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Sensors (Basel, Switzerland) Jun 2024Augmented reality (AR) technology has been widely applied across a variety of fields, with head-up displays (HUDs) being one of its prominent uses, offering immersive...
Augmented reality (AR) technology has been widely applied across a variety of fields, with head-up displays (HUDs) being one of its prominent uses, offering immersive three-dimensional (3D) experiences and interaction with digital content and the real world. AR-HUDs face challenges such as limited field of view (FOV), small eye-box, bulky form factor, and absence of accommodation cue, often compromising trade-offs between these factors. Recently, optical waveguide based on pupil replication process has attracted increasing attention as an optical element for its compact form factor and exit-pupil expansion. Despite these advantages, current waveguide displays struggle to integrate visual information with real scenes because they do not produce accommodation-capable virtual content. In this paper, we introduce a lensless accommodation-capable holographic system based on a waveguide. Our system aims to expand the eye-box at the optimal viewing distance that provides the maximum FOV. We devised a formalized CGH algorithm based on bold assumption and two constraints and successfully performed numerical observation simulation. In optical experiments, accommodation-capable images with a maximum horizontal FOV of 7.0 degrees were successfully observed within an expanded eye-box of 9.18 mm at an optimal observation distance of 112 mm.
PubMed: 38931714
DOI: 10.3390/s24123930 -
Sensors (Basel, Switzerland) Jun 2024The objective of this study was to assess the effect of sustained reading on the temporal changes in the wavefront error in the presbyopic eye. The wavefront aberration...
The objective of this study was to assess the effect of sustained reading on the temporal changes in the wavefront error in the presbyopic eye. The wavefront aberration of the eyes was measured using an IRX3 Shack-Hartmann aberrometer before and after (immediately, 5 min, and 10 min after) a reading task. Temporal changes in C20, C40, and C3-1 coefficient values of the eyes were plotted, showing a predominant number of V-shaped patterns (for C40 and C3-1) and inverse V-shaped patterns (for C20) among the study group, and the percentages (between 27 and 73%) were reported. The median of the total RMS of aberrations and the RMS of HOA (higher-order aberrations), which included comatic (3rd order) and spherical-like aberrations (4th and 6th order), increased immediately after finishing the near-vision reading task and then decreased. The median of RMS of comatic aberrations had a similar pattern of variations, while the median of RMS of spherical-like aberrations displayed an opposite pattern. Simulating the aberration changes due to lens decentration caused by relaxed zonules during 4 D accommodation in an eye model demonstrated that the expected range of changes for the vertical coma and spherical aberrations are in the order of 0.001 and 0.01 μm, respectively, which could justify why the observed changes were not statistically significant. The observed dynamic changes in HOA might be linked to the biomechanical characteristics and alterations in the displacement of the crystalline lens following prolonged near-vision tasks in presbyopic people. Although some predominant patterns under some conditions were shown, they exhibit considerable inter-subject and inter-ocular variability. This might be due to slight misalignments while fixating on the internal extended object in the aberrometer.
Topics: Humans; Reading; Presbyopia; Male; Female; Middle Aged; Aberrometry; Accommodation, Ocular; Corneal Wavefront Aberration; Aged
PubMed: 38931650
DOI: 10.3390/s24123866 -
Vision (Basel, Switzerland) Jun 2024The university population has high visual demands. It is therefore important to assess the prevalence of symptoms in these subjects, which may affect their academic...
The university population has high visual demands. It is therefore important to assess the prevalence of symptoms in these subjects, which may affect their academic performance. In this cross-sectional study, a randomized sample of 252 subjects from a university answered the Convergence Insufficiency Symptom Survey (CISS) questionnaire. In addition, questions were asked about blurred vision during and after near tasks, the number of hours per day spent in near vision, and whether or not they wore glasses. Furthermore, 110 subjects underwent an eye exam, including a refraction and accommodation assessment. The mean age of the subjects was 28.79 ± 11.36 years, 62.3% reported wearing glasses, and on average 7.20 ± 2.92 hours/day was spent in near vision. The mean of the CISS score was 18.69 ± 9.96, and according to its criteria, 38% of the subjects were symptomatic. Some symptoms were significantly ( < 0.05) more frequent in subjects wearing glasses. Accommodative dysfunctions were present in 30.9% of the subjects, the most common being insufficiency of accommodation. We emphasise the importance of assessing symptomatology during the clinical examination in this group of subjects, as they spend many hours a day in near vision, as well as assessing accommodation, binocular vision, and the ergonomic work environment, which may be at the origin of the symptoms, in addition to the need to wear glasses.
PubMed: 38922183
DOI: 10.3390/vision8020038 -
Nature Communications Jun 2024Retinal optical coherence tomography has been identified as biomarker for disease progression in relapsing-remitting multiple sclerosis (RRMS), while the dynamics of...
Retinal optical coherence tomography has been identified as biomarker for disease progression in relapsing-remitting multiple sclerosis (RRMS), while the dynamics of retinal atrophy in progressive MS are less clear. We investigated retinal layer thickness changes in RRMS, primary and secondary progressive MS (PPMS, SPMS), and their prognostic value for disease activity. Here, we analyzed 2651 OCT measurements of 195 RRMS, 87 SPMS, 125 PPMS patients, and 98 controls from five German MS centers after quality control. Peripapillary and macular retinal nerve fiber layer (pRNFL, mRNFL) thickness predicted future relapses in all MS and RRMS patients while mRNFL and ganglion cell-inner plexiform layer (GCIPL) thickness predicted future MRI activity in RRMS (mRNFL, GCIPL) and PPMS (GCIPL). mRNFL thickness predicted future disability progression in PPMS. However, thickness change rates were subject to considerable amounts of measurement variability. In conclusion, retinal degeneration, most pronounced of pRNFL and GCIPL, occurs in all subtypes. Using the current state of technology, longitudinal assessments of retinal thickness may not be suitable on a single patient level.
Topics: Humans; Retinal Degeneration; Male; Female; Tomography, Optical Coherence; Adult; Middle Aged; Disease Progression; Multiple Sclerosis, Relapsing-Remitting; Retina; Multiple Sclerosis, Chronic Progressive; Magnetic Resonance Imaging; Prognosis; Nerve Fibers; Retinal Ganglion Cells
PubMed: 38897994
DOI: 10.1038/s41467-024-49309-7 -
Sensors (Basel, Switzerland) May 2024This study investigates the effects of ambient illumination and negatively polarized text color on visual fatigue, exploring the issue of visual fatigue when using...
This study investigates the effects of ambient illumination and negatively polarized text color on visual fatigue, exploring the issue of visual fatigue when using visual display terminals in low-illumination environments. The research methodology utilizes an experimental design to collect data on changes in pupil accommodation and blink rate through an eye tracker. Participants completed a reading task while exposed to various text colors and ambient light conditions to evaluate visual fatigue and cognitive performance. The study's findings suggest that text color significantly affects visual fatigue, with red text causing the highest level of visual fatigue and yellow text causing the lowest level of visual fatigue. Improvements in ambient lighting reduce visual fatigue, but the degree of improvement varies depending on the text color. Additionally, cognitive performance is better when using yellow and white text but worse when using red text. Yellow text is the most effective choice for reducing visual fatigue under negative polarity. Increasing ambient lighting can also improve visual fatigue in low-illumination conditions. These findings will offer valuable guidance for designing visual terminal device interfaces, especially for low-illumination or night environments, to minimize visual fatigue and improve user experience.
PubMed: 38894307
DOI: 10.3390/s24113516 -
Digital Health 2024This study investigates whether virtual distant viewing technology can prevent nearwork-induced ocular parameter changes.
PURPOSE
This study investigates whether virtual distant viewing technology can prevent nearwork-induced ocular parameter changes.
METHODS
Twenty-six volunteers read a textbook on one day and the same content on a virtual distant viewing display on another day based on a randomization sequence, with both reading sessions at 33 cm for 4 hours. Visual acuity, diopter, ocular biology, visual fatigue, and accommodative function before and after the nearwork, as well as the number of pages read, were recorded.
RESULTS
After 4 hours of nearwork in the textbook group, the spherical equivalent refraction decreased from -3.13 ± 2.65 D to -3.32 ± 2.70 D ( < 0.001), corneal thickness decreased from 531.6 ± 33.5 μm to 528.9 ± 33.0 μm ( = 0.015), anterior chamber depth decreased from 3.65 ± 0.35 mm to 3.60 ± 0.30 mm ( = 0.002), accommodative facility increased from 15.1 ± 3.5 to 16.4 ± 3.9 ( = 0.018), and subjective visual fatigue increased from 14.0 ± 9.2 to 19.3 ± 7.6 ( = 0.002); no significant changes were seen in the other parameters. In the virtual distant viewing group, the spherical equivalent refraction (from -3.17 ± 2.60 D to -3.11 ± 2.73 D, = 0.427), corneal thickness (from 531.9 ± 32.8 μm to 529.7 ± 33.2 μm, = 0.054), and anterior chamber depth (from 3.67 ± 0.35 mm to 3.69 ± 0.32 mm, = 0.331) did not show significant changes, whereas accommodative facility increased from 14.7 ± 5.8 to 15.9 ± 5.5 ( = 0.042) and subjective visual fatigue increased from 13.5 ± 8.4 to 18.9 ± 8.6 ( = 0.002). In addition, choroidal thickness (from 217.7 ± 76.0 μm to 243.0 ± 85.0 μm, = 0.043), positive relative accommodation (from -2.32 ± 1.07 D to -2.85 ± 0.89 D, = 0.007), and amplitude of accommodation (from 7.26 ± 1.41 D to 7.89 ± 1.69 D, = 0.022) also significantly increased in the virtual distant viewing group. The textbook group and the virtual distant viewing group read 176.0 ± 133.1 pages and 188.0 ± 102.0 pages, respectively, and there was no significant difference between the two groups ( = 0.708).
CONCLUSION
Virtual distant viewing technology can prevent the increase in myopia degree due to nearwork and improve accommodation function without increasing visual fatigue.
PubMed: 38882254
DOI: 10.1177/20552076241259868 -
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 -
Contact Lens & Anterior Eye : the... May 2024With over a billion adults worldwide currently affected, presbyopia remains a ubiquitous, global problem. Despite over a century of study, the precise mechanism of...
With over a billion adults worldwide currently affected, presbyopia remains a ubiquitous, global problem. Despite over a century of study, the precise mechanism of ocular accommodation and presbyopia progression remains a topic of debate. Accordingly, this narrative review outlines the lenticular and extralenticular components of accommodation together with the impact of age on the accommodative apparatus, neural control of accommodation, models of accommodation, the impact of presbyopia on retinal image quality, and both historic and contemporary theories of presbyopia.
PubMed: 38796331
DOI: 10.1016/j.clae.2024.102185 -
Medicine May 2024This study was aimed to analyze ocular biometric changes following cycloplegia in pediatric patients with strabismus and amblyopia. Cycloplegia is routinely used to... (Observational Study)
Observational Study
This study was aimed to analyze ocular biometric changes following cycloplegia in pediatric patients with strabismus and amblyopia. Cycloplegia is routinely used to measure refractive error accurately by paralyzing accommodation. However, effects on axial length (AL), anterior chamber depth (ACD), keratometry (Km), and white-to-white distance (WTW) are not well studied in this population. This retrospective study examined 797 patients (1566 eyes) undergoing cycloplegic refraction at a Samsung Kangbuk hospital pediatric ophthalmology clinic from 2010 to 2023. Ocular biometry was measured before and after instilling 1% cyclopentolate and 0.5% phenylephrine/0.5% tropicamide. Patients were categorized by strabismus diagnosis, age, refractive error and amblyopia status. Differences in AL, ACD, Km, WTW, and refractive error pre- and post-cycloplegia were analyzed using paired t tests. ACD (3.44 ± 0.33 vs 3.58 ± 0.29 mm, P < .05) and WTW (12.09 ± 0.42 vs 12.30 ± 0.60 mm, P < .05) increased significantly after cycloplegia in all groups except other strabismus subgroup (Cs) in both parameters and youngest subgroup (G1) in ACD. Refractive error demonstrated a hyperopic shift from -0.48 ± 3.00 D to -0.06 ± 3.32 D (P < .05) in overall and a myopic shift from -6.97 ± 4.27 to -8.10 ± 2.26 in high myopia (HM). Also, AL and Km did not change significantly. In conclusion, cycloplegia impacts ocular biometrics in children with strabismus and amblyopia, significantly increasing ACD and WTW. Refractive error shifts hyperopically in esotropia subgroup (ET) and myopically in high myopia subgroup (HM), eldest subgroup (G3) relating more to anterior segment changes than AL/Km. Understanding cycloplegic effects on biometry is important for optimizing refractive correction in these patients.
Topics: Humans; Amblyopia; Strabismus; Retrospective Studies; Male; Female; Child; Biometry; Mydriatics; Child, Preschool; Refraction, Ocular; Cyclopentolate; Refractive Errors; Adolescent; Anterior Chamber; Axial Length, Eye
PubMed: 38758890
DOI: 10.1097/MD.0000000000038143 -
Clinical Ophthalmology (Auckland, N.Z.) 2024To evaluate the impact on the lag of accommodation (LOA) in emmetropic children after short-term wear of full-field Diffusion Optics Technology (DOT) spectacle lenses,... (Clinical Trial)
Clinical Trial
PURPOSE
To evaluate the impact on the lag of accommodation (LOA) in emmetropic children after short-term wear of full-field Diffusion Optics Technology (DOT) spectacle lenses, designed to modulate retinal contrast to control myopia progression.
PATIENTS AND METHODS
This was a single-visit, prospective, randomized, subject-masked study of emmetropes (ametropes ±1.00D or less in each meridian) with no history of myopia control treatment. Unaided logMAR visual acuity was measured, and ocular dominance was determined using the sighting method. In a randomized order, participants wore plano full-field contrast management (DOT) spectacles (no clear central aperture) or control spectacles (standard single vision spectacle lenses). Each participant was given 5 minutes for adaptation to the respective lenses before open field autorefraction measurements were taken at 6 meters and 40 cm. Ten measurements were taken for each eye. Data were evaluated from the right eye and the dominant eye separately.
RESULTS
A total of 30 participants (20 females and 10 males) with a mean age of 10.4 ± 2.8 (7 to 17) years completed the study. There was no significant difference in right eye mean LOA with contrast management spectacles 0.57 ± 0.39D versus control spectacles 0.62 ± 0.34D; Wilcoxon test, p = 0.37. For dominant eyes, LOA values were 0.60 ± 0.40D and 0.68 ± 0.33D with contrast management spectacles and control spectacles, respectively (p = 0.14). Additionally, no significant difference was observed in mean LOA between males and females or between age groups (7-11 years vs 12-17 years) for either right or dominant eyes with contrast management or control spectacles (all p > 0.05).
CONCLUSION
Full-field contrast management spectacle lenses had no significant effect on LOA compared to standard single vision spectacle lenses, indicating no differential impact on accommodative response over the short period of lens wear tested.
PubMed: 38711574
DOI: 10.2147/OPTH.S453790