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Journal of Parkinson's Disease 2024Video-oculography constitutes a highly-sensitive method of characterizing ocular movements, which could detect subtle premotor changes and contribute to the early...
BACKGROUND
Video-oculography constitutes a highly-sensitive method of characterizing ocular movements, which could detect subtle premotor changes and contribute to the early diagnosis of Parkinson's disease (PD).
OBJECTIVE
To investigate potential oculomotor differences between idiopathic PD (iPD) and PD associated with the G2019S variant of LRRK2 (L2PD), as well as to evaluate oculomotor function in asymptomatic carriers of the G2019S variant of LRRK2.
METHODS
The study enrolled 129 subjects: 30 PD (16 iPD, 14 L2PD), 23 asymptomatic carriers, 13 non-carrier relatives of L2PD patients, and 63 unrelated HCs. The video-oculographic evaluation included fixation, prosaccade, antisaccade, and memory saccade tests.
RESULTS
We did not find significant differences between iPD and L2PD. Compared to controls, PD patients displayed widespread oculomotor deficits including larger microsaccades, hypometric vertical prosaccades, increased latencies in all tests, and lower percentages of successful antisaccades and memory saccades. Non-carrier relatives showed oculomotor changes with parkinsonian features, such as fixation instability and hypometric vertical saccades. Asymptomatic carriers shared multiple similarities with PD, including signs of unstable fixation and hypometric vertical prosaccades; however, they were able to reach percentages of successful antisaccade and memory saccades similar to controls, although at the expense of longer latencies. Classification accuracy of significant oculomotor parameters to differentiate asymptomatic carriers from HCs ranged from 0.68 to 0.74, with BCEA, a marker of global fixation instability, being the parameter with the greatest classification accuracy.
CONCLUSIONS
iPD and LRRK2-G2019S PD patients do not seem to display a differential oculomotor profile. Several oculomotor changes in asymptomatic carriers of LRRK2 mutations could be considered premotor biomarkers.
Topics: Humans; Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; Parkinson Disease; Female; Male; Middle Aged; Aged; Ocular Motility Disorders; Saccades; Heterozygote; Adult
PubMed: 38701160
DOI: 10.3233/JPD-230416 -
Optics Letters May 2024Point scanning retinal imaging modalities, including confocal scanning light ophthalmoscopy (cSLO) and optical coherence tomography, suffer from fixational motion...
Point scanning retinal imaging modalities, including confocal scanning light ophthalmoscopy (cSLO) and optical coherence tomography, suffer from fixational motion artifacts. Fixation targets, though effective at reducing eye motion, are infeasible in some applications (e.g., handheld devices) due to their bulk and complexity. Here, we report on a cSLO device that scans the retina in a spiral pattern under pseudo-visible illumination, thus collecting image data while simultaneously projecting, into the subject's vision, the image of a bullseye, which acts as a virtual fixation target. An imaging study of 14 young adult volunteers was conducted to compare the fixational performance of this technique to that of raster scanning, with and without a discrete inline fixation target. Image registration was used to quantify subject eye motion; a strip-wise registration method was used for raster scans, and a novel, to the best of our knowledge, ring-based method was used for spiral scans. Results indicate a statistically significant reduction in eye motion by the use of spiral scanning as compared to raster scanning without a fixation target.
Topics: Humans; Retina; Fixation, Ocular; Ophthalmoscopy; Adult; Young Adult; Eye Movements
PubMed: 38691751
DOI: 10.1364/OL.517088 -
Nature Neuroscience Jun 2024In natural vision, primates actively move their eyes several times per second via saccades. It remains unclear whether, during this active looking, visual neurons...
In natural vision, primates actively move their eyes several times per second via saccades. It remains unclear whether, during this active looking, visual neurons exhibit classical retinotopic properties, anticipate gaze shifts or mirror the stable quality of perception, especially in complex natural scenes. Here, we let 13 monkeys freely view thousands of natural images across 4.6 million fixations, recorded 883 h of neuronal responses in six areas spanning primary visual to anterior inferior temporal cortex and analyzed spatial, temporal and featural selectivity in these responses. Face neurons tracked their receptive field contents, indicated by category-selective responses. Self-consistency analysis showed that general feature-selective responses also followed eye movements and remained gaze-dependent over seconds of viewing the same image. Computational models of feature-selective responses located retinotopic receptive fields during free viewing. We found limited evidence for feature-selective predictive remapping and no viewing-history integration. Thus, ventral visual neurons represent the world in a predominantly eye-centered reference frame during natural vision.
Topics: Animals; Visual Cortex; Macaca mulatta; Eye Movements; Neurons; Male; Photic Stimulation; Visual Perception; Fixation, Ocular; Saccades; Vision, Ocular; Female
PubMed: 38684892
DOI: 10.1038/s41593-024-01631-5 -
Sensors (Basel, Switzerland) Apr 2024Pupil size is a significant biosignal for human behavior monitoring and can reveal much underlying information. This study explored the effects of task load, task...
Pupil size is a significant biosignal for human behavior monitoring and can reveal much underlying information. This study explored the effects of task load, task familiarity, and gaze position on pupil response during learning a visual tracking task. We hypothesized that pupil size would increase with task load, up to a certain level before decreasing, decrease with task familiarity, and increase more when focusing on areas preceding the target than other areas. Fifteen participants were recruited for an arrow tracking learning task with incremental task load. Pupil size data were collected using a Tobii Pro Nano eye tracker. A 2 × 3 × 5 three-way factorial repeated measures ANOVA was conducted using R (version 4.2.1) to evaluate the main and interactive effects of key variables on adjusted pupil size. The association between individuals' cognitive load, assessed by NASA-TLX, and pupil size was further analyzed using a linear mixed-effect model. We found that task repetition resulted in a reduction in pupil size; however, this effect was found to diminish as the task load increased. The main effect of task load approached statistical significance, but different trends were observed in trial 1 and trial 2. No significant difference in pupil size was detected among the three gaze positions. The relationship between pupil size and cognitive load overall followed an inverted U curve. Our study showed how pupil size changes as a function of task load, task familiarity, and gaze scanning. This finding provides sensory evidence that could improve educational outcomes.
Topics: Humans; Pupil; Male; Female; Adult; Young Adult; Eye-Tracking Technology; Fixation, Ocular; Eye Movements
PubMed: 38676162
DOI: 10.3390/s24082545 -
Journal of Vision Apr 2024This paper reviews projection models and their perception in realistic pictures, and proposes hypotheses for three-dimensional (3D) shape and space perception in... (Review)
Review
This paper reviews projection models and their perception in realistic pictures, and proposes hypotheses for three-dimensional (3D) shape and space perception in pictures. In these hypotheses, eye fixations, and foveal vision play a central role. Many past theories and experimental studies focus solely on linear perspective. Yet, these theories fail to explain many important perceptual phenomena, including the effectiveness of nonlinear projections. Indeed, few classical paintings strictly obey linear perspective, nor do the best distortion-avoidance techniques for wide-angle computational photography. The hypotheses here employ a two-stage model for 3D human vision. When viewing a picture, the first stage perceives 3D shape for the current gaze. Each fixation has its own perspective projection, but, owing to the nature of foveal and peripheral vision, shape information is obtained primarily for a small region of the picture around the fixation. As a viewer moves their eyes, the second stage continually integrates some of the per-gaze information into an overall interpretation of a picture. The interpretation need not be geometrically stable or consistent over time. It is argued that this framework could explain many disparate pictorial phenomena, including different projection styles throughout art history and computational photography, while being consistent with the constraints of human 3D vision. The paper reviews open questions and suggests new studies to explore these hypotheses.
Topics: Humans; Fixation, Ocular; Form Perception; Depth Perception; Space Perception; Eye Movements; Fovea Centralis
PubMed: 38662346
DOI: 10.1167/jov.24.4.23 -
Scientific Reports Apr 2024Selective retrieval of context-relevant memories is critical for animal survival. A behavioral index that captures its dynamic nature in real time is necessary to...
Selective retrieval of context-relevant memories is critical for animal survival. A behavioral index that captures its dynamic nature in real time is necessary to investigate this retrieval process. Here, we found a bias in eye gaze towards the locations previously associated with individual objects during retrieval. Participants learned two locations associated with each visual object and recalled one of them indicated by a contextual cue in the following days. Before the contextual cue presentation, participants often gazed at both locations associated with the given object on the background screen (look-at-both), and the frequency of look-at-both gaze pattern increased as learning progressed. Following the cue presentation, their gaze shifted toward the context-appropriate location. Interestingly, participants showed a higher accuracy of memory retrieval in trials where they gazed at both object-associated locations, implying functional advantage of the look-at-both gaze patterns. Our findings indicate that naturalistic eye movements reflect the dynamic process of memory retrieval and selection, highlighting the potential of eye gaze as an indicator for studying these cognitive processes.
Topics: Humans; Male; Female; Mental Recall; Young Adult; Fixation, Ocular; Adult; Eye Movements; Cues; Memory; Learning
PubMed: 38658592
DOI: 10.1038/s41598-024-59815-9 -
Clinical Biomechanics (Bristol, Avon) May 2024Lower limb amputation does not affect only physical and psychological functioning but the use of a prosthetic device can also lead to increased cognitive demands....
BACKGROUND
Lower limb amputation does not affect only physical and psychological functioning but the use of a prosthetic device can also lead to increased cognitive demands. Measuring cognitive load objectively is challenging, and therefore, most studies use questionnaires that are easy to apply but can suffer from subjective bias. Motivated by this, the present study investigated whether a mobile eye tracker can be used to objectively measure cognitive load by monitoring gaze behavior during a set of motor tasks.
METHODS
Five prosthetic users and eight able-bodied controls participated in this study. Eye tracking data and kinematics were recorded during a set of motor tasks (level ground walking, walking on uneven terrain, obstacle avoidance, stairs up and ramp down, as well as ramp up and stairs down) while the participants were asked to focus their gaze on a visual target for as long as possible. Target fixation times and increase in pupil diameters were determined and correlated to subjective ratings of cognitive load.
FINDINGS
Overall, target fixation time and pupil diameter showed strong negative and positive correlations, respectively, to the subjective rating of cognitive load in the able-bodied controls (-0.75 and 0.80, respectively). However, the individual correlation strength, and in some cases, even the sign, was different across participants. A similar trend could be observed in prosthetic users.
INTERPRETATION
The results of this study showed that a mobile eye tracker may be used to estimate cognitive load in prosthesis users during locomotor tasks. This paves the way to establish a new approach to assessing cognitive load, which is objective and yet practical and simple to administer. Nevertheless, future studies should corroborate these results by comparing them to other objective measures as well as focus on translating the proposed approach outside of a laboratory.
Topics: Humans; Walking; Artificial Limbs; Male; Eye-Tracking Technology; Cognition; Adult; Female; Fixation, Ocular; Lower Extremity; Biomechanical Phenomena; Middle Aged; Amputees; Eye Movements
PubMed: 38657356
DOI: 10.1016/j.clinbiomech.2024.106250 -
Journal of Vision Apr 2024We obtain large amounts of external information through our eyes, a process often considered analogous to picture mapping onto a camera lens. However, our eyes are never...
We obtain large amounts of external information through our eyes, a process often considered analogous to picture mapping onto a camera lens. However, our eyes are never as still as a camera lens, with saccades occurring between fixations and microsaccades occurring within a fixation. Although saccades are agreed to be functional for information sampling in visual perception, it remains unknown if microsaccades have a similar function when eye movement is restricted. Here, we demonstrated that saccades and microsaccades share common spatiotemporal structures in viewing visual objects. Twenty-seven adults viewed faces and houses in free-viewing and fixation-controlled conditions. Both saccades and microsaccades showed distinctive spatiotemporal patterns between face and house viewing that could be discriminated by pattern classifications. The classifications based on saccades and microsaccades could also be mutually generalized. Importantly, individuals who showed more distinctive saccadic patterns between faces and houses also showed more distinctive microsaccadic patterns. Moreover, saccades and microsaccades showed a higher structure similarity for face viewing than house viewing and a common orienting preference for the eye region over the mouth region. These findings suggested a common oculomotor program that is used to optimize information sampling during visual object perception.
Topics: Humans; Saccades; Male; Female; Adult; Fixation, Ocular; Young Adult; Visual Perception; Photic Stimulation; Pattern Recognition, Visual
PubMed: 38656530
DOI: 10.1167/jov.24.4.20 -
Taiwan Journal of Ophthalmology 2024The purpose of the study was to report the complications of sutureless intrascleral (SIS) intraocular lens (IOL) fixation and its management.
PURPOSE
The purpose of the study was to report the complications of sutureless intrascleral (SIS) intraocular lens (IOL) fixation and its management.
MATERIALS AND METHODS
A multicenter, retrospective, consecutive interventional case series of patients with intra or postoperative complications after SIS IOL fixation during the technical learning curve of vitreoretinal surgeons from three Taiwanese referral hospitals. The used surgical techniques were the Scharioth technique for intrascleral tunnel fixation, Yamane technique (double-needle scleral fixation), and modified Yamane technique (double-needle flanged haptic scleral fixation). The IOL models and surgical instruments used as well as each patient's ocular characteristics and complication management were recorded.
RESULTS
Of the eight included patients, the complications of 3 (37.5%) and 5 (62.5%) were noted intraoperatively and postoperatively, respectively. Haptic-related complications, including haptic breakage, slippage, and haptic disinsertion, occurred in six eyes. Other complications included uveitis-glaucoma-hyphema syndrome, retinal detachment, and IOL tilt. For the two patients with haptic slippage, repositioning was achieved using a modified cow-hitch technique that resulted in favorable IOL centration and restored visual acuity.
CONCLUSION
Most complications surgeons encountered during their early exposure to SIS IOL fixation were haptic related. Surgeons should be aware of such complications to prevent and manage them during surgery. Our modified cow-hitch technique could be used to reposition IOLs with unilateral haptic slippage.
PubMed: 38654989
DOI: 10.4103/tjo.TJO-D-23-00163