The effect of sunglass filters on contrast sensitivity, monocular eye closure, and blinking rate in people with intermittent exotropia.

CLINICAL RELEVANCE: Transient monocular eye closure and photosensitivity under bright light have been reported in people with intermittent exotropia (IXT). The exact mechanism of these symptoms has not been established. BACKGROUND: This study examines the effect of sunglass filters on contrast sensitivity (CS), transient monocular eye closure, and blinking rate under bright light in people with IXT. METHODS: Forty participants with IXT and complaints of photosensitivity were included in the study. The binocular CS test was performed under mesopic and photopic conditions with and without glare, and with and without two filters with different grades of light transmission (filter 1: 44-80%; filter 2: 20-43% light transmittance). The effect of two filters on transient eye closure, contrast sensitivity, and blinking rate was assessed under bright light. Also, participants were divided into 3 groups based on their degree of control of fusion (good, fair, and poor control). RESULTS: The mean age of the participants was 12.0 years ± 8.0 (standard deviation) (range: 7-40 years). There was no significant difference between the age (p = 0.139), stereopsis (p = 0.134), as well as the near and far degree of deviation (p = 0.516, and p = 0.237) between the three groups of fusion control. Under mesopic conditions with glare, mean binocular CS was significantly higher with filters (p < 0.001). Without filters, 57.5% of the participants exhibited monocular eye closure under a photopic setting with additional glare. No participant showed eye closure using filter 2. People in the poor control group showed exodeviation before monocular eye closure (62.5% without filter and 12.5% with filter 1, p = 0.01). The blinking rate decreased from 36.0 ± 4.0 blinks per minute without filter to 21.0 ± 3.0 using filter 1, and 20.0 ± 3.0 with filter 2. CONCLUSION: In people with IXT, wearing sunglass filters of different transmittance reduces monocular eye closure and blinking rate under bright light. To improve these symptoms, sunglasses can be considered for IXT.

Attentional Bias, Pupillometry, and Spontaneous Blink Rate: Eye Characteristic Assessment Within a Translatable Nicotine Cue Virtual Reality Paradigm.

Background: Incentive salience processes are important for the development and maintenance of addiction. Eye characteristics such as gaze fixation time, pupil diameter, and spontaneous eyeblink rate (EBR) are theorized to reflect incentive salience and may serve as useful biomarkers. However, conventional cue exposure paradigms have limitations that may impede accurate assessment of these markers. Objective: This study sought to evaluate the validity of these eye-tracking metrics as indicators of incentive salience within a virtual reality (VR) environment replicating real-world situations of nicotine and tobacco product (NTP) use. Methods: NTP users from the community were recruited and grouped by NTP use patterns: nondaily (n=33) and daily (n=75) use. Participants underwent the NTP cue VR paradigm and completed measures of nicotine craving, NTP use history, and VR-related assessments. Eye-gaze fixation time (attentional bias) and pupillometry in response to NTP versus control cues and EBR during the active and neutral VR scenes were recorded and analyzed using ANOVA and analysis of covariance models. Results: Greater subjective craving, as measured by the Tobacco Craving Questionnaire-Short Form, following active versus neutral scenes was observed (F1,106=47.95; P<.001). Greater mean eye-gaze fixation time (F1,106=48.34; P<.001) and pupil diameter (F1,102=5.99; P=.02) in response to NTP versus control cues were also detected. Evidence of NTP use group effects was observed in fixation time and pupillometry analyses, as well as correlations between these metrics, NTP use history, and nicotine craving. No significant associations were observed with EBR. Conclusions: This study provides additional evidence for attentional bias, as measured via eye-gaze fixation time, and pupillometry as useful biomarkers of incentive salience, and partially supports theories suggesting that incentive salience diminishes as nicotine dependence severity increases.

Blink rate during saccadic eye movements: insights from patients with chronic pain.

Chronic pain (CP) significantly impacts quality of life and poses an increasing economic burden on healthcare systems worldwide. This study investigates the relationship between blink rate during saccadic eye movements and pain perception in patients with CP. Ninety-two patients with CP (24 men, 68 women) were assessed using eye-tracking technology during horizontal and vertical saccadic tasks. Pain perception was evaluated using the Central Sensitization Inventory - Part A and the McGill Pain Questionnaire, and anxiety levels were measured using the State-Trait Anxiety Inventory. The results revealed a significant correlation between blink rates in horizontal and vertical tasks (ρ = 0.668, P < 0.001). However, there was no correlation between blink rate and age, pain perception, or anxiety scores. Conversely, measures of pain perception were positively correlated with each other and with anxiety scores. These findings suggest that while blink rate may reflect oculomotor function, it is not directly influenced by pain perception or anxiety in patients with CP. The present study highlights the potential of eye tracking for the comprehensive assessment and management of patients with CP.

Altered pupil light and darkness reflex and eye-blink responses in late-life depression.

BACKGROUND: Late-life depression (LLD) is a prevalent neuropsychiatric disorder in the older population. While LLD exhibits high mortality rates, depressive symptoms in older adults are often masked by physical health conditions. In younger adults, depression is associated with deficits in pupil light reflex and eye blink rate, suggesting the potential use of these responses as biomarkers for LLD. METHODS: We conducted a study using video-based eye-tracking to investigate pupil and blink responses in LLD patients (n = 25), older (OLD) healthy controls (n = 29), and younger (YOUNG) healthy controls (n = 25). The aim was to determine whether there were alterations in pupil and blink responses in LLD compared to both OLD and YOUNG groups. RESULTS: LLD patients displayed significantly higher blink rates and dampened pupil constriction responses compared to OLD and YOUNG controls. While tonic pupil size in YOUNG differed from that of OLD, LLD patients did not exhibit a significant difference compared to OLD and YOUNG controls. GDS-15 scores in older adults correlated with light and darkness reflex response variability and blink rates. PHQ-15 scores showed a correlation with blink rates, while MoCA scores correlated with tonic pupil sizes. CONCLUSIONS: The findings demonstrate that LLD patients display altered pupil and blink behavior compared to OLD and YOUNG controls. These altered responses correlated differently with the severity of depressive, somatic, and cognitive symptoms, indicating their potential as objective biomarkers for LLD.

The HPA and SAM axis mediate the impairment of creativity under stress.

With the ever-changing social environment, individual creativity is facing a severe challenge induced by stress. However, little is known regarding the underlying mechanisms by which acute stress affects creative cognitive processing. The current research explored the impacts of the neuroendocrine response on creativity under stress and its underlying cognitive flexibility mechanisms. The enzyme-linked immuno sorbent assay was employed to assess salivary cortisol, which acted as a marker of stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis. Eye blink rate (EBR) and pupil diameter were measured as respective indicators of dopamine and noradrenaline released by the activation of the sympathetic-adrenal-medullary (SAM) axis. The Wisconsin card task (WCST) measured cognitive flexibility, while the alternative uses task (AUT) and the remote association task (RAT) measured separately divergent and convergent thinking in creativity. Results showed higher cortisol increments following acute stress induction in the stress group than control group. Ocular results showed that the stress manipulation significantly increased EBR and pupil diameter compared to controls, reflecting increased SAM activity. Further analysis revealed that stress-released cortisol impaired the originality component of the AUT, reducing cognitive flexibility as measured by perseverative errors on the WCST task. Serial mediation analyses showed that both EBR and pupil diameter were also associated with increased perseverative errors leading to poor originality on the AUT. These findings confirm that physiological arousal under stress can impair divergent thinking through the regulation of different neuroendocrine pathways, in which the deterioration of flexible switching plays an important mediating role.

Tear clearance rate in dogs: Measurement using anterior segment optical coherence tomography.

OBJECTIVE: The tear clearance rate (TCR), determined using anterior segment optical coherence tomography (AS-OCT) images, and its correlation with ocular surface parameters, including blink rate, Schirmer tear test-1 (STT-1) and tear film breakup time (TFBUT), were evaluated. ANIMALS STUDIED: Left eyes of 20 client-owned dogs with no ocular disease symptoms. PROCEDURES: The tear meniscus height (TMH) was evaluated using AS-OCT images before the instillation of 5 µL saline (TMHbase ), immediately post-instillation (TMH0 ), 30-s post-instillation (TMH0.5 ) and at 1 min intervals for 5 min post-instillation (TMH1 , TMH2 , TMH3 , TMH4 and TMH5 ). The TCR was calculated using the formula [(TMH0  - TMH0.5 )/TMH0 ]×100 (%). The eyes were classified into two groups with the median: 'High TMHbase ' (n = 10) and 'Low TMHbase ' (n = 10). Eyes with STT-1 values ≥15 mm/min and TFBUT ≥ 12 s were assigned to the 'Satisfied' subgroup, whereas eyes not satisfying these criteria were assigned to the 'Not satisfied' subgroup. RESULTS: TMH0 was higher than TMH0.5 (p = 0.02), wherein TMH0.5 to TMH5 did not differ significantly. The TCR and blink rate were negatively correlated (p = 0.02). The 'Not satisfied' subgroup in the low TMHbase group had a lower TCR (p = 0.02) and higher blink rate (p = 0.04) than the 'Satisfied' subgroup. CONCLUSIONS: TCR can be evaluated using AS-OCT in dogs. Eyes with a lower TCR blink more frequently. TMH merits studying to understand ocular surface health.

Development of a novel protocol to evaluate contact-lens related ocular surface health on marmosets (Callithrix jacchus).

Contact lens wear affects the ocular surface and can cause contact lens-induced dry eye (CLIDE). The purpose of this study was bifold: (1) to develop a novel protocol to assess the ocular surface in a non-human primate (NHP) model, the common marmoset (Callithrix jacchus), and (2) to characterize central corneal thickness (CCT), tear osmolarity, blink rate and tear meniscus height (TMH) longitudinally, in untreated marmosets (controls) compared to animals treated with contact lenses (CL). Longitudinal changes in CCT (N = 10 control; N = 10 treated with contact lenses, CL-treated), osmolarity (N = 4 control; N = 6 CL-treated), blink rate (N = 8 control; N = 10 CL-treated) and TMH (N = 8 control; N = 6 CL-treated) were assessed using high frequency A-scan ultrasound, the I-PEN Vet Tear Osmolarity System, a video recording system (745 frames/minute) and Image J respectively, from 70 days to 224 days (5 months) at approx. 9am, and again after 9hrs of CL wear (methafilcon A, 55% water content; Capricornia, Australia) after every 4 weeks of contact lens wear for a total of 22 weeks of treatment. Repeated measures ANOVA was used to compare eyes over time and student t-test was used to compare treated to control eyes at each time point. At baseline, untreated marmosets had a CCT (mean ± SD) of 0.31 ± 0.01 mm, tear osmolarity 311.67 ± 11.48 mOsms/L, blink rate 1.83 ± 1.79 blinks per minute (bpm) and TMH 0.07 ± 0.02 arbitrary units (au), all of which remained stable over 5 months, except blink rate that increased to 5.32 ± 1.58 bpm (p < 0.01) after 5 months. In CL-treated marmosets, however, CCT progressively increased with CL wear (baseline: 0.30 ± 0.01 mm; 5 months: 0.31 ± 0.02 mm, p < 0.05), while osmolarity decreased after 2 and 3 months of CL wear (baseline: 316.11 ± 13.63; 2 months: 302.63 ± 11.27, p < 0.05; 3 months: 302.92 ± 14.58, p < 0.05). The decrease in osmolarity occurred in parallel to an increase in blink rate (baseline: 0.98 ± 1.18 bpm; 2 months: 3.46 ± 3.04 bpm, p < 0.05; 3 months: 3.73 ± 1.50 bpm, p < 0.001). TMH decreased during the third month of CL wear (baseline: 0.06 ± 0.00 au; 3 months: 0.05 ± 0.01 au, p < 0.05), and increased after 4 months (0.08 ± 0.01 au, p < 0.05). As TMH decreased, tear osmolarity increased in both control (R = -0.66, p < 0.05) and CL-treated marmosets (R = -0.64, p < 0.05). The results suggest that marmosets treated with CL for 5 months experienced an increase in blink rate, CCT and TMH, along with a decrease in osmolarity within the first few months of CL treatment that differed from the unaffected stable ocular surface findings observed untreated animals. We hypothesize that CL wear in marmosets might induce an increased blink rate and TMH, in turn delaying the development of hyperosmolarity. These findings confirm that the marmoset is a good novel animal model for ocular surface research for the assessment of novel contact lens materials aimed to alleviate CLIDE.

Dry eye disease and blinking behaviors: A narrative review of methodologies for measuring blink dynamics and inducing blink response.

Dry eye disease (DED) is a leading cause of ophthalmology clinical encounters with prevalence ranging from 8.7% to 64% in various populations. Blinking is an endogenous process to refresh the tear film, clear debris and maintain quality vision. Altered blinking behavior is a common feature of DED and is implicated in the pathology of the disease. However, lack of a comprehensive review on the relationship between altered blinking behavior and DED is notable in the literature. Blinking behavior may be an effect of DED due to an unstable tear film sensitizing a motor response or be its cause due to destabilization of the tear film in conditions such as benign essential blepharospasm. In this comprehensive review, we summarize the current models and theories of tear film dynamics and blinking behavior to better understand their connection to DED and introduce contemporary technologies and measurement tools used in the evaluation and induction of blinking behavior. We also describe future directions of research to better understand the relationship between DED and blinking and explore therapies that address the abnormal blinking component of DED.

On the potential of pupil size as a metric of physical fatigue during a repeated handle push/pull task.

Force output and muscle activity represent the gold standards for measuring physical fatigue. This study explores using ocular metrics for tracking changes in physical fatigue during the completion of a repeated handle push/pull task. Participants completed this task over three trials, and pupil size was recorded by means of a head-mounted eye-tracker. Blink frequency was also measured. Force impulse and maximum peak force were used as ground-truth measures of physical fatigue. As expected, a reduction in peak force and impulse was observed over time as participants became more fatigued. More interestingly, pupil size was also found to decrease from trial 1 through trial 3. No changes in blink rate were found with increasing physical fatigue. While exploratory in nature, these findings add to the sparse literature exploring the use of ocular metrics in Ergonomics. They also advance the use of pupil size as a possible future alternative for physical fatigue detection.

Driver Attention Assessment Using Physiological Measures from EEG, ECG, and EDA Signals.

In this paper, we consider the evaluation of the mental attention state of individuals driving in a simulated environment. We tested a pool of subjects while driving on a highway and trying to overcome various obstacles placed along the course in both manual and autonomous driving scenarios. Most systems described in the literature use cameras to evaluate features such as blink rate and gaze direction. In this study, we instead analyse the subjects' Electrodermal activity (EDA) Skin Potential Response (SPR), their Electrocardiogram (ECG), and their Electroencephalogram (EEG). From these signals we extract a number of physiological measures, including eye blink rate and beta frequency band power from EEG, heart rate from ECG, and SPR features, then investigate their capability to assess the mental state and engagement level of the test subjects. In particular, and as confirmed by statistical tests, the signals reveal that in the manual scenario the subjects experienced a more challenged mental state and paid higher attention to driving tasks compared to the autonomous scenario. A different experiment in which subjects drove in three different setups, i.e., a manual driving scenario and two autonomous driving scenarios characterized by different vehicle settings, confirmed that manual driving is more mentally demanding than autonomous driving. Therefore, we can conclude that the proposed approach is an appropriate way to monitor driver attention.

Eyes Fixed on Heaven's Gate: An Empirical Examination of Blink Rate and Suicide.

Anecdotal and theoretical work suggests blink rate as an indicator of imminent suicide risk. We sought to empirically examine whether suicide decedents displayed a reduced blink rate in goodbye videos filmed before death, compared to several control groups. Independent raters coded blink rates from videos of 34 suicide decedents and four comparison groups: "mundane" product review, non-suicidal arousal, non-suicidal depression, and non-imminent risk of suicidal ideation. Mean blink rate was lower in the suicide decedent group relative to all comparison groups (ps < .001), except the depressed (p = .976) and suicidal ideation (p = .393) groups. Findings indicate blink rate may be reduced among individuals at imminent risk for suicide, exhibiting clinically-significant depressive symptoms, or experiencing suicidal ideation.

Distracted worker: Using pupil size and blink rate to detect cognitive load during manufacturing tasks.

This study sets out to extend the use of blink rate and pupil size to the assessment of cognitive load of completing common automotive manufacturing tasks. Nonoptimal cognitive load is detrimental to safety. Existing occupational ergonomics approaches come short of measuring dynamic changes in cognitive load during complex assembling tasks. Cognitive demand was manipulated by having participants complete two versions of the n-back task (easy, hard). Two durations of the physical task were also considered (short, long). Pupil size and blink rate increased under greater cognitive task demand. High cognitive load also resulted in longer task completion times, and higher ratings of mental and temporal demand, and effort. This exploratory study offers relevant insights on the use of ocular metrics for cognitive load assessment in occupational ergonomics. While the existing eye-tracking technology may yet limit their adoption in the field, they offer advantages over the more popular expert-based and self-reported techniques in measuring changes in cognitive load during dynamic tasks.

Change in Blink Rate in the Metaverse VR HMD and AR Glasses Environment.

Blink rate, a major physiological response in humans, directly affects ocular diseases such as keratitis and dry eye. The blink rate in normal eyes appears at a constant frequency of 6-30 times per minute and is constant for each individual. In a previous study, the blink rate decreased when viewing content with high intensity and realism. Therefore, we tried to investigate the change in blink rate when viewing the content in VR HMD (virtual reality head-mounted display) and AR (augmented reality) glasses environments. We compared and analyzed the blink rate in four environments: natural state, viewing monitor, viewing VR HMD, and viewing AR glasses. Twenty-one participants (age, 26.87 ± 3.31 years) viewed the content for 1 min in four environments. One-way repeated ANOVA was used to analyze the blink rate changes. The study showed that the blink rate was decreased in the monitor, VR HMD, and AR glasses environments compared to that in the natural environment. Comparing the VR HMD environment with the AR glasses environment showed that the blink rate decreased in the VR HMD environment. The results of this study can be used for content use safety recommendations (guidelines for safe use of contents due to decreased blink rate) in the VR HMD and AR glasses environments, which are currently attracting attention in the metaverse.

Assessing the Risk Factors For Diagnosed Symptomatic Dry Eye Using a Smartphone App: Cross-sectional Study.

BACKGROUND: Dry eye (DE) is a chronic inflammatory disease of the ocular surface of the eye that affects millions of people throughout the world. Smartphone use as an effective health care tool has grown exponentially. The "Dry eye or not?" app was created to evaluate the prevalence of symptomatic DE, screen for its occurrence, and provide feedback to users with symptomatic DE throughout Thailand. OBJECTIVE: The purpose of this study was to compare the prevalence of symptomatic dry eye (DE), blink rate, maximum blink interval (MBI), and best spectacle-corrected visual acuity (BSCVA) between people with and without symptomatic DE and to identify risk factors for symptomatic DE in Thailand. METHODS: This cross-sectional study sourced data from the "Dry eye or not?" smartphone app between November 2019 and July 2020. This app collected demographic data, Ocular Surface Disease Index (OSDI) score, blink rate, MBI, BSCVA, and visual display terminal (VDT) use data. The criterion for symptomatic DE was OSDI score ≥13. RESULTS: The prevalence of symptomatic DE among individuals using this smartphone app in Thailand was 85.8% (8131/9482), with the Northeastern region of Thailand having the highest prevalence, followed by the Northern region. Worse BSCVA (median 0.20, IQR 0.40; P=.02), increased blink rate (median 18, IQR 16; P<.001), reduced MBI (median 8.90, IQR 10.80; P<.001), female sex (adjusted OR 1.83; 95% CI 1.59-2.09; P<.001), more than 6 hours of VDT use (adjusted OR 1.59; 95% CI 1.15-2.19; P=.004), and lower than bachelor's degree (adjusted OR 1.30; 95% CI 1.03-1.64; P=.02) were significantly associated with symptomatic DE. An age over 50 years (adjusted OR 0.77; 95% CI 0.60-0.99) was significantly less associated with symptomatic DE (P=.04). CONCLUSIONS: This smartphone DE app showed that the prevalence of symptomatic DE in Thailand was 85.8%. Signs and risk factors could be also evaluated with this smartphone DE app. Screening for DE by this app may allow for the development of strategic plans for health care systems in Thailand.

Spontaneous Eye Blink Rate During the Working Memory Delay Period Predicts Task Accuracy.

Spontaneous eye blink rate (sEBR) has been linked to attention and memory, specifically working memory (WM). sEBR is also related to striatal dopamine (DA) activity with schizophrenia and Parkinson's disease showing increases and decreases, respectively, in sEBR. A weakness of past studies of sEBR and WM is that correlations have been reported using blink rates taken at baseline either before or after performance of the tasks used to assess WM. The goal of the present study was to understand how fluctuations in sEBR during different phases of a visual WM task predict task accuracy. In two experiments, with recordings of sEBR collected inside and outside of a magnetic resonance imaging bore, we observed sEBR to be positively correlated with WM task accuracy during the WM delay period. We also found task-related modulation of sEBR, including higher sEBR during the delay period compared to rest, and lower sEBR during task phases (e.g., stimulus encoding) that place demands on visual attention. These results provide further evidence that sEBR could be an important predictor of WM task performance with the changes during the delay period suggesting a role in WM maintenance. The relationship of sEBR to DA activity and WM maintenance is discussed.

Do Head-Mounted Augmented Reality Devices Affect Muscle Activity and Eye Strain of Utility Workers Who Do Procedural Work? Studies of Operators and Manhole Workers.

OBJECTIVE: The objective was to determine the effect of two head-mounted display (HMD) augmented reality (AR) devices on muscle activity and eye strain of electric utility workers. The AR devices were the Microsoft HoloLens and RealWear HMT-1. BACKGROUND: The HoloLens is an optical see-through device. The HMT-1 has a small display that is mounted to the side of one eye of the user. METHOD: Twelve power plant operators and 13 manhole workers conducted their normal procedural tasks on-site in three conditions: HoloLens, HMT-1, and "No AR" (regular method). Duration of test trials ranged up to 30 s for operators and up to 10 min for manhole workers. Mean and peak values of surface electromyographic (sEMG) signals from eight neck muscles were measured. A small eye camera measured blink rate of the right eye. RESULTS: In general, there were no differences in sEMG activity between the AR and "No AR" conditions for both groups of workers. For the manhole workers, the HoloLens blink rate was 8 to 11 blinks per min lower than the HMT-1 in two tasks and 6.5 fewer than "No AR" in one task. Subjective assessment of the two AR devices did not vary in general. CONCLUSION: The decrease in blink rate with the HoloLens may expose utility manhole workers to risk of eye strain or dry-eye syndrome. APPLICATION: HMD AR devices should be tested thoroughly with respect to risk of eye strain before deployment by manhole workers for long-duration procedural work.

The role of the SLC6A3 3' UTR VNTR in nicotine effects on cognitive, affective, and motor function.

RATIONALE: Nicotine has been widely studied for its pro-dopaminergic effects. However, at the behavioural level, past investigations have yielded heterogeneous results concerning effects on cognitive, affective, and motor outcomes, possibly linked to individual differences at the level of genetics. A candidate polymorphism is the 40-base-pair variable number of tandem repeats polymorphism (rs28363170) in the SLC6A3 gene coding for the dopamine transporter (DAT). The polymorphism has been associated with striatal DAT availability (9R-carriers > 10R-homozygotes), and 9R-carriers have been shown to react more strongly to dopamine agonistic pharmacological challenges than 10R-homozygotes. OBJECTIVES: In this preregistered study, we hypothesized that 9R-carriers would be more responsive to nicotine due to genotype-related differences in DAT availability and resulting dopamine activity. METHODS: N=194 non-smokers were grouped according to their genotype (9R-carriers, 10R-homozygotes) and received either 2-mg nicotine or placebo gum in a between-subject design. Spontaneous blink rate (SBR) was obtained as an indirect measure of striatal dopamine activity and smooth pursuit, stop signal, simple choice and affective processing tasks were carried out in randomized order. RESULTS: Reaction times were decreased under nicotine compared to placebo in the simple choice and stop signal tasks, but nicotine and genotype had no effects on any of the other task outcomes. Conditional process analyses testing the mediating effect of SBR on performance and how this is affected by genotype yielded no significant results. CONCLUSIONS: Overall, we could not confirm our main hypothesis. Individual differences in nicotine response could not be explained by rs28363170 genotype.

Maturation of Temporal Saccade Prediction from Childhood to Adulthood: Predictive Saccades, Reduced Pupil Size, and Blink Synchronization.

When presented with a periodic stimulus, humans spontaneously adjust their movements from reacting to predicting the timing of its arrival, but little is known about how this sensorimotor adaptation changes across development. To investigate this, we analyzed saccade behavior in 114 healthy humans (ages 6-24 years) performing the visual metronome task, who were instructed to move their eyes in time with a visual target that alternated between two known locations at a fixed rate, and we compared their behavior to performance in a random task, where target onsets were randomized across five interstimulus intervals (ISIs) and thus the timing of appearance was unknown. Saccades initiated before registration of the visual target, thus in anticipation of its appearance, were labeled predictive [saccade reaction time (SRT) < 90 ms] and saccades that were made in reaction to its appearance were labeled reactive (SRT > 90 ms). Eye-tracking behavior including saccadic metrics (e.g., peak velocity, amplitude), pupil size following saccade to target, and blink behavior all varied as a function of predicting or reacting to periodic targets. Compared with reactive saccades, predictive saccades had a lower peak velocity, a hypometric amplitude, smaller pupil size, and a reduced probability of blink occurrence before target appearance. The percentage of predictive and reactive saccades changed inversely from ages 8-16, at which they reached adult-levels of behavior. Differences in predictive saccades for fast and slow target rates are interpreted by differential maturation of cerebellar-thalamic-striatal pathways.SIGNIFICANCE STATEMENT From the first moments of life, humans are exposed to rhythm (i.e., mother's heartbeat in utero), but the timeline of brain development to promote the identification and anticipation of a rhythmic stimulus, known as temporal prediction, remains unknown. Here, we used saccade reaction time (SRT) in the visual metronome task to differentiate between temporally predictive and reactive responses to a target that alternated at a fixed rate in humans aged 6-24. Periods of age-related change varied little by target rate, with matured predictive performance evident by mid-adolescence for fast and slow rates. A strong correlation among saccade, pupil, and blink responses during target prediction provides evidence of oculomotor coordination and dampened noradrenergic neuronal activity when generating rhythmic motor responses.

Blink Rate Study in Patients with Alzheimer's Disease, Mild Cognitive Impairment and Subjective Cognitive Decline.

BACKGROUND: Blink rate (BR) is considered a marker of dopaminergic activity in humans. BR is increased in patients with Mild Cognitive Impairment (MCI), but no study has yet investigated whether BR changes with the progression of cognitive decline from MCI to Alzheimer's disease (AD) and whether BR abnormalities are present in subjects with Subjective Cognitive Decline (SCD). OBJECTIVE: The aim of our study was to assess BR in patients with AD, MCI, and SCD and to correlate BR with demographic and clinical features of cognitive decline. METHODS: We enrolled 22 subjects with SCD, 23 with MCI, and 18 with AD and a group of 20 age-matched healthy controls (HCs). Cognitive function was assessed by testing global cognitive status and frontal, attentional, memory, verbal, and visuospatial functions. BR was measured by counting the number of blinks per minute. RESULTS: MCI subjects had an increased BR (p <0.001), whereas AD subjects had a lower BR than HCs (p <0.05). Conversely, SCD subjects had a BR similar to HCs. No significant correlations emerged between neuropsychological scores and BR in SCD, MCI, and AD subjects. CONCLUSION: Increased BR in MCI likely reflects early compensatory mechanisms occurring before AD, whereas decreased BR in AD suggests dopaminergic system involvement in this condition.

Efficacy of blink software in improving the blink rate and dry eye symptoms in visual display terminal users - A single-blinded randomized control trial.

PURPOSE: Dry eye disease (DED) is a multifactorial disease, more prevalent among visual display terminal users. Reduced blink rate is a risk factor to dry eye disorder, innovative means to remind to blink while using computers can be helpful. METHODS: Single-blinded Randomized Control Trial enrolled computer users with dry eye. Allocation concealment was done using opaque envelope and principal investigator was blinded. After baseline examination, eligible participants were randomized to intervention group (appearance of bars is 8 times/min) and control group (appearance of bars is 1 time/min). Participants from both groups used the software for 15 days, came for first follow up, and did not use the software for next 15 days until second follow-up examination. During each visit, detailed eye examination was done including blink rate, tear film break up time, and Ocular Surface Disease Index score. RESULTS: Forty-six participants (women n = 31; men n = 15) with a mean age of 28.02 (±6.295) years completed the study. Four participants were excluded from analysis because of early dropout. In the intervention group (n = 23) and control group (n = 23), participants were allocated. At the end of first phase, there was statistically significant difference in OSDI score (P = 0.021). Statistically significant difference was noticed in OSDI (P = 0.014) and blink rate (P = 0.049) as baseline, and final visit data were compared. CONCLUSION: "Blink-Blink" software with 8 reminders/min improved DED-related symptoms by increasing the blink rate. The carry-over effect after cessation of Blink-Blink software in improving blink rate was maintained even after 1 month. TRIAL REGISTRATION: : Clinical Trials Registry-India (CTRI): CTRI/2018/08/015176.