Pupillometry measures of autonomic nervous system regulation with advancing age in a healthy pediatric cohort

Normative Values for Pupillary Light Reflex Metrics Among Healthy Service Academy Cadets

INTRODUCTION

Assessments of the pupil's response to light have long been an integral part of neurologic examinations. More recently, the pupillary light reflex (PLR) has shown promise as a potential biomarker for the diagnosis of mild traumatic brain injury. However, to date, few large-scale normative data are available for comparison and reference, particularly, in military service members. The purpose of this study was to report normative values for eight PLR measurements among healthy service academy cadets based on sex, age, sleep, race, ethnicity, anisocoria, and concussion history.

METHODS

Freshmen entering a U.S. Service Academy completed a quantitative pupillometric assessment in conjunction with baseline concussion testing. PLR measurements were conducted using a Neuroptics PLR-3000 with a 121 µW light stimulus. The device measured maximum and minimum pupil diameter (mm), latency (time to maximum pupil constriction post-light stimulus [s]), peak and average constriction velocity (mm/s), average dilation velocity (mm/s), percentage pupil constriction, and T75 (time for pupil re-dilation from minimum pupil diameter to 75% maximum diameter [s]). During baseline testing, cadets also reported concussion history (yes and no) and hours slept the night before (<5.5 and ≥5.5). Normative values for each PLR measurement were calculated as mean ± SD, percentiles, and interquartile range. Mann-Whitney U tests were used to assess differences based on sex, concussion history, ethnicity, and hours slept for each PLR measurement. Kruskall-Wallis testing was used to assess differences based on age, race, and anisocoria. Alpha was set at .05 and nonparametric effect sizes (r) were calculated for statistically significant results. Effect sizes were interpreted as no effect (r < .1), small (r ≥.1-<.3), medium (r ≥.3-<.5), or large (r ≥ .5). All procedures were reviewed and approved by the local institutional review board and the U.S. Army Human Research Protection Office before the study was conducted. Each subject provided informed consent to participate in the study before data collection.

RESULTS

Of the 1,197 participants baselined, 514 cadets (131 female; 18.91 ± 0.96 years) consented and completed a valid baseline pupillometric assessment. Eighty participants reported at least one previous concussion and participants reported an average of 5.88 ± 1.63 h slept the previous night. Mann-Whitney U results suggest females had larger initial (z = -3.240; P = .001; r = .10) and end pupil diameter (z = -3.080; P = .002; r = .10), slower average dilation velocity (z = 3.254; P = .001; r = .11) and faster T75 values (z = -3.342; P = .001; r = .11). Age, sleep, and race stratified by sex, also displayed a significant impact on specific PLR metrics with effect sizes ranging from small to medium, while ethnicity, anisocoria, and concussion history did not display an impact on PLR metrics.

CONCLUSION

This study provides the largest population-specific normative values for eight PLR measurements. Initial and end pupil diameter, dilation velocity, and the T75 metrics differed by sex; however, these differences may not be clinically significant as small effect size was detected for all metrics. Sex, age, sleep, and race may impact specific PLR metrics and are worth consideration when performing PLR assessments for mild traumatic brain injury management.

Evaluation of Quantitative Pupillometry in Acute Postinjury Pediatric Concussion

BACKGROUND

Although millions of children sustain concussions each year, a rapid and objective test for concussion has remained elusive. The aim of this study was to investigate quantitative pupillometry in pediatric patients in the acute, postinjury setting.

METHODS

This was a prospective case-control study of concussed patients presenting to the emergency department within 72 hours of injury. Pupillary measurements were gathered using NeurOptics' PLR 3000; evaluation included a symptom checklist and neurocognitive assessment. Data were analyzed using descriptive statistics and regression models.

RESULTS

A total of 126 participants were enrolled. One significant difference in pupillometry between concussed and control participants was found: left minimum pupil diameter in 12- to 18 year-olds (P = 0.02). Models demonstrating odds of a concussion revealed significant associations for time to 75% recovery (T75) of the left pupil in five- to 11-year-olds and average dilation velocity of the left pupil in 12- to 18-year-olds (P = 0.03 and 0.02 respectively). Models predicting symptom improvement showed one significant association: percent change of the right pupil in five-to-11-year-olds (P = 0.02). Models predicting neurocognitive improvement in 12- to 18-year-olds demonstrated significant association in T75 in the left pupil for visual memory, visual motor processing speed, and reaction time (P = 0.002, P = 0.04, P = 0.04).

CONCLUSIONS

The limited statistically significant associations found in this study suggest that pupillometry may not be useful in pediatrics in the acute postinjury setting for either the diagnosis of concussion or to stratify risk for prolonged recovery.

The Role of Concussion History and Biological Sex on Pupillary Light Reflex Metrics in Adolescent Rugby Players: A Cross-Sectional Study

Background: Concussion examination is based primarily on clinical evaluation and symptomatic reporting. Pupillary light reflex (PLR) metrics may provide an objective physiological marker to inform concussion diagnosis and recovery, but few studies have assessed PLR, and normative data are lacking, particularly for adolescents. Aim: To capture PLR data in adolescent rugby players and examine the effects of concussion history and biological sex. Design: Cross-sectional. Methods: Male and female adolescent rugby union players aged 16 to 18 years were recruited at the start of the 2022-2023 playing season. PLR was recorded using a handheld pupillometer which provided seven different metrics relating to pupil diameter, constriction/dilation latency, and velocity. Data were analysed using a series of 2 × 2 ANOVAs to examine the main effects of independent variables: biological sex, concussion history, and their interactions, using adjusted p-values (p < 0.05). Results: 149 participants (75% male) were included. A total of 42% reported at least one previous concussion. Most metrics were unaffected by the independent variables. There were however significant main effects for concussion history (F = 4.11 (1); p = 0.05) and sex (F = 5.42 (1); p = 0.02) in end pupil diameters, and a main effect for sex in initial pupil diameters (F = 4.45 (1); p = 0.04). Although no significant interaction effects were found, on average, females with a concussion history presented with greater pupillary diameters and velocity metrics, with many pairwise comparisons showing large effects (SMD > 0.8). Conclusions: Pupillary diameters in adolescent athletes were significantly affected by concussion history and sex. The most extreme PLR metrics were recorded in females with a history of concussion (higher pupillary diameters and velocities). This highlights the importance of establishing baseline PLR metrics prior to interpretation of the PLR post-concussion. Long-standing PLR abnormalities post-concussion may reflect ongoing autonomic nervous system dysfunction. This warrants further investigation in longitudinal studies.

Creating a data dictionary for pediatric autonomic disorders

PURPOSE

Whether evaluating patients clinically, documenting care in the electronic health record, performing research, or communicating with administrative agencies, the use of a common set of terms and definitions is vital to ensure appropriate use of language. At a 2017 meeting of the Pediatric Section of the American Autonomic Society, it was determined that an autonomic data dictionary comprising aspects of evaluation and management of pediatric patients with autonomic disorders would be an important resource for multiple stakeholders.

METHODS

Our group created the list of terms for the dictionary. Definitions were prioritized to be obtained from established sources with which to harmonize. Some definitions needed mild modification from original sources. The next tier of sources included published consensus statements, followed by Internet sources. In the absence of appropriate sources, we created a definition.

RESULTS

A total of 589 terms were listed and defined in the dictionary. Terms were organized by Signs/Symptoms, Triggers, Co-morbid Disorders, Family History, Medications, Medical Devices, Physical Examination Findings, Testing, and Diagnoses.

CONCLUSION

Creation of this data dictionary becomes the foundation of future clinical care and investigative research in pediatric autonomic disorders, and can be used as a building block for a subsequent adult autonomic data dictionary.

Investigating the development of the autonomic nervous system in infancy through pupillometry

We aim to investigate early developmental trajectories of the autonomic nervous system (ANS) as indexed by the pupillary light reflex (PLR) in infants with (i.e. preterm birth, feeding difficulties, or siblings of children with autism spectrum disorder) and without (controls) increased likelihood for atypical ANS development. We used eye-tracking to capture the PLR in 216 infants in a longitudinal follow-up study spanning 5 to 24 months of age, and linear mixed models to investigate effects of age and group on three PLR parameters: baseline pupil diameter, latency to constriction and relative constriction amplitude. An increase with age was found in baseline pupil diameter (F(3,273.21) = 13.15, p < 0.001, [Formula: see text] = 0.13), latency to constriction (F(3,326.41) = 3.84, p = 0.010, [Formula: see text] = 0.03) and relative constriction amplitude(F(3,282.53) = 3.70, p = 0.012, [Formula: see text] = 0.04). Group differences were found for baseline pupil diameter (F(3,235.91) = 9.40, p < 0.001, [Formula: see text] = 0.11), with larger diameter in preterms and siblings than in controls, and for latency to constriction (F(3,237.10) = 3.48, p = 0.017, [Formula: see text] = 0.04), with preterms having a longer latency than controls. The results align with previous evidence, with development over time that could be explained by ANS maturation. To better understand the cause of the group differences, further research in a larger sample is necessary, combining pupillometry with other measures to further validate its value.

From pupil to the brain: New insights for studying cortical plasticity through pupillometry

Pupil size variations have been associated with changes in brain activity patterns related with specific cognitive factors, such as arousal, attention, and mental effort. The locus coeruleus (LC), a key hub in the noradrenergic system of the brain, is considered to be a key regulator of cognitive control on pupil size, with changes in pupil diameter corresponding to the release of norepinephrine (NE). Advances in eye-tracking technology and open-source software have facilitated accurate pupil size measurement in various experimental settings, leading to increased interest in using pupillometry to track the nervous system activation state and as a potential biomarker for brain disorders. This review explores pupillometry as a non-invasive and fully translational tool for studying cortical plasticity starting from recent literature suggesting that pupillometry could be a promising technique for estimating the degree of residual plasticity in human subjects. Given that NE is known to be a critical mediator of cortical plasticity and arousal, the review includes data revealing the importance of the LC-NE system in modulating brain plasticity and pupil size. Finally, we will review data suggesting that pupillometry could provide a quantitative and complementary measure of cortical plasticity also in pre-clinical studies.

How are pupillary parameters affected in pseudoexfoliation syndrome? A quantitative study

PURPOSE

We evaluated the effects of pseudoexfoliation syndrome on dynamic, static pupillary parameters (scotopic, mesopic, photopic) and the pupil dilation speed, with automatic pupillometry.

MATERIAL AND METHODS

The study group included 140 eyes with clinically visible pseudoexfoliation material (PXM) of 110 patients. The study group was compared with the control group formed by including 140 eyes of 110 patients. Scotopic measurements at 0.4 lx illumination, mesopic measurements at 4 lx illumination, and photopic measurements at 40 lx illumination were performed. Dynamic measurements were made at 500 lx illumination. The mean pupil dilation speed at 10th second was calculated. In addition, the eyes (80 patients) with clinically unilateral PXM were compared with the other eyes of the patients.

RESULTS

The mean scotopic, mesopic, photopic and dynamic pupil diameters of eyes with clinical PXM were compared with the control group, all values were found to be significantly lower in eyes with PXM. (p < 0.0001, p < 0.0001, p < 0.0001, p < 0.0001, respectively). The mean speed of pupil dilation at the 10th second was also significantly lower in the pseudoexfoliation syndrome group (p < 0.0001). The measurement results of the patients with clinical PXM were significantly lower than the other unaffected eyes (p = 0.001, p = 0.004, p = 0.048, p = 0.035, respectively). The mean speed of pupil dilation at 10th second was also significantly lower in eyes with PXM (p = 0.009).

CONCLUSION

Results clearly reveal that pseudoexfoliation syndrome affects iris mechanisms. Although pseudoexfoliation syndrome is a systemic syndrome, we can say that the emergence of iris dysfunction findings is parallel with the clinical observation of PXM.

PyPlr: A versatile, integrated system of hardware and software for researching the human pupillary light reflex

We introduce PyPlr-a versatile, integrated system of hardware and software to support a broad spectrum of research applications concerning the human pupillary light reflex (PLR). PyPlr is a custom Python library for integrating a research-grade video-based eye-tracker system with a light source and streamlining stimulus design, optimisation and delivery, device synchronisation, and extraction, cleaning, and analysis of pupil data. We additionally describe how full-field, homogenous stimulation of the retina can be realised with a low-cost integrating sphere that serves as an alternative to a more complex Maxwellian view setup. Users can integrate their own light source, but we provide full native software support for a high-end, commercial research-grade 10-primary light engine that offers advanced control over the temporal and spectral properties of light stimuli as well as spectral calibration utilities. Here, we describe the hardware and software in detail and demonstrate its capabilities with two example applications: (1) pupillometer-style measurement and parametrisation of the PLR to flashes of white light, and (2) comparing the post-illumination pupil response (PIPR) to flashes of long and short-wavelength light. The system holds promise for researchers who would favour a flexible approach to studying the PLR and the ability to employ a wide range of temporally and spectrally varying stimuli, including simple narrowband stimuli.

Autonomic tone in children and adults: Pupillary, electrodermal and cardiac activity at rest

Considering the suspected involvement of the autonomic nervous system (ANS) in several neurodevelopmental disorders, a description of its tonus in typical populations and of its maturation between childhood and adulthood is necessary. We aimed to arrive at a better understanding of the maturation of the sympathetic (SNS) and parasympathetic (PNS) tonus by comparing children and adults at rest, via recordings of multiple ANS indices. We recorded simultaneously pupil diameter, electrodermal activity (EDA) and cardiac activity (RR interval and HRV: heart rate variability) in 29 children (6-12 years old) and 30 adults (20-42 years old) during a 5-min rest period. Children exhibited lower RR intervals, higher LF peak frequencies, and lower LF/HF (low frequency/high frequency) ratios compared to adults. Children also produced more spontaneous EDA peaks, reflected in a larger EDA AUC (area under the curve), in comparison with adults. Finally, children displayed a larger median pupil diameter and a higher pupillary hippus frequency than adults. Our results converged towards higher SNS and PNS tones in children compared to adults. Childhood would thus be characterized by a high autonomic tone, possibly reflecting a physiological state compatible with developmental acquisitions.

Do static and dynamic pupillary parameters differ according to childhood, adulthood, and old age? A quantitative study in healthy volunteers

Purpose

We aimed to evaluate the normative pupillometry values and mean pupil dilatation speed in healthy individuals in different age groups in our study.

Methods

The study group included 180 eyes of 90 healthy volunteers in different age groups. Group 1 consisted of 30 participants between the ages of 6 and 18, group 2 consisted of 30 participants aged 19-40, and group 3 consisted of 30 participants aged 41-75. Scotopic, mesopic, photopic, and dynamic measurements were taken with automatic pupillometry of Sirius Topographer (CSO, Firenze, Italy). The mean pupil dilation speed at the 18^th second was calculated according to dynamic measurements.

Results

Group 1 had a significantly larger pupil diameter than groups 2 and 3 in all static and dynamic parameters, and the mean pupil dilation speed was the highest among the groups (P < 0.001 for all static and dynamic parameters). In addition, group 2 had a significantly larger pupil diameter than group 3 (P < 0.001 for all static and dynamic parameters) and the mean pupil dilation speed was faster than group 3 (P = 0.027).

Conclusion

We have presented the static and dynamic parameters and the mean speed of pupil dilatation at the 18^th second with automatic pupillometry in healthy individuals in childhood, adulthood, and old age. More studies with higher participants and younger age children are needed.

Evolution of physiologic and autonomic phenotype in rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation over a decade from age at diagnosis

Rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation (ROHHAD) is a rare cause of syndromic obesity with risk of cardiorespiratory arrest and neural crest tumor. No ROHHAD-specific genetic test exists at present. Rapid weight gain of 20-30 pounds, typically between ages 2-7 years in an otherwise healthy child, followed by multiple endocrine abnormalities herald the ROHHAD phenotype. Vigilant monitoring for asleep hypoventilation (and later awake) is mandatory as hypoventilation and altered control of breathing can emerge rapidly, necessitating artificial ventilation as life support. Recurrent hypoxemia may lead to cor pulmonale and/or right ventricular hypertrophy. Autonomic dysregulation is variably manifest. Here we describe the disease onset with "unfolding" of the phenotype in a child with ROHHAD, demonstrating the presentation complexity, need for a well-synchronized team approach, and optimized management that led to notable improvement ("refolding") in many aspects of the child's ROHHAD phenotype over 10 years of care.

CITATION

Khaytin I, Stewart TM, Zelko FA, et al. Evolution of physiologic and autonomic phenotype in rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation over a decade from age at diagnosis. J Clin Sleep Med. 2022;18(3):937-944.

Dynamic volume-rendered optical coherence tomography pupillometry

PURPOSE

To assess intrapupillary space (IPS) changes in healthy subjects with regard to decreased iris motility in patients with pseudoexfoliation glaucoma (PEXG) or non-arteritic anterior ischaemic optic neuropathy (NAION) in a feasibility study in a clinical environment.

METHODS

Scotopic and photopic IPS measurements using three-dimensionally rendered swept-source optical coherence tomography (SS-OCT) data were obtained and compared for all subjects. Intrapupillary space (IPS) parameters were evaluated such as absolute volumetric differences, relative light response for volumetric ratios and pupillary ejection fraction (PEF) for functional contraction measurements.

RESULTS

From a total of 122 IPS from 66 subjects, 106 IPS were eligible for comparison providing values for 72 normal, 30 PEXG and 4 NAION eyes. In healthy, PEXG and NAION subjects, scotopic overall mean IPS was 8.90, 3.45 and 4.16 mm³ , and photopic overall mean IPS was 0.87, 0.74 and 1.13 mm³ , respectively. Three-dimensional contractility showed a mean absolute difference of 8.03 mm³ for normals (defined as 100% contractility), 2.72 mm³ for PEXG (33.88% of normal) and 3.03 mm³ for NAION (38.50% of normal) with a relative light response ratio between scotopic and photopic volumes of 10.26 (100%), 4.69 (45.70%) and 3.67 (35.78%), respectively. Pupillary ejection fraction (PEF) showed a contractile pupillary emptying of 88.11% for normals, 76.92% for PEXG and 70.91% for NAION patients.

CONCLUSION

This 3D pupillometry OCT assessment allows for quantitative measurements of pupil function, contractility and response to light. More specifically, PEF is presented as a potential (neuro)-pupillary outcome measure that could be useful in the monitoring of ophthalmic disorders that affect pupillary function.

MEYE: Web App for Translational and Real-Time Pupillometry

Pupil dynamics alterations have been found in patients affected by a variety of neuropsychiatric conditions, including autism. Studies in mouse models have used pupillometry for phenotypic assessment and as a proxy for arousal. Both in mice and humans, pupillometry is noninvasive and allows for longitudinal experiments supporting temporal specificity; however, its measure requires dedicated setups. Here, we introduce a convolutional neural network that performs online pupillometry in both mice and humans in a web app format. This solution dramatically simplifies the usage of the tool for the nonspecialist and nontechnical operators. Because a modern web browser is the only software requirement, this choice is of great interest given its easy deployment and setup time reduction. The tested model performances indicate that the tool is sensitive enough to detect both locomotor-induced and stimulus-evoked pupillary changes, and its output is comparable to state-of-the-art commercial devices.

Increasing Vegetable Diversity Consumption Impacts the Sympathetic Nervous System Activity in School-Aged Children

Evidence about the impact of vegetable and fruit diversity consumption on the autonomic nervous system (ANS) functioning is scarce. In this cross-sectional study (513 participants, 49.9% girls aged 7 to 12 years), we evaluated the association between vegetable and fruit diversity consumption and the ANS in school-aged children. Dietary intake was collected using a single 24-h recall questionnaire. Fruit and vegetable diversity consumption was estimated by summing up all the different individual vegetables and fruits consumed in one day. Pupillometry was used to assess pupillary light response, which evaluated the ANS activity. Adjusted linear regressions estimated the association between vegetable and fruit diversity consumption with pupillary light response measures. There was a positive and significant association between vegetable diversity consumption and the average dilation velocity, a measure related to the sympathetic nervous system activity (β-coefficient = 0.03, 95%CI: 0.002; 0.07). Our findings show that vegetable diversity consumption is associated with the ANS response, a possible early link between diet and health in school-aged children.

Concussion Alters Dynamic Pupillary Light Responses in Children

AIM

To investigate the impact of concussion on pupillary function in children by examining pupillometric parameters and assessing for differences in children reporting photosensitivity.

METHODS

Retrospective chart review was performed of pediatric patients referred for visual symptoms after concussion from 2017 to 2018 seen in a single academic outpatient clinic. Pupillometry data of 92 patients were included. Outcomes were compared to normative pediatric data from the same institution by 2-sample t tests. The association between photosensitivity and each outcome was assessed by use of linear mixed models with photosensitivity as a fixed effect and random patient effect.

RESULTS

Outcomes of 181 eyes in 92 concussion patients were averaged by patient and compared to normative values in scotopic conditions. Concussion patients had an average age of 13.8 ± 2.64 years. Average constriction velocity (P = .0008), maximum constriction velocity (P = .0012), and average dilation velocity (P = .0034) were faster in concussion patients, whereas 75% recovery times (P = .0027) was increased. Photosensitivity did not significantly affect measured pupillary responses.

CONCLUSION

Dynamic pupillary responses may be increased in pediatric concussion. Pupillometry may provide insight into the complex pathophysiological changes underlying pediatric concussion.

Pupillometry measurement and its relationship to retinal structural changes in children with attention deficit hyperactivity disorder

PURPOSE

This study aims to assess the pupillometry measurements of the attention deficit hyperactivity disorder (ADHD) patients and to investigate their correlations with macular and RNFL thickness parameters by comparing the values with a healthy control group.

METHODS

Newly diagnosed ADHD patients in a child and adolescent clinic of a tertiary hospital were consulted in an ophthalmology clinic. All participants had undergone a standard ophthalmological examination including refractometry, best corrected visual acuity, color vision, anterior segment biomicroscopy, fundoscopy, pupillometry, and OCT. All results were compared with a healthy control group at the same age.

RESULTS

The study group consisted of 32 patients and there were 43 children in the control group. Mean pupillary velocities of ADHD patients and control group were 0.60 ± 0.11 mm/s and 0.63 ± 0.11 mm/s, and 0.49 ± 0.12 mm/s and 0.50 ± 0.10 mm/s, for right and left eyes, respectively. The difference was statistically significant for both eyes (p < 0.05). Mean RNFL thickness measurements of the study group were 90.69 ± 8.58 μm and 89.63 ± 8.14 μm for right and left eyes, respectively and those were 87.35 ± 7.67 μm and 88.77 ± 7.44 μm, respectively in the healthy group. Correlation between right pupillary velocity and RNFL thickness was statistically significant (r = 0.339, p = 0.003).

CONCLUSION

Higher pupillary velocity values were observed in both eyes of children with ADHD and that was positively correlated with RNFL measurements of their right eyes.