Recent research supports impairments in fixational eye movements (FEMs), small motions of the eye that occur during periods when gaze is maintained on a fixed target, as an objective biomarker of concussion. Preliminary work has demonstrated that fixational saccades are larger following a concussion; however, sex differences in FEMs and fixational saccades have not been examined. In this study, we used retinal image-based eye tracking, with a tracking scanning laser ophthalmoscope (TSLO), to record FEMs while adolescents with concussion (n = 44; age range, 13–27 years) and age- and sex-matched healthy controls (n = 44; age range, 13–27 years) fixated the center or corner of the TSLO imaging raster. To improve reliability and overcome errors associated with the manual labeling of FEMs, an objective velocity-based algorithm was used to detect fixational saccades. Concussion patients made larger fixational saccades than controls but only on the center task. Females made larger fixational saccades than males on this task irrespective of injury group, whereas no significant difference was supported for the corner task. Females also made fewer horizontal and more oblique fixational saccades than males on the corner task. These findings highlight the importance of controlling for task- and sex-specific differences when evaluating FEMs as a biomarker for concussion.

BackgroundVideo-based eye trackers are widely used in vision science, psychology, clinical assessment, and neurophysiology. Many such systems track the pupil center and corneal reflection (P-CR) and compare their positions to estimate the direction of gaze. However, P-CR eye trackers are often too imprecise for applications with stringent eye tracking quality requirements.New methodWe present OpenIrisDPI, an open-source plugin for the OpenIris framework that implements dual Purkinje image (DPI) tracking. OpenIrisDPI supports simultaneous pupillography, a technique widely used in perceptual psychology and neuroscience, and it enables direct comparison between P-CR and DPI signals.ResultsData collected from macaque monkeys using OpenIrisDPI show that the P-CR method overestimates the amount of fixational drift between saccades compared to DPI. The accuracy of the DPI signal was further validated using high-density extracellular recording of neurons in the lateral geniculate nucleus. Compensating for the effects of fixational eye movements using DPI signals produced sharper estimates of neuronal receptive fields than using simultaneously collected P-CR signals.Comparison with existing methodsOpenIrisDPI is provided as open-source software and operates on consumer-grade hardware, making it more accessible than previously described DPI eye trackers and less costly than many P-CR systems. To our knowledge, OpenIrisDPI is the first eye tracker to perform both pupillography and DPI eye tracking.ConclusionOpenIrisDPI makes high-precision eye tracking readily available to the research community. It is well suited for visual neuroscience applications, where accurate knowledge of the retinal image during experiments is critical.

Non-uniform signal pooling across the foveola.

In many tasks, participants are instructed to fixate a target. While maintaining fixation, the eyes nonetheless make small fixational eye movements, such as microsaccades and drift. Previous work has examined the effect of fixation point design on fixation stability and the amount and spatial extent of fixational eye movements. However, much of this work used video-based eye trackers, which have insufficient resolution and suffer from artefacts that make them unsuitable for this topic of study. Here, we therefore use a retinal eye tracker, which offers superior resolution and does not suffer from the same artifacts to reexamine what fixation point design minimizes fixational eye movements. Participants were shown five fixation targets in two target polarity conditions, while the overall spatial spread of their gaze position during fixation, as well as their microsaccades and fixational drift, were examined. We found that gaze was more stable for white-on-black than black-on-grey fixation targets. Gaze was also more stable (lower spatial spread, microsaccade, and drift displacement) for fixation targets with a small central feature but these targets also yielded higher microsaccade rates than larger fixation targets without such a small central feature. In conclusion, there is not a single best fixation target that minimizes all aspects of fixational eye movements. Instead, if one wishes to optimize for minimal spatial spread of the gaze position, microsaccade or drift displacements, we recommend using a target with a small central feature. If one instead wishes to optimize for the lowest microsaccade rate, we recommend using a larger target without a small central feature.

Fixational saccadic eye movements (microsaccades) have been associated with cognitive processes, especially in tasks requiring spatial attention and memory. Alterations in oculomotor and cognitive control are commonly observed in Parkinson’s disease (PD), though it is unclear to what extent microsaccade activity is affected. We acquired eye movement data from sixteen participants with early-stage PD and thirteen older healthy controls to examine the effects of dopamine modulation on microsaccade activity during the delay period of a spatial working memory task. Some microsaccade characteristics, like amplitude and duration, were moderately larger in the PD participants when they were “on” their dopaminergic medication than healthy controls, or when they were “off” medication, while PD participants exhibited microsaccades with a linear amplitude–velocity relationship comparable to controls. Both groups showed similar microsaccade rate patterns across task events, with most participants showing a horizontal bias in microsaccade direction during the delay period regardless of the remembered target location. Overall, our data suggest minimal involvement of microsaccades during visuospatial working memory maintenance under conditions without explicit attentional cues in both subject groups. However, moderate effects of PD-related dopamine deficiency were observed for microsaccade size during working memory maintenance.

The N2pc is a popular human-neuroscience marker of covert and internal spatial attention that occurs 200-300 ms after being prompted to shift attention-a time window also characterized by the spatial biasing of small fixational eye movements known as microsaccades. Here, we show how co-occurring microsaccades profoundly modulate N2pc amplitude during top-down shifts of spatial attention in both perception and working memory. At the same time, we show that a significant-albeit severely weakened-N2pc can still be established in the absence of co-occurring microsaccades. Moreover, despite the strong modulation of the N2pc by microsaccade presence and direction, the N2pc does not align to the precise timing of microsaccades, ruling out that the observed N2pc modulations by microsaccades are a direct artifact of microsaccade-related eye-muscle activity, corneo-retinal dipole movement, or visual inputs moving over the retina. Thus, while microsaccades strongly modulate N2pc amplitude, microsaccades themselves are not a prerequisite for, nor a direct cause of, the N2pc.

There is limited evidence of recording eye movements in real-time while performing specific motor tasks in team games in response to environmental stimuli. This study aimed to examine how elite basketball and volleyball athletes adopted strategies during agility tasks, based on the type of team sports and gender. A total of 60 skilled players from both sports (30 males and 30 females), aged 16–18 years, participated in this study. Agility variables were assessed using the “Five-Time Shuttle Run to Gates” test, based on the “stop and go” protocol. To determine variables of fixation and saccade eye movements during the agility task, a mobile eye-tracking system was employed. MANOVA showed statistically significant main effects of gender and the type of team sport on agility (for both factors, p < 0.001, η2part > 0.14) and on the number of saccades (η2part = 0.16, p = 0.002; η2part = 0.10, p = 0.018). Additionally, gender affected the number of fixations (η2part = 0.08, p = 0.037). Regression analysis was used to explore the correlation between oculomotor variables and agility, indicating that for female basketball players, the number of saccades (ß = 1.04, B = 0.10) and the average velocity of saccades (ß = 0.79, B = 0.02) were the primary factors explaining agility variability. However, for male basketball players, agility test outcomes were largely determined by the duration of saccadic movements (ß = 0.79, B = 0.02). The findings suggest that the oculomotor scanning strategy in agility tasks significantly impacts athletic performance, and is influenced by the type of team sports and gender.

Fixational eye movements and visual acuity in patients with schizophrenia

Exploring the limits to the “illusion of relative stability” of images slipping consistent to fixational eye motion

Is to develop a method for comprehensive assessment of fixation eye movements in patients with cognitive impairment. The study uses the Pupil Invisible eye-tracker. Using the PsychoPy software, a sequence of visual stimuli with audio and text accompaniment was created. Two consecutive tasks were set for the subjects: passive examination and memorization of images and search for a specific element on the presented image. To assess the experiment, we reviewed the entire testing record with all events occurring during the test. It was found that the standard method of evaluating test results by viewing and analyzing video recordings was unacceptably time-consuming for the researcher. The large volume of obtained results and the lack of standard calculation methods complicated the mathematical processing, so additional software using Wolfram and Python was developed. A unique feature of the developed technique is the division of the constructed heat map based on the fixation movements of the eyes into a certain number of zones, which is achieved by calculating the area of a particular sector of the image related to the total area of the stimulus when performing the task. The experimental verification of the model revealed a «disorderly» direction of gaze without fixing the specified image, an increase in the size of the «heat» spot in a patient diagnosed with primary amnesic aphasia, which differed from those indicators of healthy individuals. As part of the study, a method was developed for assessing integrative indicators of eyeball movements, which may reflect the state of cognitive functions. In the second stage of the study, the sample of patients is planned to increase to identify characteristic patterns of changes in eye movements when performing cognitive tasks, both in healthy individuals and in patients with cognitive impairment caused by various nervous system diseases.

Amblyopia, a neurodevelopmental disorder, is commonly assessed through amblyopic eye visual acuity (VA) deficits, but recent studies also highlight abnormalities in the fellow eye. This study quantified binocular and fellow/dominant eye VA in individuals with amblyopia and strabismus without amblyopia and examined factors influencing these measures, including fixation eye movement (FEM) abnormalities. Identifying which subsets of patients—such as those with nystagmus, concurrent strabismus, or greater fixation instability—exhibit more pronounced deficits in binocular visual acuity and binocular summation can enhance clinical decision-making by enabling tailored interventions and aiding patient counseling. Sixty-eight amblyopic, seventeen strabismic without amblyopia, and twenty-four control subjects were assessed using an adaptive psychophysical staircase procedure and high-resolution video-oculography to evaluate FEMs and fixation instability (FI). Binocular and fellow eye VA were significantly lower in amblyopia, regardless of type or nystagmus presence, whereas binocular and dominant eye VA in strabismus without amblyopia did not differ from the controls. Despite reduced binocular acuity, amblyopic and strabismic subjects exhibited binocular summation, with binocular VA exceeding fellow/dominant eye VA. Reduced binocular VA correlated with greater fellow eye VA deficits, diminished binocular summation, and increased FI in the amblyopic eye. Fellow eye VA deficits were linked to greater amblyopic eye VA deficits, an increased degree of anisometropia, higher FI, and stronger nystagmus correlation. These findings suggest amblyopia affects both visual sensory and motor systems, impacting binocular function and fixation stability, with potential consequences for everyday visuomotor tasks like reading.

Abstract Active vision enables dynamic and robust visual perception, offering an alternative to the static, passive nature of feedforward architectures commonly used in computer vision, which depend on large datasets and high computational resources. Biological selective attention mechanisms allow agents to focus on salient regions of interest (ROIs), reducing computational demand while maintaining real-time responsiveness. Event-based cameras, inspired by the mammalian retina, further enhance this capability by capturing asynchronous scene changes, enabling efficient, low-latency processing. To distinguish moving objects while the event-based camera is also in motion, the agent requires an object motion segmentation mechanism to accurately detect targets and position them at the centre of the visual field (fovea). Integrating event-based sensors with neuromorphic algorithms represents a paradigm shift, using spiking neural networks (SNNs) to parallelise computation and adapt to dynamic environments. This work presents a spiking convolutional neural network bioinspired attention system for selective attention through object motion sensitivity. The system generates events via fixational eye movements using a dynamic vision sensor integrated into the Speck neuromorphic hardware, mounted on a Pan–Tilt unit, to identify the ROI and saccade toward it. The system, characterised using ideal gratings and benchmarked against the event camera motion segmentation dataset, reaches a mean IoU of 82.2% and a mean structural similarity index of 96% in multi-object motion segmentation. Additionally, the detection of salient objects reaches an accuracy of 88.8% in office scenarios and 89.8% in challenging indoor and outdoor low-light conditions, as evaluated on the event-assisted low-light video object segmentation dataset. A real-time demonstrator showcases the system’s capabilities of detecting the salient object through object motion sensitivity in 0.124 s in dynamic scenes. Its learning-free design ensures robustness across diverse perceptual scenes, making it a reliable foundation for real-time robotic applications and serving as a basis for more complex architectures. Media: The accompanying video can be found online7 7 https://youtu.be/dcAJlDgVR0o. .

The purpose of this study was to characterize the preferred retinal locus (PRL) structure and fixational eye movements in eyes with macular atrophy. Four participants (1 each with macular atrophy due to congenital rubella, Best macular dystrophy, cuticular drusen with macular atrophy, and Stargardt disease) were studied using adaptive optics scanning light ophthalmoscopy (AOSLO), optical coherence tomography (OCT), OCT angiography (OCT-A), and microperimetry. Imaging sessions were repeated in three of the four participants. PRL and fixation stability were measured with AOSLO. Fixation stability was compared with healthy participants and participants with RHO- and USH2A-related retinitis pigmentosa (RP). The PRL in participants with eccentric fixation was 0.44 to 1.92degrees from the anatomic fovea and visual acuity was 20/40 or better. Cones at the PRL were not visible in confocal images, despite normal-appearing and more sensitive cones at greater eccentricities. OCT at the PRL showed intact external limiting membranes but hyporeflective and disrupted inner-segment outer-segment junctions. Fixation stability in participants with eccentric PRLs was no worse than participants with RP, all with foveal PRLs. The eccentric PRL group and the USH2A group with worse visual acuity (20/30 to 20/50) had fixation stabilities that were worse than the healthy controls. Participants adopt eccentric PRLs with hyporeflective cones and reduced sensitivity despite more sensitive and normal-appearing cones at greater eccentricities, suggesting that foveal proximity is prioritized over cone integrity in establishing a PRL. Fixation stability was similar among the four participants with eccentric fixation and those with RP, indicating that small shifts in the PRL from the anatomic fovea in our participants do not make fixation less stable.

ObjectiveTo investigate the effects of myopic spherical equivalent (SE) on random dot stereopsis and influencing factors in Chinese adults with myopia.MethodsA cross-sectional design was employed, and 988 Chinese myopic individuals (520 [52.6%] females) aged 18.0–48.7 years were recruited from the People’s Hospital of Guangxi. The participants underwent assessments for visual acuity, myopic SE, random dot stereopsis at 0.8 m (RDS0.8) and at 1.5 m (RDS1.5) and binocular function parameters (such as perceptual eye position (PEP), fixational eye movement, and the signal‒noise ratio (SNR)). The data were analysed via Pearson or Spearman correlations and multivariate logistic regression.ResultsAmong the 988 participants, only 53 (5.4%) presented with abnormal RDS0.8, and 834 (84.4%) presented with abnormal RDS1.5. A significant association was found between SE and the prevalence of abnormal RDS1.5 (OR: 1.14, 95% CI: 1.03–1.26; P = 0.014) after adjusting for covariates. High myopia was more strongly associated with abnormal RDS1.5 than mild myopia was in the unadjusted model (OR: 1.85, 95% CI: 1.03–3.26; P = 0.037). Subgroup analyses revealed that the associations between SE and abnormal RDS1.5 were stronger among females, individuals aged > 25 years, those with normal fixational eye movement, and those with abnormal SNRs. Only vertical PEP (target 1°) was significantly associated with myopic group and abnormal RDS0.8, whereas vertical PEP (target 3°), horizontal PEP (target 1°), and vertical PEP (target 1°) were significantly associated with abnormal RDS1.5.ConclusionsMyopic SE was associated with the prevalence of abnormal random dot stereopsis at 1.5 m in myopic patients, indicating that increasing myopic SE may impair distance random dot stereopsis in this population.Clinical trial numberNot applicable.

Pupil dynamics and fixational eye movements are primarily involuntary processes that actively support visual perception during fixations. Both measures are known to be sensitive to ongoing cognitive and affective processing. In a visual fixation experiment (N = 116), we demonstrate that self-recognition, familiar faces, and unfamiliar faces elicit specific responses in pupil dynamics and microsaccade rate. First, the pupil response comprises an immediate pupil constriction, followed by a dilation in response to stimulus onsets. We observe attenuated constriction and greater dilation when faces are recognized compared to unknown faces. This effect is strongest for one's own face. Second, microsaccade rates, which generally show inhibitory responses to incoming stimuli, generate stronger inhibition for familiar faces compared to unknown faces. Again, the strongest inhibition is observed in response to one's own face. Our results imply that eye-related physiological measures expose hidden knowledge in face memory and could contribute to biometric authentication and identity validation procedures.

We introduce a principle, Oz, for displaying color imagery: directly controlling the human eye's photoreceptor activity via cell-by-cell light delivery. Theoretically, novel colors are possible through bypassing the constraints set by the cone spectral sensitivities and activating M cone cells exclusively. In practice, we confirm a partial expansion of colorspace toward that theoretical ideal. Attempting to activate M cones exclusively is shown to elicit a color beyond the natural human gamut, formally measured with color matching by human subjects. They describe the color as blue-green of unprecedented saturation. Further experiments show that subjects perceive Oz colors in image and video form. The prototype targets laser microdoses to thousands of spectrally classified cones under fixational eye motion. These results are proof-of-principle for programmable control over individual photoreceptors at population scale.

We explored how fixational eye movements (FEMs) affect threshold temporal summation of increment pulses using realistic simulations of early visual processing. Using the Image Systems Engineering Toolbox for Biology, we assessed performance in a spatial 2AFC increment detection task, where the observer identified whether a stimulus appeared on the left or right. The signal-known-exactly ideal observer was trained on the noise-free photocurrent output of the cone mosaic for both stimulus alternatives, with performance calculated using noisy instances of photocurrents, given FEMs knowledge. The stimuli, modelled as 0.24x2.2 arcmin increments of 543 nm light presented via an AOSLO, included both a single 2 ms flash and pairs of flashes separated by interstimulus intervals (ISI) of 17 ms, 33 ms, 100 ms, or 300 ms. Detection thresholds, defined as the stimulus contrast corresponding to 75% correct, were assessed with and without FEMs. Without FEMs, thresholds for detecting two flashes separated by 17-100 ms slightly increased with ISI but remained lower than those for a single flash. With FEMs, the modelled differences between single- and two-flash thresholds were less pronounced, suggesting that, at the level of photocurrent signals, FEMs reduce the benefits of temporal summation for detection. Future work will quantify this reduction by simulating FEMs with varying velocities and explore if adding a temporal adaptation stage improves effect of FEMs' on performance.

Fixational eye movements (FEMs) are small, fluctuating eye motions when fixating on a target. Given our visual system is evolved, we may ask why FEMs are beneficial and whether they are optimal. A possible reason for FEMs is overcoming retinal adaptation (fading perception of a fixed image). We present a simple model system allowing theoretical investigation of FEM influence on information about an external stimulus. The model incorporates temporal stimulus modulation, retinal image motion due to the drift component of FEMs, blurring due to optics and receptor size, uniform sampling by the receptor array, adaptation via a bandpass temporal filter, and added noise. We investigate how elements of the model mediate the information transmitted, via: i) mutual information between visual system response and external stimulus, ii) direct estimation of stimulus from the system response, and iii) contrast threshold for signal detection. For all these we find a common quantity that must be maximized. For each spatial frequency this quantity is a summed power transmitted due to stimulus temporal modulation and phase shifts from FEMs, when passed through the temporal filter. We demonstrate that the information transmitted can be increased by adding local persistence to an underlying diffusive process. We also quantify the contribution of FEMs to signal detection for targets of different size and duration; such predictions provide a qualitative account of human psychophysical performance.

Vision is an active process even at its finest scale in the 1-deg foveola, the visual system is primarily sensitive to changes in the visual input and it has been shown that fixational eye movements reformat the spatiotemporal flow to the retina in a way that is optimal for fine spatial vision. Using high-precision eye-tracking coupled with a system for gaze-contingent display capable of localizing the line of sight with arcminute precision, and an Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) for high-resolution retinal imaging enabling retinal-contingent manipulations of the visual input, our results show that the need for active foveolar vision also stems from the non-uniformity of fine spatial vision across this region. Further, we show that the visual system is highly sensitive even to a small sub-foveolar loss of vision and fixation behavior is readjusted to compensate for this loss. Overall, the emerging picture is that of a highly non-homogenous foveolar vision characterized by a refined level of control of attention and fixational eye movements at this scale.

Fixational eye movements (FEMs), especially microsaccades (MS), are promising biomarkers of neurodegenerative disease. In vivo images of the photoreceptor mosaic acquired using an Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) are systematically distorted by eye motion. Most methods to extract FEMs from AOSLO data rely on comparison to a motion-free reference, giving eye-position as a function of time. MS are subsequently identified using adaptive velocity thresholds (Engbert & Kliegl, 2003). We use computer vision and machine learning (ML) for detection and characterisation of MS directly from raw AOSLO images. For training and validation, we use Emulated Retinal Image CApture (ERICA), an open-source tool to generate synthetic AOSLO datasets of retinal images and ground-truth velocity profiles (Young & Smithson, 2021). To classify regions of AOSLO images that contain a MS, images were divided into a grid of 32-by-32-pixel sub-images. Predictions from rows of sub-images aligned with the fast-scan of the AOSLO were combined, giving 1ms resolution. Model performance was high (F1 scores >0.92) across plausible MS displacement magnitudes and angles, with most errors close to the velocity threshold for classification. Direct velocity predictions were also derived from regression ML models. We show that ML models can be systematically adapted for generalisation to real in vivo images, allowing characterisation of MS at much finer spatial scales than video-based eye-trackers.