The ocular surface and blinking in children

Background: Ocular surface characteristics in children have not been as well investigated as in adults. Children’s digital device usage is rapidly increasing, and smartphones are the most commonly used device. The ocular surface impacts are unknown in children. In adults, use of digital devices induces ocular symptoms, adversely impacts blinking, and disrupts ocular surface homeostasis. Although blinking is integral to a healthy ocular surface, this is yet to be characterised in children, including the effects of digital devices. This thesis aims to characterise the ocular surface of children including blinking and to examine the impact of smartphone use on ocular surface homeostasis in children. Methods: The literature on ocular surface (symptoms, clinical indices, tear film function, blinking) of healthy children was reviewed and a meta-analysis of tear film stability and tear secretion was conducted. Cross-sectional studies of healthy school-aged children were conducted to examine the utility of commonly used adult-validated dry eye symptom questionnaires (SANDE, OSDI, NRS, OCI, DEQ-5, IOSS), and to characterise ocular surface clinical indices. This included blinking which was measured in situ using a novel eye tracking headset (Pupil Labs GmbH, Germany). The impact of one hour smartphone gaming on the ocular surface (including symptoms and blink parameters) of this paediatric population was examined with an intervention study. Blinking was also examined in situ under different conditions and tasks (reading from hard copy and on digital devices, conversation, walking) using the eye tracking headset in healthy adults. Repeatability of blink measurements (blink rate and interblink interval) in adults using the eye tracking headset was determined. Results: Ocular symptoms, tear film function and blinking were sparsely reported in children. The pooled mean by tear stability measurement methods in the meta-analysis were higher than previously reported in healthy adults while the pooled mean for tear secretion by methods were within the expected normal range for adults. Six existing dry eye questionnaires could be successfully used in paediatric eye care, and their repeatability was mostly comparable to that reported previously in adults. More time and assistance were at times required for younger children and specific terms such as ‘gritty’ and ‘foreign body sensation’ were not always well understood by younger children. The DEQ-5 and IOSS are recommended for use in younger age children. Blinking was associated with greater tear volume and worse meibomian gland expressibility but not digital device use, age, sex, or symptoms in children. One hour smartphone gaming led to increased symptoms of dryness, discomfort, and tiredness but did not impact tear film function. Blinking was rapidly reduced by a third within the first minute of gaming and this effect remained unchanged throughout one hour of gaming (p<0.001). Blink rate was consistently slower during all reading tasks compared to conversation (p≤0.002) and walking (p≤0.03), irrespective of task complexity, screen brightness, working distance or device used. Blinking could be reliably measured using a wearable eye tracking headset; the coefficient of repeatability for blink rate was ±12.4 blinks/min. Conclusions: This study established that existing dry eye questionnaires can be reliably used in children to examine the impact of challenges such as digital device use. An eye tracking headset reliably measured blink rate in situ in adults and detected differences in blinking during various real-life tasks. It was successfully used in children to measure blinking in situ showing an immediate and sustained slowing of blinking, evident after up to one hour of smartphone gaming. An hour of smartphone gaming worsened ocular comfort in children but did not appear to disturb the tear film. Given the ubiquitous use of smartphones by children, future work should examine whether effects reported herein persist or get worse over the longer term, potentially causing cumulative damage to the ocular surface. Blink amplitude and relationships with ocular surface clinical indices and digital device use may be explored using the methods established in this study

Performance Under Pressure: Examination of Relevant Neurobiological and Genetic Influence

Satisfactory human performance demands the complex interaction of multiple factors such as arousal/motivation, emotion expression and regulation, intricate synchronization of central and peripheral motor processes, all recruited in the service of adaptive, moment to moment decision making. The segregation of these various factors aids in the understanding of their complex interactions. Recently, scientific investigation has focused on understanding the integration of these various factors. The complementary role of emotion and cognition in successful human performance is emphasized. As a viable metric of emotion regulation differences in asymmetry of human brain frontal activity have traditionally been utilized to index certain trait predispositions within the approach/withdrawal dimension of emotion/motivation. Researchers have begun to make a case for an acute or state difference in frontal asymmetry. This "Capability Model" posits the neural underpinnings of the relative difference in electrical activity between the left and right frontal lobes as a phasic/situational mechanism possibly sub-serving the integration of emotion and cognition during challenge. The current study demonstrates support for this situational/state model of frontal asymmetry. Thirty channels of EEG were collected along with, skin conductance, heart rate and acoustic startle amplitudes while subjects were engaged in two levels of a working memory task under three increasing levels of stress (final level=electric stimuli/shock). Hierarchical regression results implicate state frontal asymmetry differences as having a mediating role in the adaptive regulation of emotion during enhanced performance on an N-back working memory task but only in the high stress condition. During shock /threat of shock participants with higher state asymmetry scores showed significant attenuation of eye-blink startle magnitudes, faster reaction times and increased accuracy. This suggests an integration of emotion and cognition

Neurological and Mental Disorders

Mental disorders can result from disruption of neuronal circuitry, damage to the neuronal and non-neuronal cells, altered circuitry in the different regions of the brain and any changes in the permeability of the blood brain barrier. Early identification of these impairments through investigative means could help to improve the outcome for many brain and behaviour disease states.The chapters in this book describe how these abnormalities can lead to neurological and mental diseases such as ADHD (Attention Deficit Hyperactivity Disorder), anxiety disorders, Alzheimer’s disease and personality and eating disorders. Psycho-social traumas, especially during childhood, increase the incidence of amnesia and transient global amnesia, leading to the temporary inability to create new memories.Early detection of these disorders could benefit many complex diseases such as schizophrenia and depression

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 317)

This bibliography lists 182 reports, articles and other documents introduced into the NASA scientific and technical information system in November, 1988

The role of the cerebellum in the pathophysiology of dystonia

Research over the last decade has refined our understanding of the neuroanatomical substrates of dystonia. In addition to basal ganglia dysfunction a much wider sensorimotor network has been implicated and within this network the cerebellum is heralded as a core node. Much of the literature linking the cerebellum to dystonia consists of cases in which lesions of the cerebellum are linked to abnormal posture or indirect experimental associations (reviewed in chapter 1). Better defining the functional role of the cerebellum in the pathophysiology of dystonia could provide a scientific rational for future therapeutic advances, adding further weight to an early neurosurgical literature which advocates targeting the cerebellum and its outflow tracts. Within this thesis I applied experimental techniques from which direct inferences about cerebellar function could be made, trying to better define how the cerebellum is functionally involved in the pathogenesis of isolated dystonia. Methodology can be divided into major themes (i) two studies exploring cerebellar modulation of dystonic neurophysiological hallmarks; impaired motor surround inhibition (chapter 2) and excessive plasticity (chapter 3) (ii) evaluation of eye-blink conditioning a form of cerebellar associative learning (chapter 4, chapter 8) (iii) exploring whether millisecond timing, a cerebellar encoded process, is at the root of abnormal temporal discrimination thresholds (chapter 5) and finally (iv) testing adaptation a kinematic cerebellar paradigm in cervical dystonia (chapter 6) and DYT1 dystonia (chapter 7). Overall, my application of the ‘purest’ cerebellar paradigms did not provide a robust functional correlate to implicate specific cerebellar functions as a driver of dystonic pathophysiology. I present good evidence that fundamental computations such as adaptation and associative learning are intact in various groups of isolated dystonia. Thus isolated dystonia does not seem to selectively impair cerebellar functions (as currently defined). It is only with future research that we will be able to determine whether dystonia corrupts function(s) inherent to the dystonic network which includes the cerebellum or whether the cerebellar abnormalities observed experimentally are compensatory in nature

Mental-State Estimation, 1987

Reports on the measurement and evaluation of the physiological and mental state of operators are presented

Cerebellar Motor Learning Deficits: Structural mapping, neuromodulation and training-related interventions

Movement allows us to interact with our direct environment, manipulate objects and communicate with each other. Moreover, we can adjust our movements to fit a remarkable range of situations and circumstances. The ability to adjust movements in response to changes in the environment and task demands is referred to as motor learning. The cerebellum is a key neural structure for motor learning. As such, disease of the cerebellum, in addition to the clinical symptom of ataxia, results in various motor learning deficits. There is a consensus that supportive therapy (e.g. physiotherapy, occupational therapy or speech therapy) can reduce ataxia symptoms of cerebellar patients, but little is known about the mechanisms underlying the improvements, and how patients can benefit most. Additionally, motor learning deficits are associated with reduced efficacy of supportive therapy. With the work described in this thesis, we sought to unravel the structural components of cerebellar disease and the relationship between cerebellar integrity and motor learning. Furthermore, we investigated whether motor learning deficits in cerebellar patients could be ameliorated with neuromodulation or training-related interventions, under experimental conditions, hoping to support the development of interventions relevant for application in a clinical setting

Time Distortions in Mind

Time Distortions in Mind brings together current research on temporal processing in clinical populations to elucidate the interdependence between perturbations in timing and disturbances in the mind and brain. For the student, the scientist, and the stepping-stone for further research