Analysis of pupillometer results according to disease stage in patients with Parkinson's disease

Evaluation of autonomic involvement in Parkinson's disease using pupillometry

INTRODUCTION

The pupillary light reflex (PLR) indicates the function of the autonomic nervous system, which causes the pupil to constrict and dilate. Evaluation of the PLR determines the parasympathetic and sympathetic balance. We aimed to demonstrate autonomic changes by pupillometry in Parkinson'd disease (PD) and to investigate the relationship between the changes and motor stage and levodopa equivalent dose (LEDD).

METHOD

Static pupillometry measurement was performed at scotopic, mesopic and photopic settings. Dynamic pupillometry measurement was performed at 500 lux illumination and pupil diameter was recorded. Static and dynamic pupillometry parameters of Parkinson's disease patients and healthy control group of similar age and gender were compared. The relationship between Unified Parkinson's Disease Rating Scale (UPDRS)-motor, modified Hoehn and Yahr (mHYE) and levodopa equivalent daily dose (LEDD) and pupillometry parameters were analysed.

RESULTS

In static pupillometry, mesopic pupil diameter was significantly lower in PD patients (P = 0.04). In dynamic pupillometry, pupil diameter was lower and mean pupil dilation rate was lower in the PD group at 18 seconds. There was a significant negative correlation between mean pupil dilatation velocity and mHYE, UPDRS-motor and LEDD. The mean pupil dilatation velocity was statistically significantly lower in patients not receiving dopaminergic treatment.

CONCLUSION

Changes in pupillometry values in PD have emphasized that the autonomic nervous system is affected and the parasympathetic nervous system was found to be correlated with the motor involvement of the disease.

Comparison of an AI-based mobile pupillometry system and NPi-200 for pupillary light reflex and correlation with glaucoma-related markers

Introduction

Glaucoma is a leading cause of blindness, often progressing asymptomatically until significant vision loss occurs. Early detection is crucial for preventing irreversible damage. The pupillary light reflex (PLR) has proven useful in glaucoma diagnosis, and mobile technologies like the AI-based smartphone pupillometer (AI Pupillometer) offer a promising solution for accessible screening. This study assesses the reliability of the AI Pupillometer in detecting glaucoma.

Methods

In Experiment 1, 20 healthy participants were assessed using both the AI Pupillometer and the NPi-200 device to evaluate equivalence in measuring PLR. Each eye underwent three trials. Experiment 2 included 46 participants, 24 with primary open-angle glaucoma (POAG) and 22 healthy controls. PLR measurements from the AI Pupillometer were correlated with structural and functional ocular parameters. An additional study expanded the sample to 387 participants (103 glaucoma patients, 284 controls), focusing on differential pupillometry parameters to minimize ambient light interference.

Results

In Experiment 1, the AI Pupillometer demonstrated strong correlations with the NPi-200 in key parameters like initial pupil size (r = 0.700), constricted pupil size (r = 0.755), and constriction velocity (r = 0.541), confirming its reliability. In Experiment 2, although no statistically significant differences in light-corrected PLR parameters were found between groups, glaucoma patients had a marginally higher constricted pupil size (p = 0.1632). Significant correlations were observed between pupillometry and advanced ocular imaging results, notably between constriction amplitude and visual field loss. The additional study revealed significant differences in constriction amplitude (p = 0.014) and relative pupil size change (p = 0.0072) between glaucoma patients and controls, reinforcing the AI Pupillometer's diagnostic potential.

Conclusion

This study confirms the AI Pupillometer as a reliable, accessible tool for glaucoma screening. Mobile diagnostics could enhance early detection, improving outcomes for glaucoma patients.

Non-motor asymmetry and dopamine degeneration in Parkinson's disease

Asymmetric dopaminergic degeneration of the striatum is a characteristic feature of Parkinson's disease, associated with right-left asymmetry in motor function. As such, studying asymmetry provides insights into progressive neurodegeneration between cerebral hemispheres. Given the impact of Lewy pathology on various neurotransmitter systems beyond the dopaminergic, it may be that other neuronal systems in the predominantly affected hemisphere are similarly affected. According to this hypothesis, asymmetry in dopaminergic degeneration would be expected to coincide with asymmetry in other neurotransmitter systems. Consequently, asymmetry in functions primarily dependent on dopaminergic integrity, such as motor function, should correlate with asymmetry in bilateral non-motor functions that rely on other cerebral systems, such as pupillary function. Therefore, this study tested whether right-left asymmetry in bilateral non-motor measures correlates with asymmetry in dopaminergic striatal integrity. We also tested whether asymmetric striatal degeneration is associated with greater asymmetry in non-motor measures overall. Using a comparative cross-sectional design, we recruited newly diagnosed patients with Parkinson's disease with predominantly right-sided (n = 18), left-sided (n = 15) or symmetric nigrostriatal denervation (n = 15) assessed on dopamine PET. Detailed examinations of lateralized non-motor function included lacrimation, hand skin wrinkling, salivation, olfaction and pupillary function. Healthy controls were recruited for comparison. We observed a moderate-to-strong correlation between right-left asymmetry of putamen dopamine binding and asymmetry in pupillary redilation speed [Spearman's rank correlation coefficient (rs ) = -0.53, 95% confidence interval (-0.77; -0.14), P = 0.0084]. We also observed moderate correlations between non-negative putaminal asymmetry and lacrimation [rs = 0.35, (-0.00; 0.62), P = 0.0464] and word recognition [rs = 0.36, (0.01; 0.63), P = 0.0410]. However, none were significant after false discovery rate correction. We observed significant group differences in non-negative asymmetry in salivation (P = 0.0390, ANOVA) and a trend towards greater asymmetric lacrimation in participants with asymmetric striatal dopamine loss compared with healthy controls (P = 0.0330, unadjusted). Additionally, participants with asymmetric striatal dopaminergic binding showed greater, though non-significant, asymmetry in all pupillary measures compared with those with symmetric dopaminergic binding. In conclusion, this study contributes to our understanding of neurodegeneration progression in Parkinson's disease and suggests a link between dopaminergic degeneration and non-motor measures related to autonomic function, particularly salivation, lacrimation and pupillary function. While our findings do not support a strict right-left hemispheric association between non-motor functions and dopaminergic degeneration, potential relationships may exist between these features and asymmetrical degeneration in other neuronal systems, such as the cholinergic.

Improving Eye-Tracking Data Quality: A Framework for Reproducible Evaluation of Detection Algorithms

High-quality eye-tracking data are crucial in behavioral sciences and medicine. Even with a solid understanding of the literature, selecting the most suitable algorithm for a specific research project poses a challenge. Empowering applied researchers to choose the best-fitting detector for their research needs is the primary contribution of this paper. We developed a framework to systematically assess and compare the effectiveness of 13 state-of-the-art algorithms through a unified application interface. Hence, we more than double the number of algorithms that are currently usable within a single software package and allow researchers to identify the best-suited algorithm for a given scientific setup. Our framework validation on retrospective data underscores its suitability for algorithm selection. Through a detailed and reproducible step-by-step workflow, we hope to contribute towards significantly improved data quality in scientific experiments.

Nonlinear Regression Modelling: A Primer with Applications and Caveats

Use of nonlinear statistical methods and models are ubiquitous in scientific research. However, these methods may not be fully understood, and as demonstrated here, commonly-reported parameter p-values and confidence intervals may be inaccurate. The gentle introduction to nonlinear regression modelling and comprehensive illustrations given here provides applied researchers with the needed overview and tools to appreciate the nuances and breadth of these important methods. Since these methods build upon topics covered in first and second courses in applied statistics and predictive modelling, the target audience includes practitioners and students alike. To guide practitioners, we summarize, illustrate, develop, and extend nonlinear modelling methods, and underscore caveats of Wald statistics using basic illustrations and give key reasons for preferring likelihood methods. Parameter profiling in multiparameter models and exact or near-exact versus approximate likelihood methods are discussed and curvature measures are connected with the failure of the Wald approximations regularly used in statistical software. The discussion in the main paper has been kept at an introductory level and it can be covered on a first reading; additional details given in the Appendices can be worked through upon further study. The associated online Supplementary Information also provides the data and R computer code which can be easily adapted to aid researchers to fit nonlinear models to their data.

The Role of Automated Infrared Pupillometry in Traumatic Brain Injury: A Narrative Review

Pupillometry, an integral component of neurological examination, serves to evaluate both pupil size and reactivity. The conventional manual assessment exhibits inherent limitations, thereby necessitating the development of portable automated infrared pupillometers (PAIPs). Leveraging infrared technology, these devices provide an objective assessment, proving valuable in the context of brain injury for the detection of neuro-worsening and the facilitation of patient monitoring. In cases of mild brain trauma particularly, traditional methods face constraints. Conversely, in severe brain trauma scenarios, PAIPs contribute to neuro-prognostication and non-invasive neuromonitoring. Parameters derived from PAIPs exhibit correlations with changes in intracranial pressure. It is important to acknowledge, however, that PAIPs cannot replace invasive intracranial pressure monitoring while their widespread adoption awaits robust support from clinical studies. Ongoing research endeavors delve into the role of PAIPs in managing critical neuro-worsening in brain trauma patients, underscoring the non-invasive monitoring advantages while emphasizing the imperative for further clinical validation. Future advancements in this domain encompass sophisticated pupillary assessment tools and the integration of smartphone applications, emblematic of a continually evolving landscape.

Eye movements in Parkinson's disease: from neurophysiological mechanisms to diagnostic tools

Movement disorders such as Parkinson's disease (PD) impact oculomotor function - the ability to move the eyes accurately and purposefully to serve a multitude of sensory, cognitive, and secondary motor tasks. Decades of neurophysiological research in monkeys and behavioral studies in humans have characterized the neural basis of healthy oculomotor control. This review links eye movement abnormalities in persons living with PD to the underlying neurophysiological mechanisms and pathways. Building on this foundation, we highlight recent progress in using eye movements to gauge symptom severity, assess treatment effects, and serve as potential precision biomarkers. We conclude that whereas eye movements provide insights into PD mechanisms, based on current evidence they appear to lack sufficient sensitivity and specificity to serve as a standalone diagnostic tool. Their full potential may be realized when combined with other disease indicators in big datasets.

Pupil light reflex dynamics in Parkinson's disease

Introduction

Visual disturbance is common symptom in Parkinson's disease (PD), and defective pupil light reflex (PLR) is an anticipated contributing factor that may be associated to the presence of autonomic dysfunction, which is a common non-motor feature of PD. Studies investigating the intercorrelation between PLR and dysautonomia in PD are limited.

Methods

The aim of this study was to investigate differences of PLR parameters, measured by eye-tracker, between patients with PD, with and without signs of dysautonomia, and healthy controls (HC). In total, 43 HC and 50 patients with PD were recruited and PLR parameters were measured with Tobii Pro Spectrum, during a long (1,000 ms) and a short (100 ms) light stimulus. Presence of orthostatic hypotension (OH) was used as proxy marker of dysautonomia. Linear mixed-effects model and non-parametric comparative statistics were applied to investigate differences among groups.

Results

Peak constriction velocity was slower in PD compared with HC, after adjustment for age and sex in the mixed model, and the difference was greater in the subgroup of PD with OH (unadjusted). Dilation amplitude and velocity were also gradually slower in HC vs. PD without OH vs. PD with OH (unadjusted for confounders). In the mixed model, age was significant predictor of dilation response.

Discussion

Our results support previous observations on defective PLR in PD, evaluated with eye-tracker, and show a possible association with autonomic dysfunction. Further studies with more patients and rigorous evaluation of autonomic dysfunction are needed to validate these findings.

Visual Dysfunction in Parkinson's Disease

Non-motor symptoms in Parkinson's disease (PD) include ocular, visuoperceptive, and visuospatial impairments, which can occur as a result of the underlying neurodegenerative process. Ocular impairments can affect various aspects of vision and eye movement. Thus, patients can show dry eyes, blepharospasm, reduced blink rate, saccadic eye movement abnormalities, smooth pursuit deficits, and impaired voluntary and reflexive eye movements. Furthermore, visuoperceptive impairments affect the ability to perceive and recognize visual stimuli accurately, including impaired contrast sensitivity and reduced visual acuity, color discrimination, and object recognition. Visuospatial impairments are also remarkable, including difficulties perceiving and interpreting spatial relationships between objects and difficulties judging distances or navigating through the environment. Moreover, PD patients can present visuospatial attention problems, with difficulties attending to visual stimuli in a spatially organized manner. Moreover, PD patients also show perceptual disturbances affecting their ability to interpret and determine meaning from visual stimuli. And, for instance, visual hallucinations are common in PD patients. Nevertheless, the neurobiological bases of visual-related disorders in PD are complex and not fully understood. This review intends to provide a comprehensive description of visual disturbances in PD, from sensory to perceptual alterations, addressing their neuroanatomical, functional, and neurochemical correlates. Structural changes, particularly in posterior cortical regions, are described, as well as functional alterations, both in cortical and subcortical regions, which are shown in relation to specific neuropsychological results. Similarly, although the involvement of different neurotransmitter systems is controversial, data about neurochemical alterations related to visual impairments are presented, especially dopaminergic, cholinergic, and serotoninergic systems.

Pupillometry to Assess Auditory Sensation in Guinea Pigs

Noise exposure is a leading cause of sensorineural hearing loss. Animal models of noise-induced hearing loss have generated mechanistic insight into the underlying anatomical and physiological pathologies of hearing loss. However, relating behavioral deficits observed in humans with hearing loss to behavioral deficits in animal models remains challenging. Here, pupillometry is proposed as a method that will enable the direct comparison of animal and human behavioral data. The method is based on a modified oddball paradigm - habituating the subject to the repeated presentation of a stimulus and intermittently presenting a deviant stimulus that varies in some parametric fashion from the repeated stimulus. The fundamental premise is that if the change between the repeated and deviant stimulus is detected by the subject, it will trigger a pupil dilation response that is larger than that elicited by the repeated stimulus. This approach is demonstrated using a vocalization categorization task in guinea pigs, an animal model widely used in auditory research, including in hearing loss studies. By presenting vocalizations from one vocalization category as standard stimuli and a second category as oddball stimuli embedded in noise at various signal-to-noise ratios, it is demonstrated that the magnitude of pupil dilation in response to the oddball category varies monotonically with the signal-to-noise ratio. Growth curve analyses can then be used to characterize the time course and statistical significance of these pupil dilation responses. In this protocol, detailed procedures for acclimating guinea pigs to the setup, conducting pupillometry, and evaluating/analyzing data are described. Although this technique is demonstrated in normal-hearing guinea pigs in this protocol, the method may be used to assess the sensory effects of various forms of hearing loss within each subject. These effects may then be correlated with concurrent electrophysiological measures and post-hoc anatomical observations.

Do static and dynamic pupillary parameters differ according to childhood, adulthood, and old age? A quantitative study in healthy volunteers

Purpose

We aimed to evaluate the normative pupillometry values and mean pupil dilatation speed in healthy individuals in different age groups in our study.

Methods

The study group included 180 eyes of 90 healthy volunteers in different age groups. Group 1 consisted of 30 participants between the ages of 6 and 18, group 2 consisted of 30 participants aged 19-40, and group 3 consisted of 30 participants aged 41-75. Scotopic, mesopic, photopic, and dynamic measurements were taken with automatic pupillometry of Sirius Topographer (CSO, Firenze, Italy). The mean pupil dilation speed at the 18^th second was calculated according to dynamic measurements.

Results

Group 1 had a significantly larger pupil diameter than groups 2 and 3 in all static and dynamic parameters, and the mean pupil dilation speed was the highest among the groups (P < 0.001 for all static and dynamic parameters). In addition, group 2 had a significantly larger pupil diameter than group 3 (P < 0.001 for all static and dynamic parameters) and the mean pupil dilation speed was faster than group 3 (P = 0.027).

Conclusion

We have presented the static and dynamic parameters and the mean speed of pupil dilatation at the 18^th second with automatic pupillometry in healthy individuals in childhood, adulthood, and old age. More studies with higher participants and younger age children are needed.

Roles of clock genes in the pathogenesis of Parkinson's disease

Parkinson's disease (PD) is a common motor disorder that has become increasingly prevalent in the ageing population. Recent works have suggested that circadian rhythms disruption is a common event in PD patients. Clock genes regulate the circadian rhythm of biological processes in eukaryotic organisms, but their roles in PD remain unclear. Despite this, several lines of evidence point to the possibility that clock genes may have a significant impact on the development and progression of the disease. This review aims to consolidate recent understanding of the roles of clock genes in PD. We first summarized the findings of clock gene expression and epigenetic analyses in PD patients and animal models. We also discussed the potential contributory role of clock gene variants in the development of PD and/or its symptoms. We further reviewed the mechanisms by which clock genes affect mitochondrial dynamics as well as the rhythmic synthesis and secretion of endocrine hormones, the impairment of which may contribute to the development of PD. Finally, we discussed the limitations of the currently available studies, and suggested future potential studies to deepen our understanding of the roles of clock genes in PD pathogenesis.