Query: stress pupil

title: Numerical stress analysis of the iris tissue induced by pupil expansion: Comparison of commercial devices
abstract: To use finite element (FE) modelling to estimate local iris stresses (i.e. internal forces) as a result of mechanical pupil expansion; and to (2) compare such stresses as generated from several commercially available expanders (Iris hooks, APX dilator and Malyugin ring) to determine which design and deployment method are most likely to cause iris damage.  We used a biofidelic 3 part iris FE model that consisted of the stroma, sphincter and dilator muscles. Our FE model simulated expansion of the pupil from 3 mm to a maximum of 6 mm using the aforementioned pupil expanders, with uniform circular expansion used for baseline comparison. FE derived stresses, resultant forces and area of final pupil opening were compared across devices for analysis.  Our FE models demonstrated that the APX dilator generated the highest stresses on the sphincter muscles, (max: 6.446 MPa; average: 5.112 MPa) followed by the iris hooks (max: 5.680 MPa; average: 5.219 MPa) and the Malyugin ring (max: 2.144 MPa; average: 1.575 MPa) Uniform expansion generated the lowest stresses (max: 0.435MPa; average: 0.377 MPa) For pupil expansion, the APX dilator required the highest force (41.22 mN) followed by iris hooks (40.82 mN) and the Malyugin ring (18.56 mN)  Our study predicted that current pupil expanders exert significantly higher amount of stresses and forces than required during pupil expansion. Our work may serve as a guide for the development and design of next generation pupil expanders.

title: Increased pupil dilation to angry faces predicts interpersonal stress generation in offspring of depressed mothers
abstract: Interpersonal stress generation is one mechanism hypothesized to increase risk for the intergenerational transmission of depression. Although there is some evidence of stress generation in offspring of depressed mothers, specific predictors of stress generation in these youth remain unknown. The goal of this study was to examine a peripheral measure of cognitive affective reactivity (i.e. pupil dilation) to emotional interpersonal stimuli as a predictor of stress generation in offspring of depressed mothers.  The study included 129 mothers and their offspring (ages 8 15) recruited from the community who participated at two time points separated by 6 months. Youth's average pupil dilation to emotional faces (angry, happy, sad) as well as maternal lifetime history of major depressive disorder were assessed at baseline. In addition, both time points included assessments of youth's levels of self generated (dependent) and independent episodic life stress in the preceding 6 months.  Youth's pupil dilation to angry, but not sad or happy, faces predicted prospective increases in dependent interpersonal stress across the follow up. This effect was only observed in offspring of depressed mothers and was not seen in offspring of never depressed mothers.  This study highlights a potential risk factor (heightened reactivity to facial displays of anger) that may identify which offspring of depressed mothers are at greatest risk for interpersonal stress generation.

title: Stress Detection in Human Computer Interaction: Fusion of Pupil Dilation and Facial Temperature Features
abstract: In order to differentiate the affective state of a computer user as it changes from relaxation to stress, features derived from pupil dilation and periorbital temperature can be utilized. Absolute signal values and measurements computed from these can be fused to increase the accuracy of affective classification. In this study, entropy in a sliding window was used to accommodate the time differences in the physiological rise and fall profiles of pupil and thermal data. Two methods, decision tree and Adaboost with Random Forest (ABRF) were used for classification tests. Detection accuracy of stressful states varied between 65% and 83.8% Best results can be reported as 83.9% for sensitivity and 83.8% for specificity. ABRF classifier outperformed the decision tree model. This study emphasizes the importance of data fusion, particularly when physiological signals differ with respect to their rise and fall windows across time. Use of entropy within a predefined time window provides a useful set of features to combine with actual measurements. Furthermore, the collection of pupil and thermal data is feasible because surface sensors are eliminated.

title: Automatic Stress Classification With Pupil Diameter Analysis
abstract: This article proposes a method based on wavelet transform and neural networks for relating pupillary behavior to psychological stress. The proposed method was tested by recording pupil diameter and electrodermal activity during a simulated driving task. Self report measures were also collected. Participants performed a baseline run with the driving task only, followed by three stress runs where they were required to perform the driving task along with sound alerts, the presence of two human evaluators, and both. Self reports and pupil diameter successfully indexed stress manipulation, and significant correlations were found between these measures. However, electrodermal activity did not vary accordingly. After training, the four way parallel neural network classifier could guess whether a given unknown pupil diameter signal came from one of the four experimental trials with 79.2% precision. The present study shows that pupil diameter signal has good discriminating power for stress detection.

title: The effects of human relations training on reported teacher stress, pupil control ideology and locus of control.
abstract: This study presents the reported outcomes of a two year, part time Masters' programme in human relations using an experiential learning methodology based mainly on humanistic psychological theory.  The following hypotheses were examined. That as a result of the two year programme: the experience of reported stress would be reduced; reported attitudes to student classroom control would shift from custodial to humanistic; there would be an increase in reports from participants of a sense of control over their lives; changes of behaviour in work, social settings and at home related to these three variables would be reported. SAMPLE Involved in the study were 42 experienced teachers. These included 32 women and 10 men, with an average age of 35, who worked in a wide range of educational institutions. Their learning style preferences were also considered as independent variables. A control group of 42 was established with similar demographic characteristics.  Prior to the course, the experimental group and the control group were given the Maslach Burnout Inventory and the Pupil Control Ideology Form. In the early stages of the course, the experimental group completed the Kolb Learning Style Inventory and an informal measure of locus of control which was repeated at the end of the first year of the course. A sample of 32 from the experimental group were given semi structured interviews relating to changes in their professional and personal lives.  The results indicated that, following the training, there was a reduction in reported stress, indications of a more humanistic orientation towards pupil control and an increase in a sense of an internal locus of control. The quantitative data were confirmed by qualitative data generated from semi structured interviews, which involved substantial reports of applications of the training in their professional and personal lives.  These results provide support for including experiential human relations training as part of both the in service and initial teacher training programmes.

title: Pupil diameter size marker for incremental mental stress detection
abstract: This paper describes a new statistical based study of the pupil diameter marker for the detection of incremental levels of mental stress in operators who are subjected to mental stress. In order to achieve an acceptable and an incremental level of mental stress, the operators were subjected from two to four sessions each of an arithmetic operations based test of varying difficulty. The experiment was performed on 4 healthy subjects of ages varying from 27 to 45 and for a total of 13 experiment sessions. In order to account for the effect of fatigue in the experiment, the order of the difficulty levels was varied for different sessions. The results obtained demonstrate the effectiveness of the pupil diameter marker as a viable incremental predictor of mental stress as inferred from the obtained two sample statistical t test.

title: Off line and On line Stress Detection Through Processing of the Pupil Diameter Signal
abstract: The pupil diameter (PD) controlled by the autonomic nervous system, seems to provide a strong indication of affective arousal, as found by previous research, but it has not been investigated fully yet. In this study, new approaches based on monitoring and processing the PD signal for off line and on line "relaxation" vs. "stress" differentiation are proposed. For the off line approach, wavelet denoising, Kalman filtering, data normalization, and feature extraction are sequentially utilized. For the on line approach, a hard threshold, a moving average window and three stress detection steps are implemented. In order to use only the most reliable data, two types of data selection methods (paired t test based on galvanic skin response (GSR) data and subject self evaluation) are applied, achieving average classification accuracies up to 86.43 and 87.20% for off line and 72.30 and 73.55% for on line algorithms, with each set of selected data, respectively. The GSR was also monitored and processed in our experiments for comparison purposes, with the highest classification rate achieved being only 63.57% (based on the off line processing algorithm) The overall results show that the PD signal is more effective and robust for differentiating "relaxation" vs. "stress," in comparison with the traditionally used GSR signal.

title: Role of pupil dilation and facial temperature features in stress detection
abstract: In order to differentiate the affective state of a computer user as it changes from relaxation to stress, features derived from pupil dilation and periorbital temperature are processed with machine learning techniques. When absolute signal values are used together with entropy based features, the accuracy of affective classification is observed to increase. When decision tree (C4.5) is tested for classification, best accuracy of detection of neutral versus aroused states is above 90%

title: Teacher stress and pupil behaviour explored through a rational emotive behaviour therapy framework
abstract: Using the psychological framework of rational emotive behaviour therapy, the principal aim of this study was to establish whether irrational beliefs, self efficacy or pupil behaviour predicted teacher reports of stress. A secondary aim was to establish whether these variables, in addition to teachers' verbal feedback to pupils in class, predicted on task pupil behaviour. Participants consisted of 58 teachers from five secondary schools, who completed three self report questionnaires examining teacher stress, self efficacy and irrational beliefs. In addition, both teachers and pupils were systematically observed in class using a structured schedule. The results indicated that high self reported irrational beliefs and low self efficacy predicted high levels of teacher stress. In addition, high self efficacy and low levels of negative comments directed at pupils' social behaviour and academic work in the classroom predicted high levels of on task pupil behaviour. The implications for supporting teachers in these areas are discussed.

title: Analysis of Iris and pupil parameters for stress Recognition
abstract: The aim of this study was to automatically identify the iris and pupil of the eye in the video stream and to parameterize the identified structures in order to make assumptions if the subjected is stressed or not. During tests subjects were given a number of issues which they had to respond by selecting only one correct answer. Visual material was gathered using a helmet fitted stationary near infrared camera that recorded iris and pupil of the eye reactions to stimuli. Subsequently it was made an automatic iris and pupil recognition and approximation by curves in the gathered sequence of images. Each change in the pupil size is described by different time series length. Thus, it is impossible to compare the obtained data using the Euclidean distance measures. For this reason, the metrics based on periodograms was used to compare the data series. The differences calculated between the eye pupil reaction to stimuli and question show up time was introduced in multidimensional scaling algorithms for dimension reduction. It was noticed that the stimulus to the false answers tend to cluster.