-
Journal of Vision Aug 2021Vergence and accommodation can be mismatched under virtual reality viewing conditions, and this mismatch has been thought to be one of the main causes of visual...
Vergence and accommodation can be mismatched under virtual reality viewing conditions, and this mismatch has been thought to be one of the main causes of visual discomfort. The goal of this study was to investigate how optical conditions of the eyes affect accommodative responses to different convergence. Specifically, we hypothesized that extending the depth of focus (DoF) could weaken the control of the screen on accommodation, so that accommodation could be induced by convergence. To test this hypothesis, we extended the DoF using Zernike spherical aberrations (fourth and sixth orders) induced by a binocular adaptive optics (AO) vision simulator. Nine normal subjects between the ages of 21 and 34 (26 ± 5) years were recruited. Three optical conditions were generated: AO condition (aberration-free), monovision condition, and extended depth of focus (EDoF) condition. Binocular accommodative responses, along with binocular visual acuity and stereoacuity, were measured under all three optical conditions with varied binocular vergence levels. At 3 diopters of binocular convergence, the EDoF condition was the most efficient in inducing excessive accommodative response compared with the monovision condition and the AO condition. Visual acuity was impaired with EDoF as compared with the other two conditions. The average stereoscopic thresholds (at 0 vergence) under the EDoF condition were degraded compared with the AO condition but were superior to those of the monovision condition. Therefore, despite some compromise to visual performance, extending the DoF could allow for a more natural vergence-accommodation relationship, providing the potential for alleviating the vergence-accommodation conflict and associated visual fatigue symptoms in virtual reality.
Topics: Accommodation, Ocular; Adult; Convergence, Ocular; Humans; Vision, Binocular; Vision, Monocular; Visual Acuity; Young Adult
PubMed: 34415998
DOI: 10.1167/jov.21.8.21 -
Frontiers in Neuroscience 2021To investigate whether the severity of symptoms of visual fatigue might be associated with clinical visual measures and basic visual functions, such as accommodation,...
PURPOSE
To investigate whether the severity of symptoms of visual fatigue might be associated with clinical visual measures and basic visual functions, such as accommodation, vergence, and contrast sensitivity.
METHODS
In this study, 104 students were recruited (25 males, 79 females, Age 23.4 ± 2.5) for this study. Those with high myopia, strabismus, anisometropia, eye disease or history of ophthalmological surgery were excluded. The included subjects completed a questionnaire that assesses the severity of visual fatigue. Then, binocular accommodative facility, vergence facility and contrast sensitivity using a quick contrast sensitivity function approach were measured in a random sequence. Next, the correlations between each symptom of visual fatigue in the questionnaire and accommodative facility, vergence facility and contrast sensitivity were examined.
RESULTS
Factor analysis indicated that visual fatigue, as captured by the scores of a subset of the questionnaire items, could be strongly related to binocular accommodative facility and binocular contrast sensitivity, but not to vergence facility. We also found that binocular accommodative facility and contrast sensitivity at high spatial frequencies are related.
CONCLUSION
Our findings suggest that visual fatigue is related to the ability of human observers to encode visual details through their binocular vision.
PubMed: 34335163
DOI: 10.3389/fnins.2021.686740 -
Metasurface wavefront control for high-performance user-natural augmented reality waveguide glasses.Scientific Reports Apr 2022Augmented reality (AR) devices, as smart glasses, enable users to see both the real world and virtual images simultaneously, contributing to an immersive experience in...
Augmented reality (AR) devices, as smart glasses, enable users to see both the real world and virtual images simultaneously, contributing to an immersive experience in interactions and visualization. Recently, to reduce the size and weight of smart glasses, waveguides incorporating holographic optical elements in the form of advanced grating structures have been utilized to provide light-weight solutions instead of bulky helmet-type headsets. However current waveguide displays often have limited display resolution, efficiency and field-of-view, with complex multi-step fabrication processes of lower yield. In addition, current AR displays often have vergence-accommodation conflict in the augmented and virtual images, resulting in focusing-visual fatigue and eye strain. Here we report metasurface optical elements designed and experimentally implemented as a platform solution to overcome these limitations. Through careful dispersion control in the excited propagation and diffraction modes, we design and implement our high-resolution full-color prototype, via the combination of analytical-numerical simulations, nanofabrication and device measurements. With the metasurface control of the light propagation, our prototype device achieves a 1080-pixel resolution, a field-of-view more than 40°, an overall input-output efficiency more than 1%, and addresses the vergence-accommodation conflict through our focal-free implementation. Furthermore, our AR waveguide is achieved in a single metasurface-waveguide layer, aiding the scalability and process yield control.
PubMed: 35388053
DOI: 10.1038/s41598-022-09680-1 -
The Western Journal of Emergency... May 2023The emergency department (ED) is a critical service area for patients living with disabilities in the United States. Despite this, there is limited research on best...
INTRODUCTION
The emergency department (ED) is a critical service area for patients living with disabilities in the United States. Despite this, there is limited research on best practices from the patient experience regarding accommodation and accessibility for those with disabilities. In this study we investigate the ED experience from the perspective of patients living with physical and cognitive disability, as well as visual impairment and blindness, to better understand the barriers to accessibility in the ED for these populations.
METHODS
Twelve individuals with either physical or cognitive disabilities, visual impairments or blindness were interviewed regarding their ED experiences, particularly related to accessibility. Interviews were transcribed and coded for qualitative analysis with generation of significant themes relating to accessibility in the ED.
RESULTS
Major themes from coded analysis were as follows: 1) inadequate communication between staff and patients with visual impairments and physical disabilities; 2) the need for electronic delivery for after-visit summaries for individuals with cognitive and visual disabilities; 3) the importance of mindful listening and patience by healthcare staff; 4) the role of increased hospital support including greeters and volunteers; and 5) comprehensive training with both prehospital and hospital staff around assistive devices and services.
CONCLUSION
This study serves as an important first step toward improving the ED environment to ensure accessibility and inclusivity for patients presenting with various types of disabilities. Implementing specific training, policies, and infrastructure changes may improve the experiences and healthcare of this population.
Topics: Humans; United States; Disabled Persons; Qualitative Research; Emergency Service, Hospital; Vision Disorders; Blindness; Health Services Accessibility
PubMed: 37278797
DOI: 10.5811/westjem.58406 -
Ophthalmic & Physiological Optics : the... Sep 2022To determine whether accommodative errors in emmetropes and myopes are systematically different, and the effect of using different instruments and metrics.
PURPOSE
To determine whether accommodative errors in emmetropes and myopes are systematically different, and the effect of using different instruments and metrics.
METHODS
Seventy-six adults aged 18-27 years comprising 24 emmetropes (spherical equivalent refraction of the dominant eye +0.04 ± 0.03 D) and 52 myopes (-2.73 ± 0.22 D) were included. Accommodation responses were measured with a Grand Seiko WAM-5500 and a Hartmann-Shack Complete Ophthalmic Analysis System aberrometer, using pupil plane (Zernike and Seidel refraction) and retinal image plane (neural sharpness-NS; and visual Strehl ratio for modulation transfer function-VSMTF) metrics at 40, 33 and 25 cm. Accommodation stimuli were presented to the corrected dominant eye, and responses, referenced to the corneal plane, were determined in the fellow eye. Linear mixed-effects models were used to determine influence of the refractive group, the measurement method, accommodation stimulus, age, race, parental myopia, gender and binocular measures of heterophoria, accommodative convergence/accommodation and convergence accommodation/convergence ratios.
RESULTS
Lags of accommodation were affected significantly by the measurement method (p < 0.001), the refractive group (p = 0.003), near heterophoria (p = 0.002) and accommodative stimulus (p < 0.05), with significant interactions between some of these variables. Overall, emmetropes had smaller lags of accommodation than myopes with respective means ± standard errors of 0.31 ± 0.08 D and 0.61 ± 0.06 D (p = 0.003). Lags were largest for the Grand Seiko and Zernike defocus, intermediate for NS and VSMTF, and least for Seidel defocus.
CONCLUSIONS
The mean lag of accommodation in emmetropes is approximately equal to the previously reported depth of focus. Myopes had larger (double) lags than emmetropes. Differences between methods and instruments could be as great as 0.50 D, and this must be considered when comparing studies and outcomes. Accommodative lag increased with the accommodation stimulus, but only for methods using a fixed small pupil diameter.
Topics: Accommodation, Ocular; Adult; Benchmarking; Emmetropia; Humans; Myopia; Refraction, Ocular
PubMed: 35775299
DOI: 10.1111/opo.13021 -
Current Topics in Membranes 2022The architecture of the vertebrate eye is optimized for efficient delivery and transduction of photons and processing of signaling cascades downstream from...
The architecture of the vertebrate eye is optimized for efficient delivery and transduction of photons and processing of signaling cascades downstream from phototransduction. The cornea, lens, retina, vasculature, ciliary body, ciliary muscle, iris and sclera have specialized functions in ocular protection, transparency, accommodation, fluid regulation, metabolism and inflammatory signaling, which are required to enable function of the retina-light sensitive tissue in the posterior eye that transmits visual signals to relay centers in the midbrain. This process can be profoundly impacted by non-visual stimuli such as mechanical (tension, compression, shear), thermal, nociceptive, immune and chemical stimuli, which target these eye regions to induce pain and precipitate vision loss in glaucoma, diabetic retinopathy, retinal dystrophies, retinal detachment, cataract, corneal dysfunction, ocular trauma and dry eye disease. TRPV4, a polymodal nonselective cation channel, integrate non-visual inputs with homeostatic and signaling functions of the eye. The TRPV4 gene is expressed in most if not all ocular tissues, which vary widely with respect to the mechanisms of TRPV4 channel activation, modulation, oligomerization, and participation in protein- and lipid interactions. Under- and overactivation of TRPV4 may affect intraocular pressure, maintenance of blood-retina barriers, lens accommodation, neuronal function and neuroinflammation. Because TRPV4 dysregulation precipitates many pathologies across the anterior and posterior eye, the channel could be targeted to mitigate vision loss.
Topics: Animals; Cornea; Lipids; Retina; TRPV Cation Channels; Vertebrates
PubMed: 36210149
DOI: 10.1016/bs.ctm.2022.07.005 -
European Journal of Sport Science Mar 2022Olympic shooting is a sport with high demands of accuracy. Minimal visual errors could be related to performance losses. However, not all visual skills have been studied...
Olympic shooting is a sport with high demands of accuracy. Minimal visual errors could be related to performance losses. However, not all visual skills have been studied in depth in this sport. The main objectives of this study were to compare differences in shooters' visual skills by level and to analyze the competition effect on them. Sixty-six participants were distributed in three groups (non-athletes, elite and non-elite). Eleven visual variables were tested in four skills groups (visual acuity, heterophoria, accommodation functions and other visual skills). The data were collected through a pre- and post-competition simulation test. The results of the study showed differences between groups by shooting sport level. In general, shooters had higher visual acuity values than non-athletes < .001 with large size effects ( between 1.01 and 2.35), and elite shooters presented higher values of accommodation than non-elite shooters < .05 with large size effects ( between 0.88 and 0.97). Furthermore, different visual skills were modified after competition depending on the shooting level. Specifically, visual accommodation skills were only improved in elite shooters. Finally, our study suggests that elite shooters employ different visual strategies or skills to non-elite shooters and that shooting activity is closely related to some specific visual skills. This aspect should be considered by coaches in the design of optimal visual trainings and improve the shooters' performance. Shooters showed better acuity skills than non-athletes.Shooting activity seems to improve visual acuity skills, binocular visual time and eye-hand coordination in non-elite shooters, and accommodation and eye-hand coordination in elite shooters immediately after the competition simulation.Elite shooters employ different visual strategies or skills to non-elite shooters.Non-dominant eye occlusion may benefit binocular vision recovery by inhibiting aiming action and the use of accommodative flexibility could be related to the QE during the shot.
Topics: Athletes; Firearms; Humans; Sports; Vision, Binocular
PubMed: 33427595
DOI: 10.1080/17461391.2021.1874540 -
Indian Journal of Ophthalmology Jun 2021To assess pre and post vergence and accommodation parameters after monitored reading on a smartphone device.
PURPOSE
To assess pre and post vergence and accommodation parameters after monitored reading on a smartphone device.
METHODS
This prospective comparative study was performed in a tertiary eye care center for a duration of 6 months (December 2017 - May 2018). A total of 47 healthy emmetropic subjects of age group ranging from 18-30 years were recruited for the study. Participants underwent an initial visual screening protocol, followed by accommodation and vergence parameters assessment. The subjects were given reading text of optotype N6 at 40cm working distance for 30 minutes in a smart phone device. Pre and post measurements were documented.
RESULTS
Among 47 subjects there were 17 male and 30 females with mean age group of 21.2+2.06 years. There was a statistically significant worsening of accommodative components (negative & positive relative accommodation, lag of accommodation). In vergence parameters, a statistically significant deterioration of negative (12.8 + 1.65 to 12.38 + 1.93 PD) and positive fusional vergence (15.48 + 1.53 to 16.08 +1.61 PD) was observed. The mean vergence facility also showed a statistically significant change in pre and post task measurements (13.51 + 1.64 to 10.71 + 1.91 cpm (cycles per minute)).
CONCLUSION
The current study investigated that perusing text with a smart phone for 30 minutes shows significant effect on accommodative and vergence components for near task, with greater impact on vergence parameters. Drawn out exposure to digital screens at near, may bring about visual quality dysfunction.
Topics: Accommodation, Ocular; Adolescent; Adult; Convergence, Ocular; Female; Humans; Male; Prospective Studies; Smartphone; Vision, Binocular; Young Adult
PubMed: 34011725
DOI: 10.4103/ijo.IJO_2956_20 -
Scientific Reports Dec 2023Quantifying eye movement is important for diagnosing various neurological and ocular diseases as well as AR/VR displays. We developed a simple setup for real-time...
Quantifying eye movement is important for diagnosing various neurological and ocular diseases as well as AR/VR displays. We developed a simple setup for real-time dynamic gaze tracking and accommodation measurements based on Purkinje reflections, which are the reflections from front and back surfaces of the cornea and the eye lens. We used an accurate eye model in ZEMAX to simulate the Purkinje reflection positions at different focus distances of the eye, which matched the experimental data. A neural network was trained to simultaneously predict vergence and accommodation using data collected from 9 subjects. We demonstrated that the use of Purkinje reflection coordinates in machine learning resulted in precise estimation. The proposed system accurately predicted the accommodation with an accuracy better than 0.22 D using subject's own data and 0.40 D using other subjects' data with two-point calibration in tests performed with 9 subjects in our setup.
Topics: Humans; Accommodation, Ocular; Lens, Crystalline; Eye Movements; Cornea; Machine Learning
PubMed: 38062067
DOI: 10.1038/s41598-023-47572-0 -
Australian Journal of General Practice Aug 2019Ocular dysfunction, including eye movement defects, has been documented in up to 69% of patients with concussion. However, standard sports-related concussion assessment...
BACKGROUND
Ocular dysfunction, including eye movement defects, has been documented in up to 69% of patients with concussion. However, standard sports-related concussion assessment protocols do not typically include any clinical examination of the ocular system.
OBJECTIVE
The aim of this article is to inform general practitioners (GPs) about ocular defects associated with concussion, identify test procedures and highlight the important role of GPs within the concussion paradigm.
DISCUSSION
Ocular dysfunction that commonly occurs with concussion includes abnormalities of accommodation, convergence, saccades and smooth pursuits. This may cause blurred vision, double vision, ocular pain and difficulty with close work. Symptoms can severely affect daily work, school or play activities. Patients complaining of extended ocular symptoms following concussion should be referred to an ophthalmologist for a complete ocular assessment.
Topics: Accommodation, Ocular; Brain Concussion; Humans; Oculomotor Muscles; Physical Examination; Saccades; Vision Disorders
PubMed: 31370123
DOI: 10.31128/AJGP-03-19-4876