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Journal of Vision Feb 2024The longitudinal chromatic aberration (LCA) of the eye creates a chromatic blur on the retina that is an important cue for accommodation. Although this mechanism can...
The longitudinal chromatic aberration (LCA) of the eye creates a chromatic blur on the retina that is an important cue for accommodation. Although this mechanism can work optimally in broadband illuminants such as daylight, it is not clear how the system responds to the narrowband illuminants used by many modern displays. Here, we measured pupil and accommodative responses as well as visual acuity under narrowband light-emitting diode (LED) illuminants of different peak wavelengths. Observers were able to accommodate under narrowband light and compensate for the LCA of the eye, with no difference in the variability of the steady-state accommodation response between narrowband and broadband illuminants. Intriguingly, our subjects compensated more fully for LCA at nearer distances. That is, the difference in accommodation to different wavelengths became larger when the object was placed nearer the observer, causing the slope of the accommodation response curve to become shallower for shorter wavelengths and steeper for longer ones. Within the accommodative range of observers, accommodative errors were small and visual acuity normal. When comparing between illuminants, when accommodation was accurate, visual acuity was worst for blue narrowband light. This cannot be due to the sparser spacing for S-cones, as our stimuli had equal luminance and thus activated LM-cones roughly equally. It is likely because ocular LCA changes more rapidly at shorter wavelength and so the finite spectral bandwidth of LEDs corresponds to a greater dioptric range at shorter wavelengths. This effect disappears for larger accommodative errors, due to the increased depth of focus of the eye.
Topics: Humans; Accommodation, Ocular; Face; Retina; Blue Light; Pupil
PubMed: 38411958
DOI: 10.1167/jov.24.2.11 -
Journal of Vision Feb 2024Stereoscopic imagery often aims to evoke three-dimensional (3-D) percepts that are accurate and realistic-looking. The "gap" between 3-D imagery and real scenes is...
Stereoscopic imagery often aims to evoke three-dimensional (3-D) percepts that are accurate and realistic-looking. The "gap" between 3-D imagery and real scenes is small, but focus cues typically remain incorrect because images are displayed on a single focal plane. Research has concentrated on the resulting vergence-accommodation conflicts. Yet, incorrect focus cues may also affect the appearance of 3-D imagery. We investigated whether incorrect focus cues reduce perceived realism of 3-D structure ("depth realism"). Experiment 1 used a multiple-focal-planes display to compare depth realism with correct focus cues vs. conventional stereo presentation. The stimuli were random-dot stereograms, which isolated the role of focus cues. Depth realism was consistently lower with incorrect focus cues, providing proof-of-principle evidence that they contribute to perceptual realism. Experiments 2 and 3 examined whether focus cues play a similar role with realistic objects, presented with an almost complete set of visual cues using a high-resolution, high-dynamic-range multiple-focal-planes display. We also examined the efficacy of approximating correct focus cues via gaze-contingent depth-of-field rendering. Improvements in depth realism with correct focus cues were less clear in more realistic scenes, indicating that the role of focus cues in depth realism depends on scene content. Rendering-based approaches, if anything, reduced depth realism, which we attribute to their inability to present higher-order aspects of blur correctly. Our findings suggest future general 3-D display solutions may need to present focus cues correctly to maximise perceptual realism.
Topics: Humans; Cues; Accommodation, Ocular; Technology; Perception
PubMed: 38411956
DOI: 10.1167/jov.24.2.13 -
Optometry and Vision Science : Official... Feb 2024This study provides a faster method for objectively measuring accommodative amplitude with an open-field autorefractor in a research setting.
SIGNIFICANCE
This study provides a faster method for objectively measuring accommodative amplitude with an open-field autorefractor in a research setting.
PURPOSE
Objective measures of accommodative amplitude with an autorefractor take time because of the numerous stimulus demands tested. This study compares protocols using different amounts and types of demands to shorten the process.
METHODS
One hundred participants were recruited for four age bins (5 to 9, 10 to 14, 15 to 19, and 20 to 24 years) and monocular amplitude measured with an autorefractor using three protocols: proximal, proximal-lens (letter), and proximal-lens (picture). For proximal, measurements were taken as participants viewed a 0.9 mm "E" placed at 13 demands (40 to 3.3 cm = 2.5 to 30 D). The other protocols used a target (either the "E" or a detailed picture) placed at 33 and 12.5 cm followed by 12.5 cm with a series of lenses (-2, -4, and -5.5 D). Adjustments were made for lens effectivity for the three lens conditions, which were thus 9.6, 11.1, and 12.0 D for individuals without additional spectacle lenses. Accommodative amplitude was defined as the greatest response measured with each technique. One-way analysis of variance was used to compare group mean amplitudes across protocols and differences between letter protocols by age bin.
RESULTS
Amplitudes were significantly different between protocols (p < 0.001), with proximal having higher amplitudes (mean ± standard deviation, 8.04 ± 1.70 D) compared with both proximal-lens protocols (letter, 7.48 ± 1.42 D; picture, 7.43 ± 1.42 D) by post hoc Tukey analysis. Differences in amplitude between the proximal and proximal-lens (letter) protocol were different by age group (p = 0 .003), with the youngest group having larger differences (1.14 ± 1.58 D) than the oldest groups (0.17 ± 0.58 and 0.29 ± 0.48 D, respectively) by post hoc Tukey analysis.
CONCLUSIONS
The proximal-lens protocols took less time and identified the maximum accommodative amplitude in participants aged 15 to 24 years; however, they may underestimate true amplitude in younger children.
Topics: Child; Humans; Accommodation, Ocular; Lenses
PubMed: 38408308
DOI: 10.1097/OPX.0000000000002103 -
Clinical Optometry 2024Myopia control lenses have been shown to modify visual function; however, it is arguable if these changes are short-term or long-term. We investigated the changes in...
Myopia control lenses have been shown to modify visual function; however, it is arguable if these changes are short-term or long-term. We investigated the changes in accommodative behaviour and binocular vision functions of Malay myopic children who participated in a myopia control trial utilising spectacle lenses (n = 40). This article presents baseline accommodation and binocular vision measurements. The mean (± SD) age, spherical equivalent measured by cycloplegic autorefraction, and axial length (AL) for the right eyes were 10.00 ± 1.47 years, -3.02 ± 1.20 D, and 24.42 ± 0.93 mm, respectively. All participants had good distance and near visual acuities with high-contrast charts (100%), which were significantly better than low-contrast charts (10%) ( < 0.001). The mean (± SD) accommodative lag at baseline was 1.14 ± 0.35 D, while monocular and binocular accommodative amplitudes were 15.35 ± 2.07 D and 16.82 ± 2.27 D, respectively. Malay schoolchildren in this study were more esophoric at near compared to distance, with an accommodative-convergence over accommodation (AC/A) ratio of 5.64 ± 0.66 ∆/D. A higher degree of myopia was found to be associated with a longer AL ( = -0.49, < 0.05) and higher esophoria at near ( = -0.46, < 0.05). These baseline measures are consistent with data from other studies showing that myopic children have a high accommodative lag, an elevated AC/A ratio, a longer AL, and are more esophoric at near. The measures reported herein will serve as a basis for examining changes that occur within 12 months of wearing myopia control spectacle lenses.
PubMed: 38405333
DOI: 10.2147/OPTO.S432496 -
American Journal of Ophthalmology Case... Jun 2024To present an uncommon cause of intermittent angle closure in a young adult patient presenting with intermittent headache and blurry vision exacerbated by accommodation.
PURPOSE
To present an uncommon cause of intermittent angle closure in a young adult patient presenting with intermittent headache and blurry vision exacerbated by accommodation.
OBSERVATIONS
A 37-year-old man reported experiencing intermittent blurry vision, headache, and pain in both eyes associated with prolonged periods of reading beginning at age 17. Serial intraocular pressure (IOP) measurements showed an increase in IOP from 14 to 32 mmHg in the right eye and from 9 to 37 mmHg in the left eye after 145 minutes of sustained accommodation while sitting up. IOP did not normalize after laser peripheral iridotomy but did normalize after clear lens extraction.
CONCLUSIONS AND IMPORTANCE
This case characterized a rare presentation of accommodation-induced IOP elevation in a young adult male that resolved only after clear lens extraction. The clinical takeaway was the importance of considering accommodation-associated angle closure in patients presenting with high intraocular pressures, eye strain, and/or headache with accommodative activities. Notable symptoms that should raise suspicion for this syndrome include halos, changes in visual acuity, and headache with accommodation. We suggested that patients presenting with these symptoms be followed closely, with a full glaucoma evaluation including gonioscopy and possible ultrasound biomicroscopy to assess for pediatric eversional angle closure with headache, plateau iris, angle closure glaucoma, and lens-induced angle closure.
PubMed: 38389701
DOI: 10.1016/j.ajoc.2024.102014 -
Ophthalmic & Physiological Optics : the... May 2024Habitual viewing behaviour is widely believed to be an important contributing factor to the onset and progression of myopia and may be task dependent. The purpose of...
INTRODUCTION
Habitual viewing behaviour is widely believed to be an important contributing factor to the onset and progression of myopia and may be task dependent. The purpose of this study was to quantify the habitual viewing distance of children performing five different tasks on a smartphone digital device.
METHODS
The real-time viewing distance in 38 children with their habitual correction was measured using software (MyopiaApp) on a handheld (Google Pixel 3) device. Five tasks were performed in a randomised sequence: playing a game, watching video in a light (680 lux) and dark (5.5 lux) environment and reading small (8 pt) and large (16 pt) text. ANCOVA statistical analysis was used to evaluate the effect of task, group (myope vs. non-myope) and arm length on the median relative viewing distance.
RESULTS
Arm length was not correlated with viewing distance in any of the tasks, and there was no significant difference in viewing distance between any of the tasks. Specifically, a two-way mixed ANCOVA indicated that task, refractive group (myopic vs. non-myopic), age and arm length, as well as all two-way interactions were not significantly associated with viewing distance. Overall, 60% of the total variance in viewing distance was accounted for by individual differences.
CONCLUSIONS
The average handheld viewing distance was similar across a variety of everyday tasks in a representative sample of myopic and emmetropic children. Neither arm length, age nor refractive group were associated with viewing distance in any of the tasks. Importantly, myopic children of a given size did not hold the smartphone digital device at a different distance for any task than their equally sized non-myopic peers. However, both groups exhibited high inter-individual variability in mean viewing distance, indicating some subjects performed all tasks at further distances while other subjects used at nearer distances.
Topics: Child; Humans; Accommodation, Ocular; Refraction, Ocular; Myopia; Vision Tests; Emmetropia
PubMed: 38379462
DOI: 10.1111/opo.13288 -
Current Eye Research Jun 2024Accommodation mainly affects the lens, a structure of the eyeball that degrades with age. The aim of this work was to study the morphological changes of different ocular...
PURPOSE
Accommodation mainly affects the lens, a structure of the eyeball that degrades with age. The aim of this work was to study the morphological changes of different ocular structures during accommodation, both in the anterior pole and the posterior pole, which may also be involved in the accommodation process.
METHODS
The study will be carried out by stimulating accommodation through lenses of -1.00, -3.00 and -5.00 D starting from the spherical equivalent (M) of each participant in different age groups, from 18 to 66 years. To obtain the M value, aberrometry was achieved, and retinal optical coherence tomography and anterior pole tomography were performed to evaluate the possible structural modifications (central and peripheral), while accommodation was progressively stimulated.
RESULTS
It showed that as the accommodative demand increased, morphological changes were produced in retinal thickness, both in the central and peripheral retina, in all age groups. A thinning of the retina was observed in the central 3 mm, while significant progressive thickening was observed closer to the periphery (up to 6 mm from the fovea) as the required accommodative power increased. A decrease in the anterior chamber depth (ACD) and anterior chamber volume (ACV) was observed with increasing lens power.
CONCLUSION
Structural changes were observed in the central and peripheral retina, as well as in the ACD and ACV, while progressively greater accommodation was stimulated, showing that these structures were modified in the accommodation process even in advanced presbyopes.
Topics: Humans; Accommodation, Ocular; Tomography, Optical Coherence; Adult; Middle Aged; Aged; Young Adult; Anterior Chamber; Retina; Male; Adolescent; Aging; Female; Lens, Crystalline; Refraction, Ocular
PubMed: 38379315
DOI: 10.1080/02713683.2024.2320771 -
Neurology Mar 2024Myasthenia gravis (MG) has been described as a great mimicker of other neurologic and ocular motility disorders, including centrally mediated ophthalmoplegia. For...
Myasthenia gravis (MG) has been described as a great mimicker of other neurologic and ocular motility disorders, including centrally mediated ophthalmoplegia. For example, ocular myasthenia gravis (ocular MG) may cause impaired binocular visual acuity for near vision due to reduced accommodation or for distance vision due to accommodative excess. Notably, accommodative excess due to ocular MG is rare, but may occur with exotropia, with or without diplopia. We report 2 cases of ocular MG: First, a 32-year-old man with exotropia, bilateral hypometric and slowed adducting saccades with dissociated abducting nystagmus, miosis, and decreased distance vision in his right eye; second, a 45-year-old man with similar ocular motor deficits, miosis, and myopia. Both patients showed ocular motor deficits which appeared to localize to the pons but were instead due to ocular MG. Ocular MG should be considered in patients who present with reduced visual acuities due to any disruption in accommodation. Any ocular motor deficit, even if appearing to be centrally mediated or occurring without ptosis, may be caused by ocular MG.
Topics: Male; Humans; Adult; Middle Aged; Exotropia; Myasthenia Gravis; Eye; Ocular Motility Disorders; Nystagmus, Pathologic; Myopia; Miosis
PubMed: 38377456
DOI: 10.1212/WNL.0000000000209260 -
Ophthalmic & Physiological Optics : the... May 2024Previous research has shown that accommodation deficits are common in individuals with Down syndrome (DS), but the origin and mechanisms behind these deficits are still...
PURPOSE
Previous research has shown that accommodation deficits are common in individuals with Down syndrome (DS), but the origin and mechanisms behind these deficits are still unknown. The aim of this study was to investigate the characteristics of different ocular structures involved in accommodation, in particular the ciliary muscle (CM), in a population of individuals with DS to further understand this deficit and its mechanisms.
METHODS
Thirty-two volunteer participants of pre-presbyopic age with (n = 16) and without DS (n = 16) were recruited. Temporal and nasal images of the CM were acquired using anterior segment optical coherence tomography (AS-OCT) while participants fixated an eccentrically located target. Analysis of CM parameters was undertaken using validated semi-automated software. Axial length, anterior chamber depth, lens thickness and corneal curvature were obtained with the Topcon Aladdin Optical Biometer and Corneal Topographer. Non-cycloplegic refractive error and accommodative ability were obtained with an open-field autorefractor and dynamic retinoscopy, respectively. Independent t-tests were conducted to determine differences in CM and other anterior segment parameters between participants with and without DS.
RESULTS
No significant differences were found in the CM parameters studied between participants with and without DS (p > 0.05). In contrast, significant differences were found in visual acuity (p < 0.001), accommodative response (p < 0.001) and corneal curvature (K1 p = 0.003 and K2 p < 0.001) between participants with and without DS.
CONCLUSIONS
Despite having poorer accommodation, pre-presbyopic adults with DS do not have a different CM morphology to that found in typically developing adults. These findings suggest that the accommodative deficit found in this population is not due to a mechanical deficit of the CM.
Topics: Adult; Humans; Lens, Crystalline; Down Syndrome; Ciliary Body; Accommodation, Ocular; Tomography, Optical Coherence; Muscles
PubMed: 38372370
DOI: 10.1111/opo.13290 -
International Journal of Ophthalmology 2024To investigate the frequency and associated factors of accommodation and non-strabismic binocular vision dysfunction among medical university students.
AIM
To investigate the frequency and associated factors of accommodation and non-strabismic binocular vision dysfunction among medical university students.
METHODS
Totally 158 student volunteers underwent routine vision examination in the optometry clinic of Guangxi Medical University. Their data were used to identify the different types of accommodation and non-strabismic binocular vision dysfunction and to determine their frequency. Correlation analysis and logistic regression were used to examine the factors associated with these abnormalities.
RESULTS
The results showed that 36.71% of the subjects had accommodation and non-strabismic binocular vision issues, with 8.86% being attributed to accommodation dysfunction and 27.85% to binocular abnormalities. Convergence insufficiency (CI) was the most common abnormality, accounting for 13.29%. Those with these abnormalities experienced higher levels of eyestrain (=69.518, <0.001). The linear correlations were observed between the difference of binocular spherical equivalent (SE) and the index of horizontal esotropia at a distance (=0.231, =0.004) and the asthenopia survey scale (ASS) score (=0.346, <0.001). Furthermore, the right eye's SE was inversely correlated with the convergence of positive and negative fusion images at close range (=-0.321, <0.001), the convergence of negative fusion images at close range (=-0.294, <0.001), the vergence facility (VF; =-0.234, =0.003), and the set of negative fusion images at far range (=-0.237, =0.003). Logistic regression analysis indicated that gender, age, and the difference in right and binocular SE did not influence the emergence of these abnormalities.
CONCLUSION
Binocular vision abnormalities are more prevalent than accommodation dysfunction, with CI being the most frequent type. Greater binocular refractive disparity leads to more severe eyestrain symptoms.
PubMed: 38371255
DOI: 10.18240/ijo.2024.02.22