Pupil Dilation Research Articles

Far‐red, high‐resolution, reflection‐free images of the anterior segment in retroillumination

Aims/Purpose: Retroillumination observation of the anterior segment is a routine examination method as old as the slit lamp, but capturing good quality images is difficult because of patient glare, the presence of corneal and or lens reflections, and limited resolution. We have modified a slit lamp to overcome these limitations and present the first series of images obtained.Methods: On a Topcon SL‐D7 slit lamp, we replaced the light source with a far‐red LED (Thorlabs, M780L3, 200 mW, 800 mA at 780 nm) and added a monochrome camera with sufficient resolution (Baumer, VCXU‐123 M). Reflection suppression was achieved by modifying the optical path (patent pending). In a clinical trial validated by an ethics committee (IDRCB: 2021‐A01496‐35), we acquired images of 5 different diseases after pupillary dilation: cataract, posterior capsule opacification, hereditary stromal dystrophy, Fuchs' corneal endothelial dystrophy (FECD), Bowman's membrane dystrophy.Results: Our innovative prototype device made it possible to obtain images of 3000 × 4096 pixels for 13.3 × 9.7 mm (×40 magnification). In 100% of the cases, one or more clear images on the area of interest were obtained without glare, and without disturbing reflections in 90% of the cases. Some pseudophakic patients showed minimal to moderate light reflection. The images were sufficiently resolved to allow precise analysis of disease areas, such as each guttae of the FECD.Conclusions: Our retroilluminator prototype provides, for the first time to our knowledge, high‐resolution images of the different structures of the anterior segment, easy to acquire and likely to facilitate the diagnosis and follow‐up of patients. Improvements to the prototype are underway to remove some persistent reflections. One of the first applications will be the classification of the severity of endothelial damage in FECD.

Normatively irrelevant disgust interferes with decision under uncertainty: Insights from the Iowa gambling task.

This study investigates whether a not informative, irrelevant emotional reaction of disgust interferes with decision-making under uncertainty. We manipulate the Iowa Gambling Task (IGT) by associating a disgust-eliciting image with selections from Disadvantageous/Bad decks (Congruent condition) or Advantageous/Good decks (Incongruent condition). A Control condition without manipulations is also included. Results indicate an increased probability of selecting from a Good deck as the task unfolds in all conditions. However, this effect is modulated by the experimental manipulation. Specifically, we detect a detrimental effect (i.e., a significant decrease in the intercept) of the disgust-eliciting image in Incongruent condition (vs. Control), but this effect is limited to the early stages of the task (i.e., first twenty trials). No differences in performance trends are detected between Congruent and Control conditions. Anticipatory Skin Conductance Response, heart rate, and pupil dilation are also assessed as indexes of anticipatory autonomic activation following the Somatic Marker Hypothesis, but no effects are shown for the first two indexes in any of the conditions. Only a decreasing trend is detected for pupil dilation as the task unfolds in Control and Incongruent conditions. Results are discussed in line with the "risk as feelings" framework, the Somatic Marker Hypothesis, and IGT literature.

Does the Eyesi direct ophthalmoscope increase interest in ophthalmology?

Purpose: This study based on direct ophthalmoscopy (DO) teaching in medical curricula aimed to integrate both classic and simulator‐based DO techniques into the teaching of medical students.Methods: 110 medical students received a multiple‐choice questionnaire (four theory questions, six fundus photographs) prior to simulator‐based (EyeSi® Direct, Haag‐Streit Simulation, Germany) and classic DO training (Heine BETA®200, Heine Optotechnik GmbH, Germany). Simulator‐based DO training was performed in groups of up to eight students.Thereafter, they underwent an objective standardized clinical examination containing questions about (1) pupil dilation, (2) mydriasis contraindication, (3) ophthalmoscope adjustment and a practical test checking whether (1) optic nerve head, (2) macula, (3–6) upper/lower vessel arcade nasally versus temporally were identified correctly. Subsequently, classic DO was performed mutually and they reported the funduscopic structures they had recognized. Finally, the questionnaire was repeated 1 week later in combination with an evaluation of simulator‐based versus classic DO.Results: Students improved from an average of 4.0 ± 1.5/10 before to 8.8 ± 1.5/10 correctly answered questions after training (p < 0.0001, Wilcoxon matched‐pairs test). 87|34|61 students named pupil dilating time mydriasis contraindication and adjusted the ophthalmoscope correctly. They successfully identified the optic nerve head (n(simulator)|n(classic) DO: 110|68, p < 0.0001, Fisher's exact test), the macula (93|22, p < 0.0001), the upper (98|75, p = 0.0002) and lower temporal vessel arcade (101|91, p = 0.0672), the upper (84|56, p = 0.0001) and lower nasal vessel arcade (87|48, p < 0.0001). They wished for more simulator‐based training, indicated a higher interest in ophthalmology after training and stated an improvement of their ophthalmoscopy skills.Conclusion: A standardized simulator‐based approach improves medical students' skills in ophthalmoscopy and arouses professional interest in ophthalmology.

Flexible Iris Matching Based on Spatial Feature Reconstruction

In an iris recognition-at-a-distance (IAAD) system used in surveillance scenarios, the camera usually captures a large number of low-quality images. These images exhibit partial occlusions due to eyelids and eyelashes, specular reflections, and severe deformations caused by pupil dilations and contractions. Recognizing these low-quality images is a challenging yet dominant problem in IAAD. To mitigate this issue, current iris recognition systems mostly filter out low-quality images by using strict criteria based on image quality evaluation. This strategy, however, wastes device capabilities and produces low throughput of subjects. Other systems require highly cooperative users. In this work, we propose a novel occlusion-robust, deformation-robust, and alignment-free framework for low-quality iris matching, which integrates the merits of deep features and sparse representation in an end-to-end learning process known as iris spatial feature reconstruction (ISFR). Here each probe image can be sparsely reconstructed on the basis of appropriate feature maps from gallery high-quality images. ISFR uses the error from robust reconstruction over spatial pyramid features to measure similarities between two iris images, which naturally avoids the time-consuming alignment step. In summary, the distinctiveness of deep features, the robustness of sparse reconstruction, and the flexibility of multiscale matching strategy are unified in a general framework to attain more accurate and reasonable iris matching. Extensive experimental results on four public iris image databases demonstrate that the proposed method significantly outperforms both traditional and deep learning-based iris recognition methods.

Influence of preoperative dilation time on the effect of cataract ultrasonography combined with goniostomy in patients with primary closed angle glaucoma and its clinical significance.

To evaluate the impact of preoperative pupil dilation time on the outcomes of cataract ultrasonoemulsification combined with goniostomy in patients with primary angle-closure glaucoma (PACG). A retrospective analysis was conducted on 106 PACG patients who underwent cataract ultrasonoemulsification with goniostomy. Patients were divided into two groups based on pupil dilation times: group A (dilation time between 20 to 30 minutes) and group B (dilation time between 30 minutes to 1 hour). Pre- and postoperative intraocular pressure (IOP), visual acuity, pupil diameter, anterior chamber depth (ACD), and lens thickness (LT) were measured. Surgical time and cumulative dissipated energy (CDE) were also analyzed. Multivariate analysis was performed to identify independent risk factors for postoperative complications. Both groups showed significant postoperative improvement in visual acuity (P < 0.05). Group B exhibited significantly lower postoperative IOP than group A (P < 0.05). There were significant increases in ACD and pupil diameter and a decrease in LT post-dilation in both groups (all P < 0.05). Group B showed a deeper ACD, thinner LT, and larger pupil diameter compared to group A (all P < 0.05). While CDE was similar between groups, operation duration was longer in group A (P < 0.05). Disease course > 5.5 years, preoperative IOP > 25.14 mmHg, pupil diameter before dilation < 4.895 mm, ACD before dilation < 2.105 mm, and dilation time ≤ 30 minutes were independent risk factors for postoperative complications. Preoperative pupil dilation time > 30 minutes leads to better surgical outcome. Several preoperative factors, including dilation time ≤ 30 minutes, are independent risk factors for postoperative complications.

Diabetic retinopathy screening using a handheld non‐mydriatic camera

Aims/Purpose: Our objective was to compare the diagnostic accuracy of diabetic retinopathy (DR) screening using a non‐mydriatic handheld digital camera as well as a stationary digital fundus non‐mydriatic camera to the standard fundus examination in medical mydriasis by an experienced observer.Methods: The evaluation of images using a digital handheld non‐mydriatic camera in a clinical setting, coupled with pupil dilation for ungradable images, provides a valid method for identifying an advanced stage of DR requiring therapeutic measures. The hand held non mydriatic fundus camera could represent an alternative to the conventional screening in medical mydriasis in order to improve the access to DR screening in areas and populations with less access to the existinmedical infrastructure.Results: The mean age of the 100 examined diabetic participants was 61.2 years (SD ± 9.08). The proportion of upgradable images in both types of non‐mydriatic imaging was 3% (1 eye – 2%, both eyes – 1%). When compared to the detection of any stage of DR, an advanced stage of DR showed higher diagnostic accuracy. The sensitivity for the advanced stage of DR was 13% for Reviewer 1 (positive predictive value [PPV] 5%) and 14% for Reviewer 2 (PPV 6%). The specificity was 94% for Reviewer 1 (negative predictive value [NPV] 96%) and 95% for Reviewer 2 (NPV 97%).Conclusions: The evaluation of images using a digital handheld non‐mydriatic camera in a clinical setting, coupled with pupil dilation for ungradable images, provides a valid method for identifying an advanced stage of DR requiring therapeutic measures. The handheld non mydriatic fundus camera could represent an alternative to the conventional screening in medical mydriasis in order to improve the access to DR screening in areas and populations with less access to the existing medical infrastructure.

How the eyes respond to sounds.

Eye movements have been extensively studied with respect to visual stimulation. However, we live in a multisensory world, and how the eyes are driven by other senses has been explored much less. Here, we review the evidence on how audition can trigger and drive different eye responses and which cortical and subcortical neural correlates are involved. We provide an overview on how different types of sounds, from simple tones and noise bursts to spatially localized sounds and complex linguistic stimuli, influence saccades, microsaccades, smooth pursuit, pupil dilation, and eye blinks. The reviewed evidence reveals how the auditory system interacts with the oculomotor system, both behaviorally and neurally, and how this differs from visually driven eye responses. Some evidence points to multisensory interaction, and potential multisensory integration, but the underlying computational and neural mechanisms are still unclear. While there are marked differences in how the eyes respond to auditory compared to visual stimuli, many aspects of auditory-evoked eye responses remain underexplored, and we summarize the key open questions for future research.

The Influence of Seasonal Allergic Conjunctivitis and Its Treatment on Choroidal Vascular Index

Purpose: To evaluate the the effects of seasonal allergic counjunctivitis (AC) and its treatment upon choroidal structure such as choroidal thickness (ChT) and choroidal vascular index (CVI) through the use of topical antihistamine agents. Methods. The 60 eyes of 30 patients were included in the AC group. Another 30 patients were included in the control group. The choroid was imaged by using enhanced depth imaging optical coherence tomography (EDI-OCT) instrument without pupillary dilation. ChT was defined as the area between the outer hyperreflective border of the RPE and the sclerochoroidal border at the fovea, 750 µm temporal to the fovea and 750 µm nasal to the fovea. Image J was used to measure CVI. With the images obtained from EDI-OCT, the total choroidal area (TCA), luminal area (LA), stromal area (SA), and CVI were calculated using the binarization method. Results. The mean ChT value in the AC group was 358.5 ± 93.8 µm at baseline and 356.8 ± 86.6 µm following 1 month of treatment. Meanwhile, the mean ChT in the control group was 316.6 ± 60.7 µm. The mean CVI value was 66.65 ± 2.98 in the control group, 70.75 ± 3.26 in the AC group at baseline, and 69.50 ± 3.17 following 1 month of treatment. Statistically significant difference was tracked between control and AC group (p = 0.028) and control group and posttreatment values (p=0,031). There were no statistically significant difference between initial AC treatment values and posttreatment values for all of the measurements. Conclusion. ChT and CVI can increase in patients with AC due to inflammation and increased vascular permeability. Although symptoms and signs related to AC may disappear after the treatment, effects in the choroid do not immediately normalize.

Effectiveness of a Standardized Combination of Intracameral Mydriatics and Anaesthetic on Mydriasis during Cataract Surgery with Coexisting Diseases.

To examine the effectiveness of a standardized combination of intracameral mydriatics and anesthetic (SCIMA) on mydriasis in patients with coexisting diseases such as diabetes mellitus (DM) and pseudoexfoliation syndrome (PXF) during phacoemulsification. Patients with cataract were included in the study if they achieved pupil dilation diameter ≥ 6.0 mm after the administration of mydriatic eyedrops (ME) during the first visit (V1). During the second visit (V2), pupil size measurements were obtained for phacoemulsification surgery with SCIMA. Effective mydriasis was defined as a pupil diameter ≥ 6.0 mm just prior to capsulorhexis without the use of additional pupil dilating agents. The measurements after ME administration during V1 and after SCIMA use during V2 were compared. 103 patients (103 eyes) were divided into 3 groups: cataract and DM (n = 35), cataract and PXF (n = 32), and cataract without DM or PXF (n = 36). SCIMA administration allowed the achievement of effective mydriasis (≥6.0 mm) in all groups (n = 103; 100%). Mydriasis was significantly larger (p ≤ 0.001) after ME (7.3 mm) than after SCIMA (6.8 mm) administration. Patients with cataract and such comorbidities as DM or PXF are likely to achieve effective pharmacological mydriasis during cataract phacoemulsification after SCIMA application. Mydriasis after ME is slower and larger, while SCIMA is faster.

Impact of SNR, peripheral auditory sensitivity, and central cognitive profile on the psychometric relation between pupillary response and speech performance in CI users.

Despite substantial technical advances and wider clinical use, cochlear implant (CI) users continue to report high and elevated listening effort especially under challenging noisy conditions. Among all the objective measures to quantify listening effort, pupillometry is one of the most widely used and robust physiological measures. Previous studies with normally hearing (NH) and hearing-impaired (HI) listeners have shown that the relation between speech performance in noise and listening effort (as measured by peak pupil dilation) is not linear and exhibits an inverted-U shape. However, it is unclear whether the same psychometric relation exists in CI users, and whether individual differences in auditory sensitivity and central cognitive capacity affect this relation. Therefore, we recruited 17 post-lingually deaf CI adults to perform speech-in-noise tasks from 0 to 20 dB SNR with a 4 dB step size. Simultaneously, their pupillary responses and self-reported subjective effort were recorded. To characterize top-down and bottom-up individual variabilities, a spectro-temporal modulation task and a set of cognitive abilities were measured. Clinical word recognition in quiet and Quality of Life (QoL) were also collected. Results showed that at a group level, an inverted-U shape psychometric curve between task difficulty (SNR) and peak pupil dilation (PPD) was not observed. Individual shape of the psychometric curve was significantly associated with some individual factors: CI users with higher clinical word and speech-in-noise recognition showed a quadratic decrease of PPD over increasing SNRs; CI users with better non-verbal intelligence and lower QoL showed smaller average PPD. To summarize, individual differences in CI users had a significant impact on the psychometric relation between pupillary response and task difficulty, hence affecting the interpretation of pupillary response as listening effort (or engagement) at different task difficulty levels. Future research and clinical applications should further characterize the possible effects of individual factors (such as motivation or engagement) in modulating CI users' occurrence of 'tipping point' on their psychometric functions, and develop an individualized method for reliably quantifying listening effort using pupillometry.

Postoperative Nausea and Vomiting following Endoscopic Sinus Surgery under the Guidance of Adequacy of Anesthesia or Pupillometry with Intravenous Propofol/Remifentanil.

Postoperative nausea and vomiting (PONV) constitutes an adverse event after endoscopic sinus surgery (ESS) under general anesthesia (GA) with intravenous opioids, such as remifentanil (RMF). Monitoring the nociception/antinociception balance using the surgical pleth index (SPI) or pupillary dilatation reflex (PRD) helps guide intravenous RMF infusion. We aimed to investigate whether their employment could help reduce the incidence of PONV in patients undergoing ESS. The data of 30 patients from the GA group, 31 from the SPI group, and 28 from the PRD group were analyzed. The initial RMF infusion rate of 0.25 µg/kg body weight/minute was increased by 50% when the SPI, PRD, or Boezaart Bleeding Scale (BBS) were elevated by >15, >5%, or >2 points, respectively, until they normalized. PONV was present in 7/89 patients (7.9%): 2/31 patients (6.5%) of the SPI group, 1/30 patients (3.3%) of the GA group, and 4/28 patients (14.3%) of the PRD group. Neither PRD nor SPI guidance for RMF administration reduced the incidence of PONV compared to standard practice. Further studies are required in order to investigate the possibility of PONV eradication in patients undergoing ESS under GA when it is possibly combined with paracetamol/metamizole preventive analgesia, as well as those using antiemetic prophylaxis based on the Apfel Score and premedication with midazolam.

Task-evoked pulse wave amplitude tracks cognitive load

Cognitive load is a crucial factor in mentally demanding activities and holds significance across various research fields. This study aimed to investigate the effectiveness of pulse wave amplitude (PWA) as a measure for tracking cognitive load and associated mental effort in comparison to heart rate (HR) during a digit span task. The data from 78 participants were included in the analyses. Participants performed a memory task in which they were asked to memorize sequences of 5, 9, or 13 digits, and a control task where they passively listened to the sequences. PWA and HR were quantified from photoplethysmography (PPG) and electrocardiography (ECG), respectively. Pupil dilation was also assessed as a measure of cognitive load. We found that PWA showed a strong suppression with increasing memory load, indicating sensitivity to cognitive load. In contrast, HR did not show significant changes with task difficulty. Moreover, when memory load exceeded the capacity of working memory, a reversal of the PWA pattern was observed, indicating cognitive overload. In this respect, changes in PWA in response to cognitive load correlated with the dynamics of pupil dilation, suggesting a potential shared underlying mechanism. Additionally, both HR and PWA demonstrated a relationship with behavioral performance, with higher task-evoked HR and lower PWA associated with better memory performance. Our findings suggest that PWA is a more sensitive measure than HR for tracking cognitive load and overload. PWA, measured through PPG, holds significant potential for practical applications in assessing cognitive load due to its ease of use and sensitivity to cognitive overload. The findings contribute to the understanding of psychophysiological indicators of cognitive load and offer insights into the use of PWA as a non-invasive measure in various contexts.

Manipulation of phasic arousal by auditory cues is associated with subsequent changes in visual orienting to faces in infancy

This eye-tracking study investigated the effect of sound-induced arousal on social orienting under different auditory cue conditions in 5-month-old (n = 25; n = 13 males) and 10-month-old infants (n = 21; n = 14 males) participating in a spontaneous visual search task. Results showed: (1) larger pupil dilation discriminating between high and low volume (b = 0.02, p = 0.007), but not between social and non-social sounds (b = 0.004, p = 0.64); (2) faster visual orienting (b = − 0.09, p < 0.001) and better social orienting at older age (b = 0.94, p < 0.001); (3) a fast habituation effect on social orienting after high-volume sounds (χ2(2) = 7.39, p = 0.025); (4) a quadratic association between baseline pupil size and target selection (b = − 1.0, SE = 0.5, χ2(1) = 4.04, p = 0.045); (5) a positive linear association between pupil dilation and social orienting (b = 0.09, p = 0.039). Findings support adaptive gain theories of arousal, extending the link between phasic pupil dilation and task performance to spontaneous social orienting in infancy.

Empirical study on visual attention characteristics of basketball players of different levels during free-throw shooting

Background Visual attention is very important in basketball shooting, which is a prerequisite for forming good muscle proprioception and improving the shooting rate. The ability of visual instant searching information in the process of free throw plays an important role in the mobilization of free throw percentage. The aim of this study is to explore the fixation characteristics of athletes at different levels in the process of free throw shooting and to provide scientific basis for improving the free throw training of basketball players. Methods A total of 20 expert basketball players, 20 general basketball players and 20 novice basketball players participated in the experiment. Participants in the three groups wore eye tracker to make free throws, and analyzed the difference of visual attention among the three groups. Results The expert group had fewer number of fixations on the front, bottom, top-right, and top-right areas of the basket than the general and novice groups. The expert group also had smaller saccadic amplitudes than the other two groups. In terms of fixation duration, the expert group had longer fixation duration on the front and top areas of the basket than the other two groups, while in the top-right and bottom-right areas, the expert group had shorter fixation durations. The pupil dilation of the expert group was larger than that of the other two groups. Conclusion During the free throw process, the expert group had a clear attentional focus, concentrated fixation points, efficient information search, and precise processing. Profound basketball knowledge, proficient skills, and accumulated experience are the foundation of visual efficient search and precise processing during free throw attempts, and they are also the prerequisite for ensuring a high free throw shooting percentage.

Deficits in the pupillary response associated with abnormal visuospatial attention allocation in mild traumatic brain injury

ABSTRACT Introduction The ability to allocate visual attention is known to be impaired in patients with mild traumatic brain injury (mTBI). In the present study, we investigated a possible neural correlate of this cognitive deficit by examining the pupil response of patients with mTBI whilst performing a modified Posner visual search task. Method Two experiments were conducted in which the target location was either not cued (Experiment 1) or cued (Experiment 2). Additionally, in Experiment 2, the type of cue (endogenous vs exogenous cue) and cue validity were treated as independent variables. In both experiments, search efficiency was varied by changing shape similarity between target and distractor patterns. The reaction time required to judge whether the target was present or absent and pupil dilation metrics, particularly the pupil dilation latency (PDL) and amplitude (PDA), were measured. Thirteen patients with chronic mTBI and 21 age-, sex-, and IQ -matched controls participated in the study. Results In Experiment 1, patients with mTBI displayed a similar PDA for both efficient and inefficient search conditions, while control participants had a significantly larger PDA in inefficient search conditions compared to efficient search conditions. As cognitive load is positively correlated with PDA, our findings suggest that mTBI patients were unable to apply more mental effort whilst performing visual search, particularly if the task is difficult when visual search is inefficient. In Experiment 2, when the target location was cued, patients with mTBI displayed no significant pupil dilation response to the target regardless of the efficiency of the search, nor whether the cue was valid or invalid. These results contrasted with control participants, who were additionally sensitive to the validity of the cue in which PDA was smaller for cue-valid conditions than invalid conditions, particularly for efficient search conditions. Conclusion Pupillometry provided further evidence of attention allocation deficits following mTBI.

Infants’ understanding of the causal power of agents and tools

Tools are objects that are manipulated by agents with the intention to cause an effect in the world. We show that the cognitive capacity to understand tools is present in young infants, even if these tools produce arbitrary, causally opaque effects. In experiments 1–2, we used pupillometry to show that 8-mo-old infants infer an invisible causal contact to account for the—otherwise unexplained—motion of a ball. In experiments 3, we probed 8-mo-old infants’ account of a state change event (flickering of a cube) that lies outside of the explanatory power of intuitive physics. Infants repeatedly watched an intentional agent launch a ball behind an occluder. After a short delay, a cube, positioned at the other end of the occluder began flickering. Rare unoccluded events served to probe infants’ representation of what happened behind the occluder. Infants exhibited larger pupil dilation, signaling more surprise, when the ball stopped before touching the cube, than when it contacted the cube, suggesting that infants inferred that the cause of the state change was contact between the ball and the cube. This effect was canceled in experiment 4, when an inanimate sphere replaced the intentional agent. Altogether, results suggest that, in the infants’ eyes, a ball (an inanimate object) has the power to cause an arbitrary state change, but only if it inherits this power from an intentional agent. Eight-month-olds are thus capable of representing complex event structures, involving an intentional agent causing a change with a tool.

Congruent Prosody Reduces Cognitive Effort in Memory for Spoken Sentences: A Pupillometric Study with Young and Older Adults

ABSTRACTBackgroundIn spite of declines in working memory and other processes, older adults generally maintain good ability to understand and remember spoken sentences. In part this is due to preserved knowledge of linguistic rules and their implementation. Largely overlooked, however, is the support older adults may gain from the presence of sentence prosody (pitch contour, lexical stress, intra-and inter-word timing) as an aid to detecting the structure of a heard sentence.MethodsTwenty-four young and 24 older adults recalled recorded sentences in which the sentence prosody corresponded to the clausal structure of the sentence, when the prosody was in conflict with this structure, or when there was reduced prosody uninformative with regard to the clausal structure. Pupil size was concurrently recorded as a measure of processing effort.ResultsBoth young and older adults’ recall accuracy was superior for sentences heard with supportive prosody than for sentences with uninformative prosody or for sentences in which the prosodic marking and causal structure were in conflict. The measurement of pupil dilation suggested that the task was generally more effortful for the older adults, but with both groups showing a similar pattern of effort-reducing effects of supportive prosody.ConclusionsResults demonstrate the influence of prosody on young and older adults’ ability to recall accurately multi-clause sentences, and the significant role effective prosody may play in preserving processing effort.

Chronic subdural haematoma: a case series of uncommon presentations of a common disease

Abstract Chronic subdural haematoma is a common neurological condition especially among the elderly population. Its presentation can be unspecific but often attributed to pressure, cortical irritation, and/or vascular compromise. In the patients’ cohort presented below, we have a series of cases where clinical history and examination did not result in an initial clinical diagnosis or suspicion of chronic subdural haematoma, with the diagnosis made only after brain imaging. We reviewed the literature regarding the aetiopathogenesis and clinical features of our patient cohort, which included a young woman with isolated right ptosis and pupillary dilatation, an elderly man with paraplegia, another elderly man with isolated right foot drop, and a young military man with no history of trauma. Our series re-emphasizes the sometimes non-specific and varied clinical presentation of chronic subdural haematoma. We reiterate the need for early brain imaging in patients who present with neurological disorder.

Pupillometry as a marker of arousal and in relation to cognition and cortical dynamics in Alzheimer’s disease

AbstractBackgroundPupil dilation is an established measure of noradrenergic activity. Cortical EEG alpha power, a measure of attentional engagement, can be recorded simultaneously with pupillometry. Dysfunction in the noradrenergic system in Alzheimer’s disease (AD), contributes to the attentional deficits seen in patients. We investigated whether pupillometry recorded at rest can be used to show reduced noradrenergic activity in AD and how this relates to cortical dynamics.MethodWe recorded simultaneous EEG and pupillometry during 5min of eyes‐open resting‐state in 28 AD patients and 22 age‐matched controls (HC). Pupil dilations – peaks of both pupil diameter and velocity – were identified (Fig. 1A/B). Average pupil diameter and velocity were calculated across all dilations, and compared between groups (Fig. 1 C/D). We plotted EEG power spectra for the 2s pupil dilation‐centred epochs (Fig. 2A). The frequency at which there was the greatest power within the alpha band – the peak alpha frequency (PAF) – was calculated for each individual and compared across groups (Fig. 2B). We then measured the alpha power during the pupil‐dilation epochs and looked at the relationship with the pupils (Fig. 3).ResultIn HCs, the mean pupil dilations – peaks in diameter and peaks in velocity – were greater than in AD; t = ‐2.62 p = 0.01 and t = ‐2.26 p = 0.03, respectively (Fig. 1C/D). Power spectra for the 2s pupil dilation‐centred epochs showed patients’ PAF was significantly lower than HC’s; t = 2.92 p&lt;0.01 (Fig. 2). There was a corresponding peak in alpha power associated with the pupil dilations, in both groups. Regarding peaks in pupil diameter, the alpha power peaked approximately 0.5sec earlier (Fig. 3A). Regarding peaks in pupil velocity, the alpha power peaked simultaneously with the pupils (Fig. 3B).ConclusionThere is a reduction in size and velocity of spontaneous pupil dilations in AD. EEG alpha is shifted to lower frequencies in AD. There is a preserved relationship between pupil dilations and alpha peaks in AD. Pupillometry offers a means of measuring noradrenergic dysfunction in AD that relates to altered cortical dynamics.

Higher pupillary dilation during phasic transcutaneous vagus nerve stimulation (taVNS) and its relevance to the noradrenergic system of the locus coeruleus (LC‐NE)

AbstractBackgroundTranscutaneous auricular vagus nerve stimulation (taVNS) may affect the locus coeruleus‐norepinephrine system (LC‐NE system) via modulation of the vagus nerve. The LC is our main source of NE in the brainstem and declines with age and is a potential epicentre of tau pathology in Alzheimer´s diseases (AD). Besides the excessive NE release leading to the formation of amyloid plaques, the severity and duration of AD are also related to LC cell death, decreased cortical NE levels, and accelerated tau spread. An increase in NE release in the LC accompanied by reduced inflammatory markers was achieved in animal models using phasic invasive (i)VNS. In humans, phasic taVNS leads to an increase in pupil dilation, which can serve as a proxy for LC activation. Therefore, taVNS may have the potential to increase NE release and thereby impact LC function and related links to tau pathology.MethodTwenty‐four subjects (50% women; 22.96 +/‐ 2.24 years) received time‐synchronous phasic taVNS during a fixation task (∼ 18min) while recording pupillary dilation changes, which allowed systematic testing of phasic taVNS (3 sec) with low (3 mA) and high (5 mA) intensities and low (10 Hz) and high (25 Hz) frequencies at constant pulse width (250 µs).ResultDuring on stimulation pupil dilation was higher during real (0.18±0.03) as compared to sham (0.09±0.03) stimulation (χ2 = 10.29, p = 0.001) (see Fig. 1). Likewise higher (0.21±0.03) compared to lower (0.06±0.03) intensity (χ2 = 23.02, p &lt; 0.001) led to higher pupil dilation, while there was no significant difference between higher (0.13±0.03) and lower (0.14±0.03) frequencies (χ2 = 0.11, p = 0.74).ConclusionSystematic testing of different frequencies and intensities, while keeping the pulse width constant, showed that phasic real taVNS and higher intensity lead to higher pupillary dilation, which is consistent with animal and human studies. Furthermore, the results suggest that the influence of intensity on pupil dilation might be stronger than that of frequency. The increased pupillary dilation during phasic taVNS could be an indication of LC involvement, however, more detailed studies e.g., functional magnetic resonance imaging (fMRI) during taVNS are needed to confirm this association.