Inter-device reliability of the NPi-200 and NPi-300 pupillometers

Neuroradiological Correlates of Abnormal Pupillary Light Reflex Findings Among Patients in the Neuroscience Intensive Care Unit

ABSTRACT

BACKGROUND: Changes in pupil reactivity secondary to cerebral mass effect are traditionally linked to compression of the oculomotor nerve by the uncus or by horizontal midbrain displacement. The neurological pupil index (NPi) is a metric to assess the pupillary light reflex. This study explores the relationship of midline shift, cisternal, and sulcal effacement or ventricular compression in patients with a new finding of abnormal pupillary light reflex. METHODS: This retrospective study identified adult patients with serial pupillometer readings between 2018 and 2023 who had a baseline head computed tomography (CT) scan, subsequent new-onset NPi worsening from normal to abnormal, and a repeat CT scan within 2 hours of the NPi changes. Those with NPi worsening were compared with those with no NPi change. RESULTS: Among 77 patients (27 with NPi worsening, 50 without), those with NPi worsening exhibited a higher incidence of midline shift on the repeat CT. Regression models revealed a significant correlation between midline shift change and abnormal NPi ( r = 0.2260, P < .001). However, NPi worsening was not linked to changes in ventricular compression, nor sulcal or cisternal effacement. CONCLUSION: Midline shift, rather than cisternal or sulcal effacement, is associated with abnormal NPi values.

Assessing the Inter-Rater and Inter-Trial Reliability of the NeurOptics Pupillary Light Response-3000 Pupillometer

Background

An automated pupillometer is a handheld device used to stimulate the pupillary light response (PLR) and track the entirety of the response from constriction to dilation. Pupillometers provide objective data that clinicians can use to identify and assess brain injury. The validity of these devices has been previously established; however, the inter-rater and inter-trial reliability are unknown.

Purpose

The purpose of this study was to assess the inter-rater and inter-trial reliability of the NeurOptics PLR-3000 pupillometer device in measuring pupil size changes, constriction velocities, and dilation velocities. The authors hypothesized that inter-rater and inter-trial reliability would have intraclass correlation coefficients (ICC) greater than or equal to 0.70 for all PLR parameters.

Study

Design: Observational, reliability study Methods: Forty-eight healthy adults (age 18-40 years) without a history of neurological injury, optical surgery, or cognitive impairment participated. Two independent raters used the NeurOptics PLR-3000 to measure PLR parameters in the left and right eyes of each subject. Data for the average and individual trials of each PLR parameter were used to determine inter-rater and inter-trial reliability, respectively. Inter-rater and inter-trial reliability was evaluated using descriptive statistics, ICC, the standard error of measurement, Bland-Altman plots, and the minimal detectable change.

Results

Seven out of eight NeurOptics 3000-PLR parameters demonstrated moderate-to-excellent inter-rater (ICC range 0.72-0.96) and good-to-excellent inter-trial reliability (ICC range 0.76-0.98). The 75% recovery time parameter exhibited moderate inter-rater (ICC range 0.64-0.67) and poor-to-moderate inter-trial (ICC range 0.41-0.65) reliability.

Conclusion

The NeurOptics 3000-PLR demonstrated acceptable reliability in measuring initial and end pupil size, constriction and dilation velocity, and latency to change between different users and trials. However, the device exhibited unacceptable reliability when measuring the time to 75% pupil size recovery. The device can be used in detecting and monitoring brain injury but should be limited to reliable measures only.

Quantitative pupillometry as a potential biomarker in early concussion assessment

BACKGROUND

There are limited objective methods when it comes to identifying and diagnosing concussion. Pupil assessment is performed routinely as a standard-of-care following traumatic brain injury (TBI). Unlike the highly subjective and limited reliability of pupil assessment using penlights and flashlights, Quantitative pupillometry (QP) is an established, valid, and reliable method of pupillary assessment. This study aims to investigate the use of QP values in concussion evaluation.

METHODS

This observational study analyzed data collected by the North Texas Concussion Registry (ConTex). ConTex enrolls subjects who are >5-years of age and clinically diagnosed with concussion. Subjects are excluded if they had moderate or severe traumatic brain injury, spinal cord injury with an American Spinal Injury Association score of C or worse, or if the injury occurred > 6 months from enrollment. Data included demographics, medical history, time since concussion, the Sport Concussion Assessment Tool (SCAT5©) post-concussion symptom scale (PCSS), and QP assessment using the PLR3000® (Neuroptics Inc.) hand-held pupillometer. This study identified all subjects clinically diagnosed with concussion who had completed QP assessment, totaling 162. We created tertiles to describe the lowest (0-20), middle (21-43), and the highest (44-113) symptom score groupings to examine QP data.

RESULTS

Of 162 subjects, 88 were female (54.3%), with a mean age of 15.8 (SD=6.9) years. Most (49.4%) occurrences were sport-related injuries. The mean time since injury was 21 (SD=28.6) days. The mean SCAT5 PCSS score was 37.3 (SD=25.6). A significant difference within average and maximum constriction velocities (p=.041 and 0.034, respectively) was found between subjects seen early (<2weeks) versus late (>2weeks) after injury. Pupillometry values were statistically different across SCAT5 PCSS tertiles for anisocoria after light exposure (p=.046).

CONCLUSIONS

This exploratory study is among the first to show that certain QP values - latency of constriction, constriction velocity, and average dilation velocity - may be useful in providing objective metrics when evaluating more symptomatic concussion.

Automated quantitative pupillometry as a predictor for transtentorial brain herniation in patients with malignant acute ischemic stroke

Brain herniation can be a life-threatening condition, resulting in poor prognosis and higher fatality rates. We examined whether quantitative characteristics of sequential pupillary light reflex (PLR) could serve as biomarkers for identifying brain herniation in fatal acute stroke cases with anterior circulation involvement admitted to neurological intensive care unit (Neuro-ICU). Automatic pupillometer assessed PLR automatically every 4-6 hours, measuring eight specific features: NPi (Neurological pupil index) score, initial resting and constriction pupil size, constriction change, constriction velocity, constriction latency, and dilation velocity. Generalized estimating equations were used to analyze the main effects of assessment time (3-to-0 hours, just before brain herniation, and 27-to-21 hours, considerably before) and clinical groups. The study involved 59 patients (mean age 68.8 ± 1.6 years, 23 females) divided into herniation (n = 10) and non-herniation (n = 49) groups. The herniation group exhibited significantly lower ipsilateral NPi scores at 3-to-0 hours (1.80 ± 0.44, p < 0.0001) compared to 27-to-21 hours (4.26 ± 2.21). Additionally, the herniation group had a larger ipsilateral pupil size at constriction at 3-to-0 hours (4.01 ± 0.40 mm) compared to 27-to-21 hours (2.11 ± 0.17 mm). Specifically, at 3-to-0 hours, the herniation group had lower NPi scores (1.80 ± 0.44 vs. 3.97 ± 0.13, p < 0.0001) and larger pupil size at constriction (4.01 ± 0.04 mm vs. 2.90 ± 0.10 mm, p = 0.007) compared to the non-herniation group. These findings suggest that evaluating PLR characteristics can aid in the early identification of brain herniation, facilitating timely triage and appropriate surgical management.

Anisocoria After Direct Light Stimulus is Associated with Poor Outcomes Following Acute Brain Injury

BACKGROUND

Assessing pupil size and reactivity is the standard of care in neurocritically ill patients. Anisocoria observed in critically ill patients often prompts further investigation and treatment. This study explores anisocoria at rest and after light stimulus determined using quantitative pupillometry as a predictor of discharge modified Rankin Scale (mRS) scores.

METHODS

This analysis includes data from an international registry and includes patients with paired (left and right eye) quantitative pupillometry readings linked to discharge mRS scores. Anisocoria was defined as the absolute difference in pupil size using three common cut points (> 0.5 mm, > 1 mm, and > 2 mm). Nonparametric models were constructed to explore patient outcome using three predictors: the presence of anisocoria at rest (in ambient light); the presence of anisocoria after light stimulus; and persistent anisocoria (present both at rest and after light). The primary outcome was discharge mRS score associated with the presence of anisocoria at rest versus after light stimulus using the three commonly defined cut points.

RESULTS

This analysis included 152,905 paired observations from 6,654 patients with a mean age of 57.0 (standard deviation 17.9) years, and a median hospital stay of 5 (interquartile range 3-12) days. The mean admission Glasgow Coma Scale score was 12.7 (standard deviation 3.5), and the median discharge mRS score was 2 (interquartile range 0-4). The ranges for absolute differences in pupil diameters were 0-5.76 mm at rest and 0-6.84 mm after light. Using an anisocoria cut point of > 0.5 mm, patients with anisocoria after light had worse median mRS scores (2 [interquartile range 0-4]) than patients with anisocoria at rest (1 [interquartile range 0-3]; P < .0001). Patients with persistent anisocoria had worse median mRS scores (3 [interquartile range 1-4]) than those without persistent anisocoria (1 [interquartile range 0-3]; P < .0001). Similar findings were observed using a cut point for anisocoria of > 1 mm and > 2 mm.

CONCLUSIONS

Anisocoria after light is a new biomarker that portends worse outcome than anisocoria at rest. After further validation, anisocoria after light should be considered for inclusion as a reported and trended assessment value.

Quantitative Pupillometry: Clinical Applications for the Internist

From the time of Galen, examination of the pupillary light reflex has been a standard of care across the continuum of health care. The growing body of evidence overwhelmingly supports the use of quantitative pupillometry over subjective examination with flashlight or penlight. At current time, pupillometers have become standard of care in many hospitals across 6 continents. This review paper provides an overview and rationale for pupillometer use and highlights literature supporting pupillometer-derived measures of the pupillary light reflex in both neurological and non-neurological patients across the health care continuum.

Exploring the feasibility of pupillometry training and perceptions of potential use for intracranial pressure monitoring in Uganda: A mixed methods study

INTRODUCTION

Traumatic brain injury (TBI) accounts for the majority of Uganda's neurosurgical disease burden; however, invasive intracranial pressure (ICP) monitoring is infrequently used. Noninvasive monitoring could change the care of patients in such a setting through quick detection of elevated ICP.

PURPOSE

Given the novelty of pupillometry in Uganda, this mixed methods study assessed the feasibility of pupillometry for noninvasive ICP monitoring for patients with TBI.

METHODS

Twenty-two healthcare workers in Kampala, Uganda received education on pupillometry, practiced using the device on healthy volunteers, and completed interviews discussing pupillometry and its implementation. Interviews were assessed with qualitative analysis, while quantitative analysis evaluated learning time, measurement time, and accuracy of measurements by participants compared to a trainer's measurements.

RESULTS

Most participants (79%) reported a positive perception of pupillometry. Participants described the value of pupillometry in the care of patients during examination, monitoring, and intervention delivery. Commonly discussed concerns included pupillometry's cost, understanding, and maintenance needs. Perceived implementation challenges included device availability and contraindications for use. Participants suggested offering continued education and engaging hospital leadership as implementation strategies. During training, the average learning time was 13.5 minutes (IQR 3.5), and the measurement time was 50.6 seconds (IQR 11.8). Paired t-tests to evaluate accuracy showed no statistically significant difference in comparison measurements.

CONCLUSION

Pupillometry was considered acceptable for noninvasive ICP monitoring of patients with TBI, and pupillometer use was shown to be feasible during training. However, key concerns would need to be addressed during implementation to aid device utilization.

Evaluating the utility of quantitative pupillometry in a neuro-critical care setting for the monitoring of intracranial pressure: A prospective cohort study

INTRODUCTION

Assessment of the pupillary light reflex (PLR) is key in intensive care monitoring of neurosurgical patients, particularly for monitoring intracranial pressure (ICP). Quantitative pupillometry using a handheld pupillometer is a reliable method for PLR assessment. However, many variables are derived from such devices. We therefore aimed to assess the performance of these variables at monitoring ICP.

METHODS

Sedated patients admitted to neurocritical care in a tertiary neurosurgical centre with invasive ICP monitoring were included. Hourly measurement of ICP, subjective pupillometry (SP) using a pen torch device, and quantitative pupillometry (QP) using a handheld pupillometer were performed.

RESULTS

561 paired ICP, SP and QP pupillary observations from nine patients were obtained (1122 total pupillary observations). SP and QP had a moderate concordance for pupillary size (κ=0.62). SP performed poorly at detecting pupillary size changes (sensitivity=24%). In 40 (3.6%) observations, SP failed to detect a pupillary response whereas QP did. Moderate correlations with ICP were detected for maximum constriction velocity (MCV), dilation velocity (DV), and percentage change in pupillary diameter (%C). Discriminatory ability at an ICP threshold of >22 mmHg was moderate for MCV (AUC=0.631), DV (AUC=0.616), %C (AUC=0.602), and pupillary maximum size (AUC=0.625).

CONCLUSION

QP is superior to SP at monitoring pupillary reactivity and changes to pupillary size. Although effect sizes were moderate to weak across assessed variables, our data indicates MCV and %C as the most sensitive variables for monitoring ICP. Further study is required to validate these findings and to establish normal range cut-offs for clinical use.

Describing Anisocoria in Neurocritically Ill Patients

BACKGROUND

Anisocoria (unequal pupil size) has been defined using cut points ranging from greater than 0.3 mm to greater than 2.0 mm for absolute difference in pupil size. This study explored different pupil diameter cut points for assessing anisocoria as measured by quantitative pupillometry before and after light stimulus.

METHODS

An exploratory descriptive study of international registry data was performed. The first observations in patients with paired left and right quantitative pupillometry measurements were included. Measurements of pupil size before and after stimulus with a fixed light source were used to calculate anisocoria.

RESULTS

The sample included 5769 patients (mean [SD] age, 57.5 [17.6] years; female sex, 2558 patients [51.5%]; White race, 3669 patients [75.5%]). Anisocoria defined as pupil size difference of greater than 0.5 mm was present in 1624 patients (28.2%) before light stimulus; 645 of these patients (39.7%) also had anisocoria after light stimulus (P < .001). Anisocoria defined as pupil size difference of greater than 2.0 mm was present in 79 patients (1.4%) before light stimulus; 42 of these patients (53.2%) also had anisocoria after light stimulus (P < .001).

DISCUSSION

The finding of anisocoria significantly differed before and after light stimulus and according to the cut point used. At most cut points, fewer than half of the patients who had anisocoria before light stimulus also had anisocoria after light stimulus.

CONCLUSION

The profound difference in the number of patients adjudicated as having anisocoria using different cut points reinforces the need to develop a universal definition for anisocoria.

The Neurological Pupil index for outcome prognostication in people with acute brain injury (ORANGE): a prospective, observational, multicentre cohort study

BACKGROUND

Improving the prognostication of acute brain injury is a key element of critical care. Standard assessment includes pupillary light reactivity testing with a hand-held light source, but findings are interpreted subjectively; automated pupillometry might be more precise and reproducible. We aimed to assess the association of the Neurological Pupil index (NPi)-a quantitative measure of pupillary reactivity computed by automated pupillometry-with outcomes of patients with severe non-anoxic acute brain injury.

METHODS

ORANGE is a multicentre, prospective, observational cohort study at 13 hospitals in eight countries in Europe and North America. Patients admitted to the intensive care unit after traumatic brain injury, aneurysmal subarachnoid haemorrhage, or intracerebral haemorrhage were eligible for the study. Patients underwent automated infrared pupillometry assessment every 4 h during the first 7 days after admission to compute NPi, with values ranging from 0 to 5 (with abnormal NPi being <3). The co-primary outcomes of the study were neurological outcome (assessed with the extended Glasgow Outcome Scale [GOSE]) and mortality at 6 months. We used logistic regression to model the association between NPi and poor neurological outcome (GOSE ≤4) at 6 months and Cox regression to model the relation of NPi with 6-month mortality. This study is registered with ClinicalTrials.gov, NCT04490005.

FINDINGS

Between Nov 1, 2020, and May 3, 2022, 514 patients (224 with traumatic brain injury, 139 with aneurysmal subarachnoid haemorrhage, and 151 with intracerebral haemorrhage) were enrolled. The median age of patients was 61 years (IQR 46-71), and the median Glasgow Coma Scale score on admission was 8 (5-11). 40 071 NPi measurements were taken (median 40 per patient [20-50]). The 6-month outcome was assessed in 497 (97%) patients, of whom 160 (32%) patients died, and 241 (47%) patients had at least one recording of abnormal NPi, which was associated with poor neurological outcome (for each 10% increase in the frequency of abnormal NPi, adjusted odds ratio 1·42 [95% CI 1·27-1·64]; p<0·0001) and in-hospital mortality (adjusted hazard ratio 5·58 [95% CI 3·92-7·95]; p<0·0001).

INTERPRETATION

NPi has clinically and statistically significant prognostic value for neurological outcome and mortality after acute brain injury. Simple, automatic, repeat automated pupillometry assessment could improve the continuous monitoring of disease progression and the dynamics of outcome prediction at the bedside.

FUNDING

NeurOptics.

Impact of acute intoxication on quantitative pupillometry assessment in the emergency department

Study Hypothesis/Objective

This prospective cohort study aimed to assess whether and to what extent different quantitative pupillometry (QP) metrics are associated with different intoxicant drug classes as well as investigate the potential benefit of QP as a tool in the rapid assessment of clinically intoxicated patients in the emergency department (ED).

Methods

Between February 25, 2019 and April 24, 2021, 325 patients were enrolled in the EDs of the Hospital of the University of Pennsylvania (HUP) and Penn Presbyterian Medical Center (PPMC). Patients deemed clinically intoxicated or in withdrawal by an attending emergency physician were considered for eligibility. Patients <18 years old, with a chief complaint indicative of head trauma or stroke or without a urine drug screen (UDS) positive for drugs of abuse were excluded. QP data were also collected from a cohort of 82 healthy control subjects.

Results

Neurological Pupil index (NPi) values did not vary significantly between control and study groups nor between study group patients with a UDS positive for opioids. With exception of latency of constriction, all other QP metrics for the study group were depressed relative to controls (P < 0.005).

Conclusions

This work demonstrated the feasibility of QP measurement in the ED, finding that NPi remains unaffected by clinical intoxication and therefore can potentially be used for ED patient evaluation without risk of confounding by key intoxicants of abuse. Future work will evaluate the value of QP as a means of rapid and reproducible neurological assessment to identify various pathologies.