Search Results (103)

Pupil cycle time (PCT) estimates the dynamics of a biofeedback loop established between pupil size and stimulus luminance, size or colour. The PCT is useful for probing the functional integrity of the retinopupillary circuits, and is therefore potentially applicable for assessing the effects of damage due to retinopathies or neuropathies. In previous studies, PCT was measured by manually counting the number of pupil oscillations during a fixed period to calculate the PCT. This method is scarce, requires a good expertise and cannot be used to estimate several PCT parameters, such as the oscillation amplitude or variability. We have developed a computerised setup based on eye-tracking that expands the possibilities of characterising PCT along several dimensions: oscillation frequency and regularity, amplitude and variability, which can be used with a large palette of stimuli (different colours, sizes, shapes or locations), and further allows measuring blinking frequency and eye movements. We used this method to characterise the PCT in young control participants as well as in patients with several pathologies, including age-related macular degeneration (AMD), diabetic retinopathy (DR), retinitis pigmentosa (RP), Stargardt disease (SD), and Leber hereditary optic neuropathy (LHON). We found that PCT is very regular and stable in young healthy participants, with little inter-individual variability. In contrast, several PCT features are altered in older healthy participants as well as in ocular diseases, including slower dynamics, irregular oscillations, and reduced oscillation amplitude. The distinction between patients and healthy participants based on the calculation of the area under the curve of the receiver operating characteristics (AUC of ROC) were dependent on the pathologies and stimuli (0.7 < AUC < 1). PCT nevertheless provides relevant complementary information to assess the physiopathology of ocular diseases and to probe the functioning of retino-pupillary circuits. Full article

Visual behaviour in zebrafish, often measured by the optokinetic reflex (OKR), serves as a valuable model for studying aspects of human neurological and ocular diseases and for conducting therapeutic or toxicology assays. Traditional methods for OKR analysis often rely on binarization techniques (threshold-based conversion of images to black and white) or costly software, which limits their utility in low-contrast settings or hypopigmented disease models. Here, we present a novel deep learning pipeline for OKR analysis, using ResNet-50 within the DeepLabCut framework in a Python Version 3.10 environment. Our approach employs object tracking to enable robust eye movement quantification, regardless of variations in contrast or pigmentation. OKR responses were elicited in both wild-type and slc45a2 (albino) mutant zebrafish larvae at 5 days post-fertilisation, using a mini-LED arena with a rotating visual stimulus. Eye movements were recorded and analysed using both conventional software and our deep learning approach. We demonstrate that the deep learning model achieves comparable accuracy to traditional methods, with the added benefits of applicability in diverse lighting conditions and in hypopigmented larvae. Statistical analyses, including Bland–Altman tests, confirmed the reliability of the deep learning model. While this study focuses on 5-day-old zebrafish larvae under controlled conditions, the pipeline is adaptable across developmental stages, pigmentation types, and behavioural assays. With appropriate adjustments to experimental parameters, it could be applied to broader behavioural studies, including social interactions and predator–prey dynamics in ocular and neurological disease models. Full article

Previous models of extraocular mechanics have often assumed isotropic properties for ocular tissues, despite evidence indicating anisotropy in the optic nerve sheath (ONS). To investigate this further, we developed a finite element model (FEM) of horizontal eye rotation using MRI data from a living subject with normal tension glaucoma. Mechanical properties were derived from tensile tests on 17 post-mortem human eyes, revealing previously unrecognized anisotropic characteristics in the ONS. We simulated ±32° horizontal eye rotations and compared isotropic versus anisotropic ONS properties using the Holzapfel model. Strain distributions in the optic nerve (ON) were analyzed using ABAQUS 2024 software. During 32° adduction, stress and strain were concentrated at the ONS-sclera junction, reaching 8 MPa and 40% with isotropic properties, and 15 MPa and 30% with anisotropic properties. In contrast, during 32° abduction, stress was lower and strain was higher in the isotropic case (6 MPa and 30%) compared to the anisotropic case (12 MPa and 25%). Increased intraocular and intracranial pressures had minimal impact on the mechanical responses. These findings suggest that the anisotropic properties of the ONS increase stress concentration at the optic disc while reducing strain during eye movements, offering new insights into ocular biomechanics. A novel phenomenon emerged from the simulations: during larger ductions, the peripapillary Bruch’s membrane is predicted to wrinkle, forming undulations with an approximately 20 μm amplitude and 100 μm wavelength at its interface with the retina and choroid. Full article

Eye movement detection technology holds significant potential across medicine, psychology, and human–computer interaction. However, traditional methods, which primarily rely on tracking the pupil and cornea during the open-eye state, are ineffective when the eye is closed. To address this limitation, we developed a novel system capable of real-time eye movement detection even in the closed-eye state. Utilizing a micro-camera based on the OV9734 image sensor, our system captures image data to construct a dataset of eyelid images during ocular movements. We performed extensive experiments with multiple versions of the YOLO algorithm, including v5s, v8s, v9s, and v10s, in addition to testing different sizes of the YOLO v11 model (n < s < m < l < x), to achieve optimal performance. Ultimately, we selected YOLO11m as the optimal model based on its highest AP0.5 score of 0.838. Our tracker achieved a mean distance error of 0.77 mm, with 90% of predicted eye position distances having an error of less than 1.67 mm, enabling real-time tracking at 30 frames per second. This study introduces an innovative method for the real-time detection of eye movements during eye closure, enhancing and diversifying the applications of eye-tracking technology. Full article

Background: The impact of dance training on brainstem-mediated vestibular reflexes remains unclear. This study examined the vestibulo-ocular reflex (VOR) and its suppression during high-speed head movements, which may closely resemble the head-turning speeds used in dancers’ spotting techniques, using the video head impulse test. Methods: Eighteen female college students (mean age: 21 years) were divided into two groups—nine trained dancers (≥six years of dance training) and nine age-matched non-dancers—all without a history of hearing, vestibular, or neurological disorders. VOR function was assessed using the head impulse paradigm (HIMP) and the suppression head impulse paradigm (SHIMP) for right and left lateral stimulation, with minimum head velocities of 150°/s. Results: All participants exhibited VOR measures within normal limits and the VOR gain of dancers did not significantly differ from that of non-dancers. However, most dancers reported a preference for right-sided pirouettes and the right-side SHIMP gain negatively correlated with years of training, suggesting a link between preferred turning direction and VOR suppression ability. Furthermore, dancers with over 15 years of training exhibited earlier anti-compensatory saccade latencies (~75 ms) during SHIMP. Conclusions: Trained dancers maintain a healthy VOR and may develop enhanced voluntary control, enabling more effective VOR suppression. The earlier onset of anti-compensatory saccades suggests neural adaptations in eye–head coordination for high-velocity movements. Given the study’s small sample size and the inclusion of non-fulltime dancers, future research with larger samples of professional dancers is needed for enhanced generalizability. These findings provide preliminary evidence of dance-related neuroplasticity in brainstem-mediated vestibular reflexes and open new research avenues. Full article

Ocular aqueous humor plays an important role in maintaining retinal function. Recent findings indicate that aqueous humor, which flows into the vitreous body, is probably absorbed by Müller cells in the retina, and this process is mediated by aquaporin-4. In this review, we aim to summarize the results of studies on classical aqueous humor circulation and postiridial flow, a pathway proposed in the late 1980s for the inflow of aqueous humor into the vitreous body. In addition, we aim to discuss the retinal glymphatic pathway, inferred by recent findings, with a focus on the anatomical location of aquaporins and barriers that regulate water movement within the tissue. Similarly to the cerebral glymphatic flow, the function of the retinal glymphatic pathway may decline with age, as supported by our findings. In this review, we also discuss age-related ocular diseases that might be associated with the dysfunction of the retinal glymphatic pathway. Full article

(1) Introduction: The main way of spreading the herpes simplex virus 1 (HSV-1) is through direct contact, as the virus enters the host via mucous membranes. Ocular infection can occur as a primary infection or as a recurrent one. The movement of HSV-1 along the ophthalmic branch of the fifth cranial nerve from its latency phase in the trigeminal ganglion and its activation represent a process influenced by various symbiotic factors, such as environmental conditions and the host’s genetic characteristics. The aim of this study was to assess the frequency of IL28 (rs12980275) and (rs8099917) in recurrent ocular HSV infections. (2) Materials and methods: The study included 60 patients aged over 18, of both sexes, all of whom had a history of herpes simplex labialis (HSL). Patients were tested for HSV-1-specific IgG antibodies, and seropositive individuals were genotyped for single nucleotide polymorphisms (SNPs) rs12980275 and rs8099917. A total of 57 seropositive patients were included in the study. (3) Results: A statistically significant association was found between recurrent HSV keratitis (HSK) and heterozygous GT rs8099917 and homozygous TT rs8099917, as well as heterozygous AG rs12980275 and homozygous AA rs12980275 (p < 0.01). Interestingly, patients with homozygous GG polymorphism for both genotypes GG rs8099917 and GG rs12980275 did not develop recurrent HSV keratitis. (4) Conclusion: The most frequent SNP variations in patients with recurrent HSV disease were heterozygous AG rs12980275 (61.40%) and heterozygous GT rs8099917 (52.63%). Patients with recurrent HSV keratitis lacked the homozygous GG polymorphism in both GG rs8099917 and GG rs12980275 genotypes, suggesting that HSV-seropositive individuals expressing these genotypes may have lower predisposition to develop recurrent stromal HSV keratitis. Full article

Purpose: Accurate and precise navigation in space and postural stability rely on the central integration of multisensory input (vestibular, proprioceptive, visual), weighted according to its reliability, to continuously update the internal estimate of the direction of gravity. In this study, we examined both peripheral and central vestibular functions in a world-renowned 53-year-old male tightrope walker and investigated the extent to which his exceptional performance was reflected in our findings. Methods: Comprehensive assessments were conducted, including semicircular canal function tests (caloric irrigation, rotatory-chair testing, video head impulse testing of all six canals, dynamic visual acuity) and otolith function evaluations (subjective visual vertical, fundus photography, ocular/cervical vestibular-evoked myogenic potentials [oVEMPs/cVEMPs]). Additionally, static and dynamic posturography, as well as video-oculography (smooth-pursuit eye movements, saccades, nystagmus testing), were performed. The participant’s results were compared to established normative values. High-resolution diffusion tensor magnetic resonance imaging (DT-MRI) was utilized to assess motor tract integrity. Results: Semicircular canal testing revealed normal results except for a slightly reduced response to right-sided caloric irrigation (26% asymmetry ratio; cut-off = 25%). Otolith testing, however, showed marked asymmetry in oVEMP amplitudes, confirmed with two devices (37% and 53% weaker on the left side; cut-off = 30%). Bone-conducted cVEMP amplitudes were mildly reduced bilaterally. Posturography, video-oculography, and subjective visual vertical testing were all within normal ranges. Diffusion tensor MRI revealed no structural abnormalities correlating with the observed functional asymmetry. Conclusions: This professional tightrope walker’s exceptional balance skills contrast starkly with significant peripheral vestibular (otolithic) deficits, while MR imaging, including diffusion tensor imaging, remained normal. These findings highlight the critical role of central computational mechanisms in optimizing multisensory input signals and fully compensating for vestibular asymmetries in this unique case. Full article

The developmental eye movement (DEM) test is a paper-based tool used to assess ocular motor skills in children. By naming numbers in a simple and easy simulated reading task, the DEM test provides an oculomotor efficiency score without complex eye-tracking equipment. Studies have shown that its usefulness can be extended to adults, despite its name suggesting that it is used primarily for developmental ages. However, for a broader application in the adult population in a clinical setting, there are no adult-specific norms. This study aimed to develop adult normative data for the Italian-speaking population and assess whether the DEM scores were influenced by age. In this study, 521 healthy Italian adults, aged 20 to 79 years, participated. Normative data were obtained by using a regression-based framework with demographic variables as predictors. Results show that age influences all sub-measures of time such as Vertical Time (VT), Adjusted Horizontal Time (AHT), and the Ratio score, but did not influence the error score. This is in line with the processing speed reduction in aging. Errors were influenced by education and gender. DEM norms, defined and scored using percentiles and equivalent scores, allow the assessment of oculomotor efficiency in adults, making this test suitable for use in all clinical settings, particularly in neuropsychological and neurological ones. Full article

The significant number of road traffic accidents caused by fatigued drivers presents substantial risks to the public’s overall safety. In recent years, there has been a notable convergence of intelligent cameras and artificial intelligence (AI), leading to significant advancements in identifying driver drowsiness. Advances in computer vision technology allow for the identification of driver drowsiness by monitoring facial expressions such as yawning, eye movements, and head movements. These physical indications, together with assessments of the driver’s physiological condition and behavior, aid in assessing fatigue and lowering the likelihood of drowsy driving-related incidents. This study presents an extensive variety of meticulously designed algorithms that were thoroughly analyzed to assess their effectiveness in detecting drowsiness. At the core of this attempt lay the essential concept of feature extraction, an efficient technique for isolating facial and ocular regions from a particular set of input images. Following this, various deep learning models, such as a traditional CNN, VGG16, and MobileNet, facilitated detecting drowsiness. Among these approaches, the MobileNet model was a valuable choice for drowsiness detection in drivers due to its real-time processing capability and suitability for deployment in resource-constrained environments, with the highest achieved accuracy of 92.75%. Full article

This study aimed to identify if sensor technology could be used to detect sickness-type signs (caused by a live vaccine) in laying hens compared to physiological and clinical sign scoring and behaviour observation. The experiment comprised 5 replicate batches (4 hens and 12 days per batch) using previously non-vaccinated hens (n = 20). Hens were moved on day 1 to a large experimental room with various designated zones (e.g., litter, perches, nest box), where they wore two sensors (FitBark, TrackLab). Saline was applied using ocular and nasal drops on day 3 as a control. A live vaccine (Infectious Laryngotracheitis, ILT, vaccine), applied using the same method on day 6, was used to induce mild respiratory and other responses. Physiological and clinical signs, and behaviour from videos were also recorded by a single observer. There were significant changes in body weight (p < 0.001), feed intake (p = 0.031), cloacal temperature (p < 0.001) and three out of five clinical signs (ocular discharge (p < 0.001), conjunctivitis (p < 0.001) and depression (p = 0.009)) over days. A significant decrease (p < 0.001) in activity level (FitBark) and distance travelled (both sensors) were identified over the study days, and activity and distance travelled were highly significantly associated (p < 0.001) with total clinical scores, with hens showing reduced activity and distance travelled with worsening total clinical scores. With behaviour observations from videos, the proportions of sitting, foraging and feeding behaviours (p = 0.044, 0.036 and 0.004, respectively), the proportion of total visit duration to the litter zone (p < 0.001) and perch (p = 0.037) with TrackLab and the proportions of visit counts of hens in the litter zone (p = 0.012) from video scanning changed significantly with days. This study suggests that the vaccine challenge caused associated changes in clinical/physiological signs and activity/distance travelled data from the sensors. Sensors may have a role in detecting changes in activity and movement in individual hens indicative of health or welfare problems. Full article

Background/Objectives: Ocular proprioception is implicated in balance control and heterophoria is associated with abnormal posture, though previous research focused mainly on the role of vertical phoria and the use of vertical prisms. This study aims to evaluate whether ocular misalignment and prismatic correction of horizontal phoria affect posture. Methods: Sixty-nine (N = 69) young healthy subjects were included and equally divided by horizontal distance phoria: orthophoria (n = 23), esophoria (n = 23) and exophoria (n = 23). A prism of low power (two-diopter) was placed base out on the non-dominant eye, reducing misalignment in esophorics and increasing it in exophorics more than in orthophorics. Dynamic computerized posturography was performed with the sensory organization test protocol (SOT) of the EquiTest^® NeuroCom^® version 8 platform both without and with prism, always maintaining subjects unaware of prism use. A mixed model for repeated measures analysis of variance was run to evaluate the main effect of prism and the interaction effect of prism with baseline phoria. Results: Composite movement strategy score without prism was 88.1 ± 2.8% (ankle-dominant strategy) and slightly increased to 89.0 ± 3.1% with prism insertion (p = 0.004), further shifting toward ankle strategy. Composite equilibrium score without prism was 80.3 ± 6.5% and remained stable with prism insertion (81.3 ± 8.2%, p = 0.117), medio-lateral and antero-posterior projection of center of gravity did not displace significantly under prism insertion (p = 0.652 and p = 0.270, respectively). At baseline, posturographic parameters were statistically independent of individual phoria, and no significant interaction between prism insertion and individual phoria was documented for any parameters (p > 0.05 for all). Secondary analysis and pairwise comparisons confirmed that the effect of prism was strongly selective on condition SOT 5 (eyes-closed, platform sway-referenced) with improvement of equilibrium (70.4 ± 9.7% with prism vs. 65.7 ± 11.6% without) and more use of ankle strategy (81.6 ± 5.3% with prism vs. 78.2 ± 6.0% without), without any interaction of phoria and ocular dominance, while the other conditions were comparable with and without prism. Conclusions: A two-diopter prism base out on the non-dominant eye induces the body to use the ankle joint more independently of individual phoria, suggesting a small improvement in postural control, while maintaining oscillations of the center of gravity unaltered. Prism seems to enhance the function of vestibular system selectively. Phoria adjustments with prismatic correction enable intervention in postural behavior. Extraocular muscles could act as proprioceptors influencing postural stability. Full article

Purpose: This paper investigated the visual–perceptual and visual–motor skills and the reversal frequency of letters and numbers that mirror one another in one hundred children aged 6–13 years diagnosed with poor reading skills. Methods: TVPS-4th, VMI-6th, and RFT were performed. Age and sex analysis was carried out. The impact of the eye movement patterns in the perceptual–motor skills and laterality–directionality concepts was also estimated to determine the relationship among tests to predict future results. Results: Most children scored between average and 3 stds below average on the motor VMI-6th test, while half of the participants scored between average and 2 stds below average on TVPS-4th. In the RFT, the majority scored between average and 1.5 stds below average. Participants scored higher on the spatial relationship subtest of the TVPS-4th and lower in the VMI-6th test ($p<0.001$). Statistically significant differences were found between the youngest and oldest participants on the TVPS-4th overall performance, as well as VD, FC and VFG skills ($p<0.05$). A strong relationship was found between the TVPS-4th and VMI-6th, ($p<0.001$). RFT results were different among all groups ($p<0.05$). The RFT was better related to the VMI-6th than TVPS-4th; however, it was statistically insignificant. The horizontal component of the DEM test was the best predictor for the TVPS-4th and ratio for the RFT, without attaining statistical significance. No sex differences were found. Conclusions: Results showed that children with poor reading skills exhibit perceptual–motor and reversal frequency difficulties, which are independent of the oculomotor performance. Considering that visual and motor processing are essential elements of the reading and writing process, their evaluation and treatment should be included as part of the multidisciplinary approach for children with poor reading skills. This would boost the general outcome and contribute to their academic achievement. Full article

Electroencephalography (EEG) is a non-invasive technique widely used in neuroscience to diagnose neural disorders and analyse brain activity. However, ocular and myogenic artifacts from eye movements and facial muscle activity often contaminate EEG signals, compromising signal analysis accuracy. While deep learning models are a popular choice for denoising EEG signals, most focus on removing either ocular or myogenic artifacts independently. This paper introduces a novel EEG denoising model capable of handling the simultaneous occurrence of both artifacts. The model uses convolutional layers to extract spatial features and a fully connected layer to reconstruct clean signals from learned features. The model integrates the Adam optimiser, average pooling, and ReLU activation to effectively capture and restore clean EEG signals. It demonstrates superior performance, achieving low training and validation losses with a significantly reduced $RRMSE$ value of 0.35 in both the temporal and spectral domains. A high cross-correlation coefficient of 0.94 with ground-truth EEG signals confirms the model’s fidelity. Compared to the existing architectures and models (FPN, UNet, MCGUNet, LinkNet, MultiResUNet3+, Simple CNN, Complex CNN) across a range of signal-to-noise ratio values, the model shows superior performance for artifact removal. It also mitigates overfitting, underscoring its robustness in artifact suppression. Full article

Objectives: Naturally, there are several challenges, such as muscular artifacts, ocular movements and electrical interferences that depend on precise diagnosis and classification, which hamper exact epileptic seizure detection. This study has been conducted to improve seizure detection accuracy in epilepsy patients using an advanced preprocessing technique that could remove such noxious artifacts. Methods: In the frame of this paper, the core tool in the area of epilepsy, EEG, will be applied to record and analyze the electrical patterns of the brain. The dataset includes recordings of seven epilepsy patients taken by the Unit of Neurology and Neurophysiology, University of Siena. The preprocessing techniques employed include advanced artifact removal and signal enhancement methods. We introduced Peak-to-Peak Amplitude Fluctuation (PPAF) to assess amplitude variability within Event-Related Potential (ERP) waveforms. This approach was applied to data from patients experiencing 3–5 seizures, categorized into three distinct groups. Results: The results indicated that the frontal and parietal regions, particularly the electrode areas Cz, Pz and Fp2, are the main contributors to epileptic seizures. Additionally, the implementation of the PPAF metric enhanced the effectiveness of seizure detection and classification algorithms, achieving accuracy rates of 99%, 98% and 95% for datasets with three, four and five seizures, respectively. Conclusions: The present research extends the epilepsy diagnosis with clues on brain activity during seizures and further demonstrates the effectiveness of advanced preprocessing techniques. The introduction of PPAF as a metric could have promising potential in improving both the accuracy and reliability of epilepsy seizure detection algorithms. These observations provide important implications for control and treatment both in focal and in generalized epilepsy. Full article