Pupillary response abnormalities in depressive disorders

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.

Assessing hypo-arousal during reward anticipation with pupillometry in patients with major depressive disorder: replication and correlations with anhedonia

Major depressive disorder (MDD) is a devastating and heterogenous disorder for which there are no approved biomarkers in clinical practice. We recently identified anticipatory hypo-arousal indexed by pupil responses as a candidate mechanism subserving depression symptomatology. Here, we conducted a replication and extension study of these findings. We analyzed a replication sample of 40 unmedicated patients with a diagnosis of depression and 30 healthy control participants, who performed a reward anticipation task while pupil responses were measured. Using a Bayesian modelling approach taking measurement uncertainty into account, we could show that the negative correlation between pupil dilation and symptom load during reward anticipation is replicable within MDD patients, albeit with a lower effect size. Furthermore, with the combined sample of 136 participants (81 unmedicated depressed and 55 healthy control participants), we further showed that reduced pupil dilation in anticipation of reward is inversely associated with anhedonia items of the Beck Depression Inventory in particular. Moreover, using simultaneous fMRI, particularly the right anterior insula as part of the salience network was negatively correlated with depressive symptom load in general and anhedonia items specifically. The present study supports the utility of pupillometry in assessing noradrenergically mediated hypo-arousal during reward anticipation in MDD, a physiological process that appears to subserve anhedonia.

BLUES - stabilizing mood and sleep with blue blocking eyewear in bipolar disorder - a randomized controlled trial study protocol

INTRODUCTION

Chronotherapeutic interventions for bipolar depression and mania are promising interventions associated with rapid response and benign side effect profiles. Filtering of biologically active short wavelength (blue) light by orange tinted eyewear has been shown to induce antimanic and sleep promoting effects in inpatient mania. We here describe a study protocol assessing acute and long-term stabilizing effects of blue blocking (BB) glasses in outpatient treatment of bipolar disorder.

PATIENTS AND METHODS

A total of 150 outpatients with bipolar disorder and current symptoms of (hypo)-mania will be randomized 1:1 to wear glasses with either high (99%) (intervention group) or low (15%) (control group) filtration of short wavelength light (<500 nm). Following a baseline assessment including ratings of manic and depressive symptoms, sleep questionnaires, pupillometric evaluation and 48-h actigraphy, participants will wear the glasses from 6 PM to 8 AM for 7 consecutive days. The primary outcome is the between group difference in change in Young Mania Rating Scale scores after 7 days of intervention (day 9). Following the initial treatment period, the long-term stabilizing effects on mood and sleep will be explored in a 3-month treatment paradigm, where the period of BB treatment is tailored to the current symptomatology using a 14-h antimanic schedule during (hypo-) manic episodes (BB glasses or dark bedroom from 6 PM to 8 AM) and a 2-h maintenance schedule (BB glasses on two hours prior to bedtime/dark bedroom) during euthymic and depressive states.The assessments will be repeated at follow-up visits after 1 and 3 months. Throughout the 3-month study period, participants will perform continuous daily self-monitoring of mood, sleep and activity in a smartphone-based app. Secondary outcomes include between-group differences in actigraphic sleep parameters on day 9 and in day-to-day instability in mood, sleep and activity, general functioning and objective sleep markers (actigraphy) at weeks 5 and 15.

TRIAL REGISTRATION

The trial will be registered at www.clinicaltrials.gov prior to initiation and has not yet received a trial reference.

ADMINISTRATIVE INFORMATION

The current paper is based on protocol version 1.0_31.07.23. Trial sponsor: Lars Vedel Kessing.

Pretreatment pupillary reactivity is associated with outcome of Repetitive Transcranial Magnetic Stimulation (rTMS) treatment of Major Depressive Disorder (MDD)

BACKGROUND

Pre-treatment biomarkers for outcome of repetitive Transcranial Magnetic Stimulation (rTMS) treatment of Major Depressive Disorder (MDD) have proven elusive. One promising family of biomarkers involves the autonomic nervous system (ANS), which is dysregulated in individuals with MDD.

METHODS

We examined the relationship between the pre-treatment pupillary light reflex (PLR) and rTMS outcome in 51 MDD patients. Outcome was measured as the percent change in the 30-item Inventory of Depressive Symptomatology Self Rated (IDS-SR) score from baseline to treatment 30.

RESULTS

Patients showed significant improvement with rTMS treatment. There was a significant correlation between baseline pupillary Constriction Amplitude (CA) and clinical improvement over the treatment course (R = 0.41, p = 0.003).

LIMITATIONS

We examined a limited number of subjects who received heterogeneous treatment protocols. Almost all patients in the study received psychotropic medications concomitant with rTMS treatment.

CONCLUSION

PLR measured before treatment may be a predictive biomarker for clinical improvement from rTMS in subjects with MDD.

Pupillometry to differentiate idiopathic hypersomnia from narcolepsy type 1

Idiopathic hypersomnia is poorly diagnosed in the absence of biomarkers to distinguish it from other central hypersomnia subtypes. Given that light plays a main role in the regulation of sleep and wake, we explored the retinal melanopsin-based pupil response in patients with idiopathic hypersomnia and narcolepsy type 1, and healthy subjects. Twenty-seven patients with narcolepsy type 1 (women 59%, 36 ± 11.5 years old), 36 patients with idiopathic hypersomnia (women 83%, 27.2 ± 7.2 years old) with long total sleep time (> 11/24 hr), and 43 controls (women 58%, 30.6 ± 9.3 years old) were included in this study. All underwent a pupillometry protocol to assess pupil diameter, and the relative post-illumination pupil response to assess melanopsin-driven pupil responses in the light non-visual input pathway. Differences between groups were assessed using logistic regressions adjusted on age and sex. We found that patients with narcolepsy type 1 had a smaller baseline pupil diameter as compared with idiopathic hypersomnia and controls (p < 0.05). In addition, both narcolepsy type 1 and idiopathic hypersomnia groups had a smaller relative post-illumination pupil response (respectively, 31.6 ± 13.9% and 33.2 ± 9.9%) as compared with controls (38.7 ± 9.7%), suggesting a reduced melanopsin-mediated pupil response in both types of central hypersomnia (p < 0.01). Both narcolepsy type 1 and idiopathic hypersomnia showed a smaller melanopsin-mediated pupil response, and narcolepsy type 1, unlike idiopathic hypersomnia, also displayed a smaller basal pupil diameter. Importantly, we found that the basal pupil size permitted to well discriminate idiopathic hypersomnia from narcolepsy type 1 with a specificity = 66.67% and a sensitivity = 72.22%. Pupillometry may aid to multi-feature differentiation of central hypersomnia subtypes.

The impact of Alzheimer's disease risk factors on the pupillary light response

Alzheimer's disease (AD) is the leading cause of dementia, and its prevalence is increasing and is expected to continue to increase over the next few decades. Because of this, there is an urgent requirement to determine a way to diagnose the disease, and to target interventions to delay and ideally stop the onset of symptoms, specifically those impacting cognition and daily livelihood. The pupillary light response (PLR) is controlled by the sympathetic and parasympathetic branches of the autonomic nervous system, and impairments to the pupillary light response (PLR) have been related to AD. However, most of these studies that assess the PLR occur in patients who have already been diagnosed with AD, rather than those who are at a higher risk for the disease but without a diagnosis. Determining whether the PLR is similarly impaired in subjects before an AD diagnosis is made and before cognitive symptoms of the disease begin, is an important step before using the PLR as a diagnostic tool. Specifically, identifying whether the PLR is impaired in specific at-risk groups, considering both genetic and non-genetic risk factors, is imperative. It is possible that the PLR may be impaired in association with some risk factors but not others, potentially indicating different pathways to neurodegeneration that could be distinguished using PLR. In this work, we review the most common genetic and lifestyle-based risk factors for AD and identify established relationships between these risk factors and the PLR. The evidence here shows that many AD risk factors, including traumatic brain injury, ocular and intracranial hypertension, alcohol consumption, depression, and diabetes, are directly related to changes in the PLR. Other risk factors currently lack sufficient literature to make any conclusions relating directly to the PLR but have shown links to impairments in the parasympathetic nervous system; further research should be conducted in these risk factors and their relation to the PLR.

Alterations of color vision and pupillary light responses in age-related macular degeneration

Introduction

Age-related macular degeneration (AMD) is the leading cause of irreversible central vision loss in developed countries and one of the leading causes of blindness. In this work, we evaluated color vision and the pupil light reflex (PLR) to assess visual function in patients with early and neovascular AMD (NVAMD) compared with the control group.

Methods

We recruited 34 early patients with dry AMD and classified them into two groups following AREDS: 13 patients with NVAMD and 24 healthy controls. Controls and patients with early dry AMD had visual acuity (VA) best or equal to 20/25 (0.098 logMAR). Color vision was assessed in controls and patients with early dry AMD using the Cambridge Color Test (CCT) 2.0 through the Trivector protocol. The PLR was evaluated using a Ganzfeld, controlled by the RETI-port system. The stimuli consisted of 1s blue (470 nm) and red (631 nm) light flashes presented alternately at 2-min intervals. To assess the cone contribution, we used a red flash at 2.4 log cd.m^-2, with a blue background at 0.78 log cd.m^-2. For rods, we used 470-nm flashes at -3 log cd.m^-2, and for the melanopsin function of ipRGCs, we used 470 nm at 2.4 log cd.m^-2.

Results

Patients with early dry AMD had reduced color discrimination in all three axes: protan (p = 0.0087), deutan (p = 0.0180), and tritan (p = 0.0095) when compared with the control group. The PLR has also been affected in patients with early dry AMD and patients with NVAMD. The amplitude for the melanopsin-driven response was smaller in patients with early dry AMD (p = 0.0485) and NVAMD (p = 0.0035) than in the control group. The melanopsin function was lower in patients with NVAMD (p = 0.0290) than the control group. For the rod-driven response, the latency was lower in the NVAMD group (p = 0.0041) than in the control group. No changes were found in cone-driven responses between the control and AMD groups.

Conclusion

Patients with early dry AMD present diffusely acquired color vision alteration detected by CCT. Rods and melanopsin contributions for PLR are affected in NVAMD. The CCT and the PLR may be considered sensitive tests to evaluate and monitor functional changes in patients with AMD.

Blunted pupil light reflex is associated with negative symptoms and working memory in individuals with schizophrenia

Two largely separate lines of research have documented altered pupillary dynamics in individuals diagnosed with schizophrenia. An older set of studies has demonstrated reductions in the pupillary light reflex (PLR) in individuals with schizophrenia; however, clinical and cognitive correlates of this blunted PLR have been relatively unexplored. More recently, a large body of work has demonstrated reductions in pupillary dilation in response to cognitive demands in individuals with schizophrenia, and the degree of this blunted pupil dilation has been related to more severe cognitive deficits and motivational negative symptoms. These clinically relevant alterations in the cognitive modulation of pupil size have been interpreted as reflecting insufficient information processing resources or inappropriate effort allocation. To begin to bridge these two lines of work, we investigated the PLR in 34 individuals with schizophrenia and 30 healthy controls and related the amplitude of the PLR to motivational negative symptoms and cognitive performance. Consistent with prior work, we found that the PLR was reduced in individuals with schizophrenia, and furthermore, that these measurements were highly reliable across individuals. Blunted constriction was associated with more severe motivational negative symptoms and poorer working memory among individuals with schizophrenia. These observed correlates provide a bridge between older literature documenting an altered PLR and more recent work reporting associations between negative symptoms, cognition, and blunted pupillary dilation in response to cognitive demands in individuals with schizophrenia. We provide possible mechanistic interpretations of our data and consider a parsimonious explanation for reduced cognitive- and light-related modulation of pupil size.

Treatment of depression in the elderly with repetitive transcranial magnetic stimulation using theta-burst stimulation: Study protocol for a randomized, double-blind, controlled trial

Introduction

Transcranial magnetic stimulation (TMS) is a consolidated procedure for the treatment of depression, with several meta-analyses demonstrating its efficacy. Theta-burst stimulation (TBS) is a modification of TMS with similar efficacy and shorter session duration. The geriatric population has many comorbidities and a high prevalence of depression, but few clinical trials are conducted specifically for this age group. TBS could be an option in this population, offering the advantages of few side effects and no pharmacological interactions. Therefore, our aim is to investigate the efficacy of TBS in geriatric depression.

Clinical trial registration

[https://clinicaltrials.gov/ct2/], identifier [NCT04842929].

The melanopsin-mediated pupil response is reduced in idiopathic hypersomnia with long sleep time

Idiopathic hypersomnia (IH), characterized by an excessive day-time sleepiness, a prolonged total sleep time on 24 h and/or a reduced sleep latency, affects 1 in 2000 individuals from the general population. However, IH remains underdiagnosed and inaccurately treated despite colossal social, professional and personal impacts. The pathogenesis of IH is poorly known, but recent works have suggested possible alterations of phototransduction. In this context, to identify biomarkers of IH, we studied the Post-Illumination Pupil Response (PIPR) using a specific pupillometry protocol reflecting the melanopsin-mediated pupil response in IH patients with prolonged total sleep time (TST > 660 min) and in healthy subjects. Twenty-eight patients with IH (women 86%, 25.4 year-old ± 4.9) and 29 controls (women 52%, 27.1 year-old ± 3.9) were included. After correction on baseline pupil diameter, the PIPR was compared between groups and correlated to sociodemographic and sleep parameters. We found that patients with IH had a lower relative PIPR compared to controls (32.6 ± 9.9% vs 38.5 ± 10.2%, p = 0.037) suggesting a reduced melanopsin response. In addition, the PIPR was not correlated to age, chronotype, TST, nor depressive symptoms. The melanopsin-specific PIPR may be an innovative trait marker of IH and the pupillometry might be a promising tool to better characterize hypersomnia.

The pupillary light reflex (PLR) as a marker for the ability to work or drive - a feasibility study

Background

The PLR (pupillary light reflex) can be a marker for pathological medical conditions, such as neurodegenerative or mental health disorders and diseases as well as marker for physiological alterations, such as age, sex or iris color. PLR alterations have been described in people after alcohol consumption, as well. However, the effect of sleep deprivation on PLR parameters is still under debate.

Methods

The aim of this study was to investigate the feasibility of PLR measurements in sleep-deprived and alcohol-exposed participants. In addition, we wanted to identify PLR parameters that were altered by sleep deprivation and alcohol exposure.

Results

Altogether n = 50 participants have been included in this study. Differences in the PLR parameters initial diameter (d_init), latency (∆t_lat), acceleration (∆t_a), contraction velocity (ϑ_con), quarter dilatation velocity (ϑ_1/4dil), half dilatation time (∆t_1/2), and the line integral (L(0.3500)) have been evaluated between baseline, sleep deprivation, as well as alcohol exposure. In a generalized linear mixed models design, we could observe statistically significant associations between the type of exposure and the PLR parameters half dilatation time and half dilatation time after the first light pulse (all p < 0.05). The participants’ latency showed a significant association in dependence of the type of exposure after the second light pulse (p < 0.05).

Conclusion

Our study delivers first promising results to further develop devices that may identify conditions that impair the ability to work or drive.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12995-021-00330-2.

Melanopsin-driven pupil response in summer and winter in unipolar seasonal affective disorder

A retinal subsensitivity to environmental light may trigger Seasonal Affective Disorder (SAD) under low wintertime light conditions. The main aim of this study was to assess the responses of melanopsin-containing retinal ganglion cells in participants (N= 65) diagnosed with unipolar SAD compared to controls with no history of depression. Participants attended a summer visit, a winter visit, or both. Retinal responses to light were measured using the post-illumination pupil response (PIPR) to assess melanopsin-driven responses in the non-visual light input pathway. Linear mixed-effects modeling was used to test a group*season interaction on the Net PIPR (red minus blue light response, percent baseline). We observed a significant group*season interaction such that the PIPR decreased from summer to winter significantly in the SAD group while not in the control group. The SAD group PIPR was significantly lower in winter compared to controls but did not differ between groups in summer. Only 60% of the participants underwent an eye health exam, although all participants reported no history of retinal pathology, and eye exam status was neither associated with outcome nor different between groups. This seasonal variation in melanopsin driven non-visual responses to light may be a risk factor for SAD, and further highlights individual differences in responses to light for direct or indirect effects of light on mood.

Seasonal variation in neurohormones, mood and sleep in patients with primary open angle glaucoma - implications of the ipRGC-system

Primary open angle glaucoma is associated with an increased risk of mood and sleep disorders. These adversities have been suggested to relate to a disrupted function of the intrinsically photosensitive retinal ganglion cells (ipRGCs). The ipRGCs are key components in the nonvisual photoreceptive system that mediates light effects on mood, sleep and circadian rhythm. We assessed the diurnal hormone levels, pupillary responses and mood and sleep under seasons with different photoperiods in 24 patients with glaucoma and 24 age- and sex-matched healthy controls to investigate responses to naturalistic seasonal changes in daylight. The patients had moderate-to-advanced glaucoma with substantial visual field defects and reductions in the ipRGC-mediated pupillary responses (p < .001). In winter, compared with summer, patients with glaucoma had higher daytime melatonin concentration (p < .001) and lower nighttime cortisol (p = .002). In winter, the daytime melatonin level was inversely correlated with the ipRGC-mediated pupillary responses in the control group (p = .04). In the control group, there were no significant changes in hormone levels between seasons or any correlations between neurohormone levels and the ipRGC-mediated responses. The two groups showed a similar response to season with lower depression scores in summer compared with winter. In between-group comparison, the nocturnal melatonin level (area under curve from 20:00 h to 08:00 h) in summer was lower in glaucoma compared with controls (p = .03). In winter, nocturnal cortisol (at 04:00 h) was lower (p = .004) and daytime cortisol (12:00 h and 16:00 h) was higher (p = .007) in glaucoma compared with controls. In conclusion, we found that patients with glaucoma displayed a seasonal variation in diurnal hormone levels that was not present in healthy controls. Such neurohormonal changes may contribute to the increased risk of mood and sleep disorders seen in patients with glaucoma.

Pupillary light reflex as a diagnostic aid from computational viewpoint: A systematic literature review

This work presents a detailed and complete review of publications on pupillary light reflex (PLR) used to aid diagnoses. These are computational techniques used in the evaluation of pupillometry, as well as their application in computer-aided diagnoses (CAD) of pathologies or physiological conditions that can be studied by observing the movements of miosis and mydriasis of the human pupil. A careful survey was carried out of all studies published over the last 10 years which investigated, electronic devices, recording protocols, image treatment, computational algorithms and the pathologies related to PLR. We present the frontier of existing knowledge regarding methods and techniques used in this field of knowledge, which has been expanding due to the possibility of performing diagnoses with high precision, at a low cost and with a non-invasive method.

Melanopsin-mediated pupillary responses in bipolar disorder-a cross-sectional pupillometric investigation

BACKGROUND

Visible light, predominantly in the blue range, affects mood and circadian rhythm partly by activation of the melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs). The light-induced responses of these ganglion cells can be evaluated by pupillometry. The study aimed to assess the blue light induced pupil constriction in patients with bipolar disorder (BD).

METHODS

We investigated the pupillary responses to blue light by chromatic pupillometry in 31 patients with newly diagnosed bipolar disorder, 22 of their unaffected relatives and 35 healthy controls. Mood state was evaluated by interview-based ratings of depressive symptoms (Hamilton Depression Rating Scale) and (hypo-)manic symptoms (Young Mania Rating Scale).

RESULTS

The ipRGC-mediated pupillary responses did not differ across the three groups, but subgroup analyses showed that patients in remission had reduced ipRGC-mediated responses compared with controls (9%, p = 0.04). Longer illness duration was associated with more pronounced ipRGC-responses (7% increase/10-year illness duration, p = 0.02).

CONCLUSIONS

The ipRGC-mediated pupil response to blue light was reduced in euthymic patients compared with controls and increased with longer disease duration. Longitudinal studies are needed to corroborate these potential associations with illness state and/or progression.

Pupillary Responses for Cognitive Load Measurement to Classify Difficulty Levels in an Educational Video Game: Empirical Study

Background

A learning task recurrently perceived as easy (or hard) may cause poor learning results. Gamer data such as errors, attempts, or time to finish a challenge are widely used to estimate the perceived difficulty level. In other contexts, pupillometry is widely used to measure cognitive load (mental effort); hence, this may describe the perceived task difficulty.

Objective

This study aims to assess the use of task-evoked pupillary responses to measure the cognitive load measure for describing the difficulty levels in a video game. In addition, it proposes an image filter to better estimate baseline pupil size and to reduce the screen luminescence effect.

Methods

We conducted an experiment that compares the baseline estimated from our filter against that estimated from common approaches. Then, a classifier with different pupil features was used to classify the difficulty of a data set containing information from students playing a video game for practicing math fractions.

Results

We observed that the proposed filter better estimates a baseline. Mauchly’s test of sphericity indicated that the assumption of sphericity had been violated (χ²₁₄=0.05; P=.001); therefore, a Greenhouse-Geisser correction was used (ε=0.47). There was a significant difference in mean pupil diameter change (MPDC) estimated from different baseline images with the scramble filter (F_5,78=30.965; P<.001). Moreover, according to the Wilcoxon signed rank test, pupillary response features that better describe the difficulty level were MPDC (z=−2.15; P=.03) and peak dilation (z=−3.58; P<.001). A random forest classifier for easy and hard levels of difficulty showed an accuracy of 75% when the gamer data were used, but the accuracy increased to 87.5% when pupillary measurements were included.

Conclusions

The screen luminescence effect on pupil size is reduced with a scrambled filter on the background video game image. Finally, pupillary response data can improve classifier accuracy for the perceived difficulty of levels in educational video games.

Endogenous Opioid Signaling in the Mouse Retina Modulates Pupillary Light Reflex

Opioid peptides and their receptors are expressed in the mammalian retina; however, little is known about how they might affect visual processing. The melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs), which mediate important non-image-forming visual processes such as the pupillary light reflex (PLR), express β-endorphin-preferring, µ-opioid receptors (MORs). The objective of the present study was to elucidate if opioids, endogenous or exogenous, modulate pupillary light reflex (PLR) via MORs expressed by ipRGCs. MOR-selective agonist [D-Ala², MePhe⁴, Gly-ol⁵]-enkephalin (DAMGO) or antagonist D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH₂ (CTAP) was administered via intravitreal injection. PLR was recorded in response to light stimuli of various intensities. DAMGO eliminated PLR evoked by light with intensities below melanopsin activation threshold but not that evoked by bright blue irradiance that activated melanopsin signaling, although in the latter case, DAMGO markedly slowed pupil constriction. CTAP or genetic ablation of MORs in ipRGCs slightly enhanced dim-light-evoked PLR but not that evoked by a bright blue stimulus. Our results suggest that endogenous opioid signaling in the retina contributes to the regulation of PLR. The slowing of bright light-evoked PLR by DAMGO is consistent with the observation that systemically applied opioids accumulate in the vitreous and that patients receiving chronic opioid treatment have slow PLR.

Quantitative Infrared Pupillometry in Nonconvulsive Status Epilepticus

BACKGROUND

Nonconvulsive status epilepticus (NCSE) is a frequent disorder in neurocritical care and diagnosing it can be challenging. NCSE patients often show altered pupil function, but nature and extent may vary. Infrared pupillometry allows detection of subtle changes of pupil function. The neurological pupil index (NPi) is considered a surrogate marker of global pupil function which is supposed to be independent of absolute parameters such as the pupil diameter.

OBJECTIVE

Cross-sectional observational study to assess whether NPi is altered in NCSE.

METHODS

128 consecutive adult emergency patients who had experienced a suspected seizure, have not reached their prior functional level regarding level of consciousness, mental status or focal deficits, had no obvious clinical signs of status epilepticus and had an EEG indication as determined by the treating clinician for exclusion of NCSE were examined by routine EEG and pupillometry. Exclusion criteria were ocular comorbidity (n = 21) and poor EEG quality (n = 4). Pupillometry was performed once directly before the beginning of EEG recording. NCSE diagnosis (no NCSE, possible NCSE and confirmed NCSE) was established according to Salzburg consensus criteria blinded to pupillometry results. Group comparison was performed for right NPi, left NPi, lowest NPi of both sides (minNPi) and the absolute difference of both sides (diffNPi) applying non-parametric testing. In post-hoc analysis, receiver operating characteristics (ROC) of NCSE diagnosis (combined confirmed NCSE and possible NCSE) were performed for minNPi and diffNPi.

RESULTS

From 103 patients included in the final analysis, 5 (4.9%) had confirmed NCSE, 7 (6.8%) had possible NCSE. Right NPi (p = 0.002), left NPi (p < 0.001) and minNPi (p < 0.001) were significantly lower in "confirmed NCSE" and "possible NCSE" compared to "no NCSE"; diffNPi was significantly higher in "confirmed NCSE" and "possible NCSE" compared to "no NCSE" (p < 0.001). There was no significant difference of minNPi and diffNPi between "confirmed NCSE" and "possible NCSE". ROC analysis showed an optimal cut-off of minNPi for NCSE diagnosis of 4.0 (AUC = 0.93, 95% CI 0.86-0.99). Optimal ROC analysis cut-off of diffNPi for NCSE diagnosis was 0.2 (AUC = 0.89, 95% CI 0.80-0.99).

CONCLUSIONS

NPi was significantly reduced and the difference between left and right NPi was significantly higher in confirmed NCSE. An NPi < 4.0 on either side as well as an NPi difference of both sides > 0.2 may be potential indicators of NCSE. Infrared pupillometry may be a helpful diagnostic tool in the assessment of NCSE and should be studied further in larger populations.

Standards in Pupillography

The number of research groups studying the pupil is increasing, as is the number of publications. Consequently, new standards in pupillography are needed to formalize the methodology including recording conditions, stimulus characteristics, as well as suitable parameters of evaluation. Since the description of intrinsically photosensitive retinal ganglion cells (ipRGCs) there has been an increased interest and broader application of pupillography in ophthalmology as well as other fields including psychology and chronobiology. Color pupillography plays an important role not only in research but also in clinical observational and therapy studies like gene therapy of hereditary retinal degenerations and psychopathology. Stimuli can vary in size, brightness, duration, and wavelength. Stimulus paradigms determine whether rhodopsin-driven rod responses, opsin-driven cone responses, or melanopsin-driven ipRGC responses are primarily elicited. Background illumination, adaptation state, and instruction for the participants will furthermore influence the results. This standard recommends a minimum set of variables to be used for pupillography and specified in the publication methodologies. Initiated at the 32nd International Pupil Colloquium 2017 in Morges, Switzerland, the aim of this manuscript is to outline standards in pupillography based on current knowledge and experience of pupil experts in order to achieve greater comparability of pupillographic studies. Such standards will particularly facilitate the proper application of pupillography by researchers new to the field. First we describe general standards, followed by specific suggestions concerning the demands of different targets of pupil research: the afferent and efferent reflex arc, pharmacology, psychology, sleepiness-related research and animal studies.

Melanopsin-Driven Pupil Response and Light Exposure in Non-seasonal Major Depressive Disorder

Background: Melanopsin-expressing intrinsically photosensitive Retinal Ganglion Cells (ipRGCs) signal non-imaging forming effects of environmental light for circadian phoentrainment, the pupil light reflex, and mood regulation. In seasonal affective disorder, ipRGC dysfunction is thought to cause abberant transmission of the external illumination for photoentrainment. It is not known if patients with non-seasonal depression have abnormal melanospin mediated signaling and/or irregular environmental light exposure.

Methods: Twenty-one adults who live in a sub-tropical region, including eight patients with non-seasonal depression and thirteen age-matched healthy controls were recruited. The Mini International Neuropsychiatry Interview diagnosed the presence of a major depressive disorder. Light exposure was determined using actigraphy over a 2 week period. The melanopsin mediated post-illumination pupil response (PIPR) and outer retinal inputs to ipRGCs (transient pupil response and maximum pupil constriction amplitude) were measured in response to 1 s, short and long wavelength light with high and low melanopsin excitation.

Results: The mean daylight exposure as a function of clock hours and total light exposure duration (mins) to illumination levels commonly recommended for depression therapy were not significantly different between groups. Out of 84 pupil measurements (42 each in the depression and control groups), the melanopsin-mediated PIPR amplitude, transient pupil response, and pupil constriction amplitude were not significantly different between groups.

Conclusions: This report provides initial evidence of normal melanopsin function and environmental light exposures in patients with pre-dominately mid and moderate non-seasonal depression in a subtropical location in the southern hemisphere.

Decreased retinal sensitivity in depressive disorder: a controlled study

OBJECTIVE

To compare pupil responses in depressed patients with a seasonal pattern, depressed patients without a seasonal pattern and healthy controls as a function of daylight hours on the testing day.

METHOD

Patients suffering from a major depressive episode were included in wintertime. The pupil light reflex was measured at inclusion and in the following summer using a binocular pupillometer. A protocol of low (1 lux) and high (400 lux) intensity red and blue lights was used to assess rod, cone and melanopsin-containing intrinsic photosensitive retinal ganglion cell input to the pupil reflex.

RESULTS

The mean group pupil responses associated with a melanopsin-mediated sustained pupil response at 400 lux blue light were significantly reduced in the depressed subjects (N = 39) as compared to the healthy controls (N = 24) (P = 0.023). Across all groups, a reduction in number of daylight hours was significantly associated with a reduction in sustained pupil response (P = 0.007). All groups showed an equal effect of daylight hours on the melanopsin-mediated sustained pupil response.

CONCLUSION

The melanopsin-mediated sustained pupil contraction to offset of high-intensity blue light is reduced in depressed patients. These results further emphasize the interaction of light exposure with depression.

The potential influence of LED lighting on mental illness

OBJECTIVES

Two recent scientific breakthroughs may alter the treatment of mental illness, as discussed in this narrative review. The first was the invention of white light-emitting diodes (LEDs), which enabled an ongoing, rapid transition to energy-efficient LEDs for lighting, and the use of LEDs to backlight digital devices. The second was the discovery of melanopsin-expressing photosensitive retinal ganglion cells, which detect environmental irradiance and mediate non-image forming (NIF) functions including circadian entrainment, melatonin secretion, alertness, sleep regulation and the pupillary light reflex. These two breakthroughs are interrelated because unlike conventional lighting, white LEDs have a dominant spectral wavelength in the blue light range, near the peak sensitivity for the melanopsin system.

METHODS

Pertinent articles were identified.

RESULTS

Blue light exposure may suppress melatonin, increase alertness, and interfere with sleep in young, healthy volunteers and in animals. Areas of concern in mental illness include the influence of blue light on sleep, other circadian-mediated symptoms, prescribed treatments that target the circadian system, measurement using digital apps and devices, and adolescent sensitivity to blue light.

CONCLUSIONS

While knowledge in both fields is expanding rapidly, future developments must address the potential impact of blue light on NIF functions for healthy individuals and those with mental illness.

Precision Light for the Treatment of Psychiatric Disorders

Circadian timekeeping can be reset by brief flashes of light using stimulation protocols thousands of times shorter than those previously assumed to be necessary for traditional phototherapy. These observations point to a future where flexible architectures of nanosecond-, microsecond-, and millisecond-scale light pulses are compiled to reprogram the brain's internal clock when it has been altered by psychiatric illness or advanced age. In the current review, we present a chronology of seminal experiments that established the synchronizing influence of light on the human circadian system and the efficacy of prolonged bright-light exposure for reducing symptoms associated with seasonal affective disorder. We conclude with a discussion of the different ways that precision flashes could be parlayed during sleep to effect neuroadaptive changes in brain function. This article is a contribution to a special issue on Circadian Rhythms in Regulation of Brain Processes and Role in Psychiatric Disorders curated by editors Shimon Amir, Karen Gamble, Oliver Stork, and Harry Pantazopoulos.

Melanopsin-Mediated Acute Light Responses Measured in Winter and in Summer: Seasonal Variations in Adults with and without Cataracts

Seasonal adaptation is a ubiquitous behavior seen in many species on both global hemispheres and is conveyed by changing photoperiods. In humans this seasonal adaptation is less apparent, in part because changes in daylength are masked by the use of electrical lighting at night. On the other hand, cataracts which reduce light transmission, may compound seasonal changes related to the reduced daylength of winter. To better understand the effects of different photoperiod lengths in healthy adults without and with cataracts, we tested their melanopsin-mediated light responses in summer vs. winter. Fifty-two participants (mean age 67.4 years; 30 with bilateral cataracts and 22 age-matched controls with clear lenses; pseudophakes) were tested twice, once in summer and once in winter. At each test session we assessed the electroretinogram and pupil responses during daytime and we determined melatonin suppression, subjective sleepiness and mood in response to light exposure in the evening. Circadian rest-activity cycles and sleep from activity recordings were also analyzed for both seasons. Both groups had similar visual function. There were no seasonal differences in the electroretinogram. For the pupil responses to bright blue light, the post-illumination pupil response (PIPR) was greater in winter than summer in pseudophakes, but not in cataract participants, whereas melatonin suppression to acute light exposure showed no differences between both groups and seasons. Overall, intra-daily variability of rest-activity was worse in winter but participants felt sleepier and reported worse mood at the laboratory in evening time in the summer. Those with cataracts had poorer sleep quality with lower sleep efficiency, and higher activity during sleep in winter than summer. In this study, the PIPR showed a seasonal variation in which a larger response was found during winter. This variation was only detected in participants with a clear intraocular lens. In the cataract group, visual function was not impaired yet these participants showed a lack of seasonal changes in the pupil response to blue light and poorer sleep in winter. These findings raise the question for tailored lighting conditions for cataract patients in order to counter potentially deleterious effects of living with chronically lower light exposure.