62 ambulatory high-risk geriatric patients with a mean age of 70 years (range 58-90 years with “intertrochanteric” fractures, in whom external fixation was performed, are reported. Eight patients died during follow-up due to medical causes unrelated to the surgical procedure. So only 54 patients were available for final assessment. Procedure is simple, performed under local anesthesia, requires less time for surgery and is associated with less blood loss. Good fixation and early ambulation was achieved in most of the patients. Average time to union was 14 weeks. Thirty-one patients developed superficial pin tract infection and 28 patients had average shortening of 15 mm due to impaction and varus angulation. Functional outcome was assessed using Judet’s point system. Good to excellent results were achieved in 44 patients. This study demonstrated that external fixation of “intertrochantric” fractures performed under local anesthesia offers significant advantage in ambulatory high-risk geriatric patients especially in a developing country.

Improvement of design of a surgical interface using an eye tracking device.

Science.gov (United States)

Erol Barkana, Duygun; Açık, Alper; Duru, Dilek Goksel; Duru, Adil Deniz

2014-05-07

Surgical interfaces are used for helping surgeons in interpretation and quantification of the patient information, and for the presentation of an integrated workflow where all available data are combined to enable optimal treatments. Human factors research provides a systematic approach to design user interfaces with safety, accuracy, satisfaction and comfort. One of the human factors research called user-centered design approach is used to develop a surgical interface for kidney tumor cryoablation. An eye tracking device is used to obtain the best configuration of the developed surgical interface. Surgical interface for kidney tumor cryoablation has been developed considering the four phases of user-centered design approach, which are analysis, design, implementation and deployment. Possible configurations of the surgical interface, which comprise various combinations of menu-based command controls, visual display of multi-modal medical images, 2D and 3D models of the surgical environment, graphical or tabulated information, visual alerts, etc., has been developed. Experiments of a simulated cryoablation of a tumor task have been performed with surgeons to evaluate the proposed surgical interface. Fixation durations and number of fixations at informative regions of the surgical interface have been analyzed, and these data are used to modify the surgical interface. Eye movement data has shown that participants concentrated their attention on informative regions more when the number of displayed Computer Tomography (CT) images has been reduced. Additionally, the time required to complete the kidney tumor cryoablation task by the participants had been decreased with the reduced number of CT images. Furthermore, the fixation durations obtained after the revision of the surgical interface are very close to what is observed in visual search and natural scene perception studies suggesting more efficient and comfortable interaction with the surgical interface. The

Relationship of Corneal Pain Sensitivity With Dry Eye Symptoms in Dry Eye With Short Tear Break-Up Time.

Science.gov (United States)

Kaido, Minako; Kawashima, Motoko; Ishida, Reiko; Tsubota, Kazuo

2016-03-01

The purpose of this prospective comparative study was to investigate corneal sensitivity in subjects with unstable tear film, with and without dry eye (DE) symptoms. Forty-one eyes of 41 volunteers (mean age: 45.1 ± 9.4 years; age range, 23-57 years), with normal tear function and ocular surface except for tear stability, were studied. The eyes were divided into two groups depending on the presence or absence of DE symptoms: 21 eyes with DE symptoms (symptomatic group); and 20 eyes without DE symptoms (asymptomatic group). Three types of corneal sensitivity values were measured using a Cochet-Bonnet esthesiometer: the sensitivity for perception of touch (S-touch), the sensitivity for blinking (S-blink), and the sensitivity for pain (S-pain). Mean S-blink and S-pain were significantly higher in the symptomatic group than in the asymptomatic group (P 0.05). Corneal sensitivity for blinking and pain evoked by increased stimuli was higher in the symptomatic group (subjects with short break-up time DE) compared with subjects who have no DE symptoms despite decreased tear stability. The presence of both tear instability and hyperesthesia, rather than tear instability alone, may contribute to DE pathogenesis.

Response Time, Visual Search Strategy, and Anticipatory Skills in Volleyball Players

Directory of Open Access Journals (Sweden)

Alessandro Piras

2014-01-01

Full Text Available This paper aimed at comparing expert and novice volleyball players in a visuomotor task using realistic stimuli. Videos of a volleyball setter performing offensive action were presented to participants, while their eye movements were recorded by a head-mounted video based eye tracker. Participants were asked to foresee the direction (forward or backward of the setter’s toss by pressing one of two keys. Key-press response time, response accuracy, and gaze behaviour were measured from the first frame showing the setter’s hand-ball contact to the button pressed by the participants. Experts were faster and more accurate in predicting the direction of the setting than novices, showing accurate predictions when they used a search strategy involving fewer fixations of longer duration, as well as spending less time in fixating all display areas from which they extract critical information for the judgment. These results are consistent with the view that superior performance in experts is due to their ability to efficiently encode domain-specific information that is relevant to the task.

The Active Side of Stereopsis: Fixation Strategy and Adaptation to Natural Environments.

Science.gov (United States)

Gibaldi, Agostino; Canessa, Andrea; Sabatini, Silvio P

2017-03-20

Depth perception in near viewing strongly relies on the interpretation of binocular retinal disparity to obtain stereopsis. Statistical regularities of retinal disparities have been claimed to greatly impact on the neural mechanisms that underlie binocular vision, both to facilitate perceptual decisions and to reduce computational load. In this paper, we designed a novel and unconventional approach in order to assess the role of fixation strategy in conditioning the statistics of retinal disparity. We integrated accurate realistic three-dimensional models of natural scenes with binocular eye movement recording, to obtain accurate ground-truth statistics of retinal disparity experienced by a subject in near viewing. Our results evidence how the organization of human binocular visual system is finely adapted to the disparity statistics characterizing actual fixations, thus revealing a novel role of the active fixation strategy over the binocular visual functionality. This suggests an ecological explanation for the intrinsic preference of stereopsis for a close central object surrounded by a far background, as an early binocular aspect of the figure-ground segregation process.

Optical eye tracking system for real-time noninvasive tumor localization in external beam radiotherapy

International Nuclear Information System (INIS)

Via, Riccardo; Fassi, Aurora; Fattori, Giovanni; Fontana, Giulia; Pella, Andrea; Tagaste, Barbara; Ciocca, Mario; Riboldi, Marco; Baroni, Guido; Orecchia, Roberto

2015-01-01

Purpose: External beam radiotherapy currently represents an important therapeutic strategy for the treatment of intraocular tumors. Accurate target localization and efficient compensation of involuntary eye movements are crucial to avoid deviations in dose distribution with respect to the treatment plan. This paper describes an eye tracking system (ETS) based on noninvasive infrared video imaging. The system was designed for capturing the tridimensional (3D) ocular motion and provides an on-line estimation of intraocular lesions position based on a priori knowledge coming from volumetric imaging. Methods: Eye tracking is performed by localizing cornea and pupil centers on stereo images captured by two calibrated video cameras, exploiting eye reflections produced by infrared illumination. Additionally, torsional eye movements are detected by template matching in the iris region of eye images. This information allows estimating the 3D position and orientation of the eye by means of an eye local reference system. By combining ETS measurements with volumetric imaging for treatment planning [computed tomography (CT) and magnetic resonance (MR)], one is able to map the position of the lesion to be treated in local eye coordinates, thus enabling real-time tumor referencing during treatment setup and irradiation. Experimental tests on an eye phantom and seven healthy subjects were performed to assess ETS tracking accuracy. Results: Measurements on phantom showed an overall median accuracy within 0.16 mm and 0.40° for translations and rotations, respectively. Torsional movements were affected by 0.28° median uncertainty. On healthy subjects, the gaze direction error ranged between 0.19° and 0.82° at a median working distance of 29 cm. The median processing time of the eye tracking algorithm was 18.60 ms, thus allowing eye monitoring up to 50 Hz. Conclusions: A noninvasive ETS prototype was designed to perform real-time target localization and eye movement monitoring

Dynamic scanpaths: eye movement analysis methods

Science.gov (United States)

Blackmon, Theodore T.; Ho, Yeuk F.; Chernyak, Dimitri A.; Azzariti, Michela; Stark, Lawrence W.

1999-05-01

An eye movements sequence, or scanpath, during viewing of a stationary stimulus has been described as a set of fixations onto regions-of-interest, ROIs, and the saccades or transitions between them. Such scanpaths have high similarity for the same subject and stimulus both in the spatial loci of the ROIs and their sequence; scanpaths also take place during recollection of a previously viewed stimulus, suggesting that they play a similar role in visual memory and recall.

Changes in biomolecular profile in a single nucleolus during cell fixation.

Science.gov (United States)

Kuzmin, Andrey N; Pliss, Artem; Prasad, Paras N

2014-11-04

Fixation of biological sample is an essential technique applied in order to "freeze" in time the intracellular molecular content. However, fixation induces changes of the cellular molecular structure, which mask physiological distribution of biomolecules and bias interpretation of results. Accurate, sensitive, and comprehensive characterization of changes in biomolecular composition, occurring during fixation, is crucial for proper analysis of experimental data. Here we apply biomolecular component analysis for Raman spectra measured in the same nucleoli of HeLa cells before and after fixation by either formaldehyde solution or by chilled ethanol. It is found that fixation in formaldehyde does not strongly affect the Raman spectra of nucleolar biomolecular components, but may significantly decrease the nucleolar RNA concentration. At the same time, ethanol fixation leads to a proportional increase (up to 40%) in concentrations of nucleolar proteins and RNA, most likely due to cell shrinkage occurring in the presence of coagulant fixative. Ethanol fixation also triggers changes in composition of nucleolar proteome, as indicated by an overall reduction of the α-helical structure of proteins and increase in the concentration of proteins containing the β-sheet conformation. We conclude that cross-linking fixation is a more appropriate protocol for mapping of proteins in situ. At the same time, ethanol fixation is preferential for studies of RNA-containing macromolecules. We supplemented our quantitative Raman spectroscopic measurements with mapping of the protein and lipid macromolecular groups in live and fixed cells using coherent anti-Stokes Raman scattering nonlinear optical imaging.

Permanganate Fixation of Plant Cells

Science.gov (United States)

Mollenhauer, Hilton H.

1959-01-01

In an evaluation of procedures explored to circumvent some of the problems of osmium tetroxide-fixation and methacrylate embedding of plant materials, excised segments of root tips of Zea mays were fixed for electron microscopy in potassium permanganate in the following treatment variations: unbuffered and veronal-acetate buffered solutions of 0.6, 2.0, and 5.0 per cent KMnO4 at pH 5.0, 6.0, 6.7, and 7.5, and temperatures of 2–4°C. and 22°C. After fixation the segments were dehydrated, embedded in epoxy resin, sectioned, and observed or photographed. The cells of the central region of the rootcap are described. The fixation procedures employing unbuffered solutions containing 2.0 to 5.0 per cent KMnO4 at a temperature of 22°C. gave particularly good preservation of cell structure and all membrane systems. Similar results were obtained using a solution containing 2.0 per cent KMnO4, buffered with veronal-acetate to pH 6.0, and a fixation time of 2 hours at 22°C. The fixation procedure utilizing veronal-acetate buffered, 0.6 per cent KMnO4 at 2–4°C. and pH 6.7 also gave relatively good preservation of most cellular constituents. However, preservation of the plasma membrane was not so good, nor was the intensity of staining so great, as that with the group of fixatives containing greater concentrations of KMnO4. The other fixation procedures did not give satisfactory preservation of fine structure. A comparison is made of cell structures as fixed in KMnO4 or OsO4. PMID:14423414

Parallel programming of saccades during natural scene viewing: evidence from eye movement positions.

Science.gov (United States)

Wu, Esther X W; Gilani, Syed Omer; van Boxtel, Jeroen J A; Amihai, Ido; Chua, Fook Kee; Yen, Shih-Cheng

2013-10-24

Previous studies have shown that saccade plans during natural scene viewing can be programmed in parallel. This evidence comes mainly from temporal indicators, i.e., fixation durations and latencies. In the current study, we asked whether eye movement positions recorded during scene viewing also reflect parallel programming of saccades. As participants viewed scenes in preparation for a memory task, their inspection of the scene was suddenly disrupted by a transition to another scene. We examined whether saccades after the transition were invariably directed immediately toward the center or were contingent on saccade onset times relative to the transition. The results, which showed a dissociation in eye movement behavior between two groups of saccades after the scene transition, supported the parallel programming account. Saccades with relatively long onset times (>100 ms) after the transition were directed immediately toward the center of the scene, probably to restart scene exploration. Saccades with short onset times (programming of saccades during scene viewing. Additionally, results from the analyses of intersaccadic intervals were also consistent with the parallel programming hypothesis.

[Clinical characteristics of short tear film breakup time (BUT) -type dry eye].

Science.gov (United States)

Yamamoto, Yuji; Yokoi, Norihiko; Higashihara, Hisayo; Inagaki, Kayoko; Sonomura, Yukiko; Komuro, Aoi; Kinoshita, Shigeru

2012-12-01

To evaluate the clinical characteristics and management of short tear film breakup time (BUT) -type dry eye. Clinical background and post-treatment changes of symptoms in 77 patients with short BUT -type dry eye were investigated. Treatment consisted of artificial-tear eye-drop instillation and, if necessary, the addition of a low-density-level steroid, hyaluronic acid, a low-density-level cyclopentolate prepared by ourselves and punctal plugs inserted into the upper and lower lacrimal puncta. There were three times more women than men among the patients, and the peak age of occurrence was in the twenties in the men and in the sixties in the women. Our findings show that visual display terminal (VDT) work, contact lens (CL) wear, and changes in the sex hormones may initiate subjective symptoms. Some patients had simultaneous conjunctivochalasis, allergic conjunctivitis, and meibomian gland dysfunction. Nineteen patients (24.7%) were effectively treated with eye-drop instillation alone. Thirty-seven patients (48.1%) required punctal-plug insertion, which was completely effective in only 8 of them (21.6%). Mainly young men and menopausal women contract short BUT -type dry eye. Changes in sex hormones, VDT work and CL wear may be causal, and the disease cannot be controlled by eyedrop and punctal-plug treatment alone.

Visual encoding and fixation target selection in free viewing: presaccadic brain potentials

Directory of Open Access Journals (Sweden)

Andrey R Nikolaev

2013-06-01

Full Text Available In scrutinizing a scene, the eyes alternate between fixations and saccades. During a fixation, two component processes can be distinguished: visual encoding and selection of the next fixation target. We aimed to distinguish the neural correlates of these processes in the electrical brain activity prior to a saccade onset. Participants viewed color photographs of natural scenes, in preparation for a change detection task. Then, for each participant and each scene we computed an image heat map, with temperature representing the duration and density of fixations. The temperature difference between the start and end points of saccades was taken as a measure of the expected task-relevance of the information concentrated in specific regions of a scene. Visual encoding was evaluated according to whether subsequent change was correctly detected. Saccades with larger temperature difference were more likely to be followed by correct detection than ones with smaller temperature differences. The amplitude of presaccadic activity over anterior brain areas was larger for correct detection than for detection failure. This difference was observed for short scrutinizing but not for long explorative saccades, suggesting that presaccadic activity reflects top-down saccade guidance. Thus, successful encoding requires local scanning of scene regions which are expected to be task-relevant. Next, we evaluated fixation target selection. Saccades moving up in temperature were preceded by presaccadic activity of higher amplitude than those moving down. This finding suggests that presaccadic activity reflects attention deployed to the following fixation location. Our findings illustrate how presaccadic activity can elucidate concurrent brain processes related to the immediate goal of planning the next saccade and the larger-scale goal of constructing a robust representation of the visual scene.

Impaired exploratory eye movements in children with Asperger's syndrome.

Science.gov (United States)

Ohya, Takashi; Morita, Kiichiro; Yamashita, Yushiro; Egami, Chiyomi; Ishii, Youhei; Nagamitsu, Shinichiro; Matsuishi, Toyojiro

2014-03-01

Previous eye-tracking studies using an eye mark recorder have reported that disturbances in exploratory eye movements in adult schizophrenic patients are associated with social functioning. The current study sought to determine whether exploratory eye-movement disturbances are present in children with Asperger's syndrome (AS) compared with typically developing (TD) children. MATERIALS/PARTICIPANTS: The participants were 23 children with AS and 23 age-matched TD children. We measured exploratory eye movements using an EMR-8B eye mark recorder and an exploratory eye movement-measuring device. Eye movements were recorded while participants freely observed a geometric figure (free viewing task), and while they complied with the instructions of an experimenter (repeat-comparison task). We assessed eye fixation points (EFPs) and total eye scanning length (TESL) in all tasks, and measured the responsive search score (RSS) in the repeat-comparison task. In the free viewing task, children with AS exhibited significantly shorter TESL compared with TD children. In the repeat-comparison task, children with AS exhibited significantly lower RSS. Autism Spectrum Screening Questionnaire scores were negatively correlated with both EFP and TESL, but not RSS. The current results revealed that children with AS exhibited dysfunction in exploratory eye movements. Thus, assessing exploratory eye movements in a repeat-comparison task may be useful for detecting social impairment among children with AS. Copyright © 2013 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Attention to food and beverage advertisements as measured by eye-tracking technology and the food preferences and choices of youth.

Science.gov (United States)

Velazquez, Cayley E; Pasch, Keryn E

2014-04-01

The purpose of this study was to examine how objective measures of attention to food/beverage advertising were associated with the unhealthy food/beverage preferences and choices of children and adolescents. A self-report survey and eye-tracking session were completed by 102 youth (mean age=11.6 years; 56.4% were white; 43.1% were female) between April and November 2010. Participants viewed 40 food/beverage advertisements on a computer and their eye movements were recorded. Objective attention measures included total viewing time, fixation length (time spent viewing characters/logos, unhealthy food/beverage items), and fixation count (number of times an individual stops to examine characters/logos, unhealthy food/beverage items). Food/beverage preferences and choices were measured by self-report. The preferences index summed responses to 12 questions measuring snack food and sugar-sweetened beverage preferences and the choices index summed responses to eight questions measuring consumption of snack foods and sugar-sweetened beverages. Regression models examined whether attention to food/beverage advertising was associated with food preferences and choices, controlling for sex, age, and body mass index z score. The length of time and number of times participants looked at unhealthy food and beverage items within advertisements were each significantly associated with unhealthy food/beverage preferences of youth (Ppurchase requests, given the important role of parents in the decision-making process surrounding food choice. Copyright © 2014 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

[Comparison of external fixation with or without limited internal fixation for open knee fractures].

Science.gov (United States)

Li, K N; Lan, H; He, Z Y; Wang, X J; Yuan, J; Zhao, P; Mu, J S

2018-03-01

Objective: To explore the characteristics and methods of different fixation methods and prevention of open knee joint fracture. Methods: The data of 86 cases of open knee joint fracture admitted from January 2002 to December 2015 in Department of Orthopaedics, Affiliated Hospital of Chengdu University were analyzed retrospectively.There were 65 males and 21 females aged of 38.6 years. There were 38 cases treated with trans articular external fixation alone, 48 cases were in the trans articular external fixation plus auxiliary limited internal fixation group. All the patients were treated according to the same three stages except for different fixation methods. Observation of external fixation and fracture fixation, fracture healing, wound healing and treatment, treatment and related factors of infection control and knee function recovery. χ(2) test was used to analyze data. Results: Eleven patients had primary wound healing, accounting for 12.8%. Seventy-five patients had two wounds healed, accounting for 87.2%. Only 38 cases of trans articular external fixator group had 31 cases of articular surface reduction, accounting for 81.6%; Five cases of trans articular external fixator assisted limited internal fixation group had 5 cases of poor reduction, accounting for 10.4%; There was significant difference between the two groups (χ(2)=44.132, P external fixation group, a total of 23 cases of patients with infection, accounted for 60.5% of external fixation group; trans articular external fixation assisted limited internal fixation group there were 30 cases of patients with infection, accounting for the assistance of external fixator and limited internal fixation group 62.5%; There was significant difference between the two groups(χ(2)=0.035, P >0.05). Five cases of fracture nonunion cases of serious infection, patients voluntarily underwent amputation. The Lysholm Knee Scale: In the external fixation group, 23 cases were less than 50 points, accounting for 60

Your Aging Eyes: How You See as Time Goes By

Science.gov (United States)

... Subscribe Special Issue: Seniors Print this issue Your Aging Eyes How You See as Time Goes By ... Building Social Bonds Coping with Caregiving Osteoporosis in Aging Wise Choices Protect Your Vision Have a comprehensive ...

Pigment dispersion syndrome and pigmentary glaucoma after secondary sulcus transscleral fixation of single-piece foldable posterior chamber intraocular lenses in Chinese aphakic patients.

Science.gov (United States)

Tong, Nianting; Liu, Fuling; Zhang, Ting; Wang, Liangyu; Zhou, Zhanyu; Gong, Huimin; Yuan, Fuxiang

2017-05-01

To describe secondary pigment dispersion syndrome (PDS) and pigmentary glaucoma after secondary sulcus transscleral fixation of 1-piece hydrophobic acrylic foldable posterior chamber intraocular lenses (PC IOLs) in aphakic patients in a Chinese population. Department of Ophthalmology, Qingdao Municipal Hospital, Qingdao, China. Retrospective case series. This chart review included eyes that had secondary sulcus transscleral fixation of a 1-piece hydrophobic acrylic foldable PC IOL (Tecnis ZCB00) between March 2011 and March 2014. The patients' demographic data, clinical data, postoperative complications, intervals between initial surgery and the onset of PDS, pigmentary glaucoma occurrences, and findings on slitlamp biomicroscopy, gonioscopy, and ultrasound biomicroscopy (UBM) were recorded. The study comprised 23 consecutive eyes of 21 patients. Seventeen eyes of 16 patients were diagnosed with PDS, and 7 eyes of 6 patients were diagnosed with pigmentary glaucoma. The slitlamp examination and UBM showed that the location between the IOL optic and the posterior surface of the iris was very close. Slitlamp examination of the anterior chamber angle using a gonioscope showed dense pigment deposition on the IOL surfaces. A reverse pupillary block was found in 10 eyes of 9 patients. Other postoperative complications included intraocular hemorrhage, pupillary capture of the IOL optic, IOL tilt, IOL decentration, IOL dislocation, and suture erosion. The 1-piece hydrophobic acrylic foldable PC IOL was not suitable for sulcus transscleral fixation because of a high incidence of PDS and pigmentary glaucoma after surgery in a Chinese population. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Lens artifacts in human fetal eyes - the challenge of interpreting the histomorphology of human fetal lenses.

Science.gov (United States)

Herwig, Martina C; Müller, Annette M; Klarmann-Schulz, Ute; Holz, Frank G; Loeffler, Karin U

2014-01-01

Evaluation of the lens, including cataractous changes, is often of paramount importance in the classification of fetal syndromes or forensic questions. On histology, the crystalline lens is - especially in fetal and infant eyes - an organ susceptible to numerous artifacts. Thus, the aim of our study was to study various factors (including fixatives) that might have an impact on lens histomorphology. Twenty eyes from ten fetuses (formalin fixation: n = 10, glutaraldehyde fixation: n = 10), matched for gestational age and abortion (spontaneous vs. induced), were investigated macroscopically and by light microscopy. Sections were stained with routine hematoxylin & eosin (H&E), and periodic acid schiff (PAS). The age of the fetal eyes ranged from 15 to 36 weeks of gestation. Lens artifacts were analyzed and compared to fetal and adult lenses with definitive cataractous changes. In addition, 34 eyes from 27 fetuses with trisomy 21 were investigated for lens changes. All lenses showed artifacts of varying extent, in particular globules, vacuoles, clefts, anterior/posterior capsular separation, subcapsular proteinaceous material, fragmentation of the lens capsule/epithelium, and a posterior umbilication. Glutaraldehyde-fixed lenses displayed less artifacts compared to those fixed in formalin. Slight differences in the appearance of artifacts were found dependent on the fixative (formaldehyde vs glutaraldehyde) and the kind of abortion (iatrogenous vs spontaneous). The gestational age did not have a significant influence on the type and extent of lens artifacts. The lenses from fetuses with trisomy 21 displayed similar lens artifacts with no specific findings. Alterations in fetal lens morphology are extremely frequent and variable. These artifacts have to be carefully taken into account when interpreting post-mortem findings. Thus, the postmortem diagnosis of a fetal cataract should be made with great caution, and should include, in adherence to our proposed

The Effects of Campus Bump on Drivers’ Fixation Dispersion and Speed Reduction

Directory of Open Access Journals (Sweden)

Qian Xu

2015-01-01

Full Text Available To evaluate the effects of campus speed bumps on drivers’ speed and fixation distribution, a quasinaturalistic driving test was conducted on a Chinese campus. Seven randomly selected drivers, wearing the Dikablis eye tracking devices, were required to drive an OPEL SUV passing the speed bumps. The area close to the bump was divided into ten subsegments (15 m for each one. The degree of fixation dispersion within each subsegment was defined as the distance from each subcenter to the whole fixation center. All traffic data were recorded using mounted camera, and the trajectories were extracted in Matlab. The speed and trajectory data was divided into two groups: the before group for bump-free case and the after group for a 5 cm bump case. The observational before-after analysis shows statistical significance between the two cases. The individual vehicular speed analysis reveals that bump reduces nearly 60% of vehicles’ speeds to a certain extent within the distance from 30 m upstream to 15 m downstream. The drivers’ fixation points begin to disperse 30–45 m before they see the bump, and it falls back to normal level 15–30 m downstream of the bump. These findings will help engineers install speed bumps at the most appropriate locations.

Fixation of strategies with the Moran and Fermi processes in evolutionary games

Science.gov (United States)

Liu, Xuesong; He, Mingfeng; Kang, Yibin; Pan, Qiuhui

2017-10-01

A model of stochastic evolutionary game dynamics with finite population was built. It combines the standard Moran and Fermi rules with two strategies cooperation and defection. We obtain the expressions of fixation probabilities and fixation times. The one-third rule which has been found in the frequency dependent Moran process also holds for our model. We obtain the conditions of strategy being an evolutionarily stable strategy in our model, and then make a comparison with the standard Moran process. Besides, the analytical results show that compared with the standard Moran process, fixation occurs with higher probabilities under a prisoner's dilemma game and coordination game, but with lower probabilities under a coexistence game. The simulation result shows that the fixation time in our mixed process is lower than that in the standard Fermi process. In comparison with the standard Moran process, fixation always takes more time on average in spatial populations, regardless of the game. In addition, the fixation time decreases with the growth of the number of neighbors.

Outcomes and Complications of Scleral-Fixated Intraocular Lens Combined with Ahmed Tube Surgery

Directory of Open Access Journals (Sweden)

Nikhel Sachdev

2018-01-01

Full Text Available Background. To evaluate the outcome and complications of transscleral suture-fixated posterior chamber intraocular lens (PCIOL implantation combined with Ahmed glaucoma valve (AGV surgery in Asian eyes. Design. This was a retrospective study that included 22 eyes from 22 participants. The surgeries were performed at Singapore’s National University Hospital. Participants underwent an Ahmed tube surgery, together with transscleral suture-fixated posterior chamber intraocular lens. Main Outcome Measures. Complete success was defined as 6 ≤ intraocular pressure (IOP ≤ 21 mmHg without medications at the last follow-up visit, with no reoperation required and no progression to no perception of light (NPL. Results. At the last follow-up, there was a significant reduction in mean IOP (22.4 ± 6.5 mmHg versus 13.9 ± 3.9 mmHg; p<0.001 and mean number of intraocular pressure-lowering medications (2.45 ± 1.30 versus 0.05 ± 0.21; p<0.001. There was no significant change in visual acuity [1.43 ± 1.21 (LogMAR versus 1.09 ± 1.31 (p=0.204]. Sixteen eyes (72.7% achieved complete success. The 3 commonest complications were bullous keratopathy, choroidal detachment, and displacement of intraocular lens. Conclusion and Relevance. This technique showed good success for intraocular pressure control and vision preservation. Postoperative complications were relatively common although most were self-limiting. Patients at increased risk of trabeculectomy failure may be suitable for this procedure.

Viewing-position effects in the Stroop task: Initial fixation position modulates Stroop effects in fully colored words.

Science.gov (United States)

Perret, Patrick; Ducrot, Stéphanie

2010-08-01

In two experiments that we conducted with adult (Experiment 1) and child (Experiment 2) participants, we experimentally controlled the eyes' first fixation in the word using a variable viewing-position technique in a classical all-letter-coloring Stroop procedure. We explored the impact of initial-fixation position (optimal viewing position [OVP] vs. end of the word) on the magnitude of Stroop effects (both interference and facilitation). The results showed that both interference and facilitation effects were reduced when the first fixation was located at the end of the word rather than at the OVP. These data make a new contribution to the study of the role of low-level processes in Stroop effects and add support to the growing body of research indicating that oculomotor processes can act as moderators of cognitive processes in the determination of Stroop effects.

Efference copy failure during smooth pursuit eye movements in schizophrenia.

Science.gov (United States)

Spering, Miriam; Dias, Elisa C; Sanchez, Jamie L; Schütz, Alexander C; Javitt, Daniel C

2013-07-17

Abnormal smooth pursuit eye movements in patients with schizophrenia are often considered a consequence of impaired motion perception. Here we used a novel motion prediction task to assess the effects of abnormal pursuit on perception in human patients. Schizophrenia patients (n = 15) and healthy controls (n = 16) judged whether a briefly presented moving target ("ball") would hit/miss a stationary vertical line segment ("goal"). To relate prediction performance and pursuit directly, we manipulated eye movements: in half of the trials, observers smoothly tracked the ball; in the other half, they fixated on the goal. Strict quality criteria ensured that pursuit was initiated and that fixation was maintained. Controls were significantly better in trajectory prediction during pursuit than during fixation, their performance increased with presentation duration, and their pursuit gain and perceptual judgments were correlated. Such perceptual benefits during pursuit may be due to the use of extraretinal motion information estimated from an efference copy signal. With an overall lower performance in pursuit and perception, patients showed no such pursuit advantage and no correlation between pursuit gain and perception. Although patients' pursuit showed normal improvement with longer duration, their prediction performance failed to benefit from duration increases. This dissociation indicates relatively intact early visual motion processing, but a failure to use efference copy information. Impaired efference function in the sensory system may represent a general deficit in schizophrenia and thus contribute to symptoms and functional outcome impairments associated with the disorder.

Opacification of the C-flex 570C intraocular lens after sulcus fixation.

Science.gov (United States)

Daigle, Patrick; Carbonneau, Marjorie

2017-09-08

To report a case of diffuse intraocular lens (IOL) opacification in a patient who started complaining of blurred vision in his left eye over the course of three years after having phacoemulsification surgery combined with capsular bag fixation of a C-flex 570C IOL. The IOL had been repositioned in the ciliary sulcus following its subluxation. An IOL exchange was performed, and the explanted IOL was sent for histopathological analysis. Scanning electron microscopy identified multiple crystalline-like deposits on both sides of the IOL. The optic was more extensively involved than the haptics. Energy-dispersive X-ray spectroscopy confirmed the predominance of calcium within the deposits. The breakdown of the blood-aqueous barrier seems to be a key component of this calcification process. Ciliary sulcus fixation is not a suitable option for C-flex 570C IOLs.

Perceptually specific and perceptually non-specific influences on rereading benefits for spatially transformed text: evidence from eye movements.

Science.gov (United States)

Sheridan, Heather; Reingold, Eyal M

2012-12-01

The present study used eye tracking methodology to examine rereading benefits for spatially transformed text. Eye movements were monitored while participants read the same target word twice, in two different low-constraint sentence frames. The congruency of perceptual processing was manipulated by either applying the same type of transformation to the word during the first and second presentations (i.e., the congruent condition), or employing two different types of transformations across the two presentations of the word (i.e., the incongruent condition). Perceptual specificity effects were demonstrated such that fixation times for the second presentation of the target word were shorter for the congruent condition compared to the incongruent condition. Moreover, we demonstrated an additional perceptually non-specific effect such that second reading fixation times were shorter for the incongruent condition relative to a baseline condition that employed a normal typography (i.e., non-transformed) during the first presentation and a transformation during the second presentation. Both of these effects (i.e., perceptually specific and perceptually non-specific) were similar in magnitude for high and low frequency words, and both effects persisted across a 1 week lag between the first and second readings. We discuss the present findings in the context of the distinction between conscious and unconscious memory, and the distinction between perceptually versus conceptually driven processing. Copyright © 2012 Elsevier Inc. All rights reserved.

Eye movements as an index of pathologist visual expertise: a pilot study.

Directory of Open Access Journals (Sweden)

Tad T Brunyé

Full Text Available A pilot study examined the extent to which eye movements occurring during interpretation of digitized breast biopsy whole slide images (WSI can distinguish novice interpreters from experts, informing assessments of competency progression during training and across the physician-learning continuum. A pathologist with fellowship training in breast pathology interpreted digital WSI of breast tissue and marked the region of highest diagnostic relevance (dROI. These same images were then evaluated using computer vision techniques to identify visually salient regions of interest (vROI without diagnostic relevance. A non-invasive eye tracking system recorded pathologists' (N = 7 visual behavior during image interpretation, and we measured differential viewing of vROIs versus dROIs according to their level of expertise. Pathologists with relatively low expertise in interpreting breast pathology were more likely to fixate on, and subsequently return to, diagnostically irrelevant vROIs relative to experts. Repeatedly fixating on the distracting vROI showed limited value in predicting diagnostic failure. These preliminary results suggest that eye movements occurring during digital slide interpretation can characterize expertise development by demonstrating differential attraction to diagnostically relevant versus visually distracting image regions. These results carry both theoretical implications and potential for monitoring and evaluating student progress and providing automated feedback and scanning guidance in educational settings.

Real-Time Control of a Video Game Using Eye Movements and Two Temporal EEG Sensors.

Science.gov (United States)

Belkacem, Abdelkader Nasreddine; Saetia, Supat; Zintus-art, Kalanyu; Shin, Duk; Kambara, Hiroyuki; Yoshimura, Natsue; Berrached, Nasreddine; Koike, Yasuharu

2015-01-01

EEG-controlled gaming applications range widely from strictly medical to completely nonmedical applications. Games can provide not only entertainment but also strong motivation for practicing, thereby achieving better control with rehabilitation system. In this paper we present real-time control of video game with eye movements for asynchronous and noninvasive communication system using two temporal EEG sensors. We used wavelets to detect the instance of eye movement and time-series characteristics to distinguish between six classes of eye movement. A control interface was developed to test the proposed algorithm in real-time experiments with opened and closed eyes. Using visual feedback, a mean classification accuracy of 77.3% was obtained for control with six commands. And a mean classification accuracy of 80.2% was obtained using auditory feedback for control with five commands. The algorithm was then applied for controlling direction and speed of character movement in two-dimensional video game. Results showed that the proposed algorithm had an efficient response speed and timing with a bit rate of 30 bits/min, demonstrating its efficacy and robustness in real-time control.

Dating the time of birth: A radiocarbon calibration curve for human eye-lens crystallines

International Nuclear Information System (INIS)

Kjeldsen, Henrik; Heinemeier, Jan; Heegaard, Steffen; Jacobsen, Christina; Lynnerup, Niels

2010-01-01

Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth, in accordance with expectations. Moreover, it has been possible to develop an age model for the formation of the eye-lens crystallines. From this model a radiocarbon calibration curve for lens crystallines has been calculated. As a consequence, the time of birth of humans can be determined with an accuracy of a few years by radiocarbon dating.

Dating the time of birth: A radiocarbon calibration curve for human eye-lens crystallines

Energy Technology Data Exchange (ETDEWEB)

Kjeldsen, Henrik, E-mail: kjeldsen@phys.au.d [AMS 14C Dating Centre, Department of Physics and Astronomy, University of Aarhus, Aarhus (Denmark); Heinemeier, Jan [AMS 14C Dating Centre, Department of Physics and Astronomy, University of Aarhus, Aarhus (Denmark); Heegaard, Steffen [Eye Pathology Section, Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen (Denmark); Jacobsen, Christina; Lynnerup, Niels [Department of Forensic Medicine, University of Copenhagen, Copenhagen (Denmark)

2010-04-15

Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth, in accordance with expectations. Moreover, it has been possible to develop an age model for the formation of the eye-lens crystallines. From this model a radiocarbon calibration curve for lens crystallines has been calculated. As a consequence, the time of birth of humans can be determined with an accuracy of a few years by radiocarbon dating.

A novel evaluation of two related and two independent algorithms for eye movement classification during reading.

Science.gov (United States)

Friedman, Lee; Rigas, Ioannis; Abdulin, Evgeny; Komogortsev, Oleg V

2018-05-15

Nystrӧm and Holmqvist have published a method for the classification of eye movements during reading (ONH) (Nyström & Holmqvist, 2010). When we applied this algorithm to our data, the results were not satisfactory, so we modified the algorithm (now the MNH) to better classify our data. The changes included: (1) reducing the amount of signal filtering, (2) excluding a new type of noise, (3) removing several adaptive thresholds and replacing them with fixed thresholds, (4) changing the way that the start and end of each saccade was determined, (5) employing a new algorithm for detecting PSOs, and (6) allowing a fixation period to either begin or end with noise. A new method for the evaluation of classification algorithms is presented. It was designed to provide comprehensive feedback to an algorithm developer, in a time-efficient manner, about the types and numbers of classification errors that an algorithm produces. This evaluation was conducted by three expert raters independently, across 20 randomly chosen recordings, each classified by both algorithms. The MNH made many fewer errors in determining when saccades start and end, and it also detected some fixations and saccades that the ONH did not. The MNH fails to detect very small saccades. We also evaluated two additional algorithms: the EyeLink Parser and a more current, machine-learning-based algorithm. The EyeLink Parser tended to find more saccades that ended too early than did the other methods, and we found numerous problems with the output of the machine-learning-based algorithm.

Evaluation of functional outcome of pilon fractures managed with limited internal fixation and external fixation: A prospective clinical study.

Science.gov (United States)

Meena, Umesh Kumar; Bansal, Mahesh Chand; Behera, Prateek; Upadhyay, Rahul; Gothwal, Gyan Chand

2017-11-01

The management of pilon fractures is controversial primarily due to the high rate of complications irrespective of the mode of treatment. Limited internal fixation with external fixation is associated with minimal soft tissue handling. This may reduce the chances of wound dehiscence and infection. This study was designed to evaluate the functional and clinical outcomes in patients treated with limited internal fixation combined with external fixation in pilon fractures. This study was conducted as a prospective clinical study on 56 skeletally mature patients with closed fractures with poor skin condition, and with open grade 1 and grade 2 distal tibial intra-articular fractures. All patients were treated with combined limited internal fixation and ankle spanning external fixation. All fractures in this series united with an average time period of union of 18.3weeks (ranging from 13 weeks to 30 weeks). There was no non-union in any case. There was malunion in 4 cases, varus malunion (>5 degree) in 2 cases and recurvatum in another 2 cases). Excellent to good functional results were observed in 88% cases based on the modified Ovadia and Beals score. The mean ankle dorsiflexion and planter flexion movements were 10.2±5.3 degrees and 27.4±7.2 degrees respectively. infections occurred in 6 patients which included 4 pin tract infections and 2 superficial wound infection, all 6 healed after removal of pin tract and with oral antibiotics. The technique of combined external fixation with internal fixation is safe and effective management option for intra-articular distal tibial fractures.

Spontaneous eye movements and trait empathy predict vicarious learning of fear.

Science.gov (United States)

Kleberg, Johan L; Selbing, Ida; Lundqvist, Daniel; Hofvander, Björn; Olsson, Andreas

2015-12-01

Learning to predict dangerous outcomes is important to survival. In humans, this kind of learning is often transmitted through the observation of others' emotional responses. We analyzed eye movements during an observational/vicarious fear learning procedure, in which healthy participants (N=33) watched another individual ('learning model') receiving aversive treatment (shocks) paired with a predictive conditioned stimulus (CS+), but not a control stimulus (CS-). Participants' gaze pattern towards the model differentiated as a function of whether the CS was predictive or not of a shock to the model. Consistent with our hypothesis that the face of a conspecific in distress can act as an unconditioned stimulus (US), we found that the total fixation time at a learning model's face increased when the CS+ was shown. Furthermore, we found that the total fixation time at the CS+ during learning predicted participants' conditioned responses (CRs) at a later test in the absence of the model. We also demonstrated that trait empathy was associated with stronger CRs, and that autistic traits were positively related to autonomic reactions to watching the model receiving the aversive treatment. Our results have implications for both healthy and dysfunctional socio-emotional learning. Copyright © 2015 Elsevier B.V. All rights reserved.

New pediatric vision screener employing polarization-modulated, retinal-birefringence-scanning-based strabismus detection and bull's eye focus detection with an improved target system: opto-mechanical design and operation

Science.gov (United States)

Irsch, Kristina; Gramatikov, Boris I.; Wu, Yi-Kai; Guyton, David L.

2014-06-01

Amblyopia ("lazy eye") is a major public health problem, caused by misalignment of the eyes (strabismus) or defocus. If detected early in childhood, there is an excellent response to therapy, yet most children are detected too late to be treated effectively. Commercially available vision screening devices that test for amblyopia's primary causes can detect strabismus only indirectly and inaccurately via assessment of the positions of external light reflections from the cornea, but they cannot detect the anatomical feature of the eyes where fixation actually occurs (the fovea). Our laboratory has been developing technology to detect true foveal fixation, by exploiting the birefringence of the uniquely arranged Henle fibers delineating the fovea using retinal birefringence scanning (RBS), and we recently described a polarization-modulated approach to RBS that enables entirely direct and reliable detection of true foveal fixation, with greatly enhanced signal-to-noise ratio and essentially independent of corneal birefringence (a confounding variable with all polarization-sensitive ophthalmic technology). Here, we describe the design and operation of a new pediatric vision screener that employs polarization-modulated, RBS-based strabismus detection and bull's eye focus detection with an improved target system, and demonstrate the feasibility of this new approach.

New pediatric vision screener employing polarization-modulated, retinal-birefringence-scanning-based strabismus detection and bull's eye focus detection with an improved target system: opto-mechanical design and operation.

Science.gov (United States)

Irsch, Kristina; Gramatikov, Boris I; Wu, Yi-Kai; Guyton, David L

2014-06-01

Amblyopia ("lazy eye") is a major public health problem, caused by misalignment of the eyes (strabismus) or defocus. If detected early in childhood, there is an excellent response to therapy, yet most children are detected too late to be treated effectively. Commercially available vision screening devices that test for amblyopia's primary causes can detect strabismus only indirectly and inaccurately via assessment of the positions of external light reflections from the cornea, but they cannot detect the anatomical feature of the eyes where fixation actually occurs (the fovea). Our laboratory has been developing technology to detect true foveal fixation, by exploiting the birefringence of the uniquely arranged Henle fibers delineating the fovea using retinal birefringence scanning (RBS), and we recently described a polarization-modulated approach to RBS that enables entirely direct and reliable detection of true foveal fixation, with greatly enhanced signal-to-noise ratio and essentially independent of corneal birefringence (a confounding variable with all polarization-sensitive ophthalmic technology). Here, we describe the design and operation of a new pediatric vision screener that employs polarization-modulated, RBS-based strabismus detection and bull's eye focus detection with an improved target system, and demonstrate the feasibility of this new approach.

Ball-joint versus single monolateral external fixators for definitive treatment of tibial shaft fractures.

Science.gov (United States)

Beltsios, Michail; Mavrogenis, Andreas F; Savvidou, Olga D; Karamanis, Eirineos; Kokkalis, Zinon T; Papagelopoulos, Panayiotis J

2014-07-01

To compare modular monolateral external fixators with single monolateral external fixators for the treatment of open and complex tibial shaft fractures, to determine the optimal construct for fracture union. A total of 223 tibial shaft fractures in 212 patients were treated with a monolateral external fixator from 2005 to 2011; 112 fractures were treated with a modular external fixator with ball-joints (group A), and 111 fractures were treated with a single external fixator without ball-joints (group B). The mean follow-up was 2.9 years. We retrospectively evaluated the operative time for fracture reduction with the external fixator, pain and range of motion of the knee and ankle joints, time to union, rate of malunion, reoperations and revisions of the external fixators, and complications. The time for fracture reduction was statistically higher in group B; the rate of union was statistically higher in group B; the rate of nonunion was statistically higher in group A; the mean time to union was statistically higher in group A; the rate of reoperations was statistically higher in group A; and the rate of revision of the external fixator was statistically higher in group A. Pain, range of motion of the knee and ankle joints, rates of delayed union, malunion and complications were similar. Although modular external fixators are associated with faster intraoperative fracture reduction with the external fixator, single external fixators are associated with significantly better rates of union and reoperations; the rates of delayed union, malunion and complications are similar.

Gender Classification Based on Eye Movements: A Processing Effect During Passive Face Viewing.

Science.gov (United States)

Sammaknejad, Negar; Pouretemad, Hamidreza; Eslahchi, Changiz; Salahirad, Alireza; Alinejad, Ashkan

2017-01-01

Studies have revealed superior face recognition skills in females, partially due to their different eye movement strategies when encoding faces. In the current study, we utilized these slight but important differences and proposed a model that estimates the gender of the viewers and classifies them into two subgroups, males and females. An eye tracker recorded participant's eye movements while they viewed images of faces. Regions of interest (ROIs) were defined for each face. Results showed that the gender dissimilarity in eye movements was not due to differences in frequency of fixations in the ROI s per se. Instead, it was caused by dissimilarity in saccade paths between the ROIs. The difference enhanced when saccades were towards the eyes. Females showed significant increase in transitions from other ROI s to the eyes. Consequently, the extraction of temporal transient information of saccade paths through a transition probability matrix, similar to a first order Markov chain model, significantly improved the accuracy of the gender classification results.

Integration time for the perception of depth from motion parallax.

Science.gov (United States)

Nawrot, Mark; Stroyan, Keith

2012-04-15

The perception of depth from relative motion is believed to be a slow process that "builds-up" over a period of observation. However, in the case of motion parallax, the potential accuracy of the depth estimate suffers as the observer translates during the viewing period. Our recent quantitative model for the perception of depth from motion parallax proposes that relative object depth (d) can be determined from retinal image motion (dθ/dt), pursuit eye movement (dα/dt), and fixation distance (f) by the formula: d/f≈dθ/dα. Given the model's dynamics, it is important to know the integration time required by the visual system to recover dα and dθ, and then estimate d. Knowing the minimum integration time reveals the incumbent error in this process. A depth-phase discrimination task was used to determine the time necessary to perceive depth-sign from motion parallax. Observers remained stationary and viewed a briefly translating random-dot motion parallax stimulus. Stimulus duration varied between trials. Fixation on the translating stimulus was monitored and enforced with an eye-tracker. The study found that relative depth discrimination can be performed with presentations as brief as 16.6 ms, with only two stimulus frames providing both retinal image motion and the stimulus window motion for pursuit (mean range=16.6-33.2 ms). This was found for conditions in which, prior to stimulus presentation, the eye was engaged in ongoing pursuit or the eye was stationary. A large high-contrast masking stimulus disrupted depth-discrimination for stimulus presentations less than 70-75 ms in both pursuit and stationary conditions. This interval might be linked to ocular-following response eye-movement latencies. We conclude that neural mechanisms serving depth from motion parallax generate a depth estimate much more quickly than previously believed. We propose that additional sluggishness might be due to the visual system's attempt to determine the maximum dθ/dα ratio

Comparison of Outcomes of Operatively Treated Bicondylar Tibial Plateau Fractures by External Fixation and Internal Fixation

Directory of Open Access Journals (Sweden)

CC Chan

2012-03-01

Full Text Available The outcome of bicondylar tibial plateau fractures treated with either external fixation (35 patients or internal fixation (24 patients was reviewed. Outcome measures included the Rasmussen score, clinical complications, development of osteoarthritis and the requirement for total knee replacement (TKR. Twenty-two (92% anatomical reductions were achieved in the internal fixation group compared to 27 (77% in the external fixation group. Infective complications were more common in the external fixation group (9 patients, 26% due to pin tract infection. There were no deep infections in the internal fixation group. The mean Rasmussen score was not significantly different (mean score 32 in external fixation and 29 in internal fixation between the two groups and the incidence of osteoarthritis was the same in both groups. Four patients in the external fixation group underwent a TKR compared to 5 patients in the internal fixation group. Bicondylar tibial plateau fractures have similar outcomes following external or internal fixation.

Validation of mobile eye tracking as novel and efficient means for differentiating progressive supranuclear palsy from Parkinson’s disease

Directory of Open Access Journals (Sweden)

Svenja eMarx

2012-12-01

Full Text Available Background: The decreased ability to carry out vertical saccades is a key symptom of Progressive Supranuclear Palsy (PSP. Objective measurement devices can help to reliably detect subtle eye-movement disturbances to improve sensitivity and specificity of the clinical diagnosis. The present study aims at transferring findings from restricted stationary video-oculography to a wearable head-mounted device, which can be readily applied in clinical practice.Methods: We investigated the eye movements in 10 possible or probable PSP patients, 11 Parkinson’s disease (PD patients and 10 age-matched healthy controls (HC using a mobile, gaze-driven video camera setup (EyeSeeCam. Ocular movements were analyzed during a standardized fixation protocol and in an unrestricted real-life scenario while walking along a corridor.Results: The EyeSeeCam detected prominent impairment of both saccade velocity and amplitude in PSP patients, differentiating them from PD and HCs. Differences were particularly evident for saccades in the vertical plane, and stronger for saccades than for other eye movements. Differences were more pronounced during the standardized protocol than in the real-life scenario. Conclusions: Combined analysis of saccade velocity and saccade amplitude during the fixation protocol with the EyeSeeCam provides a simple, rapid (< 20s and reliable tool to differentiate clinically established PSP patients from PD and HCs. As such, our findings prepare the ground for using wearable eye-tracking in patients with uncertain diagnoses.

Real-Time Control of a Video Game Using Eye Movements and Two Temporal EEG Sensors

Directory of Open Access Journals (Sweden)

Abdelkader Nasreddine Belkacem

2015-01-01

Full Text Available EEG-controlled gaming applications range widely from strictly medical to completely nonmedical applications. Games can provide not only entertainment but also strong motivation for practicing, thereby achieving better control with rehabilitation system. In this paper we present real-time control of video game with eye movements for asynchronous and noninvasive communication system using two temporal EEG sensors. We used wavelets to detect the instance of eye movement and time-series characteristics to distinguish between six classes of eye movement. A control interface was developed to test the proposed algorithm in real-time experiments with opened and closed eyes. Using visual feedback, a mean classification accuracy of 77.3% was obtained for control with six commands. And a mean classification accuracy of 80.2% was obtained using auditory feedback for control with five commands. The algorithm was then applied for controlling direction and speed of character movement in two-dimensional video game. Results showed that the proposed algorithm had an efficient response speed and timing with a bit rate of 30 bits/min, demonstrating its efficacy and robustness in real-time control.

Eye Movement Correlates of Expertise in Visual Arts.

Science.gov (United States)

Francuz, Piotr; Zaniewski, Iwo; Augustynowicz, Paweł; Kopiś, Natalia; Jankowski, Tomasz

2018-01-01

versions due to dwell time, first and average fixation duration and number of fixations. The familiarity of paintings turned out to be the factor significantly affects both the aesthetic evaluation of paintings and eye movement.

Eye Movement Correlates of Expertise in Visual Arts

Directory of Open Access Journals (Sweden)

Piotr Francuz

2018-03-01

their altered versions due to dwell time, first and average fixation duration and number of fixations. The familiarity of paintings turned out to be the factor significantly affects both the aesthetic evaluation of paintings and eye movement.

Using the eye fixation speculum as an adjunct to pterygium surgery.

LENUS (Irish Health Repository)

Mulhern, M G

2012-02-03

A technique is described that overcomes the two biggest problems facing the surgeon when dissecting a pterygium from the cornea-bleeding and eye movement. Our technique however, requires only minimal anesthesia (topical and subconjunctival) and the use of a disposable speculum and suction ring. An added advantage is this particular speculum gives good exposure of the superior bulbar conjunctiva; this facilitates harvesting a conjunctival autograft.

Eye movements, visual search and scene memory, in an immersive virtual environment.

Directory of Open Access Journals (Sweden)

Dmitry Kit

Full Text Available Visual memory has been demonstrated to play a role in both visual search and attentional prioritization in natural scenes. However, it has been studied predominantly in experimental paradigms using multiple two-dimensional images. Natural experience, however, entails prolonged immersion in a limited number of three-dimensional environments. The goal of the present experiment was to recreate circumstances comparable to natural visual experience in order to evaluate the role of scene memory in guiding eye movements in a natural environment. Subjects performed a continuous visual-search task within an immersive virtual-reality environment over three days. We found that, similar to two-dimensional contexts, viewers rapidly learn the location of objects in the environment over time, and use spatial memory to guide search. Incidental fixations did not provide obvious benefit to subsequent search, suggesting that semantic contextual cues may often be just as efficient, or that many incidentally fixated items are not held in memory in the absence of a specific task. On the third day of the experience in the environment, previous search items changed in color. These items were fixated upon with increased probability relative to control objects, suggesting that memory-guided prioritization (or Surprise may be a robust mechanisms for attracting gaze to novel features of natural environments, in addition to task factors and simple spatial saliency.

Eye movements, visual search and scene memory, in an immersive virtual environment.

Science.gov (United States)

Kit, Dmitry; Katz, Leor; Sullivan, Brian; Snyder, Kat; Ballard, Dana; Hayhoe, Mary

2014-01-01

Visual memory has been demonstrated to play a role in both visual search and attentional prioritization in natural scenes. However, it has been studied predominantly in experimental paradigms using multiple two-dimensional images. Natural experience, however, entails prolonged immersion in a limited number of three-dimensional environments. The goal of the present experiment was to recreate circumstances comparable to natural visual experience in order to evaluate the role of scene memory in guiding eye movements in a natural environment. Subjects performed a continuous visual-search task within an immersive virtual-reality environment over three days. We found that, similar to two-dimensional contexts, viewers rapidly learn the location of objects in the environment over time, and use spatial memory to guide search. Incidental fixations did not provide obvious benefit to subsequent search, suggesting that semantic contextual cues may often be just as efficient, or that many incidentally fixated items are not held in memory in the absence of a specific task. On the third day of the experience in the environment, previous search items changed in color. These items were fixated upon with increased probability relative to control objects, suggesting that memory-guided prioritization (or Surprise) may be a robust mechanisms for attracting gaze to novel features of natural environments, in addition to task factors and simple spatial saliency.

Eye movement analysis for activity recognition using electrooculography.

Science.gov (United States)

Bulling, Andreas; Ward, Jamie A; Gellersen, Hans; Tröster, Gerhard

2011-04-01

In this work, we investigate eye movement analysis as a new sensing modality for activity recognition. Eye movement data were recorded using an electrooculography (EOG) system. We first describe and evaluate algorithms for detecting three eye movement characteristics from EOG signals-saccades, fixations, and blinks-and propose a method for assessing repetitive patterns of eye movements. We then devise 90 different features based on these characteristics and select a subset of them using minimum redundancy maximum relevance (mRMR) feature selection. We validate the method using an eight participant study in an office environment using an example set of five activity classes: copying a text, reading a printed paper, taking handwritten notes, watching a video, and browsing the Web. We also include periods with no specific activity (the NULL class). Using a support vector machine (SVM) classifier and person-independent (leave-one-person-out) training, we obtain an average precision of 76.1 percent and recall of 70.5 percent over all classes and participants. The work demonstrates the promise of eye-based activity recognition (EAR) and opens up discussion on the wider applicability of EAR to other activities that are difficult, or even impossible, to detect using common sensing modalities.

Classification of visual and linguistic tasks using eye-movement features.

Science.gov (United States)

Coco, Moreno I; Keller, Frank

2014-03-07

The role of the task has received special attention in visual-cognition research because it can provide causal explanations of goal-directed eye-movement responses. The dependency between visual attention and task suggests that eye movements can be used to classify the task being performed. A recent study by Greene, Liu, and Wolfe (2012), however, fails to achieve accurate classification of visual tasks based on eye-movement features. In the present study, we hypothesize that tasks can be successfully classified when they differ with respect to the involvement of other cognitive domains, such as language processing. We extract the eye-movement features used by Greene et al. as well as additional features from the data of three different tasks: visual search, object naming, and scene description. First, we demonstrated that eye-movement responses make it possible to characterize the goals of these tasks. Then, we trained three different types of classifiers and predicted the task participants performed with an accuracy well above chance (a maximum of 88% for visual search). An analysis of the relative importance of features for classification accuracy reveals that just one feature, i.e., initiation time, is sufficient for above-chance performance (a maximum of 79% accuracy in object naming). Crucially, this feature is independent of task duration, which differs systematically across the three tasks we investigated. Overall, the best task classification performance was obtained with a set of seven features that included both spatial information (e.g., entropy of attention allocation) and temporal components (e.g., total fixation on objects) of the eye-movement record. This result confirms the task-dependent allocation of visual attention and extends previous work by showing that task classification is possible when tasks differ in the cognitive processes involved (purely visual tasks such as search vs. communicative tasks such as scene description).

Dating the time of birth: A radiocarbon calibration curve for human eye-lens crystallines

DEFF Research Database (Denmark)

Kjeldsen, Henrik; Heinemeier, Jan; Heegaard, Steffen

2010-01-01

Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth...

The perceptual cognitive processes underpinning skilled performance in volleyball: evidence from eye-movements and verbal reports of thinking involving an in situ representative task.

Science.gov (United States)

Afonso, José; Garganta, Jêlio; McRobert, Allistair; Williams, Andrew M; Mesquita, Isabel

2012-01-01

An extensive body of work has focused on the processes underpinning perceptual-cognitive expertise. The majority of researchers have used film-based simulations to capture superior performance. We combined eye movement recording and verbal reports of thinking to explore the processes underpinning skilled performance in a complex, dynamic, and externally paced representative volleyball task involving in situ data collection. Altogether, 27 female volleyball players performed as centre backcourt defenders in simulated sessions while wearing an eye-tracking device. After each sequence, athletes were questioned concerning their perception of the situation. The visual search strategies employed by the highly-skilled players were more exploratory than those used by skilled players, involving more fixations to a greater number of locations. Highly-skilled participants spent more time fixating on functional spaces between two or more display areas, while the skilled participants fixated on the ball trajectory and specific players. Moreover, highly-skilled players generated more condition concepts with higher levels of sophistication than their skilled counterparts. Findings highlight the value of using representative task designs to capture performance in situ. Key pointsDecision-making in complex sports relies deeply on perceptual-cognitive expertise. In turn, the effect of expertise is highly dependent on the nature and complexity of the task.Nonetheless, most researchers use simple tasks in their research designs, risking not capturing performance in a meaningful way. We proposed to use a live action setting with a complex task design, representative of real world situations.We combined eye movement registration with collection of immediate retrospective verbal reports. Although the two data sets are not directly comparable, they may be used in a complementary manner, providing a deeper and fuller understanding of the processes underpinning superior performance

Word segmentation by alternating colors facilitates eye guidance in Chinese reading.

Science.gov (United States)

Zhou, Wei; Wang, Aiping; Shu, Hua; Kliegl, Reinhold; Yan, Ming

2018-02-12

During sentence reading, low spatial frequency information afforded by spaces between words is the primary factor for eye guidance in spaced writing systems, whereas saccade generation for unspaced writing systems is less clear and under debate. In the present study, we investigated whether word-boundary information, provided by alternating colors (consistent or inconsistent with word-boundary information) influences saccade-target selection in Chinese. In Experiment 1, as compared to a baseline (i.e., uniform color) condition, word segmentation with alternating color shifted fixation location towards the center of words. In contrast, incorrect word segmentation shifted fixation location towards the beginning of words. In Experiment 2, we used a gaze-contingent paradigm to restrict the color manipulation only to the upcoming parafoveal words and replicated the results, including fixation location effects, as observed in Experiment 1. These results indicate that Chinese readers are capable of making use of parafoveal word-boundary knowledge for saccade generation, even if such information is unfamiliar to them. The present study provides novel support for the hypothesis that word segmentation is involved in the decision about where to fixate next during Chinese reading.

The eye-tracking of social stimuli in patients with Rett syndrome and autism spectrum disorders: a pilot study

Directory of Open Access Journals (Sweden)

José Salomão Schwartzman

2015-05-01

Full Text Available Objective To compare visual fixation at social stimuli in Rett syndrome (RT and autism spectrum disorders (ASD patients. Method Visual fixation at social stimuli was analyzed in 14 RS female patients (age range 4-30 years, 11 ASD male patients (age range 4-20 years, and 17 children with typical development (TD. Patients were exposed to three different pictures (two of human faces and one with social and non-social stimuli presented for 8 seconds each on the screen of a computer attached to an eye-tracker equipment. Results Percentage of visual fixation at social stimuli was significantly higher in the RS group compared to ASD and even to TD groups. Conclusion Visual fixation at social stimuli seems to be one more endophenotype making RS to be very different from ASD.

Stimulation of nitrogen fixation in soddy-podzolic soils with fungi

Science.gov (United States)

Kurakov, A. V.; Prokhorov, I. S.; Kostina, N. V.; Makhova, E. G.; Sadykova, V. S.

2006-09-01

Stimulation of nitrogen fixation in soddy-podzolic soils is related to the hydrolytic activity of fungi decomposing plant polymers. It was found that the rate of nitrogen fixation upon the simultaneous inoculation of the strains of nitrogen-fixing bacteria Bacillus cereus var. mycoides and the cellulolytic fungus Trichoderma asperellum into a sterile soil enriched with cellulose or Jerusalem artichoke residues is two to four times higher than upon the inoculation of the strains of Bacillus cereus var. mycoides L1 only. The increase in the nitrogen fixation depended on the resistance of the substrates added into the soil to fungal hydrolysis. The biomass of the fungi decomposing plant polymers increased by two-four times. The nitrogen-fixing activity of the soil decreased when the growth of the fungi was inhibited with cycloheximide, which attested to a close correlation between the intensity of the nitrogen fixation and the decomposition of the plant polymers by fungi. The introduction of an antifungal antibiotic, together with starch or with plant residues, significantly (by 60-90%) decreased the rate of nitrogen fixation in the soll.

Fusion Surgery Required for Recurrent Pediatric Atlantoaxial Rotatory Fixation after Failure of Temporary Fixation with Instrumentation

Directory of Open Access Journals (Sweden)

Yoshiyuki Matsuyama

2017-01-01

Full Text Available In cases of chronic irreducible and recurrent unstable atlantoaxial rotatory fixation (AARF, closed reduction and its maintenance are often unsuccessful, requiring surgical treatment. The purpose of the present report is to describe a rare case of pediatric AARF that required multiple treatments. A 6-year-old boy was diagnosed as having type 2 AARF. After conservative treatment, the patient was treated with temporary fixation surgery (C1-C2 Magerl without a bone graft in consideration of motion preservation after screw removal. AARF recurred after the screw removal and required fusion surgery (Magerl–Brooks with an iliac bone graft. Ultimately, bone union was achieved and the screws were removed 11 months after the surgery. We recommend surgeons be cautious when choosing temporary fixation surgery for AARF in small children. Further investigation is needed to determine the optimal time before screw removal.

The processing of spatial information in short-term memory: insights from eye tracking the path length effect.

Science.gov (United States)

Guérard, Katherine; Tremblay, Sébastien; Saint-Aubin, Jean

2009-10-01

Serial memory for spatial locations increases as the distance between successive stimuli locations decreases. This effect, known as the path length effect [Parmentier, F. B. R., Elford, G., & Maybery, M. T. (2005). Transitional information in spatial serial memory: Path characteristics affect recall performance. Journal of Experimental Psychology: Learning, Memory & Cognition, 31, 412-427], was investigated in a systematic manner using eye tracking and interference procedures to explore the mechanisms responsible for the processing of spatial information. In Experiment 1, eye movements were monitored during a spatial serial recall task--in which the participants have to remember the location of spatially and temporally separated dots on the screen. In the experimental conditions, eye movements were suppressed by requiring participants to incessantly move their eyes between irrelevant locations. Ocular suppression abolished the path length effect whether eye movements were prevented during item presentation or during a 7s retention interval. In Experiment 2, articulatory suppression was combined with a spatial serial recall task. Although articulatory suppression impaired performance, it did not alter the path length effect. Our results suggest that rehearsal plays a key role in serial memory for spatial information, though the effect of path length seems to involve other processes located at encoding, such as the time spent fixating each location and perceptual organization.

Fixation and partitioning of heavy metals in slag after incineration of sewage sludge.

Science.gov (United States)

Chen, Tao; Yan, Bo

2012-05-01

Fixation of heavy metals in the slag produced during incineration of sewage sludge will reduce emission of the metals to the atmosphere and make the incineration process more environmentally friendly. The effects of incineration conditions (incineration temperature 500-1100°C, furnace residence time 0-60min, mass fraction of water in the sludge 0-75%) on the fixation rates and species partitioning of Cd, Pb, Cr, Cu, Zn, Mn and Ni in slag were investigated. When the incineration temperature was increased from 500 to 1100°C, the fixation rate of Cd decreased from 87% to 49%, while the fixation rates of Cu and Mn were stable. The maximum fixation rates for Pb and Zn and for Ni and Cr were reached at 900 and 1100°C, respectively. The fixation rates of Cu, Ni, Cd, Cr and Zn decreased as the residence time increased. With a 20min residence time, the fixation rates of Pb and Mn were low. The maximum fixation rates of Ni, Mn, Zn, Cu and Cr were achieved when the mass fraction of water in the sludge was 55%. The fixation rate of Cd decreased as the water mass fraction increased, while the fixation rate of Pb increased. Partitioning analysis of the metals contained in the slag showed that increasing the incineration temperature and residence time promoted complete oxidation of the metals. This reduced the non-residual fractions of the metals, which would lower the bioavailability of the metals. The mass fraction of water in the sludge had little effect on the partitioning of the metals. Correlation analysis indicated that the fixation rates of heavy metals in the sludge and the forms of heavy metals in the incinerator slag could be controlled by optimization of the incineration conditions. These results show how the bioavailability of the metals can be reduced for environmentally friendly disposal of the incinerator slag. Copyright © 2011 Elsevier Ltd. All rights reserved.

Attachment Avoidance Is Significantly Related to Attentional Preference for Infant Faces: Evidence from Eye Movement Data.

Science.gov (United States)

Jia, Yuncheng; Cheng, Gang; Zhang, Dajun; Ta, Na; Xia, Mu; Ding, Fangyuan

2017-01-01

Objective: To determine the influence of adult attachment orientations on infant preference. Methods: We adopted eye-tracking technology to monitor childless college women's eye movements when looking at pairs of faces, including one adult face (man or woman) and one infant face, with three different expressions (happy, sadness, and neutral). The participants ( N = 150; 84% Han ethnicity) were aged 18-29 years ( M = 19.22, SD = 1.72). A random intercepts multilevel linear regression analysis was used to assess the unique contribution of attachment avoidance, determined using the Experiences in Close Relationships scale, to preference for infant faces. Results: Women with higher attachment avoidance showed less infant preference, as shown by less sustained overt attentional bias to the infant face than the adult face based on fixation time and count. Conclusion: Adult attachment might be related to infant preference according to eye movement indices. Women with higher attachment avoidance may lack attentional preference for infant faces. The findings may aid the treatment and remediation of the interactions between children and mothers with insecure attachment.

Eighth international congress on nitrogen fixation

Energy Technology Data Exchange (ETDEWEB)

1990-01-01

This volume contains the proceedings of the Eighth International Congress on Nitrogen Fixation held May 20--26, 1990 in Knoxville, Tennessee. The volume contains abstracts of individual presentations. Sessions were entitled Recent Advances in the Chemistry of Nitrogen Fixation, Plant-microbe Interactions, Limiting Factors of Nitrogen Fixation, Nitrogen Fixation and the Environment, Bacterial Systems, Nitrogen Fixation in Agriculture and Industry, Plant Function, and Nitrogen Fixation and Evolution.

Outcomes of iris-claw anterior chamber versus iris-fixated foldable intraocular lens in subluxated lens secondary to Marfan syndrome.

Science.gov (United States)

Hirashima, Denise E; Soriano, Eduardo S; Meirelles, Rodrigo L; Alberti, Gustave N; Nosé, Walton

2010-08-01

To compare the outcome of phacoemulsification using 2 different iris-fixation techniques for intraocular lens (IOL) replacement, a foldable posterior chamber IOL (PCIOL; AcrySof MA60AC, Alcon Laboratories Inc, Fort Worth, TX) and an iris-claw anterior chamber IOL (ACIOL; Artisan, Ophtec BV), for treatment of subluxated lenses in patients with Marfan syndrome (MFS). Randomized, controlled trial. A total of 31 eyes of 16 patients with subluxated lenses associated with MFS and a preoperative corrected visual acuity (CVA) IOL type. Preoperative and postoperative ophthalmologic examination, optical coherence tomography, and endothelial cell counts were performed. We recorded CVA results at 3, 6, and 12 months, complications, endothelial cell loss, and central retinal thickness. In the iris-fixated PCIOL group, CVA was significantly improved at 3 (P = 0.011; n = 16), 6 (P = 0.006; n = 16), and 12 months (P = 0.002; n = 16). In the iris-claw ACIOL group, CVA was significantly improved at 3 (P = 0.001; n=15), 6 (P = 0.001; n = 15), and 12 months (P = 0.009; n = 12). The CVA results did not differ significantly between groups. Dislocation of the IOL occurred in 3 of 16 (18.75%) eyes in the PCIOL group. Retinal detachment occurred in 3 eyes (2 in the PCIOL group and 1 in the ACIOL group) and was successfully repaired. Postoperative foveal tomograms in both groups revealed a decrease in the mean foveal thickness (MFT; IOL dislocation tended to occur more frequently in the iris-fixated PCIOL group, the difference was not significant. At 6 months postoperatively, all study patients tended to have a thinner MFT. None of the patients in either group developed cystoid macular edema. Copyright 2010 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Influences of dwell time and cursor control on the performance in gaze driven typing

OpenAIRE

Helmert, Jens R.; Pannasch, Sebastian; Velichkovsky, Boris M.

2008-01-01

In gaze controlled computer interfaces the dwell time is often used as selection criterion. But this solution comes along with several problems, especially in the temporal domain: Eye movement studies on scene perception could demonstrate that fixations of different durations serve different purposes and should therefore be differentiated. The use of dwell time for selection implies the need to distinguish intentional selections from merely per-ceptual processes, described as the Midas touch ...

Exposure of surgeons-in-training to radiation during intramedullary fixation of femoral shaft fractures

International Nuclear Information System (INIS)

Coetzee, J.C.; Van der Merwe, E.J.

1992-01-01

Owing to the continuous turnover of registrars and radiographers, most of the trauma-related orthopedic surgery in this academic hospital is done by inexperienced surgeons-in-training and the fluoroscopy by junior radiographers. This could result in excessive radiation doses. Calibrated lithium fluoride thermoluminescent chips were secured to various parts of the primary surgeon's body to quantify the radiation dose received during the insertion of an intramedullary nail. Closed intramedullary fixation of 15 fractures of the femur was done with interlocking as necessary. The total average exposure time was 14 minutes 45 seconds per procedure. Distal locking took up 31% of this time. The mean radiation dose to the surgeon's eyes and thyroid was 0,13 mGy and to the dominant hand 2,10 mGy. This would allow the performance of about 350 such procedures per year before the maximum permissible dose level was reached. Recommendations to decrease irradiation dosage are made. 6 refs., 6 tabs

Isotopes in biological dinitrogen fixation

Energy Technology Data Exchange (ETDEWEB)

1978-10-01

Nineteen papers were presented at the conference. Some topics discussed are as follows: biochemistry and genetics of dinitrogen fixation; genetics of the Rhizobium-legume symbiosis and of the nitrogen-fixing bacteria; studies on nonsymbiotic dinitrogen fixation in grass-bacteria associations and blue--green algae; use of /sup 15/N and /sup 13/N for the assay of dinitrogen fixation; effects of management practices on dinitrogen fixation; economy of C and N in nitrogen-fixing legumes; and survey of international and national programs on dinitrogen fixation. (HLW)

Internal Versus External Fixation of Charcot Midfoot Deformity Realignment.

Science.gov (United States)

Lee, Daniel J; Schaffer, Joseph; Chen, Tien; Oh, Irvin

2016-07-01

Internal and external fixation techniques have been described for realignment and arthrodesis of Charcot midfoot deformity. There currently is no consensus on the optimal method of surgical reconstruction. This systematic review compared the clinical results of surgical realignment with internal and external fixation, specifically in regard to return to functional ambulation, ulcer occurrence, nonunion, extremity amputation, unplanned further surgery, deep infection, wound healing problems, peri- or intraoperative fractures, and total cases with any complication. A search of multiple databases for all relevant articles published from January 1, 1990, to March 22, 2014, was performed. A logistic regression model evaluated each of the outcomes and its association with the type of fixation method. The odds of returning to functional ambulation were 25% higher for internal fixation (odds ratio [OR], 1.259). Internal fixation had a 42% reduced rate of ulcer occurrence (OR, 0.578). External fixation was 8 times more likely to develop radiographic nonunion than internal fixation (OR, 8.2). Internal fixation resulted in a 1.5-fold increase in extremity amputation (OR, 1.488), a 2-fold increase in deep infection (OR, 2.068), a 3.4-fold increase in wound healing complications (OR, 3.405), and a 1.5-fold increase in the total number of cases experiencing any complication (OR, 1.525). This was associated with a 20% increase in the need for unplanned further surgery with internal fixation (OR, 1.221). Although internal fixation may decrease the risk of nonunion and increase return to functional ambulation, it had a higher rate of overall complications than external fixation for realignment and arthrodesis of Charcot midfoot deformity. [Orthopedics. 2016; 39(4):e595-e601.]. Copyright 2016, SLACK Incorporated.

Modeling eye movements in visual agnosia with a saliency map approach: bottom-up guidance or top-down strategy?

Science.gov (United States)

Foulsham, Tom; Barton, Jason J S; Kingstone, Alan; Dewhurst, Richard; Underwood, Geoffrey

2011-08-01

Two recent papers (Foulsham, Barton, Kingstone, Dewhurst, & Underwood, 2009; Mannan, Kennard, & Husain, 2009) report that neuropsychological patients with a profound object recognition problem (visual agnosic subjects) show differences from healthy observers in the way their eye movements are controlled when looking at images. The interpretation of these papers is that eye movements can be modeled as the selection of points on a saliency map, and that agnosic subjects show an increased reliance on visual saliency, i.e., brightness and contrast in low-level stimulus features. Here we review this approach and present new data from our own experiments with an agnosic patient that quantifies the relationship between saliency and fixation location. In addition, we consider whether the perceptual difficulties of individual patients might be modeled by selectively weighting the different features involved in a saliency map. Our data indicate that saliency is not always a good predictor of fixation in agnosia: even for our agnosic subject, as for normal observers, the saliency-fixation relationship varied as a function of the task. This means that top-down processes still have a significant effect on the earliest stages of scanning in the setting of visual agnosia, indicating severe limitations for the saliency map model. Top-down, active strategies-which are the hallmark of our human visual system-play a vital role in eye movement control, whether we know what we are looking at or not. Copyright © 2011 Elsevier Ltd. All rights reserved.

The Impact of Task Demands on Fixation-Related Brain Potentials during Guided Search.

Directory of Open Access Journals (Sweden)

Anthony J Ries

Full Text Available Recording synchronous data from EEG and eye-tracking provides a unique methodological approach for measuring the sensory and cognitive processes of overt visual search. Using this approach we obtained fixation related potentials (FRPs during a guided visual search task specifically focusing on the lambda and P3 components. An outstanding question is whether the lambda and P3 FRP components are influenced by concurrent task demands. We addressed this question by obtaining simultaneous eye-movement and electroencephalographic (EEG measures during a guided visual search task while parametrically modulating working memory load using an auditory N-back task. Participants performed the guided search task alone, while ignoring binaurally presented digits, or while using the auditory information in a 0, 1, or 2-back task. The results showed increased reaction time and decreased accuracy in both the visual search and N-back tasks as a function of auditory load. Moreover, high auditory task demands increased the P3 but not the lambda latency while the amplitude of both lambda and P3 was reduced during high auditory task demands. The results show that both early and late stages of visual processing indexed by FRPs are significantly affected by concurrent task demands imposed by auditory working memory.

Eye movement control in reading unspaced text: the case of the Japanese script.

Science.gov (United States)

Kajii, N; Nazir, T A; Osaka, N

2001-09-01

The present study examines the landing-site distributions of the eyes during natural reading of Japanese script: a script that mixes three different writing systems (Kanji, Hiragana, and Katakana) and that misses regular spacing between words. The results show a clear preference of the eyes to land at the beginning rather than the center of the word. In addition, it was found that the eyes land on Kanji characters more frequently than on Hiragana or Katakana characters. Further analysis for two- and three-character words indicated that the eye's landing-site distribution differs depending on type of the characters in the word: the eyes prefer to land at the word beginning only when the initial character of the word is a Kanji character. For pure Hiragana words, the proportion of initial fixations did not differ between character positions. Thus, as already indicated by Kambe (National Institute of Japanese Language Report 85 (1986) 29), the visual distinctiveness of the three Japanese scripts plays a role in guiding eye movements in reading Japanese.

Skin Graft Fixation Using Hydrofiber (Aquacel® Extra).

Science.gov (United States)

Yen, Ya-Hui; Lin, Chih-Ming; Hsu, Honda; Chen, Ying-Chen; Chen, Yi-Wen; Li, Wan-Yu; Hsieh, Chia-Nan; Huang, Chieh-Chi

2018-06-01

The traditional method of skin graft fixation is with tie-over bollus dressing. The use of splints in the extremities for skin graft fixation is a common practice. However, these splints are heavy and uncomfortable and contribute considerably to our overall medical waste. Hydrofiber (Aquacel Extra) has a strong fluid absorption property and fixates well to the underlying wound once applied. In this study, we used hydrofiber for fixation, avoiding the use of splints after skin grafting. A total of 56 patients reconstructed with split-thickness skin graft that was fixated only with hydrofiber between March 2015 and March 2016 were included in this retrospective study. There were 44 men and 12 women with a mean age of 61 ± 18 years. The defect size ranged from 1 × 1 cm for fingertips to 30 × 12 cm for lower limb defects. The average defect size was 61 ± 78 cm. The mean skin graft take was 96% ± 6%. Because splints were not required, we saved around 48 kg of medical waste over the space of 1 year. The use of hydrofiber for skin graft fixation was effective and technically very simple. Splints were not required with this method, decreasing the medical waste created and increasing patient comfort. We suggest that this is an excellent alternative for skin graft fixation while at the same time decreasing our carbon footprint as surgeons.

Using eye movements to investigate selective attention in chronic daily headache.

Science.gov (United States)

Liossi, Christina; Schoth, Daniel E; Godwin, Hayward J; Liversedge, Simon P

2014-03-01

Previous research has demonstrated that chronic pain is associated with biased processing of pain-related information. Most studies have examined this bias by measuring response latencies. The present study extended previous work by recording eye movement behaviour in individuals with chronic headache and in healthy controls while participants viewed a set of images (i.e., facial expressions) from 4 emotion categories (pain, angry, happy, neutral). Biases in initial orienting were assessed from the location of the initial shift in gaze, and biases in the maintenance of attention were assessed from the duration of gaze on the picture that was initially fixated, and the mean number of visits, and mean fixation duration per image category. The eye movement behaviour of the participants in the chronic headache group was characterised by a bias in initial shift of orienting to pain. There was no evidence of individuals with chronic headache visiting more often, or spending significantly more time viewing, pain images compared to other images. Both participant groups showed a significantly greater bias to maintain gaze longer on happy images, relative to pain, angry, and neutral images. Results are consistent with a pain-related bias that operates in the orienting of attention on pain-related stimuli, and suggest that chronic pain participants' attentional biases for pain-related information are evident even when other emotional stimuli are present. Pain-related information-processing biases appear to be a robust feature of chronic pain and may have an important role in the maintenance of the disorder. Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Real Time Eye Detector with Cascaded Convolutional Neural Networks

Directory of Open Access Journals (Sweden)

Bin Li

2018-01-01

Full Text Available An accurate and efficient eye detector is essential for many computer vision applications. In this paper, we present an efficient method to evaluate the eye location from facial images. First, a group of candidate regions with regional extreme points is quickly proposed; then, a set of convolution neural networks (CNNs is adopted to determine the most likely eye region and classify the region as left or right eye; finally, the center of the eye is located with other CNNs. In the experiments using GI4E, BioID, and our datasets, our method attained a detection accuracy which is comparable to existing state-of-the-art methods; meanwhile, our method was faster and adaptable to variations of the images, including external light changes, facial occlusion, and changes in image modality.

[Case-control study on T-shaped locking internal fixation and external fixation for the treatment of dorsal Barton's fracture].

Science.gov (United States)

Chen, Huan-qing; Wen, Xi-le; Li, Yang-ming; Wen, Cong-you

2015-06-01

To compare clinical effect of T-shaped locking internal fixation and external fixation in treating dorsal Barton's fracture,and investigate selective strategy of internal fixation. From January 2008 to January 2013, 100 patients with dorsal Barton's fracture were randomly divided into two groups. In treatment group, there were 30 males and 20 females with an average age of (33.8±3.6) years old;30 cases were type B, 20 cases were type C;and treated with T-shaped locking internal fixation. In control group, there were 32 male and 18 females with an average age of (32.9±3.4) years old; 29 cases were type B, 21 cases were type C; and treated with external fixation. Volar tilt, ulnar deviation and radial height at 3 months after operation were detected and compared between two groups. Mechara functional evaluation were used to evaluate postoperative clinical effects. Clinical cure time, postoperative complications,joint mobility and function score were recorded and compared between two groups. In treatment group,volar tilt was (11.9±2.7)°, ulnar deviation was (20.8+ 2.9)°,and radial height was (10.9±1.8) mm; while volar tilt was (9.1±1.6)°, ulnar deviation was (17.1±2.9)°, and radial height was (8.1±1.5) mm in control group. Treatment group was better than control group in volar tilt, ulnar deviation and radial height. Clinical cure time in treatment group was(12.0±2.3) weeks, shorter than control group (18.0±4.1) weeks. The incidence of complications in treatment group was lower than control group. According to Mehara functional evaluation,20 cases got excellent results, 25 good, 3 moderate and 2 poor in treatment group; 16 cases got excellent results, 14 good, 10 moderate and 10 poor in control group. Treatment group was better than control group in clinical effects. T-shaped locking internal fixation with postoperative functional exercise for the treatment of dorsal Barton's fracture fits for biomechanics demands,and has advantages of stable fixation

MODELLING SYNERGISTIC EYE MOVEMENTS IN THE VISUAL FIELD

Directory of Open Access Journals (Sweden)

BARITZ Mihaela

2015-06-01

Full Text Available Some theoretical and practical considerations about eye movements in visual field are presented in the first part of this paper. These movements are developed into human body to be synergistic and are allowed to obtain the visual perception in 3D space. The theoretical background of the eye movements’ analysis is founded on the establishment of movement equations of the eyeball, as they consider it a solid body with a fixed point. The exterior actions, the order and execution of the movements are ensured by the neural and muscular external system and thus the position, stability and movements of the eye can be quantified through the method of reverse kinematic. The purpose of these researches is the development of a simulation model of human binocular visual system, an acquisition methodology and an experimental setup for data processing and recording regarding the eye movements, presented in the second part of the paper. The modeling system of ocular movements aims to establish the binocular synergy and limits of visual field changes in condition of ocular motor dysfunctions. By biomechanical movements of eyeball is established a modeling strategy for different sort of processes parameters like convergence, fixation and eye lens accommodation to obtain responses from binocular balance. The results of modelling processes and the positions of eye ball and axis in visual field are presented in the final part of the paper.

Visual Processing of Faces in Individuals with Fragile X Syndrome: An Eye Tracking Study

Science.gov (United States)

Farzin, Faraz; Rivera, Susan M.; Hessl, David

2009-01-01

Gaze avoidance is a hallmark behavioral feature of fragile X syndrome (FXS), but little is known about whether abnormalities in the visual processing of faces, including disrupted autonomic reactivity, may underlie this behavior. Eye tracking was used to record fixations and pupil diameter while adolescents and young adults with FXS and sex- and…

Guide to radiation fixatives

International Nuclear Information System (INIS)

Tawil, J.J.; Bold, F.C.

1983-11-01

This report identifies and then characterizes a variety of substances available in the market place for potential effectiveness as a fixative on radiologically contaminated surfaces. The substances include both generic chemicals and proprietary products. In selecting a fixative for a particular application, several attributes of the fixative may be relevant to the choice. These attributes include: toxicity, durability, and cleanliness and removability. In addition to the attributes of the fixative, one should also take into account certain characteristics of the site to be treated. These characteristics relate to climate, nature of the surface, use to which the treated surface will be put, subsequent cleanup operations, and type of neighboring surfaces. Finally, costs and potential environmental effects may influence the decision. A variety of fixatives are evaluated with respect to these various attributes and summarized in a reference table

Vergence-mediated changes in the axis of eye rotation during the human vestibulo-ocular reflex can occur independent of eye position.

Science.gov (United States)

Migliaccio, Americo A; Cremer, Phillip D; Aw, Swee T; Halmagyi, G Michael; Curthoys, Ian S; Minor, Lloyd B; Todd, Michael J

2003-07-01

The aim of this study was to determine whether vergence-mediated changes in the axis of eye rotation in the human vestibulo-ocular reflex (VOR) would obey Listing's Law (normally associated with saccadic eye movements) independent of the initial eye position. We devised a paradigm for disassociating the saccadic velocity axis from eye position by presenting near and far targets that were centered with respect to one eye. We measured binocular 3-dimensional eye movements using search coils in ten normal subjects and 3-dimensional linear head acceleration using Optotrak in seven normal subjects. The stimuli consisted of passive, unpredictable, pitch head rotations with peak acceleration of approximately 2000 degrees /s(2 )and amplitude of approximately 20 degrees. During the pitch head rotation, each subject fixated straight ahead with one eye, whereas the other eye was adducted 4 degrees during far viewing (94 cm) and 25 degrees during near viewing (15 cm). Our data showed expected compensatory pitch rotations in both eyes, and a vergence-mediated horizontal rotation only in the adducting eye. In addition, during near viewing we observed torsional eye rotations not only in the adducting eye but also in the eye looking straight ahead. In the straight-ahead eye, the change in torsional eye velocity between near and far viewing, which began approximately 40 ms after the start of head rotation, was 10+/-6 degrees /s (mean +/- SD). This change in torsional eye velocity resulted in a 2.4+/-1.5 degrees axis tilt toward Listing's plane in that eye. In the adducting eye, the change in torsional eye velocity between near and far viewing was 16+/-6 degrees /s (mean +/- SD) and resulted in a 4.1+/-1.4 degrees axis tilt. The torsional eye velocities were conjugate and both eyes partially obeyed Listing's Law. The axis of eye rotation tilted in the direction of the line of sight by approximately one-third of the angle between the line of sight and a line orthogonal to Listing

Effect of occlusion amblyopia after prescribed full-time occlusion on long-term visual acuity outcomes.

Science.gov (United States)

Longmuir, Susannah; Pfeifer, Wanda; Scott, William; Olson, Richard

2013-01-01

To investigate the incidence and characteristics of occlusion amblyopia with prescribed full-time patching and determine its effect on long-term visual acuity outcomes. The records of patients younger than 10 years diagnosed as having amblyopia between 1970 and 2000 were retrospectively reviewed. Patients were prescribed full-time occlusion and observed until completion of therapy. Of 597 patients treated for amblyopia by full-time patching, 115 were diagnosed as having occlusion amblyopia (19.3%). Seventy-five percent (86 of 115) developed occlusion amblyopia during the first episode of full-time patching. Occlusion amblyopia occurred more frequently in children prescribed full-time patching at an earlier age (P = .0002), with an odds ratio of 8.56 (95% confidence interval: 2.73, 26.84) in children younger than 36 months and 2.66 (95% confidence interval: 0.96, 7.37) in children between 36 and 59 months old. Seven of the patients with occlusion amblyopia did not reverse fixation and continued to fixate with the initially amblyopic eye after treatment. Final visual acuity in these eyes with occlusion amblyopia was 20/30 or better. After cessation of treatment, the final interocular difference in visual acuity was less in patients with a history of occlusion amblyopia (P = .003). Occlusion amblyopia occurred at all ages, but the incidence decreased with increasing age. Patients who developed occlusion amblyopia with prescribed full-time occlusion had less interocular visual acuity difference than patients who did not, suggesting that development of occlusion amblyopia can indicate the potential for the development of better vision in the originally amblyopic eye. Copyright 2013, SLACK Incorporated.

Response mode, compatibility, and dual-processes in the evaluation of simple gambles: An eye-tracking investigation

Directory of Open Access Journals (Sweden)

Paul Slovic

2012-07-01

Full Text Available We employed simple gambles to investigate information processing in relation to the compatibility effect. Subjects should be more likely to engage in a deliberative thinking strategy when completing a pricing task rather than a rating task. We used eye-tracking methodology to measure information acquisition and processing in order to test the above hypothesis as well as to show that losses and alternatives with uncertain outcomes are more likely than gains and alternatives with sure outcomes to be processed through a deliberative thinking process. Results showed that pupil dilations, fixation duration and number of fixations increased when subjects evaluated the gambles with a pricing task. Additionally, the number of fixations increased as the gamble outcome became increasingly negative and when the outcome was uncertain (vs. sure. Fixations were also predictive of subjects' final evaluations of the gambles. We discuss our results in light of the cognitive processes underlying different response modes in economic preferences.

Biomechanics of lumbar cortical screw-rod fixation versus pedicle screw-rod fixation with and without interbody support.

Science.gov (United States)

Perez-Orribo, Luis; Kalb, Samuel; Reyes, Phillip M; Chang, Steve W; Crawford, Neil R

2013-04-15

Seven different combinations of posterior screw fixation, with or without interbody support, were compared in vitro using nondestructive flexibility tests. To study the biomechanical behavior of a new cortical screw (CS) fixation construct relative to the traditional pedicle screw (PS) construct. The CS is an alternative to the PS for posterior fixation of the lumbar spine. The CS trajectory is more sagittally and cranially oriented than the PS, being anchored in the pars interarticularis. Like PS fixation, CS fixation uses interconnecting rods fastened with top-locking connectors. Stability after bilateral CS fixation was compared with stability after bilateral PS fixation in the setting of intact disc and with direct lateral interbody fixation (DLIF) or transforaminal lateral interbody fixation (TLIF) support. Standard nondestructive flexibility tests were performed in cadaveric lumbar specimens, allowing non-paired comparisons of specific conditions from 28 specimens (4 groups of 7) within a larger experiment of multiple hardware configurations. Condition tested and group from which results originated were as follows: (1) intact (all groups); (2) with L3-L4 bilateral PS-rods (group 1); (3) with bilateral CS-rods (group 2); (4) with DLIF (group 3); (5) with DLIF + CS-rods (group 4); (6) with DLIF + PS-rods (group 3); (7) with TLIF + CS-rods (group 2), and (8) with TLIF + PS-rods (group 2). To assess spinal stability, the mean range of motion, lax zone, and stiff zone at L3-L4 were compared during flexion-extension, lateral bending, and axial rotation. With intact disc, stability was equivalent after PS-rod and CS-rod fixation, except that PS-rod fixation was stiffer during axial rotation. With DLIF support, there was no significant difference in stability between PS-rod and CS-rod fixation. With TLIF support, PS-rod fixation was stiffer than CS-rod fixation during lateral bending. Bilateral CS-rod fixation provided about the same stability in cadaveric specimens

Eye Movements Reveal Optimal Strategies for Analogical Reasoning.

Science.gov (United States)

Vendetti, Michael S; Starr, Ariel; Johnson, Elizabeth L; Modavi, Kiana; Bunge, Silvia A

2017-01-01

Analogical reasoning refers to the process of drawing inferences on the basis of the relational similarity between two domains. Although this complex cognitive ability has been the focus of inquiry for many years, most models rely on measures that cannot capture individuals' thought processes moment by moment. In the present study, we used participants' eye movements to investigate reasoning strategies in real time while solving visual propositional analogy problems (A:B::C:D). We included both a semantic and a perceptual lure on every trial to determine how these types of distracting information influence reasoning strategies. Participants spent more time fixating the analogy terms and the target relative to the other response choices, and made more saccades between the A and B items than between any other items. Participants' eyes were initially drawn to perceptual lures when looking at response choices, but they nonetheless performed the task accurately. We used participants' gaze sequences to classify each trial as representing one of three classic analogy problem solving strategies and related strategy usage to analogical reasoning performance. A project-first strategy, in which participants first extrapolate the relation between the AB pair and then generalize that relation for the C item, was both the most commonly used strategy as well as the optimal strategy for solving visual analogy problems. These findings provide new insight into the role of strategic processing in analogical problem solving.

Eye Movements Reveal Optimal Strategies for Analogical Reasoning

Directory of Open Access Journals (Sweden)

Michael S. Vendetti

2017-06-01

Full Text Available Analogical reasoning refers to the process of drawing inferences on the basis of the relational similarity between two domains. Although this complex cognitive ability has been the focus of inquiry for many years, most models rely on measures that cannot capture individuals' thought processes moment by moment. In the present study, we used participants' eye movements to investigate reasoning strategies in real time while solving visual propositional analogy problems (A:B::C:D. We included both a semantic and a perceptual lure on every trial to determine how these types of distracting information influence reasoning strategies. Participants spent more time fixating the analogy terms and the target relative to the other response choices, and made more saccades between the A and B items than between any other items. Participants' eyes were initially drawn to perceptual lures when looking at response choices, but they nonetheless performed the task accurately. We used participants' gaze sequences to classify each trial as representing one of three classic analogy problem solving strategies and related strategy usage to analogical reasoning performance. A project-first strategy, in which participants first extrapolate the relation between the AB pair and then generalize that relation for the C item, was both the most commonly used strategy as well as the optimal strategy for solving visual analogy problems. These findings provide new insight into the role of strategic processing in analogical problem solving.

Real-time sharing of gaze data between multiple eye trackers-evaluation, tools, and advice.

Science.gov (United States)

Nyström, Marcus; Niehorster, Diederick C; Cornelissen, Tim; Garde, Henrik

2017-08-01

Technological advancements in combination with significant reductions in price have made it practically feasible to run experiments with multiple eye trackers. This enables new types of experiments with simultaneous recordings of eye movement data from several participants, which is of interest for researchers in, e.g., social and educational psychology. The Lund University Humanities Laboratory recently acquired 25 remote eye trackers, which are connected over a local wireless network. As a first step toward running experiments with this setup, demanding situations with real time sharing of gaze data were investigated in terms of network performance as well as clock and screen synchronization. Results show that data can be shared with a sufficiently low packet loss (0.1 %) and latency (M = 3 ms, M A D = 2 ms) across 8 eye trackers at a rate of 60 Hz. For a similar performance using 24 computers, the send rate needs to be reduced to 20 Hz. To help researchers conduct similar measurements on their own multi-eye-tracker setup, open source software written in Python and PsychoPy are provided. Part of the software contains a minimal working example to help researchers kick-start experiments with two or more eye trackers.

Reading Words or Pictures: Eye Movement Patterns in Adults and Children Differ by Age Group and Receptive Language Ability.

Science.gov (United States)

An, Licong; Wang, Yifang; Sun, Yadong

2017-01-01

This study was conducted to explore the differences in the degree of attention given to Chinese print and pictures by children and adults when they read picture books with and without Chinese words. We used an eye tracker from SensoMotoric Instruments to record the visual fixations of the subjects. The results showed that the adults paid more attention to Chinese print and looked at the print sooner than the children did. The stronger the children's receptive language abilities were, the less time it took them to view the pictures. All participants spent the same amount of time looking at the pictures whether Chinese words were present or absent.

An ocular biomechanic model for dynamic simulation of different eye movements.

Science.gov (United States)

Iskander, J; Hossny, M; Nahavandi, S; Del Porto, L

2018-04-11

Simulating and analysing eye movement is useful for assessing visual system contribution to discomfort with respect to body movements, especially in virtual environments where simulation sickness might occur. It can also be used in the design of eye prosthesis or humanoid robot eye. In this paper, we present two biomechanic ocular models that are easily integrated into the available musculoskeletal models. The model was previously used to simulate eye-head coordination. The models are used to simulate and analyse eye movements. The proposed models are based on physiological and kinematic properties of the human eye. They incorporate an eye-globe, orbital suspension tissues and six muscles with their connective tissues (pulleys). Pulleys were incorporated in rectus and inferior oblique muscles. The two proposed models are the passive pulleys and the active pulleys models. Dynamic simulations of different eye movements, including fixation, saccade and smooth pursuit, are performed to validate both models. The resultant force-length curves of the models were similar to the experimental data. The simulation results show that the proposed models are suitable to generate eye movement simulations with results comparable to other musculoskeletal models. The maximum kinematic root mean square error (RMSE) is 5.68° and 4.35° for the passive and active pulley models, respectively. The analysis of the muscle forces showed realistic muscle activation with increased muscle synergy in the active pulley model. Copyright © 2018 Elsevier Ltd. All rights reserved.

The geometric preference subtype in ASD: identifying a consistent, early-emerging phenomenon through eye tracking.

Science.gov (United States)

Moore, Adrienne; Wozniak, Madeline; Yousef, Andrew; Barnes, Cindy Carter; Cha, Debra; Courchesne, Eric; Pierce, Karen

2018-01-01

The wide range of ability and disability in ASD creates a need for tools that parse the phenotypic heterogeneity into meaningful subtypes. Using eye tracking, our past studies revealed that when presented with social and geometric images, a subset of ASD toddlers preferred viewing geometric images, and these toddlers also had greater symptom severity than ASD toddlers with greater social attention. This study tests whether this "GeoPref test" effect would generalize across different social stimuli. Two hundred and twenty-seven toddlers (76 ASD) watched a 90-s video, the Complex Social GeoPref test, of dynamic geometric images paired with social images of children interacting and moving. Proportion of visual fixation time and number of saccades per second to both images were calculated. To allow for cross-paradigm comparisons, a subset of 126 toddlers also participated in the original GeoPref test. Measures of cognitive and social functioning (MSEL, ADOS, VABS) were collected and related to eye tracking data. To examine utility as a diagnostic indicator to detect ASD toddlers, validation statistics (e.g., sensitivity, specificity, ROC, AUC) were calculated for the Complex Social GeoPref test alone and when combined with the original GeoPref test. ASD toddlers spent a significantly greater amount of time viewing geometric images than any other diagnostic group. Fixation patterns from ASD toddlers who participated in both tests revealed a significant correlation, supporting the idea that these tests identify a phenotypically meaningful ASD subgroup. Combined use of both original and Complex Social GeoPref tests identified a subgroup of about 1 in 3 ASD toddlers from the "GeoPref" subtype (sensitivity 35%, specificity 94%, AUC 0.75.) Replicating our previous studies, more time looking at geometric images was associated with significantly greater ADOS symptom severity. Regardless of the complexity of the social images used (low in the original GeoPref test vs high in

Results of application of external fixation with different types of fixators

Directory of Open Access Journals (Sweden)

Grubor Predrag

2012-01-01

Full Text Available Introduction. Extra-focal or external fixation is the method of fracture fixation through the healthy part of the bone using pins or wires. Objective. The aim was to determine which external splints (Ortofix, Mitković, Charnley and Ilizarov had the best biomechanical properties in primary stabilization of spiral, transverse and commutative bone fractures. Methods. To determine the investigation methodology of biomechanical characteristics of the external fixator we used mathematical and computer simulator (software, juvidur physical model and clinical examination. Results. Values of advancing fragments in millimetres obtained by the study of mathematical and computer simulator (software: Charnley - 0.080 mm, Mitković M 20 - 0.785 mm, Ilizarov - 2.245 mm and Ortofix - 1.400 mm. In testing the juvidur model the following values were obtained: the external fixator Mitković M20 - 1.380 mm, Ortofix - 1.470 mm, Ilizarov - 2.410 mm, and Charnley - 2.510 mm. Clinical research of biomechanical characteristics of the effect of vertical force yielded the following results: Mitković M20 - 0.89 mm, Ortofix - 0.14 mm, Charnley - 0.80 mm and Ilizarov - 1.23 mm. Conclusion. When determining the total number of the stability test splints under the effect of vertical force (compression and force effect in antero-posterior, later-lateral plane of cross, spiral and comminuted long bone fractures, the best unified biomechanical stability was shown by the following external fixators: firstly, Mitković M20 (0.93mm, secondly, Charnley fixator (1.14 mm, thirdly, Ortofix (1.22 mm, and fourthly, Ilizarov (1.60 mm.

External fixation for closed pediatric femoral shaft fractures: where are we now?

Science.gov (United States)

Kong, Heather; Sabharwal, Sanjeev

2014-12-01

Recent advances in external fixation technique and pin design have sought to minimize complications such as pin site infection and premature removal of the external fixator. Although newer forms of internal fixation have gained popularity, external fixation may still have a role in managing pediatric femoral shaft fractures. We sought to assess the time to healing, limb alignment, and complications observed in a cohort of pediatric patients with closed femoral shaft fractures who were treated with external fixation. Over a 15-year period, one surgeon treated 289 pediatric patients with femur fractures, 31 (11%) of whom received an external fixator. The general indications for use of an external fixator during the period in question included length-unstable fractures, metadiaphyseal location, refracture, and pathologic fracture. Six patients (19%) had inadequate followup data and four patients (13%) were treated with a combination of flexible intramedullary nails and external fixation, leaving 21 patients for analysis. Mean age at injury was 10 years (range, 6-15 years) and followup averaged 22 months (range, 5-45 months) after removal of the fixator. Radiographs were examined for alignment and limb length discrepancy. Complications were recorded from a chart review. Mean time in the fixator was 17 weeks (range, 9-24 weeks). One patient sustained a refracture and one patient with an isolated femur fracture had a leg length discrepancy > 2 cm. There were no pin site infections requiring intravenous antibiotics or additional surgery. One patient with Blount disease and previous tibial osteotomy developed transient peroneal nerve palsy. Despite improvements in pin design and predictable fracture healing, complications such as refracture and leg length discrepancy after external fixation of pediatric femoral shaft fractures can occur. However, external fixation remains a viable alternative for certain fractures such as length-unstable fractures, metadiaphyseal

Eye-Tracking Study on Facial Emotion Recognition Tasks in Individuals with High-Functioning Autism Spectrum Disorders

Science.gov (United States)

Tsang, Vicky

2018-01-01

The eye-tracking experiment was carried out to assess fixation duration and scan paths that individuals with and without high-functioning autism spectrum disorders employed when identifying simple and complex emotions. Participants viewed human photos of facial expressions and decided on the identification of emotion, the negative-positive emotion…

Biomechanical Evaluation of Standard Versus Extended Proximal Fixation Olecranon Plates for Fixation of Olecranon Fractures.

Science.gov (United States)

Boden, Allison L; Daly, Charles A; Dalwadi, Poonam P; Boden, Stephanie A; Hutton, William C; Muppavarapu, Raghuveer C; Gottschalk, Michael B

2018-01-01

Small olecranon fractures present a significant challenge for fixation, which has resulted in development of plates with proximal extension. Olecranon-specific plates with proximal extensions are widely thought to offer superior fixation of small proximal fragments but have distinct disadvantages: larger dissection, increased hardware prominence, and the increased possibility of impingement. Previous biomechanical studies of olecranon fracture fixation have compared methods of fracture fixation, but to date there have been no studies defining olecranon plate fixation strength for standard versus extended olecranon plates. The purpose of this study is to evaluate the biomechanical utility of the extended plate for treatment of olecranon fractures. Sixteen matched pairs of fresh-frozen human cadaveric elbows were used. Of the 16, 8 matched pairs received a transverse osteotomy including 25% and 8 including 50% of the articular surface on the proximal fragment. One elbow from each pair was randomly assigned to a standard-length plate, and the other elbow in the pair received the extended-length plate, for fixation of the fracture. The ulnae were cyclically loaded and subsequently loaded to failure, with ultimate load, number of cycles, and gap formation recorded. There was no statistically significant difference between the standard and extended fixation plates in simple transverse fractures at either 25% or 50% from the proximal most portion of the articular surface of the olecranon. Standard fixation plates are sufficient for the fixation of small transverse fractures, but caution should be utilized particularly with comminution and nontransverse fracture patterns.

Object detection via eye tracking and fringe restraint

Science.gov (United States)

Pan, Fei; Zhang, Hanming; Zeng, Ying; Tong, Li; Yan, Bin

2017-07-01

Object detection is a computer vision problem which caught a large amount of attention. But the candidate boundingboxes extracted from only image features may end up with false-detection due to the semantic gap between the top-down and the bottom up information. In this paper, we propose a novel method for generating object bounding-boxes proposals using the combination of eye fixation point, saliency detection and edges. The new method obtains a fixation orientated Gaussian map, optimizes the map through single-layer cellular automata, and derives bounding-boxes from the optimized map on three levels. Then we score the boxes by combining all the information above, and choose the box with the highest score to be the final box. We perform an evaluation of our method by comparing with previous state-ofthe art approaches on the challenging POET datasets, the images of which are chosen from PASCAL VOC 2012. Our method outperforms them on small scale objects while comparable to them in general.

Operative Fixation of Rib Fractures Indications, Techniques, and Outcomes.

Science.gov (United States)

Galos, David; Taylor, Benjamin; McLaurin, Toni

2017-01-01

Rib fractures are extremely common injuries and vary in there severity from single nondisplaced fractures to multiple segmental fractures resulting in flail chest and respiratory compromise. Historically, rib fractures have been treated conservatively with pain control and respiratory therapy. However this method may not be the best treatment modality in all situations. Operative fixation of select rib fractures has been increasing in popularity especially in patients with flail chest and respiratory compromise. Newer techniques use muscle sparing approaches and precontoured locking plate technology to obtain stable fixation and allow improved respiration. Current reports shows that rib fracture fixation offers the benefits of improved respiratory mechanics and improved pain control in the severe chest wall injury with resultant improvement in patient outcomes by decreasing time on the ventilator, time in the intensive care unit, and overall hospital length of stay.

Attentional Modulation of Eye Torsion Responses

Science.gov (United States)

Stevenson, Scott B.; Mahadevan, Madhumitha S.; Mulligan, Jeffrey B.

2016-01-01

Eye movements generally have both reflexive and voluntary aspects, but torsional eye movements are usually thought of as a reflexive response to image rotation around the line of sight (torsional OKN) or to head roll (torsional VOR). In this study we asked whether torsional responses could be modulated by attention in a case where two stimuli rotated independently, and whether attention would influence the latency of responses. The display consisted of rear-projected radial "pinwheel" gratings, with an inner annulus segment extending from the center to 22 degrees eccentricity, and an outer annulus segment extending from 22 degrees out to 45 degrees eccentricity. The two segments rotated around the center in independent random walks, stepping randomly 4 degrees clockwise or counterclockwise at 60 Hz. Subjects were asked to attend to one or the other while keeping fixation steady at the center of the display. To encourage attention on one or the other segment of the display, subjects were asked to move a joystick in synchrony with the back and forth rotations of one part of the image while ignoring the other. Eye torsion was recorded with the scleral search coil technique, sampled at 500 Hz. All four subjects showed roughly 50% stronger torsion responses to the attended compared to unattended segments. Latency varied from 100 to 150 msec across subjects and was unchanged by attention. These findings suggest that attention can influence eye movement responses that are not typically under voluntary control.

Integrating Click-Through and Eye-Tracking Logs for Decision-Making Process Mining

Directory of Open Access Journals (Sweden)

Razvan PETRUSEL

2014-01-01

Full Text Available In current software every click of the users is logged, therefore a wealth of click-through information exists. Besides, recent technologies have made eye-tracking affordable and an alternative to other human-computer interaction means (e.g. mouse, touchscreens. A big challenge is to make sense of all this data and convert it into useful information. This paper introduces a possible solution placed in the context of decision-making processes. We show how the decision maker's activity can be traced using two means: mouse tracing (i.e. clicks and eye-tracking (i.e. eye fixations. Then, we discuss a mining approach, based on the log, which extracts a Decision Data Model (DDM. We use the DDM to determine, post-hoc, which decision strategy was employed. The paper concludes with a validation based on a controlled experiment.

Glue versus suture for mesh fixation in inguinal hernia repair.

Science.gov (United States)

Chandrasekar, Shruthi; Jeyakumar, S; Ganapathy, Tharun

2018-03-22

Inguinal hernia is one of the most common surgical problem presenting to the surgical OPD. Surgery is the mainstay of treatment for inguinal hernia today. Surgery for inguinal hernia has undergone a great evolution over a period of several centuries. Lichenstein's tension free hernioplasty is the one of the first surgeries taught to a surgical resident. The main aim of surgeries in this era is to give the best possible results with the least possible pain, scar and time. This has given rise to so many modifications to the classical Lichenstein's procedure and also to laparoscopic hernioplasty. Pain after inguinal hernia surgery is found to be debilitating and altering the quality of life in several patients, which has been attributed to the traumatic fixation of the mesh with sutures. This has paved way to the development of various atraumatic methods of fixation, tissue glue is one such development. Hence this study, to compare traumatic and atraumatic methods of mesh fixation in inguinal hernia repair. The aim of this study was to compare suture fixation versus tissue glue fixation of the mesh in inguinal hernia repair. Primary objective was to compare the immediate and chronic post-operative pain. Secondary objective was to compare the time taken for the procedure by the two methods in use and also to compare the presence of any complications. and methodology: This study was done in the General Surgery department of XXX hospital, medical college and research centre, kattangulathur after Ethics committee clearance. It is a single blinded study. The study was done on 51 patients consenting for the study and meeting the inclusion criterias from the period of March 2016 to August 2017 out of which 26 were selected for glue mesh fixation and 25 for suture mesh fixation according to simple randomization. The suture group patients underwent classical Lichenstein's tension free hernioplasty and the glue group underwent Lichenstein's hernioplasty with glue where dots of

Oxytocin increases attention to the eyes and selectively enhances self-reported affective empathy for fear.

Science.gov (United States)

Hubble, Kelly; Daughters, Katie; Manstead, Antony S R; Rees, Aled; Thapar, Anita; van Goozen, Stephanie H M

2017-11-01

Oxytocin (OXT) has previously been implicated in a range of prosocial behaviors such as trust and emotion recognition. Nevertheless, recent studies have questioned the evidence for this link. In addition, there has been relatively little conclusive research on the effect of OXT on empathic ability and such studies as there are have not examined the mechanisms through which OXT might affect empathy, or whether OXT selectively facilitates empathy for specific emotions. In the current study, we used eye-tracking to assess attention to socially relevant information while participants viewed dynamic, empathy-inducing video clips, in which protagonists expressed sadness, happiness, pain or fear. In a double-blind, within-subjects, randomized control trial, 40 healthy male participants received 24 IU intranasal OXT or placebo in two identical experimental sessions, separated by a 2-week interval. OXT led to an increase in time spent fixating upon the eye-region of the protagonist's face across emotions. OXT also selectively enhanced self-reported affective empathy for fear, but did not affect cognitive or affective empathy for other emotions. Nevertheless, there was no positive relationship between eye-gaze patterns and affective empathy, suggesting that although OXT influences eye-gaze and may enhance affective empathy for fear, these two systems are independent. Future studies need to further examine the effect of OXT on eye-gaze to fully ascertain whether this can explain the improvements in emotional behavior. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hydrologic Control on Bacterial Nitrogen Fixation in the Holocene Black Sea

Science.gov (United States)

Fulton, J. M.; Arthur, M. A.; Freeman, K. H.

2008-12-01

Stratified oceans of the Phanerozoic Oceanic Anoxic Events apparently were dominated by bacterial nitrogen fixation. Decreased marine N:P nutrient ratios resulting from increased denitrification and decreased phosphate burial efficiency under anoxic waters drove this nutrient regime. This model is upheld by the presence of cyanobacterial hopanoid biomarkers in sedimentary records and δ15N values indicative of nitrogen fixation. However, in the largest modern redox-stratified marine basin, the Black Sea, bacterial nitrogen fixation seems to be only a minor contributor to the nitrogen cycle. In this study, we use geochemical proxies to evaluate the role of bacterial nitrogen fixation during the deposition of the Holocene Black Sea sapropel, starting 7.8 ka. We report compound-specific nitrogen and carbon stable isotope values of pyropheophytin a, a chlorophyll degradation product, and bacteriochlorophyll e produced by green sulfur bacteria. We also present the surprising finding of scytonemin, a pigment produced only by filamentous cyanobacteria exposed to ultraviolet radiation, in certain intervals in these sediments. In the Holocene, nitrogen fixation in the Black Sea is most prominent during times of reduced river water influx. This directly decreases the external flux of nitrate into the surface waters. Reduced freshwater influx also decreases the volume of low salinity water dispersed around the sea by the Rim Current, allowing the chemocline to shoal along the margins. Previous geochemical studies have described this changing chemocline geometry. The exposure of shallow water sediments to anoxic waters further stimulates nitrogen fixation by releasing more phosphorus to the system. Nitrogen fixation is recorded in the sediments as bulk and compound-specific pyropheophytin a δ15N values near 0 ‰ and -5 ‰, respectively. We have also detected scytonemin in two intervals characterized by especially low δ15N values. This compound suggests abundant filamentous

Eye movement evidence for defocused attention in dysphoria--a perceptual span analysis.

Science.gov (United States)

Brzezicka, Aneta; Krejtz, Izabela; von Hecker, Ulrich; Laubrock, Jochen

2012-07-01

The defocused attention hypothesis (von Hecker and Meiser, 2005) assumes that negative mood broadens attention, whereas the analytical rumination hypothesis (Andrews and Thompson, 2009) suggests a narrowing of the attentional focus with depression. We tested these conflicting hypotheses by directly measuring the perceptual span in groups of dysphoric and control subjects, using eye tracking. In the moving window paradigm, information outside of a variable-width gaze-contingent window was masked during reading of sentences. In measures of sentence reading time and mean fixation duration, dysphoric subjects were more pronouncedly affected than controls by a reduced window size. This difference supports the defocused attention hypothesis and seems hard to reconcile with a narrowing of attentional focus. Copyright © 2011 Elsevier B.V. All rights reserved.

Subluxation of suture-fixated posterior chamber intraocular lenses a clinicopathologic study.

Science.gov (United States)

Parekh, Parag; Green, W Richard; Stark, Walter J; Akpek, Esen Karamursel

2007-02-01

To report the occurrence of subluxation of suture-fixated posterior chamber (PC) intraocular lenses (IOL) and elucidate the mechanisms involved. Prospective clinicopathologic study. A single 10-0 Prolene suture explanted from a patient who experienced subluxation of his PC-IOL, 11.5 years after placement. Furthermore, multiple 10-0 Prolene sutures and PC-IOLs used for iris fixation were studied as controls. Scanning electron microscopy (SEM) was used to analyze the surface of the explanted suture. In addition, randomly selected 10-0 Prolene sutures cut with Vannas scissors and cut with the positioning holes of a randomly selected PC-IOL identical to that implanted in the patient's eye were examined as controls. Finally, the positioning holes of several randomly selected, iris-fixated PC-IOLs were studied using SEM with particular attention to surface quality and edge finish. Presence of any signs of suture degradation, the character of the cut edge of the suture, as well as the characteristics of the positioning holes of the PC-IOLs. Scanning electron microscopy of the explanted suture revealed sharply cut edges, without significant degradation of the suture, and no intact loop. Scanning electron microscopy of the control suture cut with a PC-IOL demonstrated a similarly cut edge. The positioning holes of the examined PC-IOLs had a sharp edge, and some also had an imperfect finish. We conclude that the surface properties of the positioning holes lead to cutting of the suture, and subsequent subluxation of the PC-IOL.

Nonexplicit change detection in complex dynamic settings: what eye movements reveal.

Science.gov (United States)

Vachon, François; Vallières, Benoît R; Jones, Dylan M; Tremblay, Sébastien

2012-12-01

We employed a computer-controlled command-and-control (C2) simulation and recorded eye movements to examine the extent and nature of the inability to detect critical changes in dynamic displays when change detection is implicit (i.e., requires no explicit report) to the operator's task. Change blindness-the failure to notice significant changes to a visual scene-may have dire consequences on performance in C2 and surveillance operations. Participants performed a radar-based risk-assessment task involving multiple subtasks. Although participants were not required to explicitly report critical changes to the operational display, change detection was critical in informing decision making. Participants' eye movements were used as an index of visual attention across the display. Nonfixated (i.e., unattended) changes were more likely to be missed than were fixated (i.e., attended) changes, supporting the idea that focused attention is necessary for conscious change detection. The finding of significant pupil dilation for changes undetected but fixated suggests that attended changes can nonetheless be missed because of a failure of attentional processes. Change blindness in complex dynamic displays takes the form of failures in establishing task-appropriate patterns of attentional allocation. These findings have implications in the design of change-detection support tools for dynamic displays and work procedure in C2 and surveillance.

Eye gaze tracking based on the shape of pupil image

Science.gov (United States)

Wang, Rui; Qiu, Jian; Luo, Kaiqing; Peng, Li; Han, Peng

2018-01-01

Eye tracker is an important instrument for research in psychology, widely used in attention, visual perception, reading and other fields of research. Because of its potential function in human-computer interaction, the eye gaze tracking has already been a topic of research in many fields over the last decades. Nowadays, with the development of technology, non-intrusive methods are more and more welcomed. In this paper, we will present a method based on the shape of pupil image to estimate the gaze point of human eyes without any other intrusive devices such as a hat, a pair of glasses and so on. After using the ellipse fitting algorithm to deal with the pupil image we get, we can determine the direction of the fixation by the shape of the pupil.The innovative aspect of this method is to utilize the new idea of the shape of the pupil so that we can avoid much complicated algorithm. The performance proposed is very helpful for the study of eye gaze tracking, which just needs one camera without infrared light to know the changes in the shape of the pupil to determine the direction of the eye gazing, no additional condition is required.

[Treatment of femoral neck fracture--preference to internal fixation].

Science.gov (United States)

Minato, Izumi

2011-03-01

In the guidelines for the treatment of femoral neck fracture, prosthetic replacement is recommended in displaced one and internal fixation is in undisplaced one. However, in the long view, survived femoral head after internal fixation can be superior to prosthesis which will deteriorate as time goes by. Surgical method should be considered not only by type of fracture but general status of the patient.

Large fluctuations and fixation in evolutionary games

International Nuclear Information System (INIS)

Assaf, Michael; Mobilia, Mauro

2010-01-01

We study large fluctuations in evolutionary games belonging to the coordination and anti-coordination classes. The dynamics of these games, modeling cooperation dilemmas, is characterized by a coexistence fixed point separating two absorbing states. We are particularly interested in the problem of fixation that refers to the possibility that a few mutants take over the entire population. Here, the fixation phenomenon is induced by large fluctuations and is investigated by a semiclassical WKB (Wentzel–Kramers–Brillouin) theory generalized to treat stochastic systems possessing multiple absorbing states. Importantly, this method allows us to analyze the combined influence of selection and random fluctuations on the evolutionary dynamics beyond the weak selection limit often considered in previous works. We accurately compute, including pre-exponential factors, the probability distribution function in the long-lived coexistence state and the mean fixation time necessary for a few mutants to take over the entire population in anti-coordination games, and also the fixation probability in the coordination class. Our analytical results compare excellently with extensive numerical simulations. Furthermore, we demonstrate that our treatment is superior to the Fokker–Planck approximation when the selection intensity is finite

[Complications of open reduction and internal fixation versus external fixation for unstable distal radius fractures: a meta-analysis].

Science.gov (United States)

Yang, Z; Yuan, Z Z; Ma, J X; Ma, X L

2016-12-20

Objective: To make a systematic assessment of the complications of open reduction and internal fixation versus external fixation for unstable distal radius fractures. Method: A computer-based online search of PubMed, ScienceDirect, EMBASE, BIOSIS, Springer and Cochrane Library were performed.The randomized and controlled trials of open reduction and internal fixation versus external fixation for unstable distal radius fractures were collected.The included trials were screened out strictly based on the criterion of inclusion and exclusion.The quality of included trials was evaluated.RevMan 5.0 was used for data analysis. Result: A total of 17 studies involving 1 402 patients were included.There were 687 patients with open reduction and internal fixation and 715 with external fixation.The results of Meta-analysis indicated that there were statistically significant differences with regard to the postoperatively total complications, infection, malunion, tendon rupture ( I 2 =8%, RR =0.77(95% CI 0.65-0.91, Z =3.10, P 0.05). Conclusion: Postoperative complications are present in both open reduction and internal fixation and external fixation.Compared with external fixation, open reduction and internal fixation is lower in total complications postoperatively, infection and malunion, but external fixation has lower tendon rupture incidence.

Effectiveness of external fixator combined with T-plate internal fixation for the treatment of comminuted distal radius fractures.

Science.gov (United States)

Han, L R; Jin, C X; Yan, J; Han, S Z; He, X B; Yang, X F

2015-03-31

This study compared the efficacy between external fixator combined with palmar T-plate internal fixation and simple plate internal fixation for the treatment of comminuted distal radius fractures. A total of 61 patients classified as type C according to the AO/ASIF classification underwent surgery for comminuted distal radius fractures. There were 54 and 7 cases of closed and open fractures, respectively. Moreover, 19 patients received an external fixator combined with T-plate internal fixation, and 42 received simple plate internal fixation. All patients were treated successfully during 12-month postoperative follow-up. The follow-up results show that the palmar flexion and dorsiflexion of the wrist, radial height, and palmar angle were significantly better in those treated with the external fixator combined with T-plate compared to those treated with the simple plate only (P 0.05). Hence, the effectiveness of external fixator combined with T-plate internal fixation for the treatment of comminuted distal radius fractures was satisfactory. Patients sufficiently recovered wrist, forearm, and hand function. In conclusion, compared to the simple T-plate, the external fixator combined with T-plate internal fixation can reduce the possibility of the postoperative re-shifting of broken bones and keep the distraction of fractures to maintain radial height and prevent radial shortening.

Eye Movement Control in Scene Viewing and Reading: Evidence from the Stimulus Onset Delay Paradigm

Science.gov (United States)

Luke, Steven G.; Nuthmann, Antje; Henderson, John M.

2013-01-01

The present study used the stimulus onset delay paradigm to investigate eye movement control in reading and in scene viewing in a within-participants design. Short onset delays (0, 25, 50, 200, and 350 ms) were chosen to simulate the type of natural processing difficulty encountered in reading and scene viewing. Fixation duration increased…

Corrective response times in a coordinated eye-head-arm countermanding task.

Science.gov (United States)

Tao, Gordon; Khan, Aarlenne Z; Blohm, Gunnar

2018-06-01

Inhibition of motor responses has been described as a race between two competing decision processes of motor initiation and inhibition, which manifest as the reaction time (RT) and the stop signal reaction time (SSRT); in the case where motor initiation wins out over inhibition, an erroneous movement occurs that usually needs to be corrected, leading to corrective response times (CRTs). Here we used a combined eye-head-arm movement countermanding task to investigate the mechanisms governing multiple effector coordination and the timing of corrective responses. We found a high degree of correlation between effector response times for RT, SSRT, and CRT, suggesting that decision processes are strongly dependent across effectors. To gain further insight into the mechanisms underlying CRTs, we tested multiple models to describe the distribution of RTs, SSRTs, and CRTs. The best-ranked model (according to 3 information criteria) extends the LATER race model governing RTs and SSRTs, whereby a second motor initiation process triggers the corrective response (CRT) only after the inhibition process completes in an expedited fashion. Our model suggests that the neural processing underpinning a failed decision has a residual effect on subsequent actions. NEW & NOTEWORTHY Failure to inhibit erroneous movements typically results in corrective movements. For coordinated eye-head-hand movements we show that corrective movements are only initiated after the erroneous movement cancellation signal has reached a decision threshold in an accelerated fashion.

[Comparison study on locking compress plate external fixator and standard external fixator for treatment of tibial open fractures].

Science.gov (United States)

Wu, Gang; Luo, Xiaozhong; Tan, Lun; Lin, Xu; Wu, Chao; Guo, Yong; Zhong, Zewei

2013-11-01

To compare the clinical results of locking compress plate (LCP) as an external fixator and standard external fixator for treatment of tibial open fractures. Between May 2009 and June 2012, 59 patients with tibial open fractures were treated with LCP as an external fixator in 36 patients (group A), and with standard external fixator in 23 patients (group B). There was no significant difference in gender, age, cause of injury, affected side, type of fracture, location, and interval between injury and surgery between 2 groups (P > 0.05). The time of fracture healing and incision healing, the time of partial weight-bearing, the range of motion (ROM) of knee and ankle, and complications were compared between 2 groups. The incidence of pin-track infection in group A (0) was significantly lower than that in group B (21.7%) (P=0.007). No significant difference was found in the incidence of superficial infection and deep infection of incision, and the time of incision healing between 2 groups (P > 0.05). Deep vein thrombosis occurred in 5 cases of group A and 2 cases of group B, showing no significant difference (Chi(2)=0.036, P=0.085). All patients were followed up 15.2 months on average (range, 9-28 months) in group A, and 18.6 months on average (range, 9-47 months) in group B. The malunion rate and nonunion rate showed no significant difference between groups A and B (0 versus 13.0% and 0 versus 8.7%, P > 0.05); the delayed union rate of group A (2.8%) was significantly lower than that of group B (21.7%) (Chi(2)=5.573, P=0.018). Group A had shorter time of fracture healing, quicker partial weight-bearing, greater ROM of the knee and ankle than group B (P fracture, and has good patients' compliance, so it is helpful to do functional exercise, improve fracture healing and function recovery, and reduce the complication incidence.

Semantic guidance of eye movements in real-world scenes.

Science.gov (United States)

Hwang, Alex D; Wang, Hsueh-Cheng; Pomplun, Marc

2011-05-25

The perception of objects in our visual world is influenced by not only their low-level visual features such as shape and color, but also their high-level features such as meaning and semantic relations among them. While it has been shown that low-level features in real-world scenes guide eye movements during scene inspection and search, the influence of semantic similarity among scene objects on eye movements in such situations has not been investigated. Here we study guidance of eye movements by semantic similarity among objects during real-world scene inspection and search. By selecting scenes from the LabelMe object-annotated image database and applying latent semantic analysis (LSA) to the object labels, we generated semantic saliency maps of real-world scenes based on the semantic similarity of scene objects to the currently fixated object or the search target. An ROC analysis of these maps as predictors of subjects' gaze transitions between objects during scene inspection revealed a preference for transitions to objects that were semantically similar to the currently inspected one. Furthermore, during the course of a scene search, subjects' eye movements were progressively guided toward objects that were semantically similar to the search target. These findings demonstrate substantial semantic guidance of eye movements in real-world scenes and show its importance for understanding real-world attentional control. Copyright © 2011 Elsevier Ltd. All rights reserved.

Eye tracking, strategies, and sex differences in virtual navigation.

Science.gov (United States)

Andersen, Nicolas E; Dahmani, Louisa; Konishi, Kyoko; Bohbot, Véronique D

2012-01-01

Reports of sex differences in wayfinding have typically used paradigms sensitive to the female advantage (navigation by landmarks) or sensitive to the male advantage (navigation by cardinal directions, Euclidian coordinates, environmental geometry, and absolute distances). The current virtual navigation paradigm allowed both men and women an equal advantage. We studied sex differences by systematically varying the number of landmarks. Eye tracking was used to quantify sex differences in landmark utilisation as participants solved an eight-arm radial maze task within different virtual environments. To solve the task, participants were required to remember the locations of target objects within environments containing 0, 2, 4, 6, or 8 landmarks. We found that, as the number of landmarks available in the environment increases, the proportion of time men and women spend looking at landmarks and the number of landmarks they use to find their way increases. Eye tracking confirmed that women rely more on landmarks to navigate, although landmark fixations were also associated with an increase in task completion time. Sex differences in navigational behaviour occurred only in environments devoid of landmarks and disappeared in environments containing multiple landmarks. Moreover, women showed sustained landmark-oriented gaze, while men's decreased over time. Finally, we found that men and women use spatial and response strategies to the same extent. Together, these results shed new light on the discrepancy in landmark utilisation between men and women and help explain the differences in navigational behaviour previously reported. Copyright © 2011 Elsevier Inc. All rights reserved.

Cognitive Food Processing in Binge-Eating Disorder: An Eye-Tracking Study.

Science.gov (United States)

Sperling, Ingmar; Baldofski, Sabrina; Lüthold, Patrick; Hilbert, Anja

2017-08-19

Studies indicate an attentional bias towards food in binge-eating disorder (BED); however, more evidence on attentional engagement and disengagement and processing of multiple attention-competing stimuli is needed. This study aimed to examine visual attention to food and non-food stimuli in BED. In n = 23 participants with full-syndrome and subsyndromal BED and n = 23 individually matched healthy controls, eye-tracking was used to assess attention to food and non-food stimuli during a free exploration paradigm and a visual search task. In the free exploration paradigm, groups did not differ in their initial fixation position. While both groups fixated non-food stimuli significantly longer than food stimuli, the BED group allocated significantly more attention towards food than controls. In the visual search task, groups did not differ in detection times. However, a significant detection bias for food was found in full-syndrome BED, but not in controls. An increased initial attention towards food was related to greater BED symptomatology and lower body mass index (BMI) only in full-syndrome BED, while a greater maintained attention to food was associated with lower BMI in controls. The results suggest food-biased visual attentional processing in adults with BED. Further studies should clarify the implications of attentional processes for the etiology and maintenance of BED.

Fixation not required: characterizing oculomotor attention capture for looming stimuli.

Science.gov (United States)

Lewis, Joanna E; Neider, Mark B

2015-10-01

A stimulus moving toward us, such as a ball being thrown in our direction or a vehicle braking suddenly in front of ours, often represents a stimulus that requires a rapid response. Using a visual search task in which target and distractor items were systematically associated with a looming object, we explored whether this sort of looming motion captures attention, the nature of such capture using eye movement measures (overt/covert), and the extent to which such capture effects are more closely tied to motion onset or the motion itself. We replicated previous findings indicating that looming motion induces response time benefits and costs during visual search Lin, Franconeri, & Enns(Psychological Science 19(7): 686-693, 2008). These differences in response times were independent of fixation, indicating that these capture effects did not necessitate overt attentional shifts to a looming object for search benefits or costs to occur. Interestingly, we found no differences in capture benefits and costs associated with differences in looming motion type. Combined, our results suggest that capture effects associated with looming motion are more likely subserved by covert attentional mechanisms rather than overt mechanisms, and attention capture for looming motion is likely related to motion itself rather than the onset of motion.

Headspace analysis of foams and fixatives

Energy Technology Data Exchange (ETDEWEB)

Harper, Kyle [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Truong, Thanh-Tam [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Magwood, Leroy [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Peters, Brent [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Nicholson, James [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Washington, II, Aaron L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2017-07-27

In the process of decontaminating and decommissioning (D&D) older nuclear facilities, special precautions must be taken with removable or airborne contamination. One possible strategy utilizes foams and fixatives to affix these loose contaminants. Many foams and fixatives are already commercially available, either generically or sold specifically for D&D. However, due to a lack of revelant testing in a radioactive environment, additional verification is needed to confirm that these products not only affix contamination to their surfaces, but also will function in a D&D environment. Several significant safety factors, including flammability and worker safety, can be analyzed through the process of headspace analysis, a technique that analyzes the off gas formed before or during the curing process of the foam/fixative, usually using gas chromatography-mass spectrometry (GC-MS). This process focuses on the volatile components of a chemical, which move freely between the solid/liquid form within the sample and the gaseous form in the area above the sample (the headspace). Between possibly hot conditions in a D&D situation and heat created in a foaming reaction, the volatility of many chemicals can change, and thus different gasses can be released at different times throughout the reaction. This project focused on analysis of volatile chemicals involved in the process of using foams and fixatives to identify any potential hazardous or flammable compounds.

[DESIGN AND CLINICAL APPLICATION OF LESSER TROCHANTERIC REDUCTION FIXATION SYSTEM].

Science.gov (United States)

Guo, Xiaoze; Zhang, Ying; Xiao, Jin; Xie, Huibin; Yu, Jiefeng

2015-02-01

To design and produce a lesser trochanteric reduction fixation system and verify its value and effectiveness. A lesser trochanteric reduction fixation system was designed and produced according to the anatomical features of the lesser trochanteric fractures. Sixty-six patients with intertrochanteric fractures of Evans type III were included between January 2010 and July 2012. Of 66 patients, 32 were treated with dynamic hip screw (DHS) assisted with the lesser trochanteric reduction fixation system (study group), and 34 cases were treated with DHS only (control group). The 2 groups were comparable with no significant difference in gender, age, the reasons, and the types of the fractures (P > 0.05). The operation time, intraoperative blood loss, neck-shaft angle, bone healing time, ratio of successful fixations, and the functional evaluation of the hip joint after operation were compared between 2 groups. The study group had shorter operation time [(58.4 ± 5.3) minutes] and less intraoperative blood loss [(186.3 ± 6.6) mL than the control group [(78.5 ± 6.2)minutes and (246.2 ± 8.7) mL], showing significant differences (t = -14.040, P = 0.000; t = -31.145, P = 0.000). There was no significant difference in neck-shaft angle between study group [(138.6 ± 3.0)] and control group [(139.4 ± 2.9) degrees] (t = -1.044, P = 0.301). The wounds healed by first intention in both groups. The 30 and 31 patients were followed up 12 to 24 months (mean, 15 months) in the study group, and 13 to 25 months (mean, 16 months) in the control group, respectively. All fractures healed well in 2 groups. The study group had significantly shorter healing time [(8.8 ± 2.0) weeks] than the control group [(10.7 ± 3.4) weeks] (t = -2.871, P = 0.006). At 12 months after operation, coxa vara happened in 2 cases of the study group with a successful fixation ratio of 93.3% and in 10 cases of the control group with a successful fixation ratio of 67.7%, showing significant difference (Χ2 = 6

Eye size and visual acuity influence vestibular anatomy in mammals.

Science.gov (United States)

Kemp, Addison D; Christopher Kirk, E

2014-04-01

The semicircular canals of the inner ear detect head rotations and trigger compensatory movements that stabilize gaze and help maintain visual fixation. Mammals with large eyes and high visual acuity require precise gaze stabilization mechanisms because they experience diminished visual functionality at low thresholds of uncompensated motion. Because semicircular canal radius of curvature is a primary determinant of canal sensitivity, species with large canal radii are expected to be capable of more precise gaze stabilization than species with small canal radii. Here, we examine the relationship between mean semicircular canal radius of curvature, eye size, and visual acuity in a large sample of mammals. Our results demonstrate that eye size and visual acuity both explain a significant proportion of the variance in mean canal radius of curvature after statistically controlling for the effects of body mass and phylogeny. These findings suggest that variation in mean semicircular canal radius of curvature among mammals is partly the result of selection for improved gaze stabilization in species with large eyes and acute vision. Our results also provide a possible functional explanation for the small semicircular canal radii of fossorial mammals and plesiadapiforms. Copyright © 2014 Wiley Periodicals, Inc.

CSF coccidioides complement fixation

Science.gov (United States)

... this page: //medlineplus.gov/ency/article/003526.htm CSF coccidioides complement fixation test To use the sharing features on this page, please enable JavaScript. CSF coccidioides complement fixation is a test that checks ...

Time course of attentional modulation in the frontal eye field during curve tracing

NARCIS (Netherlands)

Khayat, P. S.; Pooresmaeili, A.; Roelfsema, P. R.

2009-01-01

Neurons in the frontal eye fields (FEFs) register incoming visual information and select visual stimuli that are relevant for behavior. Here we investigated the timing of the visual response and the timing of selection by recording from single FEF neurons in a curve-tracing task that requires shifts

Time Course of Attentional Modulation in the Frontal Eye Field During Curve Tracing

NARCIS (Netherlands)

Khayat, P.S.; Pooresmaeili, A.; Roelfsema, P.R.

2009-01-01

Neurons in the frontal eye fields (FEFs) register incoming visual information and select visual stimuli that are relevant for behavior. Here we investigated the timing of the visual response and the timing of selection by recording from single FEF neurons in a curve-tracing task that requires shifts

Complement fixation test to C burnetii

Science.gov (United States)

... complement fixation test; Coxiella burnetii - complement fixation test; C burnetii - complement fixation test ... a specific foreign substance ( antigen ), in this case, C burnetii . Antibodies defend the body against bacteria, viruses, ...

Exploring differences in speech processing among elderly hearing-impaired listeners with or without hearing aid experience: Eye-tracking and fMRI measurements

DEFF Research Database (Denmark)

Habicht, Julia; Behler, Oliver; Kollmeier, Birger

2018-01-01

on the cognitive processes underlying speech comprehension. Eye-tracking and functional magnetic resonance imaging (fMRI) measurements were carried out with acoustic sentence-in-noise (SIN) stimuli complemented by pairs of pictures that either correctly (target) or incorrectly (competitor) depicted the sentence...... meanings. For the eye-tracking measurements, the time taken by the participants to start fixating the target picture (the ‘processing time’) was measured. For the fMRI measurements, brain activation inferred from blood oxygenation level dependent (BOLD) responses following sentence comprehension...... frontal areas for SIN relative to noise-only stimuli in the eHA group compared to the iHA group. Together, these results imply that HA experience leads to faster speech-in-noise processing, possibly related to less recruitment of brain regions outside the core sentence-comprehension network. Follow...

Modeling control of eye orientation in three dimensions. I. Role of muscle pulleys in determining saccadic trajectory.

Science.gov (United States)

Raphan, T

1998-05-01

This study evaluates the effects of muscle axis shifts on the performance of a vector velocity-position integrator in the CNS. Earlier models of the oculomotor plant assumed that the muscle axes remained fixed relative to the head as the eye rotated into secondary and tertiary eye positions. Under this assumption, the vector integrator model generates torsional transients as the eye moves from secondary to tertiary positions of fixation. The torsional transient represents an eye movement response to a spatial mismatch between the torque axes that remain fixed in the head and the displacement plane that changes by half the angle of the change in eye orientation. When muscle axis shifts were incorporated into the model, the torque axes were closer to the displacement plane at each eye orientation throughout the trajectory, and torsional transients were reduced dramatically. Their size and dynamics were close to reported data. It was also shown that when the muscle torque axes were rotated by 50% of the eye rotation, there was no torsional transient and Listing's law was perfectly obeyed. When muscle torque axes rotated >50%, torsional transients reversed direction compared with what occurred for muscle axis shifts of law is implemented by the oculomotor plant subject to a two-dimensional command signal that is confined to the pitch-yaw plane, having zero torsion. Saccades that bring the eye to orientations outside Listing's plane could easily be corrected by a roll pulse that resets the roll state of the velocity-position integrator to zero. This would be a simple implementation of the corrective controller suggested by Van Opstal and colleagues. The model further indicates that muscle axis shifts together with the torque orientation relationship for tissue surrounding the eye and Newton's laws of motion form a sufficient plant model to explain saccadic trajectories and periods of fixation when driven by a vector command confined to the pitch-yaw plane. This implies

Sutureless Intrascleral Fixated Intraocular Lens Implantation.

Science.gov (United States)

Karadag, Remzi; Celik, Haci Ugur; Bayramlar, Huseyin; Rapuano, Christopher J

2016-08-01

To review sutureless intrascleral intraocular lens (IOL) fixation methods. Review of published literature. Sutureless intrascleral IOL fixation methods are newer and have been developed to eliminate the suture-related complications of sutured scleral fixation methods such as suture-induced inflammation or infection and IOL dislocation or subluxation due to suture degradation or suture breakage. Sutureless intrascleral fixation methods aim for intrascleral haptic fixation to achieve stability of the IOL. Various methods of sutureless scleral fixation have been described. Using a needle, a blade, or a trochar, sclerostomies are created in all techniques for intraocular access. Some surgeons prefer to create scleral tunnels, whereas others use scleral flaps for scleral fixation of haptics. The stability of IOLs is attained by the scar tissue formed around the haptics. Short-term results of these new methods are acceptable; studies including more cases with longer follow-up are needed to determine their long-term success. [J Cataract Refract Surg. 2016;32(9):586-597.]. Copyright 2016, SLACK Incorporated.

Listening to music reduces eye movements.

Science.gov (United States)

Schäfer, Thomas; Fachner, Jörg

2015-02-01

Listening to music can change the way that people visually experience the environment, probably as a result of an inwardly directed shift of attention. We investigated whether this attentional shift can be demonstrated by reduced eye movement activity, and if so, whether that reduction depends on absorption. Participants listened to their preferred music, to unknown neutral music, or to no music while viewing a visual stimulus (a picture or a film clip). Preference and absorption were significantly higher for the preferred music than for the unknown music. Participants exhibited longer fixations, fewer saccades, and more blinks when they listened to music than when they sat in silence. However, no differences emerged between the preferred music condition and the neutral music condition. Thus, music significantly reduces eye movement activity, but an attentional shift from the outer to the inner world (i.e., to the emotions and memories evoked by the music) emerged as only one potential explanation. Other explanations, such as a shift of attention from visual to auditory input, are discussed.

Nonphotosynthetic CO2 fixation by alfalfa (Medicago sativa L.) roots and nodules

International Nuclear Information System (INIS)

Anderson, M.P.; Heichel, G.H.; Vance, C.P.

1987-01-01

The dependence of alfalfa (Medicago sativa L.) root and nodule nonphotosynthetic CO 2 fixation on the supply of currently produced photosynthate and nodule nitrogenase activity was examined a various times after phloem-girdling and exposure of nodules to Ar:O 2 . Phloem-girdling was effected 20 hours and exposure to Ar:O 2 was effected 2 to 3 hours before initiation of experiments. Nodule and root CO 2 fixation rates of phloem-girdled plants were reduced to 38 and 50%, respectively, of those of control plants. Exposure to Ar:O 2 decreased nodule CO 2 fixation rates to 45%, respiration rates to 55%, and nitrogenase activities to 51% of those of the controls. The products of nodule CO 2 fixation were exported through the xylem to the shoot mainly as amino acids within 30 to 60 minutes after exposure to 14 CO 2 . In contrast to nodules, roots exported very little radioactivity, and most of the 14 C was exported as organic acids. The nonphotosynthetic CO 2 fixation rate of roots and nodules averaged 26% of the gross respiration rate, i.e. the sum of net respiration and nonphotosynthetic CO 2 assimilation. Nodules fixed CO 2 at a rate 5.6 times that of roots, but since nodules comprised a small portion of root system mass, roots accounted for 76% of the nodulated roots system CO 2 fixation. The results indicate that nodule CO 2 fixation in alfalfa is associated with N assimilation

Attention Switching during Scene Perception: How Goals Influence the Time Course of Eye Movements across Advertisements

Science.gov (United States)

Wedel, Michel; Pieters, Rik; Liechty, John

2008-01-01

Eye movements across advertisements express a temporal pattern of bursts of respectively relatively short and long saccades, and this pattern is systematically influenced by activated scene perception goals. This was revealed by a continuous-time hidden Markov model applied to eye movements of 220 participants exposed to 17 ads under a…

Discrimination of curvature from motion during smooth pursuit eye movements and fixation.

Science.gov (United States)

Ross, Nicholas M; Goettker, Alexander; Schütz, Alexander C; Braun, Doris I; Gegenfurtner, Karl R

2017-09-01

Smooth pursuit and motion perception have mainly been investigated with stimuli moving along linear trajectories. Here we studied the quality of pursuit movements to curved motion trajectories in human observers and examined whether the pursuit responses would be sensitive enough to discriminate various degrees of curvature. In a two-interval forced-choice task subjects pursued a Gaussian blob moving along a curved trajectory and then indicated in which interval the curve was flatter. We also measured discrimination thresholds for the same curvatures during fixation. Motion curvature had some specific effects on smooth pursuit properties: trajectories with larger amounts of curvature elicited lower open-loop acceleration, lower pursuit gain, and larger catch-up saccades compared with less curved trajectories. Initially, target motion curvatures were underestimated; however, ∼300 ms after pursuit onset pursuit responses closely matched the actual curved trajectory. We calculated perceptual thresholds for curvature discrimination, which were on the order of 1.5 degrees of visual angle (°) for a 7.9° curvature standard. Oculometric sensitivity to curvature discrimination based on the whole pursuit trajectory was quite similar to perceptual performance. Oculometric thresholds based on smaller time windows were higher. Thus smooth pursuit can quite accurately follow moving targets with curved trajectories, but temporal integration over longer periods is necessary to reach perceptual thresholds for curvature discrimination. NEW & NOTEWORTHY Even though motion trajectories in the real world are frequently curved, most studies of smooth pursuit and motion perception have investigated linear motion. We show that pursuit initially underestimates the curvature of target motion and is able to reproduce the target curvature ∼300 ms after pursuit onset. Temporal integration of target motion over longer periods is necessary for pursuit to reach the level of precision found

[Treatment of pediatric distal femur fractures by external fixator combined with limited internal fixation].

Science.gov (United States)

Wei, Sheng-wang; Shi, Zhan-ying; Hu, Ju-zheng; Wu, Hao

2016-03-01

To discuss the clinical effects of external fixator combined with limited internal fixation in the treatment of pediatric distal femur fractures. From January 2008 to June 2014, 17 children of distal femur fractures were treated by external fixator combined with limited internal fixation. There were 12 males and 5 females, aged from 6 to 13 years old with an average of 10.2 years, ranged in the course of disease from 1 h to 2 d. Preoperative diagnoses were confirmed by X-ray films in all children. There were 11 patients with supracondylar fracture , and 6 patients with intercondylar comminuted fracture. According to AO/ASIF classification, 9 fractures were type A1, 5 cases were type A2,and 3 cases were type C1. The intraoperative and postoperative complications, postoperative radiological examination, lower limbs length and motion of knee joints were observed. Knee joint function was assessed by KSS score. All the patients were followed up from 6 to 38 months with an average of 24.4 months. No nerve or blood vessel injury was found. One case complicated with the external fixation loosening, 2 cases with the infection of pin hole and 3 cases with the leg length discrepancy. Knee joint mobility and length measurement (compared with the contralateral), the average limited inflexion was 10 degrees (0 degrees to 20 degrees), the average limited straight was 4 degrees (0 degrees to 10), the average varus or valgus angle was 3 degrees (0 degrees to 5 degrees). KSS of the injured side was (96.4 +/- 5.0) points at final follow-up, 16 cases got excellent results and 1 good. All fractures obtained healing and no epiphyseal closed early was found. External fixator combined with limited internal fixation has advantages of simple operation, reliable fixation, early functional exercise in treating pediatric distal femurs fractures.

Comparison of screw fixation with elastic fixation methods in the treatment of syndesmosis injuries in ankle fractures.

Science.gov (United States)

Seyhan, Mustafa; Donmez, Ferdi; Mahirogullari, Mahir; Cakmak, Selami; Mutlu, Serhat; Guler, Olcay

2015-07-01

17 patients with ankle syndesmosic injury were treated with a 4.5mm single cortical screw fixation (passage of screw 4 cortices) and 15 patients were treated with single-level elastic fixation material. All patients were evaluated according to the AOFAS ankle and posterior foot scale at the third, sixth and twelfth months after the fixation. The ankle range of movement was recorded together with the healthy side. The Student's t test was used for statistical comparisons. No statistical significant difference was observed between the AOFAS scores (p>0.05). The range of dorsiflexion and plantar flexion motion of the elastic fixation group at the 6th and 12th months were significantly better compared to the screw fixation group (pankle syndesmosis injuries. The unnecessary need of a second surgical intervention for removal of the fixation material is another advantageous aspect of this method of fixation. Copyright © 2015. Published by Elsevier Ltd.

High-speed adaptive optics line scan confocal retinal imaging for human eye.

Science.gov (United States)

Lu, Jing; Gu, Boyu; Wang, Xiaolin; Zhang, Yuhua

2017-01-01

Continuous and rapid eye movement causes significant intraframe distortion in adaptive optics high resolution retinal imaging. To minimize this artifact, we developed a high speed adaptive optics line scan confocal retinal imaging system. A high speed line camera was employed to acquire retinal image and custom adaptive optics was developed to compensate the wave aberration of the human eye's optics. The spatial resolution and signal to noise ratio were assessed in model eye and in living human eye. The improvement of imaging fidelity was estimated by reduction of intra-frame distortion of retinal images acquired in the living human eyes with frame rates at 30 frames/second (FPS), 100 FPS, and 200 FPS. The device produced retinal image with cellular level resolution at 200 FPS with a digitization of 512×512 pixels/frame in the living human eye. Cone photoreceptors in the central fovea and rod photoreceptors near the fovea were resolved in three human subjects in normal chorioretinal health. Compared with retinal images acquired at 30 FPS, the intra-frame distortion in images taken at 200 FPS was reduced by 50.9% to 79.7%. We demonstrated the feasibility of acquiring high resolution retinal images in the living human eye at a speed that minimizes retinal motion artifact. This device may facilitate research involving subjects with nystagmus or unsteady fixation due to central vision loss.

Quiet Eye Duration Is Responsive to Variability of Practice and to the Axis of Target Changes

Science.gov (United States)

Horn, Robert R.; Okumura, Michelle S.; Alexander, Melissa G. F.; Gardin, Fredrick A.; Sylvester, Curtis T.

2012-01-01

We tested the hypothesis that quiet eye, the final fixation before the initiation of a movement in aiming tasks, is used to scale the movement's parameters. Two groups of 12 participants (N = 24) threw darts to targets in the horizontal and vertical axes under conditions of higher (random) or lower (blocked) target variability. Supporting our…

Reading Words or Pictures: Eye Movement Patterns in Adults and Children Differ by Age Group and Receptive Language Ability

Directory of Open Access Journals (Sweden)

Licong An

2017-05-01

Full Text Available This study was conducted to explore the differences in the degree of attention given to Chinese print and pictures by children and adults when they read picture books with and without Chinese words. We used an eye tracker from SensoMotoric Instruments to record the visual fixations of the subjects. The results showed that the adults paid more attention to Chinese print and looked at the print sooner than the children did. The stronger the children’s receptive language abilities were, the less time it took them to view the pictures. All participants spent the same amount of time looking at the pictures whether Chinese words were present or absent.

Double attention bias for positive and negative emotional faces in clinical depression: evidence from an eye-tracking study.

Science.gov (United States)

Duque, Almudena; Vázquez, Carmelo

2015-03-01

According to cognitive models, attentional biases in depression play key roles in the onset and subsequent maintenance of the disorder. The present study examines the processing of emotional facial expressions (happy, angry, and sad) in depressed and non-depressed adults. Sixteen unmedicated patients with Major Depressive Disorder (MDD) and 34 never-depressed controls (ND) completed an eye-tracking task to assess different components of visual attention (orienting attention and maintenance of attention) in the processing of emotional faces. Compared to ND, participants with MDD showed a negative attentional bias in attentional maintenance indices (i.e. first fixation duration and total fixation time) for sad faces. This attentional bias was positively associated with the severity of depressive symptoms. Furthermore, the MDD group spent a marginally less amount of time viewing happy faces compared with the ND group. No differences were found between the groups with respect to angry faces and orienting attention indices. The current study is limited by its cross-sectional design. These results support the notion that attentional biases in depression are specific to depression-related information and that they operate in later stages in the deployment of attention. Copyright © 2014 Elsevier Ltd. All rights reserved.

External fixation of tibial pilon fractures and fracture healing.

Science.gov (United States)

Ristiniemi, Jukka

2007-06-01

Distal tibial fractures are rare and difficult to treat because the bones are subcutaneous. External fixation is commonly used, but the method often results in delayed union. The aim of the present study was to find out the factors that affect fracture union in tibial pilon fractures. For this purpose, prospective data collection of tibial pilon fractures was carried out in 1998-2004, resulting in 159 fractures, of which 83 were treated with external fixation. Additionally, 23 open tibial fractures with significant > 3 cm bone defect that were treated with a staged method in 2000-2004 were retrospectively evaluated. The specific questions to be answered were: What are the risk factors for delayed union associated with two-ring hybrid external fixation? Does human recombinant BMP-7 accelerate healing? What is the role of temporary ankle-spanning external fixation? What is the healing potential of distal tibial bone loss treated with a staged method using antibiotic beads and subsequent autogenous cancellous grafting compared to other locations of the tibia? The following risk factors for delayed healing after external fixation were identified: post-reduction fracture gap of >3 mm and fixation of the associated fibula fracture. Fracture displacement could be better controlled with initial temporary external fixation than with early definitive fixation, but it had no significant effect on healing time, functional outcome or complication rate. Osteoinduction with rhBMP-7 was found to accelerate fracture healing and to shorten the sick leave. A staged method using antibiotic beads and subsequent autogenous cancellous grafting proved to be effective in the treatment of tibial bone loss. Healing potential of the bone loss in distal tibia was at least equally good as in other locations of the tibia.

Management and follow up of tibial plateau fractures by ′T′ clamp external fixator and limited internal fixation

Directory of Open Access Journals (Sweden)

Thimmegowda M

2005-01-01

Full Text Available Background: Tibial plateau fractures are difficult to treat especially when soft tissue is compromised by open reduction and internal fixation. Many methods have be1en tried in the past to manage these cases of which external fixation were shown to be effective as they limit the soft tissue and wound complications. Methods: Complex tibial plateau fractures of sixteen patients were treated by closed reduction, fixation of articular fragments by screws and application of unilateral external fixator. The external fixator was kept in place till fracture united clinically and radiologically. The patients were followed up for at least one year to assess the function of the knee joint Results: The average duration of external fixation was 13 weeks. All the fractures healed. Pin track infection (five patients and instability (six patients of the knee were encountered with this procedure. The average duration of follow up was 62 weeks. The mean range of motion was 1250 arc. The IOWA knee score averaged 90.3 points. Conclusions: External fixation with limited internal fixation may be effective in the management of complex tibial plateau fractures which requires further support from studies with large sample size. ′T′ clamp external fixation with limited Internal fixation is the procedure of choice when alignment, stability, early mobilisation is required in a soft tissue compromised tibial plateau fractures.

Visual attention to emotional face in schizophrenia: an eye tracking study.

Directory of Open Access Journals (Sweden)

Mania Asgharpour

2015-03-01

Full Text Available Deficits in the processing of facial emotions have been reported extensively in patients with schizophrenia. To explore whether restricted attention is the cause of impaired emotion processing in these patients, we examined visual attention through tracking eye movements in response to emotional and neutral face stimuli in a group of patients with schizophrenia and healthy individuals. We also examined the correlation between visual attention allocation and symptoms severity in our patient group.Thirty adult patients with schizophrenia and 30 matched healthy controls participated in this study. Visual attention data were recorded while participants passively viewed emotional-neutral face pairs for 500 ms. The relationship between the visual attention and symptoms severity were assessed by the Positive and Negative Syndrome Scale (PANSS in the schizophrenia group. Repeated Measures ANOVAs were used to compare the groups.Comparing the number of fixations made during face-pairs presentation, we found that patients with schizophrenia made fewer fixations on faces, regardless of the expression of the face. Analysis of the number of fixations on negative-neutral pairs also revealed that the patients made fewer fixations on both neutral and negative faces. Analysis of number of fixations on positive-neutral pairs only showed more fixations on positive relative to neutral expressions in both groups. We found no correlations between visual attention pattern to faces and symptom severity in schizophrenic patients.The results of this study suggest that the facial recognition deficit in schizophrenia is related to decreased attention to face stimuli. Finding of no difference in visual attention for positive-neutral face pairs between the groups is in line with studies that have shown increased ability to positive emotional perception in these patients.

Nonunited humerus shaft fractures treated by external fixator augmented by intramedullary rod

Directory of Open Access Journals (Sweden)

Mahmoud A El-Rosasy

2012-01-01

Full Text Available Background: Nonunion of humeral shaft fractures after previously failed surgical treatment presents a challenging therapeutic problem especially in the presence of osteoporosis, bone defect, and joint stiffness. It would be beneficial to combine the use of external fixation technique and intramedullary rod in the treatment of such cases. The present study evaluates the results of using external fixator augmented by intramedullary rod and autogenous iliac crest bone grafting (ICBG for the treatment of humerus shaft nonunion following previously failed surgical treatment. Materials and Methods: Eighteen patients with atrophic nonunion of the humeral shaft following previous implant surgery with no active infection were included in the present study. The procedure included exploration of the nonunion, insertion of intramedullary rod (IM rod, autogenous ICBG and application of external fixator for compression. Ilizarov fixator was used in eight cases and monolateral fixator in ten cases. The monolateral fixator was preferred for females and obese patients to avoid abutment against the breast or chest wall following the use of Ilizarov fixator. The fixator was removed after clinical and radiological healing of the nonunion, but the IM rod was left indefinitely. The evaluation of results included both bone results (union rate, angular deformity and limb shortening and functional outcome using the University of California, Los Angeles (UCLA rating scale. Results: The mean follow-up was 35 months (range 24 to 52 months. Bone union was obtained in all cases. The functional outcome was satisfactory in 15 cases (83% and unsatisfactory in 3 cases (17% due to joint stiffness. The time to bone healing averaged 4.2 months (range 3 to 7 months. The external fixator time averaged 4.5 months (range 3.2 to 8 months. Superficial pin tract infection occurred in 39% (28/72 of the pins. No cases of nerve palsy, refracture, or deep infection were encountered