Eye Blink Rate as a biological marker of Mild Cognitive Impairment

The psychophysiology of Mastermind: Characterizing response times and blinking in a high-stakes television game show

Television game shows have proven to be a valuable resource for studying human behavior under conditions of high stress and high stakes. However, previous work has focused mostly on choices-ignoring much of the rich visual information that is available on screen. Here, we take a first step to extracting more of this information by investigating the response times and blinking of contestants in the BBC show Mastermind. In Mastermind, contestants answer rapid-fire quiz questions while a camera slowly zooms in on their faces. By labeling contestants' behavior and blinks from 25 episodes, we asked how accuracy, response times, and blinking varied over the course of the game. For accuracy and response times, we tested whether contestants responded more accurately and more slowly after an error-exhibiting the "post-error increase in accuracy" and "post-error slowing" which has been repeatedly observed in the lab. For blinking, we tested whether blink rates varied according to the cognitive demands of the game-decreasing during periods of cognitive load, such as when pondering a response, and increasing at event boundaries in the task, such as the start of a question. In contrast to the lab, evidence for post-error changes in accuracy and response time was weak, with only marginal effects observed. In line with the lab, blinking varied over the course of the game much as we predicted. Overall, our findings demonstrate the potential of extracting dynamic signals from game shows to study the psychophysiology of behavior in the real world.

Look into my eyes: What can eye-based measures tell us about the relationship between physical activity and cognitive performance?

BACKGROUND

There is a growing interest to understand the neurobiological mechanisms that drive the positive associations of physical activity and fitness with measures of cognitive performance. To better understand those mechanisms, several studies have employed eye-based measures (e.g., eye movement measures such as saccades, pupillary measures such as pupil dilation, and vascular measures such as retinal vessel diameter) deemed to be proxies for specific neurobiological mechanisms. However, there is currently no systematic review providing a comprehensive overview of these studies in the field of exercise-cognition science. Thus, this review aimed to address that gap in the literature.

METHODS

To identify eligible studies, we searched 5 electronic databases on October 23, 2022. Two researchers independently extracted data and assessed the risk of bias using a modified version of the Tool for the assEssment of Study qualiTy and reporting in EXercise (TESTEX scale, for interventional studies) and the critical appraisal tool from the Joanna Briggs Institute (for cross-sectional studies).

RESULTS

Our systematic review (n = 35 studies) offers the following main findings: (a) there is insufficient evidence available to draw solid conclusions concerning gaze-fixation-based measures; (b) the evidence that pupillometric measures, which are a proxy for the noradrenergic system, can explain the positive effect of acute exercise and cardiorespiratory fitness on cognitive performance is mixed; (c) physical training- or fitness-related changes of the cerebrovascular system (operationalized via changes in retinal vasculature) are, in general, positively associated with cognitive performance improvements; (d) acute and chronic physical exercises show a positive effect based on an oculomotor-based measure of executive function (operationalized via antisaccade tasks); and (e) the positive association between cardiorespiratory fitness and cognitive performance is partly mediated by the dopaminergic system (operationalized via spontaneous eye-blink rate).

CONCLUSION

This systematic review offers confirmation that eye-based measures can provide valuable insight into the neurobiological mechanisms that may drive positive associations between physical activity and fitness and measures of cognitive performance. However, due to the limited number of studies utilizing specific methods for obtaining eye-based measures (e.g., pupillometry, retinal vessel analysis, spontaneous eye blink rate) or investigating a possible dose-response relationship, further research is necessary before more nuanced conclusions can be drawn. Given that eye-based measures are economical and non-invasive, we hope this review will foster the future application of eye-based measures in the field of exercise-cognition science.

Synergy through integration of digital cognitive tests and wearable devices for mild cognitive impairment screening

Introduction

Advances in mobile computing platforms and the rapid development of wearable devices have made possible the continuous monitoring of patients with mild cognitive impairment (MCI) and their daily activities. Such rich data can reveal more subtle changes in patients' behavioral and physiological characteristics, providing new ways to detect MCI anytime, anywhere. Therefore, we aimed to investigate the feasibility and validity of digital cognitive tests and physiological sensors applied to MCI assessment.

Methods

We collected photoplethysmography (PPG), electrodermal activity (EDA) and electroencephalogram (EEG) signals from 120 participants (61 MCI patients, 59 healthy controls) during rest and cognitive testing. The features extracted from these physiological signals involved the time domain, frequency domain, time-frequency domain and statistics. Time and score features during the cognitive test are automatically recorded by the system. In addition, selected features of all modalities were classified by tenfold cross-validation using five different classifiers.

Results

The experimental results showed that the weighted soft voting strategy combining five classifiers achieved the highest classification accuracy (88.9%), precision (89.9%), recall (88.2%), and F1 score (89.0%). Compared to healthy controls, the MCI group typically took longer to recall, draw, and drag. Moreover, during cognitive testing, MCI patients showed lower heart rate variability, higher electrodermal activity values, and stronger brain activity in the alpha and beta bands.

Discussion

It was found that patients' classification performance improved when combining features from multiple modalities compared to using only tablet parameters or physiological features, indicating that our scheme could reveal MCI-related discriminative information. Furthermore, the best classification results on the digital span test across all tasks suggest that MCI patients may have deficits in attention and short-term memory that came to the fore earlier. Finally, integrating tablet cognitive tests and wearable sensors would provide a new direction for creating an easy-to-use and at-home self-check MCI screening tool.

Alterations in blink and masseter reflex latencies in older adults with neurocognitive disorder and/or diabetes mellitus

BACKGROUND

Blink and masseter reflexes provide reliable, quantifiable data on the function of the central nervous system: Delayed latencies have been found in patients with neurocognitive disorder (ND) and type 2 diabetes mellitus (T2DM), but this has not been studied in patients with both pathologies.

AIM

To investigate if older adults with ND plus T2DM have prolonged latencies of blink and masseter-reflex and if they were associated with disease progression.

METHODS

This cross-sectional study included 227 older adults (> 60 years) from Colima, Mexico. Neurocognitive disorder was identified by a neuropsychological battery test, and T2DM identified by medical history, fasting glucose, and glycosylated hemoglobin. Latencies in the early reflex (R1), ipsilateral late (R2), and contralateral late (R2c) components of the blink reflex were analyzed for all subjects, and 183 subjects were analyzed for latency of the masseter reflex.

RESULTS

In 20.7% of participants, ND was detected. In 37%, T2DM was detected. Latencies in R1, R2, and R2c were significantly prolonged for groups with ND plus T2DM, ND, and T2DM, compared with the control group (P < 0.0001). The masseter reflex was only prolonged in older adults (regardless of T2DM status) with ND vs controls (P = 0.030). In older adults with ND and without T2DM, the more the cognitive impairment progressed, the more prolonged latencies in R2 and R2c presented (P < 0.01).

CONCLUSION

These findings suggest that blink and masseter reflexes could be used to evaluate possible changes in brainstem circuits in older adults with ND and T2DM.

Examining the effect of depressive symptoms on habit formation and habit-breaking

BACKGROUND AND OBJECTIVES

Dysfunction in reward processing is a hallmark feature of depression. In the context of reinforcement learning, previous research has linked depression with reliance on simple habit-driven ('model-free') learning strategies over more complex, goal-directed ('model-based') strategies. However, the relationship between depression and habit-breaking remains an under-explored research area. The current study sought to bridge this gap by investigating the effect of depressive symptoms on habit formation and habit-breaking under monetary and social feedback conditions. Additionally, we examined whether spontaneous eyeblink rate (EBR), an indirect marker for striatal dopamine levels, would modulate such effects.

METHODS

Depressive symptoms were operationalized using self-report measures. To examine differences in habit formation and habit breaking, undergraduate participants (N = 156) completed a two-stage reinforcement learning task with a devaluation procedure using either monetary or social feedback.

RESULTS

Regression results showed that in the monetary feedback condition, spontaneous EBR moderated the relationship between depressive symptoms and model-free strategies; individuals with more depressive symptomatology and high EBR (higher dopamine levels) exhibited increased reliance on model-free strategies. Depressive symptoms negatively predicted devaluation sensitivity, indicative of difficulty in habit-breaking, in both monetary and social feedback contexts.

LIMITATIONS

Social feedback relied on fixed feedback rather than real-time peer evaluations; depressive symptoms were measured using self-report rather than diagnostic criteria for Major Depressive Disorder; dopaminergic functioning was measured using EBR rather than PET imaging; potential confounds were not controlled for.

CONCLUSIONS

These findings have implications for identifying altered patterns of habit formation and deficits in habit-breaking among those experiencing depressive symptoms.

Identifying New Factors Associated With Cognitive Decline and Delirium After Transcatheter Aortic Valve Implantation: A Study Protocol

Background: Transcatheter aortic valve implantation (TAVI) has become the standard-of-care for treatment of severe symptomatic aortic stenosis and is also being increasingly recommended for low-risk patients. While TAVI boasts positive post-procedural outcomes, it is also associated with cognitive complications, namely delirium and cognitive decline. There is a pressing need for accurate risk tools which can identify TAVI patients at risk of delirium and cognitive decline, as risk scores designed for general cardiovascular surgery fall short. The present effect-finding exploratory study will assess the utility of various measures in the context of aging and frailty in predicting who will and who will not develop delirium or cognitive impairment following TAVI. The measures we propose include gait, visual symptoms, voice, swallowing, mood and sleep. Methods: This is an observational prospective cohort study focused on identifying pre-procedural risk factors for the development of delirium and cognitive decline following TAVI. Potential risk factors will be measured prior to TAVI. Primary outcomes will be post-procedure cognitive decline and delirium. Secondary outcomes include activities of daily living, quality of life, and mortality. Delirium presence will be measured on each of the first 2 days following TAVI. All other outcomes will be assessed at 3-, 6-, and 12-months post-operatively. A series of logistic regressions will be run to investigate the relationship between potential predictors and outcomes (presence vs. absence of either delirium or cognitive decline). Discussion: This study will assess the strengths of associations between a range of measures drawn from frailty and aging literature in terms of association with cognitive decline and delirium following TAVI. Identified measures can be used in future development of TAVI risk prediction models, which are essential for the accurate identification of cognitive at-risk patients and successful application of pre-procedural interventions. Clinical Trial Registration: This trial is registered with the Australian New Zealand Clinical Trials Registry. [https://bit.ly/2PAotP5], [ACTRN12618001114235].

Spontaneous Eye Blinks Predict Executive Functioning in Seniors

As the world’s population is aging rapidly, cognitive training is an extensively used approach to attempt improvement of age-related cognitive functioning. With increasing numbers of older adults required to remain in the workforce, it is important to be able to reliably predict future functional decline, as well as the individual advantages of cognitive training. Given the correlation between age-related decline and striatal dopaminergic function, we investigated whether eye blink rate (EBR), a non-invasive, indirect indicator of dopaminergic activity, could predict executive functioning (response inhibition, switching and working memory updating) as well as trainability of executive functioning in older adults. EBR was collected before and after a cognitive flexibility training, cognitive training without flexibility, or a mock training. EBR predicted working memory updating performance on two measures of updating, as well as trainability of working memory updating, whereas performance and trainability in inhibition and switching tasks could not be predicted by EBR. Our findings tentatively indicate that EBR permits prediction of working memory performance in older adults. To fully interpret the relationship with executive functioning, we suggest future research should assess both EBR and dopamine receptor availability among seniors.

Blink-sensing glasses: A flexible iontronic sensing wearable for continuous blink monitoring

Blink reflex has long been considered closely related to physiological states, from which abundant information on ocular health and activities can be revealed. In this study, a smart glasses wearable has been developed, incorporating a flexible and sensitive pressure sensor, to monitor blink patterns by continuously detecting ocular muscular movements, referred to as blink-sensing glasses. By applying the emerging flexible iontronic sensing (FITS) sensor with the sensitivity of 340 pF/mmHg, the skin pressure variations induced by movements of the orbicularis oculi muscles can be monitored in real time. The blink-sensing glasses can successfully capture blink patterns with a high accuracy of 96.3% and have been used to differentiate the blink features from both dry-eye subjects and healthy controls. This device can be potentially used as a new clinical and research monitoring tool for continuous eye blink analysis, while providing patients with high comfortableness in long-term ambulatory and home settings.

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Blink-sensing glasses can capture blink patterns with clinical-grade high accuracy

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A FITS sensor is applied to monitor the blink by detecting the muscle movement

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Blink-sensing glasses can be of potential use to prognose the dry eye

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The glasses are a continuous detection manner with immunity to ambient lights

Affective Computing for Late-Life Mood and Cognitive Disorders

Affective computing (also referred to as artificial emotion intelligence or emotion AI) is the study and development of systems and devices that can recognize, interpret, process, and simulate emotion or other affective phenomena. With the rapid growth in the aging population around the world, affective computing has immense potential to benefit the treatment and care of late-life mood and cognitive disorders. For late-life depression, affective computing ranging from vocal biomarkers to facial expressions to social media behavioral analysis can be used to address inadequacies of current screening and diagnostic approaches, mitigate loneliness and isolation, provide more personalized treatment approaches, and detect risk of suicide. Similarly, for Alzheimer's disease, eye movement analysis, vocal biomarkers, and driving and behavior can provide objective biomarkers for early identification and monitoring, allow more comprehensive understanding of daily life and disease fluctuations, and facilitate an understanding of behavioral and psychological symptoms such as agitation. To optimize the utility of affective computing while mitigating potential risks and ensure responsible development, ethical development of affective computing applications for late-life mood and cognitive disorders is needed.

Substance use is associated with reduced devaluation sensitivity

Substance use has been linked to impairments in reward processing and decision-making, yet empirical research on the relationship between substance use and devaluation of reward in humans is limited. We report findings from two studies that tested whether individual differences in substance use behavior predicted reward learning strategies and devaluation sensitivity in a nonclinical sample. Participants in Experiment 1 (N = 66) and Experiment 2 (N = 91) completed subscales of the Externalizing Spectrum Inventory and then performed a two-stage reinforcement learning task that included a devaluation procedure. Spontaneous eye blink rate was used as an indirect proxy for dopamine functioning. In Experiment 1, correlational analysis revealed a negative relationship between substance use and devaluation sensitivity. In Experiment 2, regression modeling revealed that while spontaneous eyeblink rate moderated the relationship between substance use and reward learning strategies, substance use alone was related to devaluation sensitivity. These results suggest that once reward-action associations are established during reinforcement learning, substance use predicted reduced sensitivity to devaluation independently of variation in eyeblink rate. Thus, substance use is not only related to increased habit formation but also to difficulty disengaging from learned habits. Implications for the role of the dopaminergic system in habitual responding in individuals with substance use problems are discussed.

The interaction effect between dopamine and task difficulty: Spontaneous eye blink rates diversely relate with Nogo-N2 across various task difficulties

Nogo- N2 and P3 are the two major components in the neural time course of response inhibition (RI) and are both related, albeit differently, to dopamine (DA). However, contradictory results from previous studies imply that there may be an interaction effect between DA and task difficulty on the neural time course of RI. To investigate this, we assessed the correlation between spontaneous eye blink rate (EBR) and N2/P3 elicited by the Go/Nogo tasks across various task difficulties, manipulated by the Nogo-stimuli probability (NP) and Go-stimuli response deadline (RTD). In experiment 1, there were two conditions, low (20%) and high (40%) NP, both of which were fixed on an RTD of 1000 ms. We found that higher EBR was significantly related to a more negative Nogo-N2 amplitude. In experiment 2, there were also two conditions, long (1000 ms) and short (300 ms) RTD, both of which were fixed on an NP of 20%. We found that higher EBR was significantly related to more negative Nogo-N2 amplitude in both conditions, however, there was no significant correlation between EBR and P3 in both of the experiments. These results confirmed the interaction effect between DA and task difficulty on the neural course of the Go/Nogo task. This suggests that task difficulty should be considered in future studies that investigate the influence of DA on RI.

Digital biomarkers for Alzheimer's disease: the mobile/ wearable devices opportunity

Alzheimer's Disease (AD) represents a major and rapidly growing burden to the healthcare ecosystem. A growing body of evidence indicates that cognitive, behavioral, sensory, and motor changes may precede clinical manifestations of AD by several years. Existing tests designed to diagnose neurodegenerative diseases, while well-validated, are often less effective in detecting deviations from normal cognitive decline trajectory in the earliest stages of the disease. In the quest for gold standards for AD assessment, there is a growing interest in the identification of readily accessible digital biomarkers, which harness advances in consumer grade mobile and wearable technologies. Topics examined include a review of existing early clinical manifestations of AD and a path to the respective sensor and mobile/wearable device usage to acquire domain-centric data towards objective, high frequency and passive digital phenotyping.

Dementia clinical trial implications of mild behavioral impairment

The World Alzheimer Report 2016 estimated that 47 million people are living with dementia worldwide (Alzheimer's Disease International, 2016). In the inaugural World Health Organization Ministerial Conference on Global Action against Dementia, six of the top ten research priorities were focused on prevention, identification, and reduction of dementia risk, and on delivery and quality of care for people with dementia and their carers (Shah et al., 2016). While the Lancet Neurology Commission has suggested that even minor advances to delay progression or ameliorate symptoms might have substantial financial and societal benefits (Winblad et al., 2016), advances have been slow.

Blink: Characteristics, Controls, and Relation to Dry Eyes

Blink is a complex phenomenon that is profoundly affected by diverse endogenous and exogenous stimuli. It has been studied in the context of cognition, emotional, and psychological states, as an indicator of fatigue and sleepiness, particularly in the automobile and transportation industry, in visual tasking, and finally, as it relates to tear film stability and ocular surface health. The fact that it is highly variable and has input from so many sources makes it very difficult to study. In the present review, the behavior of blink in many of these systems is discussed, ultimately returning in each instance to a discussion of how these factors affect blink in the context of dry eyes. Blink is important to ocular surface health and to an individual's optimal functioning and quality of life. Disturbances in blink, as cause or effect, result in a breakdown of tear film stability, optical clarity, and visual function.

Dopamine, depressive symptoms, and decision-making: the relationship between spontaneous eye blink rate and depressive symptoms predicts Iowa Gambling Task performance

Depressive symptomatology has been associated with alterations in decision-making, although conclusions have been mixed, with depressed individuals showing impairments in some contexts but advantages in others. The dopaminergic system may link depressive symptoms with decision-making performance. We assessed the role of striatal dopamine D2 receptor density, using spontaneous eye blink rates, in moderating the relationship between depressive symptoms and decision-making performance in a large undergraduate sample that had not been screened for mental illness (N = 104). The regression results revealed that eye blink rate moderated the relationship between depressive symptoms and advantageous decisions on the Iowa Gambling Task, in which individuals with more depressive symptomatology and high blink rates (higher striatal dopamine D2 receptor density) performed better on the task. Our computational modeling results demonstrated that depressive symptoms alone were associated with enhanced loss-aversive behavior, whereas individuals with high blink rates and elevated depressive symptoms tended to persevere in selecting options that led to net gains (avoiding options with net losses). These findings suggest that variation in striatal dopamine D2 receptor availability in individuals with depressive symptoms may contribute to differences in decision-making behavior.

Striatal Dopamine, Externalizing Proneness, and Substance Abuse: Effects on Wanting and Learning during Reward-Based Decision Making

We examined whether striatal dopamine moderates the impact of externalizing proneness (disinhibition) on reward-based decision-making. Participants completed disinhibition and substance abuse subscales of the brief form Externalizing Spectrum Inventory, and then performed a delay discounting task to assess preference for immediate rewards along with a dynamic decision-making task that assessed long-term reward learning (i.e., inclination to choose larger delayed versus smaller immediate rewards). Striatal tonic dopamine levels were operationalized using spontaneous eyeblink rate. Regression analyses revealed that high disinhibition predicted greater delay discounting among participants with lower levels of striatal dopamine only, while substance abuse was associated with poorer long-term learning among individuals with lower levels of striatal dopamine, but better long-term learning in those with higher levels of striatal dopamine. These results suggest that disinhibition is more strongly associated with the wanting component of reward-based decision-making, whereas substance abuse behavior is associated more with learning of long-term action-reward contingencies.

Spontaneous eye blink rate as predictor of dopamine-related cognitive function-A review

An extensive body of research suggests the spontaneous eye blink rate (EBR) is a non-invasive indirect marker of central dopamine (DA) function, with higher EBR predicting higher DA function. In the present review we provide a comprehensive overview of this literature. We broadly divide the available research in studies that aim to disentangle the dopaminergic underpinnings of EBR, investigate its utility in diagnosis of DA-related disorders and responsivity to drug treatment, and, lastly, investigate EBR as predictor of individual differences in DA-related cognitive performance. We conclude (i) EBR can reflect both DA receptor subtype D1 and D2 activity, although baseline EBR might be most strongly related to the latter, (ii) EBR can predict hypo- and hyperdopaminergic activity as well as normalization of this activity following treatment, and (iii) EBR can reliably predict individual differences in performance on many cognitive tasks, in particular those related to reward-driven behavior and cognitive flexibility. In sum, this review establishes EBR as a useful predictor of DA in a wide variety of contexts.

Staring Down Death

Abstract. Background: Lowered eye blink rate may be a clinically useful indicator of acute, imminent, and severe suicide risk. Diminished eye blink rates are often seen among individuals engaged in heightened concentration on a specific task that requires careful planning and attention. Indeed, overcoming one’s biological instinct for survival through suicide necessitates premeditation and concentration; thus, a diminished eye blink rate may signal imminent suicidality. Aims: This article aims to spur research and clinical inquiry into the role of eye blinks as an indicator of acute suicide risk. Method: Literature relevant to the potential connection between eye blink rate and suicidality was reviewed and synthesized. Results: Anecdotal, cognitive, neurological, and conceptual support for the relationship between decreased blink rate and suicide risk is outlined. Conclusion: Given that eye blinks are a highly observable behavior, the potential clinical utility of using eye blink rate as a marker of suicide risk is immense. Research is warranted to explore the association between eye blink rate and acute suicide risk.

The dopamine D1 receptor agonist SKF-82958 effectively increases eye blinking count in common marmosets

Eye blinking is a spontaneous behavior observed in all mammals, and has been used as a well-established clinical indicator for dopamine production in neuropsychiatric disorders, including Parkinson's disease and Tourette syndrome [1,2]. Pharmacological studies in humans and non-human primates have shown that dopamine agonists/antagonists increase/decrease eye blinking rate. Common marmosets (Callithrix jacchus) have recently attracted a great deal of attention as suitable experimental animals in the psychoneurological field due to their more developed prefrontal cortex than rodents, easy handling compare to other non-human primates, and requirement for small amounts of test drugs. In this study, we evaluated the effects of dopamine D1-4 receptors agonists on eye blinking in common marmosets. Our results show that the dopamine D1 receptor agonist SKF-82958 and the non-selective dopamine receptor agonist apomorphine significantly increased common marmosets eye blinking count, whereas the dopamine D2 agonist (+)-PHNO and the dopamine D3 receptor agonist (+)-PD-128907 produced somnolence in common marmosets resulting in a decrease in eye blinking count. The dopamine D4 receptor agonists PD-168077 and A-41297 had no effect on common marmosets' eye blinking count. Finally, the dopamine D1 receptor antagonist SCH 39166 completely blocked apomorphine-induced increase in eye blinking count. These results indicate that eye blinking in common marmosets may be a useful tool for in vivo screening of novel dopamine D1 receptor agonists as antipsychotics.

Modulation of resource allocation by intelligent individuals in linguistic, mathematical and visuo-spatial tasks

This study investigates two questions: first, how individuals with high-intelligence allocate cognitive resources while solving linguistic, mathematical and visuo-spatial tasks with varying degree of difficulty as compared to individuals with low intelligence? Second, how to distinguish between high and low intelligent individuals by analyzing pupil dilation and eye blink together? We measured the response time, error rates along with pupil dilation and eye blink rate that indicate resource allocation. We divided the whole processing into three stages namely: pre-stimuli (5s prior to stimuli onset), during stimuli and post stimuli (until 5s after the response) for better assessment of preparation and resource allocation strategies. Individuals with high intelligence showed greater task evoked pupil dilation, decreased eye blink with less response time and error rates during-stimuli stage (processing) of tough linguistic and visuo-spatial tasks but not during mathematical tasks. The finding suggests that individuals with high intelligence allocate more resources if the task demands are high else they allocate less resources. Greater pre-stimuli pupil dilation and increased eye blink of high intelligent individuals in all tasks indicated their attentiveness and preparedness. The result of our study shows that individuals with high intelligence are more attentive and flexible in terms of altering the resource allocation strategy according to task demand. Eye-blinks along with pupil dilation and other behavioral parameters can be reliably used to assess the intelligence of an individual and the analysis of pupil dilation and blink rate at pre-stimuli stage can be crucial in distinguishing individuals with varying intelligence.

Contact lens sensors in ocular diagnostics

Contact lenses as a minimally invasive platform for diagnostics and drug delivery have emerged in recent years. Contact lens sensors have been developed for analyzing the glucose composition of tears as a surrogate for blood glucose monitoring and for the diagnosis of glaucoma by measuring intraocular pressure. However, the eye offers a wider diagnostic potential as a sensing site and therefore contact lens sensors have the potential to improve the diagnosis and treatment of many diseases and conditions. With advances in polymer synthesis, electronics and micro/nanofabrication, contact lens sensors can be produced to quantify the concentrations of many biomolecules in ocular fluids. Non- or minimally invasive contact lens sensors can be used directly in a clinical or point-of-care setting to monitor a disease state continuously. This article reviews the state-of-the-art in contact lens sensor fabrication, their detection, wireless powering, and readout mechanisms, and integration with mobile devices and smartphones. High-volume manufacturing considerations of contact lenses are also covered and a case study of an intraocular pressure contact lens sensor is provided as an example of a successful product. This Review further analyzes the contact lens market and the FDA regulatory requirements for commercialization of contact lens sensors.

A Methodology for the Analysis of Spontaneous Reactions in Automated Hearing Assessment

Audiology is the science of hearing and auditory processes study. The evaluation of hearing capacity is commonly performed by an audiologist using an audiometer, where the patient is asked to show some kind of sign when he or she recognizes the stimulus. This evaluation becomes much more complicated when the patient suffers some type of cognitive decline that hinders the emission of visible signs of recognition. With this group of patients, a typical question-answer interaction is not applicable, so the audiologist must focus his attention on the patient's spontaneous gestural reactions. This manual evaluation entails a number of problems: it is highly subjective, difficult to determine in real time (since the expert must pay attention simultaneously to the audiological process and the patient's reactions), etc. Considering this, in this paper, we present an automatic methodology for processing video sequences recorded during the performance of the hearing test in order to assist the audiologist in the detection of these spontaneous reactions. This screening method analyzes the movements that occur within the eye area, which has been pointed out by the audiologists as the most representative for these patients. By the analysis of these movements, the system helps the audiologist to determine when a positive gestural reaction has taken place increasing the objectivity and reproducibility.