Light Reflex Research Articles

Automated Pupillometry Is Able to Discriminate Patients with Acute Stroke from Healthy Subjects: An Observational, Cross-Sectional Study.

Automated pupillometry (AP) is a handheld, non-invasive tool that is able to assess pupillary light reflex dynamics and is useful for the detection of intracranial hypertension. Limited evidence is available on acute ischemic stroke (AIS) patients. The primary objective was to evaluate the ability of AP to discriminate AIS patients from healthy subjects (HS). Secondly, we aimed to compute a predictive score for AIS diagnosis based on clinical, demographic, and AP variables. We included 200 consecutive patients admitted to a comprehensive stroke center who underwent AP assessment through NPi-200 (NeurOptics®) within 72 h of stroke onset and 200 HS. The mean values of AP parameters and the absolute differences between the AP parameters of the two eyes were considered in the analyses. Predictors of stroke diagnosis were identified through univariate and multivariate logistic regressions; we then computed a nomogram based on each variable's β coefficient. Finally, we developed a web app capable of displaying the probability of stroke diagnosis based on the predictive algorithm. A high percentage of pupil constriction (CH, p < 0.001), a low constriction velocity (CV, p = 0.002), and high differences between these two parameters (p = 0.036 and p = 0.004, respectively) were independent predictors of AIS. The highest contribution in the predictive score was provided by CH, the Neurological Pupil Index, CV, and CV absolute difference, disclosing the important role of AP in the discrimination of stroke patients. The results of our study suggest that AP parameters, and in particular, those concerning pupillary constriction, may be useful for the early diagnosis of AIS.

Quantitative Pupillometry Predicts Return to Play and Tracks the Clinical Evolution of Mild Traumatic Brain Injury in US Military Academy Cadets: A Military Traumatic Brain Injury Initiative Study.

The objective of this study was to determine the utility of the pupillary light reflex use as a biomarker of mild traumatic brain injury (mTBI). This prospective cohort study was conducted at The US Military Academy at West Point. Cadets underwent a standard battery of tests including Balance Error Scoring System, Sports Concussion Assessment Tool Fifth Edition Symptom Survey, Standard Assessment of Concussion, and measure of pupillary responses. Cadets who sustained an mTBI during training events or sports were evaluated with the same battery of tests and pupillometry within 48 hours of the injury (T1), at the initiation of a graded return to activity protocol (T2), and at unrestricted return to activity (T3). Pupillary light reflex metrics were obtained in 1300 cadets at baseline. During the study period, 68 cadets sustained mTBIs. At T1 (<48 hours), cadets manifested significant postconcussion symptoms (Sports Concussion Assessment Tool Fifth Edition P < .001), and they had decreased cognitive performance (Standardized Assessment of Concussion P < .001) and higher balance error scores (Balance Error Scoring System P < .001) in comparison with their baseline assessment (T0). The clinical parameters showed normalization at time points T2 and T3. The pupillary responses demonstrated a pattern of significant change that returned to normal for several measures, including the difference between the constricted and initial pupillary diameter (T1 P < .001, T2 P < .05), dilation velocity (T1 P < .01, T2 P < .001), and percent of pupillary constriction (T1 P < .05). In addition, a combination of dilation velocity and maximum constriction velocity demonstrates moderate prediction ability regarding who can return to duty before or after 21 days (area under the curve = 0.71, 95% CI [0.56-0.86]). This study's findings indicate that quantitative pupillometry has the potential to assist with injury identification and prediction of symptom severity and duration.

The role of retinal irradiance estimates in melanopsin-driven retinal responsivity: a reanalysis of the post-illumination pupil response in seasonal affective disorder.

To isolate melanopsin contributions to retinal sensitivity measured by the post-illumination pupil response (PIPR), controlling for individual differences in non-melanopsin contributions including retinal irradiance is required. When methodologies to negate such differences present barriers, statistical controls have included age, baseline diameter, iris pigmentation, and circadian time of testing. Alternatively, the pupil light reflex (PLR) and calculations estimating retinal irradiance both reflect retinal irradiance, while the PLR also reflects downstream pathways. We reanalyzed data from an observational, correlational study comparing the PIPR across seasons in seasonal affective disorder (SAD) and controls. The PIPR was measured in 47 adults in Pittsburgh, Pennsylvania (25 SAD) over 50 seconds after 1 second of red and blue stimuli of 15.3 log photons/cm2/s. The PLR was within 1 second while PIPR was averaged over 10-40 seconds post-stimulus. Two raters ranked iris pigmentation using a published scale. We evaluated model fit using Akaike's Information Criterion (AIC) across different covariate sets. The best-fitting models included either estimated retinal irradiance or PLR, and circadian time of testing. The PLR is collected contemporaneously in PIPR studies and is an individually specific measure of nonspecific effects, while being minimally burdensome. This work extends the prior publication by introducing theoretically grounded covariates that improved analytic model fits based on AIC specific to the present methods and sample. Such quantitative methods could be helpful in studies which must balance participant and researcher burden against tighter methodological controls of individual differences in retinal irradiance.

Rare micropupil secondary to congenital cataract surgery favoring the development of the affected eye: a case report

BackgroundCongenital microcoria has been extensively reported and usually leads to visual dysfunction or blindness. However, micropupil development secondary to cataract surgery has never been reported. Here, we describe a rare case of micropupil development in infancy that occurred secondary to combined cataract extraction and intraocular lens implantation for treatment of congenital cataract. When the patient reached adulthood, the affected eye not only gained good vision but also showed better ocular development and refractive status than the fellow eye.Case presentationA 17-year-old boy presented to our outpatient clinic with decreased vision in his left eye related to congenital cataract surgery at 6 months of age. The affected eye had exhibited a pinhole pupil since the third month postoperatively. The condition had been managed with observation and regular monocular occlusion treatment. Upon presentation to our clinic, the best-corrected visual acuity (BCVA) in his fellow eye was 0.0 logMAR(20/20) with a refraction of − 5.75 diopters cylinder/−2.25 diopters sphere, and the BCVA in his affected eye was 0.5 logMAR(20/40) with a refraction of 0.00 diopters. Ophthalmic examination of the affected eye revealed a pinhole pupil (approximately 0.5 mm) with high light reflex sensitivity but no response to pupil-dilating drugs. The patient underwent pupilloplasty of the affected eye under corneal surface anesthesia. Postoperative examination revealed better ocular development in the affected eye than in the fellow eye (axial length: 24.21 vs. 27.02 mm, respectively) as well as better refractive status in the affected eye (BCVA of 0.0 logMAR(20/20) with a refraction of − 2.23 diopters cylinder/−3.00 diopters sphere vs. 0logMAR(20/20) with a refraction of -5.75 diopters cylinder/-2.25 diopters sphere).ConclusionsWe have reported a rare case of micropupil development secondary to congenital cataract surgery, which is an uncommon complication, especially in children. However, unlike congenital microcoria, the secondary pinhole pupil may have reduced imaging haze and halos, possibly favoring the development of the affected eye. This case provides further insight into the treatment of congenital cataract.

Early Tracheostomy versus Late Tracheostomy in Patients with Moderate-to-Severe Traumatic Brain Injury.

Objective The aim of this article was to study the impact of early versus late tracheostomy on clinical outcomes of moderate-to-severe traumatic brain injury (TBI). Materials and Methods A retrospective cross-sectional study was conducted in the Neurosurgery Department, Mayo Hospital, Lahore, in which a sample size of 50 cases was calculated over a period of 6 months from January 1, 2022, to June 30, 2022. The included cases were patients who suffered from moderate-to-severe TBI, isolated TBI, needed elective ventilation, required intensive care unit (ICU) admission during their hospital stay, and were between the ages of 18 and 65 years. All the rest were excluded. A structured proforma was used by the physician to collect data after the informed consent of the patient. The results were computed and analyzed statistically using Statistical Package for Social Sciences , version 26. Results The median age of patients was 40 (interquartile [IQ] range 34) years and were predominantly male (72%). The most common mode of injury was road traffic accidents (58%). The median Glasgow Coma Scale (GCS) score at arrival was 8 (IQ range 6) and the most common pupillary light reflex at presentation was bilaterally equally responsive to light (68%). Neurologic deficits were mostly absent or cannot be assessed on presentation (86%) and in 38% of the cases multiple findings were noted on computed tomography (CT) scan while among single findings seen on CT scan, subdural hematoma was the most common (22%). Multiple regression analysis was done through two separate models using age, gender, mode of injury, presenting GCS score, number of CT-scan findings, number of days after endotracheal intubation after which tracheostomy was done, and the timing of tracheostomy (early vs. late) as predictors, and a significant relationship was noted between the timing of tracheostomy (early vs. late) and GCS at discharge ( p = 0.001) as well as extended Glasgow Outcome Score (GOS) at discharge ( p = 0.013). Conclusion This study suggests that moderate-to-severe TBIs are most common in middle-aged males and mostly involve road traffic accidents. In most cases, multiple CT-scan findings are seen as compared with a single predominant finding. In such patients, early tracheostomy is superior to late tracheostomy as it results in significantly better GCS and GOS scores at discharge as well as a decreased duration of mechanical ventilation and ICU stay.

Immediate effect of Kaki Mudra on pupillary light reflex among healthy individuals – A study protocol of a Randomized control trial

Abstract Background Kaki Mudra is a yogic gesture that involves nasikagara drishti focusing on the nose tip without the eyes blinking and pursing the lips, which form beaks during inhalation, and exhaling slowly through the nose. However, there is a lack of evidence on the impact of kaki mudra on cardiovascular changes and autonomic function using pupillary light reflex (PLR). Methods A randomized control study design will be adopted for this study with 80 healthy participants with more than 18 years of age, will be recruited. Subjects will be randomly divided into the study (n = 40) and control groups (n = 40). The study group will be advised to practice Kaki Mudra for 20 min, whereas the control group will be asked to relax in sitting posture for 20 min. Results The baseline and post-assessment will be immediately evaluated for all the individuals; five leads to ECG for heart rate variability (HRV) and dynamic pupillometry for PLR. Discussion The immediate effect of kaki mudra is an effective and simple technique that might improve HRV and PLR variable, which may improve overall health and enhance parasympathetic dominance among healthy participants. The study is prospectively registered in the Clinical Trial Registry of India (CTRI/2024/05/067289).

Association Between Pupil Light Reflex and Delirium in Adults With Traumatic Brain Injury: Preliminary Findings.

BACKGROUND: Delirium is a common neurological complication in patients admitted to the intensive care unit (ICU) after moderate to severe traumatic brain injury (TBI). Although current clinical guidelines prioritize delirium prevention, no specific tool is tailored to detect early signs of delirium in TBI patients. This preliminary 2-phase observational study investigated the correlation between the pupillary light reflex (PLR), measured with a pupillometer during mechanical ventilation, and the development of postextubation delirium in TBI patients. METHODS: A convenience sample of 26 adults with moderate to severe TBI under mechanical ventilation was recruited during their ICU stay. In phase I, PLR measurements were performed in the first 3 days of ICU admission using automated infrared pupillometry. In phase II, 2 raters independently extracted delirium data in the 72 hours post extubation period from medical records. Delirium was confirmed with a documented medical diagnosis. Point-biserial correlations ( rpb ) were used to examine the association between PLR scores and the presence of postextubation delirium. Student t tests were also performed to compare mean PLR scores between patients with and without delirium. RESULTS: Ten TBI patients (38%) were diagnosed with postextubation delirium, whereas 16 (62%) were not. Significant correlations between delirium and 2 PLR variables were found: pupil constriction percentage ( rpb (24) = -0.526, P = .006) and constriction velocity ( rpb (24) = -0.485, P = .012). The t test also revealed a significant difference in constriction percentage and velocity scores between TBI patients with and without delirium ( P ≤ .01). CONCLUSION: Our findings suggest that the use of pupillometry in the first 3 days of mechanical ventilation during an ICU stay may help identify TBI patients at risk for delirium after extubation. Although further research is necessary to support its validity, this technological tool may enable ICU nurses to better screen TBI patients for delirium and prevent its development.

Neuro-ophthalmic Tests for Assessment of Vision Before and After Phacoemulsification in Cataractous Dogs

Background: The aim of current study was to assess pre and post-operative vision status through neuro-ophthalmic examination of 24 canine eyes after phacoemulsification with implantation of different acrylic intra ocular lenses. Methods: The study was conducted on 24 canine eyes. Preoperatively, detailed neuro-ophthalmic tests viz. Menace response, Pupillary light reflex (PLR), Obstacle Course and Moving object (cotton ball) were conducted for assessment of vision due to cataract and to exclude other ocular pathologies. Dogs were divided in four groups with 6 eyes in each group and subjected to phacoemulsification procedure for removal of cataractous lens and implanted with square edge or round edge, hydrophilic or hydrophobic intra ocular lenses (IOL). Post operatively, aforementioned neuro-ophthalmic tests were conducted on 3, 7 and 15 days and scores were given and comparatively analysed for vision acuity. Result: Preoperatively, neuro-opthalmic tests indicated poor and absent vision in eyes affected with various stages of cataract. Post operatively, the visual outcome in dogs of all treatment groups were assessed from the scores obtained in various neuro-ophthalmic tests. Neuro-ophthalmic evaluation revealed restoration of vision in 50% dogs in group I, II, IV and in 66.66% dogs of group III on day 15 after phacoemulsification and intraocular lens (IOL) implantation. It was concluded that neuro-ophthalmic tests are useful and mandatory protocols for pre and post-operative vision assessment in dogs with cataract.

Pupillometry as a Potential Objective Measurement of Pain Assessment in Healthy Volunteers.

Pain leads to activation of the autonomic nervous system and thus, among other things, to pupillary reflex dilation (PRD). Previous studies have already confirmed a correlation between the perception of pain and the pupillary reaction, measured using pupillometry. However, the previous study populations were under the influence of medication for analgesia in perioperative setting or suffered from pain. This study examines the relationship between pupillary reaction and pain perception in healthy controls and addresses the question of whether endogenous pain inhibition, clinically tested by conditioned pain modulation (CPM), can be quantified using pupillometry. Forty-two healthy volunteers (21 females, 21 males, mean age 27.9 ± 5.8 years, range 20-39 years) were included in this study. The PRD, as a measure of the pupillary reaction (variance from the base diameter in percent), was investigated during baseline, heat application and during CPM testing and results compared to the reported pain intensity on the numerical rating scale (NRS). The volunteers showed higher variances under painful conditions compared to the measurement at rest corresponding to higher sympathetic activity during pain. Volunteers with a higher variance, ie a stronger pupillary reaction, gave higher pain ratings than subjects with a lower pupil variance. However, there was no correlation between the NRS and PRD. PRD and pain ratings during CPM were significantly lower compared to heat pain application alone. However, there was no correlation between the calculated CPM effect and the PRD. Pupillometry is capable of objectively reflecting the pain response, eg pain relief through CPM testing. However, the CPM effect calculated from the subjective pain ratings and the objective PRD measurements is not associated suggesting that both measure different aspects of pain perception. It must be discussed whether the CPM effect can be the correct measure for the functionality of the pain system.

Recovery of Oculomotor Nerve Palsy After Surgical and Endovascular Repair of Unruptured Internal Carotid-Posterior Communicating Artery Aneurysms

Unruptured posterior communicating artery (Pcom) aneurysms cause oculomotor nerve palsy (ONP). However, the time course of recovery after aneurysm repair remains unclear. We aimed to evaluate the ONP course after clipping and coiling for unruptured Pcom aneurysms. We retrospectively reviewed the medical records of 25 consecutive patients with ONP due to unruptured Pcom aneurysms, undergoing aneurysm repair at our institution during 2010-2022. We analyzed the clinical data, angiographic results, and surgical complications. The time to ONP recovery was evaluated using the Kaplan-Meier method. This study included 14 patients undergoing surgical clipping and 11 undergoing endovascular coiling. The two groups exhibited no significant differences in complete or partial ONP percentage or in symptom presentation (ptosis, diplopia, ocular paralysis, pupillary light reflex disorder, or mydriasis). All patients achieved complete or partial recovery during the follow-up period. The median time to partial or complete improvement in ONP was significantly shorter for clipping compared to coiling (2days vs. 33days; P= 0.009). Preoperative partial and complete ONP were stratified; clipping improved significantly earlier than coiling in the complete ONP group (P= 0.010). In the early treatment group (based on the median duration of treatment), clipping resulted in earlier improvement than coiling (P= 0.014). In the small aneurysm group (based on the median of the aneurysm maximum diameter), clipping resulted in earlier improvement than coiling (P= 0.005). In ONP caused by an unruptured Pcom aneurysm, clipping may provide faster recovery than coiling, particularly in cases of early onset, complete palsy, and small aneurysms.

High-speed eye tracking based on a synchronized imaging mechanism by a dual-ring infrared lighting source

It is a challenge for conventional monocular-camera single-light source eye-tracking methods to achieve high-speed eye tracking. In this work, a dual-ring infrared lighting source was designed to achieve bright and dark pupils in high speed. The eye-tracking method used a dual-ring infrared lighting source and synchronized triggers for the even and odd camera frames to capture bright and dark pupils. A pupillary corneal reflex was calculated by the center coordinates of the Purkinje spot and the pupil. A map function was established to map the relationship between the pupillary corneal reflex and gaze spots. The gaze coordinate was calculated based on the mapping function. The average detection time of each gaze spot was 3.76 ms.

Prognostic factors and clinical features of rhino-orbital-mucormycosis cases: an update for patient and visual survivals.

To determine the frequency of patients' vision survival and prognostic factors and evaluate clinical features in rhino-orbital mucormycosis. Forty-three eyes of 43 patients followed up with orbital mucormycosis infections were included in the study. Demographic characteristics of the patients, symptoms at admission, ophthalmologic and non-ophthalmologic examination findings, clinical findings during follow-up, medical and surgical procedures, and complications were recorded. Patient survival was determined by assessing the incidence of mortality, and vision survival was defined as achieving a final visual acuity of at least light perception. Twenty-seven (62.8%) patients were male, and 16 (37.2%) were female. When the underlying disease status of the patients was examined, it was observed that all patients had an underlying disease and diabetes constituted the majority (65.2%). Periorbital swelling (69.8%) and ophthalmoplegia (53.5%) were the most common symptoms and findings at the admission of patients with mucormycosis infection. The disease resulted in death in 22 (51.2%) patients. The presence of fever and shorter duration of antifungal therapy were associated with lower patient survival. Exenteration surgery was not found to be associated with the survival of the patients. Frozen eye, loss of pupillary light reflex, and development of central retinal artery occlusion were associated with lower vision survival. This study presents one of the most extensive patient series in the literature on rhino-orbital mucormycosis. Knowing the patients' symptoms at the time of admission and the clinical findings during the infection process will increase awareness about the disease.

Management of Eye Protrusion in Cats with Acute Trauma

Preventing permanent vision loss and damage to the bulbus oculi in cases of proptosis, which is very important in small animal eye emergencies, and protecting the anatomical structures of the eye. Early intervention is important for protection. In this study, patients with proptosis who had experienced acute trauma. It was aimed to report the treatment and results of cats. Proptosis was diagnosed in 11 of 96 cats (11.45%) who presented to eye emergencies. On examination, all cats had eye. It was determined that the edges of the eyelids were not visible, the bulbus oculi was muffled, the bulbus oculi was hyperemic and edematous, there was a pupillary light reflex in 9 cases, and there was no pupillary light reflex in 2 cases. In the treatment, enucleation was applied in 2 cases, canthotomy and temporary blepharraphy were applied in 3 cases, and temporary blepharraphy was applied in 6 cases. It was determined that there were no postoperative complications in all cases and visual function was observed in all cases except for those who underwent enucleation. As a result, urgent intervention is important to protect the anatomical structures of the eye and maintain visual function in proptosis. The results obtained from this study are satisfactory for cats and their caregivers.

Predicting the cognitive impairment with multimodal ophthalmic imaging and artificial neural network for community screening

Background/aimsTo investigate the comprehensive prediction ability for cognitive impairment in a general elder population using the combination of the multimodal ophthalmic imaging and artificial neural networks.MethodsPatients with cognitive impairment and...

A pupillary contrast response in mice and humans: Neural mechanisms and visual functions

In the pupillary light response (PLR), increases in ambient light constrict the pupil to dampen increases in retinal illuminance. Here, we report that the pupillary reflex arc implements a second input-output transformation; it senses temporal contrast to enhance spatial contrast in the retinal image and increase visual acuity. The pupillary contrast response (PCoR) is driven by rod photoreceptors via type 6 bipolar cells and M1 ganglion cells. Temporal contrast is transformed into sustained pupil constriction by the M1's conversion of excitatory input into spike output. Computational modeling explains how the PCoR shapes retinal images. Pupil constriction improves acuity in gaze stabilization and predation in mice. Humans exhibit a PCoR with similar tuning properties to mice, which interacts with eye movements to optimize the statistics of the visual input for retinal encoding. Thus, we uncover a conserved component of active vision, its cell-type-specific pathway, computational mechanisms, and optical and behavioral significance.

Eye involvement in patients with rheumatoid arthritis: a cross-sectional study

Background: Rheumatoid arthritis (RA) is a systemic immune disease. The authors aimed to report the characteristics of ocular manifestations in patients with RA. Methods: Demographic and clinical characteristics were collected including: age, sex, and BMI. Disease data included the duration, the present main complaint, including the number of painful and swollen joints, duration of morning stiffness, and the patient’s self-evaluation form had also been applied and registered. Eye symptom including pain, dryness, redness, photophobia, discharge, and blurred vision was asked and registered, in addition to full medical history, treatment, and evaluation of clinical disease activity index. Rheumatologic examination included: the number of tender and swollen joints in patients was done. All study subjects underwent complete ophthalmological examination in the following manner: visual acuity assessment by Snellen’s chart, evaluation of pupil diameter and reflexes as well as eyeball movements, tear film evaluation by using Schirmer’s test, intraocular pressure measurement, slit-lamp evaluation of the anterior segment with concentration on ocular surface assessment, followed by installation of topical mydriatic/cycloplegic eyedrops for posterior eye segment exam and fundoscopy. Laboratory tests included rheumatic factor, anti cytoplasmic citrulinted peptide, C-reactive protein, and erythrocyte sedimentation rate were performed and analyzed. Results: Mean age of study group was 41.5±10 years,78.59% of which were females. Ocular manifestations were present in 31.14%. Dry eye was diagnosed in (36.71%), among which burning sensation was found in (35.15%), and photophopia in (27.34%). The most frequent ocular manifestation was episcleritis (66.40%), while scleritis was diagnosed in (22.65%), and keratoconjuctivitis was present in (7.04%). Discussion: The most common manifestations of ocular involvement in our RA patients was episcleritis, dry eye, and scleritis. Positive serum rheumatoid factor and anticitrulinated peptide antibody significantly increased the risk of having ocular manifestations, especially dry eyes, and the ocular manifestations prevalence was higher among male patients, long disease duration and treatment with biologics and disease-modifying antirheumatic drugs. Conclusion: Ocular symptoms are relatively frequent manifestation of RA. Regular ophthalmological examinations are essential among patients with RA.

Ayurveda Approach in the Management of Hypertensive Retinal Hemorrhage: A Case Report

Abstract Hypertensive retinopathy (HR) refers to changes in the retinal microvasculature that occur with elevated blood pressure and are a visible manifestation of vascular damage. A 54-year-old female patient presented with complaints of headache and blurred vision in both eyes over the last year and with a 5-year history of hypertension. On fundus examination, a flame-shaped hemorrhage associated with arteriolar light reflex changes (copper wiring) was observed in the inferior quadrant of the right eye with deflection of veins at the arteriovenous crossing (Salu’s sign). Management was done on an outpatient basis for 1 month, which included oral administration of Avipattikara Churna, Kaishora Guggulu, Brihat Manjishtadi Kwatha, and Saptamrita Lauha. The retinal features of HR underwent complete resolution with the Ayurveda treatment regimen for 26 days. HR-induced retinal hemorrhage can be successfully managed with the Ayurveda treatment approach.

Normal baseline cardiac autonomic function and increased pupillary parasympathetic tone in patients with vasovagal syncope.

It is controversial whether people with vasovagal syncope (VVS) have abnormal autonomic responses at baseline and whether specific diagnostic manoeuvres have a diagnostic value. We investigated whether the pupillary light reflex and cardiac autonomic tests can be used to identify autonomic dysfunction in volunteers with a medical history of VVS. The study groups included 128 healthy volunteers, of whom 31 reported a history of typical VVS. The right pupil was evaluated using an automated, commercial infra-red pupillometer under strict conditions. In addition to miosis and mydriasis kinetics, pupil diameters were measured. Heart rate variability at rest and heart rate changes to standing were quantified with high-resolution electrocardiography and designated software. The demographic and clinical characteristics of both groups were statistically similar. Average constriction velocity (ACV) was significantly higher in VVS patients following a univariate analysis (3.83 ± 0.59vs. 3.56 ± 0.73 mm/s, p = 0.042) and after correcting for potential confounders (p = 0.049). All other pupillometric and heart rate indices were comparable between groups. Patients with a history of VVS depict pupillary parasympathetic overactivity in response to light stimuli, manifested as increased ACV. The prognostic implications of this finding and the significance of using this simple clinical tool to identify patients who are at risk for developing frequent episodes of VVS or physical injuries following a syncope merits further study.

A Study of Pupil Response to Light as a Digital Biomarker of Recent Cannabis Use

Introduction: Given the traffic safety and occupational injury prevention implications associated with cannabis impairment, there is a need for objective and validated measures of recent cannabis use. Pupillary light response may offer an approach for detection. Method: Eighty-four participants (mean age: 32, 42% female) with daily, occasional, and no-use cannabis use histories participated in pupillary light response tests before and after smoking cannabis ad libitum or relaxing for 15 min (no use). The impact of recent cannabis consumption on trajectories of the pupillary light response was modeled using functional data analysis tools. Logistic regression models for detecting recent cannabis use were compared, and average pupil trajectories across cannabis use groups and times since light test administration were estimated. Results: Models revealed small, significant differences in pupil response to light after cannabis use comparing the occasional use group to the no-use control group, and similar statistically significant differences in pupil response patterns comparing the daily use group to the no-use comparison group. Trajectories of pupillary light response estimated using functional data analysis found that acute cannabis smoking was associated with less initial and sustained pupil constriction compared to no cannabis smoking. Conclusion: These analyses show the promise of pairing pupillary light response and functional data analysis methods to assess recent cannabis use.

0024 Measuring Melanopsin-driven Retinal Responses in Sleep and Circadian Health: Performance of the Pupil Light Reflex

0024 Measuring Melanopsin-driven Retinal Responses in Sleep and Circadian Health: Performance of the Pupil Light Reflex