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.

The value of pupillary diameter in evaluating pain perception after awakening in patients undergoing general anesthesia during orthopedic surgery.

BACKGROUND: The pupillary response to tetanic electrical stimulation reflects the balance between nociceptive stimulation and analgesia. Although pupillary pain index (PPI) was utilized to predict postoperative pain, it depended on tetanic stimulation and was complex. We aim to describe the potential relationship between PD in the presence of surgical stimulation and pain levels after awakening. METHODS: According to the Verbal Rating Scale (VRS) score after extubation, the patients were divided into painless group (VRS = 0) and pain group (VRS ≥ 1). Pupillary diameter (PD) and pupillary light reflex velocity (PLRV) were compared between two groups when patients entered the operating room (T1), before incision (T2), 10 s after incision (T3), 30 s after incision (T4), 1 h after incision (T5), at the end of surgery (T6), shortly after extubation (T7), and when patients expressed pain clearly (T8). The magnitude of PD change (ΔPD) compared to the baseline value after anesthesia induction (T2) was calculated. The correlations between pupillary parameters and pain after awakening were calculated. RESULTS: Patients with VRS ≥ 1 had greater PD than painless patients at T3-7 (P = 0.04, 0.04, 0.003, <0.001, <0.001), and it was positively correlated with VRS score after awakening at T4-7 (r = 0.188, 0.217, 0.684, 0.721). The ability of T6ΔPD to predict VRS ≥ 1 was strong [threshold: 20.53%, area under the curve (AUC): 0.93, 95% confidence interval (CI): 0.89-0.97 ]. CONCLUSION: Our study indicates that PD is a useful index to direct the individualized analgesics used during operation, to better avoid the occurrence of pain during the postoperative emergence period. TRIAL REGISTRATION: This study was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR2000040908, registration date: 15/12/2020).

Prospective study examining the impact of cerebral angiography on quantitative pupillometer values in the interventional radiology suite.

OBJECTIVES: The purpose of this pilot study was to obtain baseline quantitative pupillometry (QP) measurements before and after catheter-directed cerebral angiography (DCA) to explore the hypothesis that cerebral angiography is an independent predictor of change in pupillary light reflex (PLR) metrics. DESIGN: This was a prospective, observational pilot study of PLR assessments obtained using QP 30 min before and after DCA. All patients had QP measurements performed with the NPi-300 (Neuroptics) pupillometer. SETTING: Recruitment was done at a single-centre, tertiary-care academic hospital and comprehensive stroke centre in Dallas, Texas. PARTICIPANTS: Fifty participants were recruited undergoing elective or emergent angiography. Inclusion criteria were a physician-ordered interventional neuroradiological procedure, at least 18 years of age, no contraindications to PLR assessment with QP, and nursing transport to and from DCA. Patients with a history of eye surgery were excluded. MAIN OUTCOME MEASURES: Difference in PLR metric obtained from QP 30 min before and after DCA. RESULTS: Statistically significant difference was noted in the pre and post left eye readings for the minimum pupil size (a.k.a., pupil diameter on maximum constriction). The mean maximum constriction diameter prior to angiogram of 3.2 (1.1) mm was statistically larger than after angiogram (2.9 (1.0) mm; p<0.05); however, this was not considered clinically significant. Comparisons for all other PLR metrics pre and post angiogram demonstrated no significant difference. Using change in NPi pre and post angiogram (Δpre=0.05 (0.77) vs Δpost=0.08 (0.67); p=0.62), we calculated the effect size as 0.042. Hence, detecting a statistically significant difference in NPi, if a difference exists, would require a sample size of ~6000 patients. CONCLUSIONS: Our study provides supportive data that in an uncomplicated angiogram, even with intervention, there is no effect on the PLR.

Feasibility of USG-Guided Objective Initial Assessment of Pupillary Size and Pupillary Reflexes Versus Clinical Examination in Patients With Altered Mental Status: A Cross-Sectional Study.

BACKGROUND: Pupillary assessment is an important part of the neurological assessment which provides vital information in critically ill patients. However, clinical pupillary assessment is subjective. The ultrasound-guided pupillary examination is objective. There are limited pieces of literature regarding its use in assessing patients with altered mental status. So, we studied the extent of agreement of B-mode ultrasound with clinical examination for assessment of the pupillary size and reflex in patients with altered mental status. OBJECTIVES: The primary objective was to determine the extent of agreement between clinical examination and ultrasound-based examination for assessing pupillary reflex and size in patients with altered mental status in two settings (trauma and non-trauma patients). METHODS: Exactly 200 subjects (158 males, mean [range] age 43.56 [18-92 years]) with no history of partial globe rupture or dementia were included in this cross-sectional study from March 2019 to March 2020. B-mode ultrasound was performed with the subject's eyes closed using a 7-12 MHz linear probe and a standardized light stimulus. ICC score, paired t-test, kappa, Wilcoxon signed-rank test, and Bland-Altman plots were used for statistical analysis. RESULTS: The clinical-USG agreement for pupillary light reflex examination (Pupillary Diameter [PD] at rest, after direct light stimulation [Dstim ] and consensual light stimulation [Cstim ]) was excellent (ICC, 0.93-0.96). The Kappa coefficient (0.74 ± 0.07) showed an agreement of 87.36% between clinical and USG examination for pupillary reflex (reactive or non-reactive). CONCLUSION: USG-guided pupillary examination proves to be a better adjunct to neurological assessment in patients with altered mental status.

Nociception assessment with videopupillometry in deeply sedated intensive care patients: Discriminative and criterion validations.

BACKGROUND: Nociceptive assessment in deeply sedated patients is challenging. Validated instruments are lacking for this unresponsive population. Videopupillometry is a promising tool but has not been established in intensive care settings. AIM/OBJECTIVE: To test the discriminate validity of pupillary dilation reflex (PDR) between non-noxious and noxious procedures for assessing nociception in non-neurological intensive care unit (ICU) patients and to test the criterion validity of pupil dilation using recommended PDR cut-off points to determine nociception. METHODS: A single-centre prospective observational study was conducted in medical-surgical ICU patients. Two independent investigators performed videopupillometer measurements during a non-noxious and a noxious procedure, once a day (up to 7 days), when the patient remained deeply sedated (Richmond Agitation-Sedation Scale score: -5 or -4). The non-noxious procedures consisted of a gentle touch on each shoulder and the noxious procedures were endotracheal suctioning or turning onto the side. Bivariable and multivariable general linear mixed models were used to account for multiple measurements in same patients. Sensitivity and specificity, and areas under the curve of the receiver operating characteristic curve were calculated. RESULTS: Sixty patients were included, and 305 sets of 3 measurements (before, during, and after), were performed. PDR was higher during noxious procedures than before (mean difference between noxious and non-noxious procedures = 31.66%). After testing all variables of patient and stimulation characteristics in bivariable models, age and noxious procedures were kept in the multivariable model. Adjusting for age, noxious procedures (coefficient = -15.14 (95% confidence interval = -20.17 to -15.52, p < 0.001) remained the only predictive factor for higher pupil change. Testing recommended cut-offs, a PDR of >12% showed a sensitivity of 65%, and a specificity of 94% for nociception prediction, with an area under the receiver operating curve of 0.828 (95% confidence interval = 0.779-0.877). CONCLUSIONS: In conclusion, PDR is a potentially appropriate measure to assess nociception in deeply sedated ICU patients, and we suggest considering its utility in daily practices. REGISTRATION: This study was not preregistered in a clinical registry. TWEETABLE ABSTRACT: Pupillometry may help clinicians to assess nociception in deeply sedated ICU patients.

Overlooked evidence for transmission deficit of pupillary light reflex can be secondary to trigeminal nerve ganglion degeneration following subarachnoid hemorrhage; preliminary experimental study.

OBJECTIVE: Although the effect of oculomotor and cervical sympathetic networks on pupil diameter is well known; the effect of the trigeminal nerve on pupil diameter has not been investigated yet. This subject was investigated. MATERIALS AND METHODS: Five of 23 rabbits were used as a control group (GI; n = 5); 0.5 ccs saline solution into cisterna magna injected animals used as SHAM (GII; n = 5); autologous blood injected to produce SAH used as the study group (GIII; n = 13) and followed up three weeks. Light-stimulated pupil diameters were measured with an ocular tomography device before, middle, and at the end of the experiment. Considering the sclera area/pupil area ratio index (PRI) as the pupillary reaction area, we used this equation for the pupil's rush to light. Degenerated neuron densities of trigeminal ganglia and pupil diameters compared with the Mann-Whitney U test. RESULTS: The PRI, degenerated neuron density of trigeminal ganglia (n/mm3) were: (2.034 ± 0.301)/(13 ± 3) in GI; (1.678 ± 0.211)/(46 ± 9) in GII; and (0.941 ± 0.136)/(112 ± 21) in GIII. P-values between groups as: p < 0.005 in GI/GII; p < 0.0001 in GII/GIII and p < 0.00001 in GI/GIII. CONCLUSION: Light stimulates the cornea which is innervated by the trigeminal nerves. This experimental study indicates that the pupil remains mydriatic as the cornea is damaged by trigeminal ischemia following SAH and blocks the light flow.

Linear integration of multisensory signals in the pupil.

The pupil of the eye responds to various salient signals from different modalities, but there is no consensus on how these pupillary responses are integrated when multiple signals appear simultaneously. Both linear and nonlinear integration have been found previously. The current study aimed to reexamine the nature of pupillary integration, and specifically focused on the early, transient pupillary responses due to its close relationship with orienting. To separate the early pupillary responses out of the pupil time series, we adopted a pupil oscillation paradigm in which sensory stimuli were periodically presented. The simulation analysis confirmed that the amplitude of the pupil oscillation, induced by stimuli repeatedly presented at relatively high rates, can precisely reflect the early, transient pupillary responses without involving the late and sustained pupillary responses. The experimental results then showed that the amplitude of pupil oscillation induced by a series of simultaneous audiovisual stimuli equaled to a linear summation of the oscillatory amplitudes when unisensory stimuli were presented alone. Moreover, the tonic arousal levels, indicated by the baseline pupil size, cannot shift the summation from linear to nonlinear. These findings together support the additive nature of multisensory pupillary integration for the early, orienting-related pupillary responses. The additive nature of pupillary integration further implies that multiple pupillary responses may be independent of each other, irrespective of their potential cognitive and neural drivers.

A smartphone pupillometry tool for detection of acute large vessel occlusion.

OBJECTIVES: Pupillary light reflex (PLR) parameters can be used as quantitative biomarkers of neurological function. Since digital infrared pupillometry is expensive, we sought to examine alterations in PLR parameters using a smartphone quantitative pupillometry platform in subjects with acute ischemic stroke (AIS). MATERIALS AND METHODS: Patients were enrolled if they presented to the emergency department as a stroke code activation and had evidence of a large vessel occlusion (LVO) on computed tomography angiography. Controls were enrolled from hospital staff. A smartphone pupillometer was used in AIS patients with LVO pre-mechanical thrombectomy, immediately post-thrombectomy, and at 24 h post-thrombectomy. Clinical and demographic data were collected, along with the proprietary Neurological Pupil index (NPi) score from the NPi-200 digital infrared pupillometer. PLR parameters were compared using mean differences. The absolute and non-absolute inter-eye difference in each parameter for each subject were also analyzed by measuring 1 - (R:L) to determine alteration in the equilibrium between subject pupils. The NPi was analyzed for mean differences between cohorts. RESULTS: Healthy controls (n = 132) and AIS patients (n = 31) were enrolled. Significant differences were observed in PLR parameters for healthy subjects when compared to pre-thrombectomy subjects in both mean and absolute inter-eye differences after post hoc Bonferroni correction. The proprietary NPi score was not significantly different for all groups and comparisons. CONCLUSIONS: Significant alterations in the PLR were observed in AIS patients with LVO before thrombectomy, indicating the potential use of smartphone pupillometry for detection of LVO.

Chromatic Pupillometry - a New Technique for Assessing Function in Glaucoma? / Chromatische Pupillometrie ­ ein neuer Weg zur funktionellen Glaukomdiagnostik?

Chromatic pupillometry allows quantification of photoreceptor-driven (extrinsic) and melanopsin-driven (intrinsic) responses of the intrinsic-photosensitive retinal ganglion cells (ipRGCs). This small subpopulation of retinal ganglion cells is also affected by glaucoma, making chromatic pupillometry a potential diagnostic tool. Studies show reduced phasic and tonic responses in glaucoma patients. The diagnostic value in earlier studies depended on the technical details and the study design. The purpose of this article is to give an introduction into the principles of chromatic pupillometry and to discuss the potential applications in the management of glaucoma.

The photic blink reflex as an index of photophobia.

Two recent studies of eye closure triggered by intense luminance increase suggest that this behavior reflects the melanopsin-based retinal activity known to underlie photophobia, the pathological aversion to light (Kardon, 2012; Kaiser et al., 2021). Early studies of the photic blink reflex (PBR) are reviewed to help guide future research on this possible objective index of photophobia. Electromyographic recordings of the lid-closure muscle, orbicularis oculi, reveal distinct bursts with typical onset latencies of 50 and 80 ms, R50 and R80, respectively. The latter component appears to be especially sensitive to visual signals from intrinsically photosensitive retinal ganglion cells (ipRGCs) and to prior trigeminal nociceptive stimuli. The authors argue that the R80's function, in addition to protecting the eyeballs from physical contact, is to shape the upper and lower eyelids into a narrow slit to restrict incoming light. This serves to prevent retinal bleaching or injury, while allowing continued visual function.

Effect of Light Intensity on the Relative Afferent Pupillary Defect in Unilateral Neuro-ophthalmic Pathology.

SIGNIFICANCE: Objective pupillometry with standardized light intensities allows a comprehensive assessment of the relative afferent pupillary defect in patients with unilateral neuro-ophthalmic pathology. PURPOSE: This study aimed to determine the impact of varying light intensities on the grade of relative afferent pupillary defect in unilateral neuro-ophthalmic pathology vis-à-vis healthy controls. METHODS: Monocular pupillary light reflexes of 20 controls (14 to 50 years) and 31 cases (12 to 72 years) with clinically diagnosed relative afferent pupillary defect were measured thrice using 1-second-long light pulses, followed by 3 seconds of darkness, at eight light intensities (6.4 to 1200 lux) using objective pupillometry. The relative afferent pupillary defect was quantified as the ratio of the percentage change in the direct light reflexes of the left and right eyes. Its change with light intensity was described using standard exponential fits. RESULTS: The median (25th to 75th interquartile range) defect score of 54.8% cases decreased from baseline values of 1.58 (1.25 to 1.87) for right eye pathology and 0.45 (0.39 to 0.55) for left eye pathology to saturation values of 1.18 (1.05 to 1.31) and 0.98 (0.95 to 1.06), respectively, at light intensities between 56.9 and 300.5 lux. Like controls (1.01 [1.00 to 1.06]), the defect scores of the remaining 45.2% cases were constant with light intensity at 1.23 (1.18 to 1.46) and 0.87 (0.86 to 0.89) for right and left eye pathologies, respectively. CONCLUSIONS: Relative afferent pupillary defects may decrease with test light intensity in a significant proportion of patients with unilateral neuro-ophthalmic pathology. This highlights the importance of objective pupillometry with standardization light intensities for clinical assessment of afferent pupillary defects.

Pupillary dilation reflex and behavioural pain scale: Study of diagnostic test.

BACKGROUND: The objective of this study was to assess the value of the pupillary dilation reflex as an assessment pain tool in critically ill patients. It is important to continue working for the well-being and security of critically ill patients. METHODS: We studied the diagnostic accuracy of the pupillary dilation reflex against the Behavioral Pain Scale. Inclusion criteria were: age greater than 18, receiving mechanical ventilation, with a basal score of the Behavioural Pain Scale of three and a Richmond Agitation and Sedation score between -1 and -4. We studied the responses to a non-painful stimulus, four calibrated stimuli, after a tracheal aspiration and with and without pain. The receiver operating curve was plotted and we calculated the area under the curve. We identified the cut-off points showing the highest sensitivity and specificity and studied diagnostic performance based on negative predictive value, positive predictive value, and accuracy. These were reported with their 95% confidence intervals. RESULTS: 183 measurements were performed. An AUC of 0.88(95% CI 0.83-0.94) was obtained. The pupillary dilation reflex of 11.5% had a sensitivity of 89.8%(95% CI 78.2-95.6) and a specificity of 78.4%(95% CI 70.6-84.5) with an accuracy of 81.4(75.2-86.4). The pupillary dilation reflex detected nociceptive pain response in 15.8% of the measurements that did not show pain according to the Behavioural Pain Scale. CONCLUSIONS: Pupillometry may be a valid alternative for identifying pain in critically ill patients.

Validation of a Smartphone Pupillometry Application in Diagnosing Severe Traumatic Brain Injury.

The pupillary light reflex (PLR) is an important biomarker for the detection and management of traumatic brain injury (TBI). We investigated the performance of PupilScreen, a smartphone-based pupillometry app, in classifying healthy control subjects and subjects with severe TBI in comparison to the current gold standard NeurOptics pupillometer (NPi-200 model with proprietary Neurological Pupil Index [NPi] TBI severity score). A total of 230 PLR video recordings taken using both the PupilScreen smartphone pupillometer and NeurOptics handheld device (NPi-200) pupillometer were collected from 33 subjects with severe TBI (sTBI) and 132 subjects who were healthy without self-reported neurological disease. Severe TBI status was determined by Glasgow Coma Scale (GCS) at the time of recording. The proprietary NPi score was collected from the NPi-200 pupillometer for each subject. Seven PLR curve morphological parameters were collected from the PupilScreen app for each subject. A comparison via t-test and via binary classification algorithm performance using NPi scores from the NPi-200 and PLR parameter data from the PupilScreen app was completed. This was used to determine how the frequently used NPi-200 proprietary NPi TBI severity score compares to the PupilScreen app in ability to distinguish between healthy and sTBI subjects. Binary classification models for this task were trained for the diagnosis of healthy or severe TBI using logistic regression, k-nearest neighbors, support vector machine, and random forest machine learning classification models. Overall classification accuracy, sensitivity, specificity, area under the curve, and F1 score values were calculated. Median GCS was 15 for the healthy cohort and 6 (interquartile range 2) for the severe TBI cohort. Smartphone app PLR parameters as well as NPi from the digital infrared pupillometer were significantly different between healthy and severe TBI cohorts; 33% of the study cohort had dark eye colors defined as brown eyes of varying shades. Across all classification models, the top performing PLR parameter combination for classifying subjects as healthy or sTBI for PupilScreen was maximum diameter, constriction velocity, maximum constriction velocity, and dilation velocity with accuracy, sensitivity, specificity, area under the curve (AUC), and F1 score of 87%, 85.9%, 88%, 0.869, and 0.85, respectively, in a random forest model. The proprietary NPi TBI severity score demonstrated greatest AUC value, F1 score, and sensitivity of 0.648, 0.567, and 50.9% respectively using a random forest classifier and greatest overall accuracy and specificity of 67.4% and 92.4% using a logistic regression model in the same classification task on the same dataset. The PupilScreen smartphone pupillometry app demonstrated binary healthy versus severe TBI classification ability greater than that of the NPi-200 proprietary NPi TBI severity score. These results may indicate the potential benefit of future study of this PupilScreen smartphone pupillometry application in comparison to the NPi-200 digital infrared pupillometer across the broader TBI spectrum, as well as in other neurological diseases.

[Paying attention to the clinical significance of pupil abnormalities].

Pupil abnormalities may be physiological, pathological or pharmacological. It can indicate the underlying disease of the visual afferent system or visual efferent system. Examination of the pupils is therefore a part of eye examination. Insufficient knowledge and inconsistent methods in the pupillary examination by some ophthalmologists lead to mistakes or unreliable results, hampering the disease diagnosis and clinical assessment. This article emphasizes the significance of pupillary examination outcomes, advocates for standardized examination methods, and highlights the need to enhance the awareness of pupillary abnormalities, aiming to provide a guide on how to recognize and interpret the clinical implications of pupillary abnormalities, and to offer valuable insights for clinical practice.

Comparison between pupillometry and numeric pain rating scale for pain assessments in communicating adult patients in the emergency department.

OBJECTIVE: The adequate assessment of pain in the emergency department (ED) can be challenging. Two dynamic pupillary measures used in conscious subjects after a surgical procedure were previously shown to correlate to the magnitude of ongoing pain. The objective of this study was to test the ability of dynamic measures derived from pupillometry to evaluate pain intensity in conscious adult patients admitted to the ED. METHODS: This prospective, interventional, single-centre study was performed between August 2021 and January 2022 (NCT05019898). An assessment of self-reported pain intensity was performed on ED admission by the triage nurse using a numeric rating scale (NRS). This was followed by two dynamic measures derived from pupillometry that were previously correlated with pain perception: the pupillary unrest under ambient light (PUAL) and the pupillary light reflex (PLR). RESULTS: Among the 313 analysed patients, the median age was 41 years, and 52% were women. No correlation was found between self-reported pain ratings and PUAL (r = 0.007) or PLR (baseline diameter r = -0.048; decrease r = 0.024; latency r = 0.019; slope = -0.051). Similarly, the pupillometry measures could not discriminate patients with moderate to severe pain (defined as NRS ≥4). CONCLUSIONS: Pupillometry does not appear to be an effective tool to evaluate pain in the ED environment. Indeed, too many factors influencing the sympathetic system-and thus the dynamic pupillary measures-are not controllable in the ED. SIGNIFICANCE: Pupillometry does not appear to be an effective tool to evaluate pain in the ED environment. There are several possible explanations for these negative results. The factors influencing the sympathetic system-and thus the PD fluctuations-are controllable in the postoperative period but not in the ED (e.g. full bladder, hypothermia). In addition, numerous psychological phenomena can impact pupillometry measurements such as emotional reactions or cognitive tasks. These phenomena are particularly difficult to control in the ED environment.

Review on age-related differences in non-visual effects of light: melatonin suppression, circadian phase shift and pupillary light reflex in children to older adults.

Physiological effects of light exposure in humans are diverse. Among them, the circadian rhythm phase shift effect in order to maintain a 24-h cycle of the biological clock is referred to as non-visual effects of light collectively with melatonin suppression and pupillary light reflex. The non-visual effects of light may differ depending on age, and clarifying age-related differences in the non-visual effects of light is important for providing appropriate light environments for people of different ages. Therefore, in various research fields, including physiological anthropology, many studies on the effects of age on non-visual functions have been carried out in older people, children and adolescents by comparing the effects with young adults. However, whether the non-visual effects of light vary depending on age and, if so, what factors contribute to the differences have remained unclear. In this review, results of past and recent studies on age-related differences in the non-visual effects of light are presented and discussed in order to provide clues for answering the question of whether non-visual effects of light actually vary depending on age. Some studies, especially studies focusing on older people, have shown age-related differences in non-visual functions including differences in melatonin suppression, circadian phase shift and pupillary light reflex, while other studies have shown no differences. Studies showing age-related differences in the non-visual effects of light have suspected senile constriction and crystalline lens opacity as factors contributing to the differences, while studies showing no age-related differences have suspected the presence of a compensatory mechanism. Some studies in children and adolescents have shown that children's non-visual functions may be highly sensitive to light, but the studies comparing with other age groups seem to have been limited. In order to study age-related differences in non-visual effects in detail, comparative studies should be conducted using subjects having a wide range of ages and with as much control as possible for intensity, wavelength component, duration, circadian timing, illumination method of light exposure, and other factors (mydriasis or non-mydriasis, cataracts or not in the older adults, etc.).

Cognitive workload affects ocular accommodation and pupillary response / La carga de trabajo cognitivo afecta la acomodación ocular y la respuesta pupilar

Significance: Cognitive involvement in reading causes variations in the tonus of autonomic nerve system. The aim of this study was to examine the effect of short-term cognitive load on accommodation and pupils’ absolute values and temporal variability in test persons performing three different types of tasks. Purpose: We aimed to show how cognitive tasks of different type and difficulty level affect accommodation and pupil behavior during a short time interval. Methods: Participants (n = 58; mean age 16.4 years, SD = 0.56) performed reading from a 10-inch LCD screen placed at 40 cm distance. Three different types of tasks (numerical, textual, and the Stroop task), each at three different levels of cognitive load were introduced. Participants had 90 s to complete each task. Accommodative and pupillary responses were measured with videoretinoscope Power Refractor 3 at 50 Hz. Results: Pupil size was largest in the Stroop task (M = 5.20 mm, SD = 0.75 mm), followed by the numerical tasks (M = 5.02 mm, SD = 0.72 mm) and textual tasks (M = 4.78 mm, SD = 0.71 mm). Accommodative fluctuations – measured as accommodation SD – were largest in the textual tasks (M = 0.67 D, SD = 0.34 D), followed by the numerical tasks (M = 0.61 D, SD = 0.40 D) and the Stroop task (M = 0.52 D, SD = 0.21 D). Conclusions: In our experiment, short-term cognitive load was associated with altered pupillary and accommodative response to near tasks. In conflicting tasks (Stroop) or in performing continuing calculations, the pupils were larger; in tasks requiring logical reasoning, the accommodative fluctuations were greater. These effects can potentially be associated with current near-point stress and myopia growth models.(AU)

Reproducibility of the pupillary light reflex over short intervals in psychiatric patients and community volunteers.

The pupillary light reflex (PLR) is a method for measuring dynamic responses within the autonomic nervous system, and would have potential value as a point-of-care test in a psychiatry clinic if reproducible results could be obtained in a short period of time. We collected PLR from adult community volunteers and depressed outpatients with the purpose of demonstrating (1) that valid data could be obtained >90% of the time from both the community volunteers and the patients, and (2) that reproducible results could be obtained with repeated measurement over short periods of time. Valid data were captured for 90.3% of 76 participants, allowing for two attempts of the PLR per participant. Success rates were similar for depressed patients and community volunteers. Eighteen of these 76 participants provided repeated paired measurements after 5 and 10 min of dark adaptation, producing high correlations for maximum constriction velocity (MCV) between assay 1 and 2 (Pearson's r = 0.71, p < 0.001), but there was a significant 8% increase in velocity for MCV between assay 1 and 2 (∆ = 0.34 ± 0.59 mm/s, p < 0.05). In contrast, PLR measurements were stable when tested in a separate cohort of 21 additional participants at 10 and 15 min of dark adaptation with an MCV Pearson's correlation of r = 0.84, p < 0.001, with a nonsignificant 1% difference between the two time points. These findings indicate an acceptable rate of collecting valid and reproducible PLR data when contrasting two measurements of PLR after 10 or 15 min of dark adaptation in depressed and suicidal patients.