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Biomedical Optics Express May 2024Accommodation is the process by which the eye changes focus. These changes are the result of changes to the shape of the crystalline lens. Few prior studies have...
Accommodation is the process by which the eye changes focus. These changes are the result of changes to the shape of the crystalline lens. Few prior studies have quantified the relation between lens shape and ocular accommodation, primarily at discrete static accommodation states. We present an instrument that enables measurements of the relation between changes in lens shape and changes in optical power continuously during accommodation. The system combines an autorefractor to measure ocular power, a visual fixation target to stimulate accommodation, and an optical coherence tomography (OCT) system to image the anterior segment and measure ocular distances. Measurements of ocular dimensions and refraction acquired dynamically on three human subjects are presented. The individual accommodative responses are analyzed to correlate the ocular power changes with changes in ocular dimensions.
PubMed: 38855690
DOI: 10.1364/BOE.512193 -
Journal of Vision Jun 2024The interception (or avoidance) of moving objects is a common component of various daily living tasks; however, it remains unclear whether precise alignment of foveal...
The interception (or avoidance) of moving objects is a common component of various daily living tasks; however, it remains unclear whether precise alignment of foveal vision with a target is important for motor performance. Furthermore, there has also been little examination of individual differences in visual tracking strategy and the use of anticipatory gaze adjustments. We examined the importance of in-flight tracking and predictive visual behaviors using a virtual reality environment that required participants (n = 41) to intercept tennis balls projected from one of two possible locations. Here, we explored whether different tracking strategies spontaneously arose during the task, and which were most effective. Although indices of closer in-flight tracking (pursuit gain, tracking coherence, tracking lag, and saccades) were predictive of better interception performance, these relationships were rather weak. Anticipatory gaze shifts toward the correct release location of the ball provided no benefit for subsequent interception. Nonetheless, two interceptive strategies were evident: 1) early anticipation of the ball's onset location followed by attempts to closely track the ball in flight (i.e., predictive strategy); or 2) positioning gaze between possible onset locations and then using peripheral vision to locate the moving ball (i.e., a visual pivot strategy). Despite showing much poorer in-flight foveal tracking of the ball, participants adopting a visual pivot strategy performed slightly better in the task. Overall, these results indicate that precise alignment of the fovea with the target may not be critical for interception tasks, but that observers can adopt quite varied visual guidance approaches.
Topics: Humans; Male; Female; Young Adult; Motion Perception; Adult; Individuality; Psychomotor Performance; Fixation, Ocular; Virtual Reality; Saccades; Fovea Centralis; Eye Movements
PubMed: 38842836
DOI: 10.1167/jov.24.6.4 -
Scientific Reports Jun 2024Accurate, and objective diagnosis of brain injury remains challenging. This study evaluated useability and reliability of computerized eye-tracker assessments (CEAs)...
Accurate, and objective diagnosis of brain injury remains challenging. This study evaluated useability and reliability of computerized eye-tracker assessments (CEAs) designed to assess oculomotor function, visual attention/processing, and selective attention in recent mild traumatic brain injury (mTBI), persistent post-concussion syndrome (PPCS), and controls. Tests included egocentric localisation, fixation-stability, smooth-pursuit, saccades, Stroop, and the vestibulo-ocular reflex (VOR). Thirty-five healthy adults performed the CEA battery twice to assess useability and test-retest reliability. In separate experiments, CEA data from 55 healthy, 20 mTBI, and 40 PPCS adults were used to train a machine learning model to categorize participants into control, mTBI, or PPCS classes. Intraclass correlation coefficients demonstrated moderate (ICC > .50) to excellent (ICC > .98) reliability (p < .05) and satisfactory CEA compliance. Machine learning modelling categorizing participants into groups of control, mTBI, and PPCS performed reasonably (balanced accuracy control: 0.83, mTBI: 0.66, and PPCS: 0.76, AUC-ROC: 0.82). Key outcomes were the VOR (gaze stability), fixation (vertical error), and pursuit (total error, vertical gain, and number of saccades). The CEA battery was reliable and able to differentiate healthy, mTBI, and PPCS patients reasonably well. While promising, the diagnostic model accuracy should be improved with a larger training dataset before use in clinical environments.
Topics: Humans; Adult; Male; Female; Eye-Tracking Technology; Brain Concussion; Machine Learning; Middle Aged; Young Adult; Eye Movements; Reproducibility of Results; Reflex, Vestibulo-Ocular; Post-Concussion Syndrome; Saccades; Attention
PubMed: 38830966
DOI: 10.1038/s41598-024-63540-8 -
International Medical Case Reports... 2024Although ab-interno trabeculotomy-related (goniotomy-related) surgeries has a favorable safety profile, cyclodialysis cleft refractory to conservative management could...
INTRODUCTION
Although ab-interno trabeculotomy-related (goniotomy-related) surgeries has a favorable safety profile, cyclodialysis cleft refractory to conservative management could occur, thereby requiring additional surgical treatment. External and, more recently, internal cycloplexy have been attempted to treat cyclodialysis clefts with hypotony maculopathy, however the traditional methods require conjunctival or scleral incisions and have been inappropriate for glaucoma patients who need to undergo future trabeculectomy. Therefore, we report two cases who underwent a novel reliable technique for suture fixation of the detached ciliary body onto the original scleral bed directly through the intraocular approach without conjunctival or scleral incision, minimally invasive direct internal cyclopexy, in the management of goniotomy-related cyclodialysis cleft with hypotony maculopathy.
CASE DESCRIPTION
Goniotomy-related cyclodialysis cleft exceeded 45° and vision-threatening hypotony maculopathy was observed in two eyes in two patients with normal tension glaucoma and myopia gravis without a prior history of trauma who had undergone Kahook Dual Blade goniotomy combined with cataract surgery. The patients were followed conservatively for a while, however the cyclodialysis clefts and hypotony maculopathies did not resolve. Therefore, a 72-year-old man underwent minimally invasive direct internal cyclopexy on postoperative day 65 after the goniotomy, and another 67-year-old man underwent minimally invasive direct internal cyclopexy on postoperative day 149. In both cases, topical antibiotic and steroid eye drops were prescribed postoperatively. The cyclodialysis clefts were repaired successfully; however, the latter patient developed delayed-onset acute transient ocular hypertension 33 days after minimally invasive direct internal cyclopexy and required glaucoma medications. The hypotony maculopathies resolved approximately 3 months after suturing, and eventually visual acuity improved from preoperative levels and good intraocular pressure control was achieved in both. No further postoperative complications have been observed to date.
CONCLUSION
We successfully managed two cases of goniotomy-related cyclodialysis cleft with hypotony maculopathy using minimally invasive direct internal cyclopexy.
PubMed: 38828363
DOI: 10.2147/IMCRJ.S469028 -
Scientific Reports May 2024During the pandemic, digital communication became paramount. Due to the discrepancy between the placement of the camera and the screen in typical smartphones, tablets...
During the pandemic, digital communication became paramount. Due to the discrepancy between the placement of the camera and the screen in typical smartphones, tablets and laptops, mutual eye contact cannot be made in standard video communication. Although the positive effect of eye contact in traditional communication has been well-documented, its role in virtual contexts remains less explored. In this study, we conducted experiments to gauge the impact of gaze direction during a simulated online job interview. Twelve university students were recruited as interviewees. The interview consisted of two recording sessions where they delivered the same prepared speech: in the first session, they faced the camera, and in the second, they directed their gaze towards the screen. Based on the recorded videos, we created three stimuli: one where the interviewee's gaze was directed at the camera (CAM), one where the interviewee's gaze was skewed downward (SKW), and a voice-only stimulus without camera recordings (VO). Thirty-eight full-time workers participated in the study and evaluated the stimuli. The results revealed that the SKW condition garnered significantly less favorable evaluations than the CAM condition and the VO condition. Moreover, a secondary analysis indicated a potential gender bias in evaluations: the female evaluators evaluated the interviewees of SKW condition more harshly than the male evaluators did, and the difference in some evaluation criteria between the CAM and SKW conditions was larger for the female interviewees than for the male interviewees. Our findings emphasize the significance of gaze direction and potential gender biases in online interactions.
Topics: Humans; Female; Male; Adult; Fixation, Ocular; Young Adult; Video Recording; Eye Movements; Interviews as Topic; COVID-19
PubMed: 38821979
DOI: 10.1038/s41598-024-60371-5 -
Journal of Vision May 2024What is the link between eye movements and sensory learning? Although some theories have argued for an automatic interaction between what we know and where we look that...
What is the link between eye movements and sensory learning? Although some theories have argued for an automatic interaction between what we know and where we look that continuously modulates human information gathering behavior during both implicit and explicit learning, there exists limited experimental evidence supporting such an ongoing interplay. To address this issue, we used a visual statistical learning paradigm combined with a gaze-contingent stimulus presentation and manipulated the explicitness of the task to explore how learning and eye movements interact. During both implicit exploration and explicit visual learning of unknown composite visual scenes, spatial eye movement patterns systematically and gradually changed in accordance with the underlying statistical structure of the scenes. Moreover, the degree of change was directly correlated with the amount and type of knowledge the observers acquired. This suggests that eye movements are potential indicators of active learning, a process where long-term knowledge, current visual stimuli and an inherent tendency to reduce uncertainty about the visual environment jointly determine where we look.
Topics: Humans; Eye Movements; Learning; Male; Young Adult; Female; Adult; Photic Stimulation; Visual Perception; Fixation, Ocular
PubMed: 38819805
DOI: 10.1167/jov.24.5.17 -
The Medical Journal of Malaysia May 2024Acute acquired concomitant esotropia (AACE) is an uncommon type of strabismus that occurs due to interruption of fusion. Limited data are available on AACE from Asian...
INTRODUCTION
Acute acquired concomitant esotropia (AACE) is an uncommon type of strabismus that occurs due to interruption of fusion. Limited data are available on AACE from Asian countries especially from the Southeast Asian region. We aim to describe the clinical profile and surgical outcomes of AACE patients treated in a tertiary hospital in Malaysia.
MATERIALS AND METHODS
We conducted a retrospective study of 20 patients aged 3-26 years who were diagnosed with AACE and attended Hospital Universiti Sains Malaysia, Kelantan, Malaysia, between January 2020 and June 2022 with follow-up periods a minimum of 12 months. Demographic data, clinical features, neuroimaging, surgical intervention, and final ocular alignment outcomes were recorded.
RESULTS
The mean age of onset was 9.7±6.6 years. There were equal numbers of males and females in this study. Hypermetropia (45%) was the leading refractive error. Angle of deviation of 50 PD and more was documented in 50% of the patients at distance, and 70% of the patients at near fixation. Fifty per cent had an absence of stereoacuity at presentation. Neuroimaging was performed on 13 patients (65%), and two patients had intracranial pathology. All patients underwent bilateral medial rectus recession during primary surgery. Eighteen patients (90%) experienced excessive near work-related activities for >4 hours per day, and 19 patients (95%) achieved good ocular alignment, restoration of stereoacuity and resolved diplopia after the surgical intervention.
CONCLUSION
The mean age of onset was 9.7±6.6 years. Almost half of our patients had uncorrected hypermetropia. Furthermore, 90% of patients had excessive near-work activities, and 95% achieved good post-surgery alignment.
Topics: Humans; Esotropia; Male; Female; Malaysia; Retrospective Studies; Tertiary Care Centers; Adult; Adolescent; Child; Young Adult; Child, Preschool; Ophthalmologic Surgical Procedures; Treatment Outcome; Oculomotor Muscles
PubMed: 38817064
DOI: No ID Found -
Canadian Journal of Ophthalmology.... May 2024To evaluate wolfram as a photon and beta absorber in the management of uveal melanoma with radiotherapy, examining its potential ocular adverse effects and physiologic... (Review)
Review
OBJECTIVE
To evaluate wolfram as a photon and beta absorber in the management of uveal melanoma with radiotherapy, examining its potential ocular adverse effects and physiologic tolerance using an in vivo rabbit ocular model.
METHODS
A method of manufacturing implants from mixtures of wolfram and silicone was developed. Their shielding effect on the radiation of sources used in ocular brachytherapy was investigated by dosimetric measurement in an eye phantom as well as numerical simulations. Different wolfram implantation techniques, such as extraocular fixation of a wolfram-silicone implant (n = 1), vitrectomy with silicone oil and intravitreal injection of a wolfram-silicone oil suspension (n = 2), and concurrent attachment of a wolfram implant onto the sclera (n = 2), were tested to investigate the long-term effects of wolfram. A vitrectomy with silicone oil without wolfram implantation was carried out in 2 rabbits (n = 2), constituting the control group. The eyes were enucleated after 3 months for histologic analysis.
RESULTS
Wolfram-silicone mixtures have been dosimetrically proven to be very effective radiation absorbers for use in ocular brachytherapy. Severe complications, such as endophthalmitis, secondary glaucoma, cornea decompensation, and vessel occlusion, were not documented in the tested rabbit eyes after the application of wolfram. Histologic examination of the bulbi after enucleation showed epiretinal gliosis without further pathologic findings in all eyes after vitrectomy.
CONCLUSIONS
The results of this study show that wolfram and wolfram-silicone implants constitute a promising candidate as potential radiation shielding substrates.
PubMed: 38815956
DOI: 10.1016/j.jcjo.2024.04.011 -
NeuroImage Jul 2024Distinguishing the direction of another person's eye gaze is extremely important in everyday social interaction, as it provides critical information about people's...
Distinguishing the direction of another person's eye gaze is extremely important in everyday social interaction, as it provides critical information about people's attention and, therefore, intentions. The temporal dynamics of gaze processing have been investigated using event-related potentials (ERPs) recorded with electroencephalography (EEG). However, the moment at which our brain distinguishes the gaze direction (GD), irrespectively of other facial cues, remains unclear. To solve this question, the present study aimed to investigate the time course of gaze direction processing, using an ERP decoding approach, based on the combination of a support vector machine and error-correcting output codes. We recorded EEG in young healthy subjects, 32 of them performing GD detection and 34 conducting face orientation tasks. Both tasks presented 3D realistic faces with five different head and gaze orientations each: 30°, 15° to the left or right, and 0°. While the classical ERP analyses did not show clear GD effects, ERP decoding analyses revealed that discrimination of GD, irrespective of head orientation, started at 140 ms in the GD task and at 120 ms in the face orientation task. GD decoding accuracy was higher in the GD task than in the face orientation task and was the highest for the direct gaze in both tasks. These findings suggest that the decoding of brain patterns is modified by task relevance, which changes the latency and the accuracy of GD decoding.
Topics: Humans; Male; Female; Young Adult; Electroencephalography; Adult; Evoked Potentials; Fixation, Ocular; Facial Recognition; Support Vector Machine; Attention; Brain; Social Perception
PubMed: 38815675
DOI: 10.1016/j.neuroimage.2024.120659 -
PloS One 2024Saccadic eye movements enable us to search for the target of interest in a crowded scene or, in the case of goal-directed saccades, to simply bring the image of the...
Saccadic eye movements enable us to search for the target of interest in a crowded scene or, in the case of goal-directed saccades, to simply bring the image of the peripheral target to the very centre of the fovea. This mechanism extends the use of the superior image processing performance of the fovea over a large visual field. We know that visual information is processed quickly at the end of each saccade but estimates of the times involved remain controversial. This study aims to investigate the processing of visual information during post fixation oscillations of the eyeball. A new psychophysical test measures the combined eye movement response latencies, including fixation duration and visual processing times. When the test is used in conjunction with an eye tracker, each component that makes up the 'integrated saccade latency' time, from the onset of the peripheral stimulus to the correct interpretation of the information carried by the stimulus, can be measured and the discrete components delineated. The results show that the time required to process and encode the stimulus attribute of interest at the end of a saccade is longer than the time needed to carry out the same task in the absence of an eye movement. We propose two principal hypotheses, each of which can account for this finding. 1. The known inhibition of afferent retinal signals during fast eye movements extends beyond the end point of the saccade. 2. The extended visual processing times measured when saccades are involved are caused by the transient loss of spatial resolution due to eyeball instability during post-saccadic oscillations. The latter can best be described as retinal image smear with greater loss of spatial resolution expected for stimuli of low luminance contrast.
Topics: Humans; Saccades; Adult; Male; Female; Reaction Time; Visual Perception; Fixation, Ocular; Young Adult; Photic Stimulation; Visual Fields; Time Factors
PubMed: 38809939
DOI: 10.1371/journal.pone.0302459