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Kaida T, Ono T, Tokunaga T, Takada K, Tokuda S, Kuwabara N, Kawamorita T, Kamiya K, Shoji N, Miyata K. Prevalence of Accommodative Microfluctuations in Eyes after Cataract Surgery. J Clin Med 2023; 12:5135. [PMID: 37568536 PMCID: PMC10419933 DOI: 10.3390/jcm12155135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 07/18/2023] [Accepted: 08/03/2023] [Indexed: 08/13/2023] Open
Abstract
BACKGROUND We aimed to evaluate the existence of accommodative microfluctuations in eyes after cataract surgery. METHODS This retrospective observational cohort study included 1160 eyes of 713 patients (mean age: 72.5 ± 8.3 years) who underwent phacoemulsification, intraocular lens insertion, and an evaluation of accommodative microfluctuations with an autorefractometer. Patients with posterior segment disorders resulting in visual acuity impairment and those with unavailable medical information were excluded. High-frequency components (HFCs), between 1.0-2.3 Hz, based on fast Fourier transform analysis of the accommodative microfluctuation data were examined at postoperative 2-3 (2 M) and 6 months (6 M). The relationships between the HFCs and patient age, manifest refraction, and axial length were analyzed. RESULTS Increased HFC values (>65) were observed at a constant rate after cataract surgery, with prevalence rates of 33.4% at 2 M and 34.7% at 6 M. Postoperatively, at 2 M, increased HFC values were significantly more common for eyes with axial length ≥26 mm than for those with axial length <26 mm (p = 0.0056). However, they were not significantly correlated to age or postoperative manifest refraction. CONCLUSIONS At 2 M postoperatively, increased HFC values presented more frequently in eyes with a greater axial length; hence, the precise detection and understanding of postoperative accommodative spasms in high myopia patients is important.
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Affiliation(s)
- Tomoko Kaida
- Department of Ophthalmology, Miyata Eye Hospital, Miyazaki 885-0051, Japan (T.T.); (S.T.)
| | - Takashi Ono
- Department of Ophthalmology, Miyata Eye Hospital, Miyazaki 885-0051, Japan (T.T.); (S.T.)
- Department of Ophthalmology, Graduate School of Medicine, University of Tokyo, Tokyo 113-8654, Japan
| | - Tadatoshi Tokunaga
- Department of Ophthalmology, Miyata Eye Hospital, Miyazaki 885-0051, Japan (T.T.); (S.T.)
| | - Keita Takada
- Department of Ophthalmology, Miyata Eye Hospital, Miyazaki 885-0051, Japan (T.T.); (S.T.)
| | - Shota Tokuda
- Department of Ophthalmology, Miyata Eye Hospital, Miyazaki 885-0051, Japan (T.T.); (S.T.)
| | - Naoto Kuwabara
- Department of Ophthalmology, Miyata Eye Hospital, Miyazaki 885-0051, Japan (T.T.); (S.T.)
| | - Takushi Kawamorita
- Department of Orthoptics and Visual Science, Kitasato University School of Allied Health Sciences, Sagamihara 252-0373, Japan
| | - Kazutaka Kamiya
- Department of Orthoptics and Visual Science, Kitasato University School of Allied Health Sciences, Sagamihara 252-0373, Japan
| | - Nobuyuki Shoji
- Department of Ophthalmology, School of Medicine, Kitasato University, Sagamihara 252-0374, Japan
| | - Kazunori Miyata
- Department of Ophthalmology, Miyata Eye Hospital, Miyazaki 885-0051, Japan (T.T.); (S.T.)
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Mihelčič M, Podlesek A. Cognitive workload affects ocular accommodation and pupillary response. JOURNAL OF OPTOMETRY 2023; 16:107-115. [PMID: 35764479 PMCID: PMC10104792 DOI: 10.1016/j.optom.2022.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 03/14/2022] [Accepted: 05/12/2022] [Indexed: 06/15/2023]
Abstract
SIGNIFICANCE Cognitive involvement in reading causes variations in the tonus of autonomic nerve system. The aim of this study was to examine the effect of short-term cognitive load on accommodation and pupils' absolute values and temporal variability in test persons performing three different types of tasks. PURPOSE We aimed to show how cognitive tasks of different type and difficulty level affect accommodation and pupil behavior during a short time interval. METHODS Participants (n = 58; mean age 16.4 years, SD = 0.56) performed reading from a 10-inch LCD screen placed at 40 cm distance. Three different types of tasks (numerical, textual, and the Stroop task), each at three different levels of cognitive load were introduced. Participants had 90 s to complete each task. Accommodative and pupillary responses were measured with videoretinoscope Power Refractor 3 at 50 Hz. RESULTS Pupil size was largest in the Stroop task (M = 5.20 mm, SD = 0.75 mm), followed by the numerical tasks (M = 5.02 mm, SD = 0.72 mm) and textual tasks (M = 4.78 mm, SD = 0.71 mm). Accommodative fluctuations - measured as accommodation SD - were largest in the textual tasks (M = 0.67 D, SD = 0.34 D), followed by the numerical tasks (M = 0.61 D, SD = 0.40 D) and the Stroop task (M = 0.52 D, SD = 0.21 D). CONCLUSIONS In our experiment, short-term cognitive load was associated with altered pupillary and accommodative response to near tasks. In conflicting tasks (Stroop) or in performing continuing calculations, the pupils were larger; in tasks requiring logical reasoning, the accommodative fluctuations were greater. These effects can potentially be associated with current near-point stress and myopia growth models.
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Affiliation(s)
| | - Anja Podlesek
- Department of Psychology, University of Ljubljana, Slovenia
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3
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Rohman L, Ruggeri M, Ho A, Parel JM, Manns F. Lens Thickness Microfluctuations in Young and Prepresbyopic Adults During Steady-State Accommodation. Invest Ophthalmol Vis Sci 2023; 64:12. [PMID: 36753168 PMCID: PMC9919620 DOI: 10.1167/iovs.64.2.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 01/22/2023] [Indexed: 02/09/2023] Open
Abstract
Purpose To determine whether lens mechanical dynamics change with age and with accommodative demands. Methods Lens thickness microfluctuations were measured using a high-speed custom-built spectral domain optical coherence tomography system in five young adults (20 to 25 years old) at 0 diopters (D), 2 D, 4 D, and maximum accommodative demand and in five prepresbyopes (38 to 45 years old) under relaxed and maximal accommodation. For each state, the measurements were repeated four times during the same session. Images of the central 2-mm zone of the lens comprising 170 A-lines/frame were acquired for 10 seconds, and axial lens thickness change was measured. Lens thickness microfluctuations (µm²/Hz) were assessed by integrating the power spectrum of lens thickness microfluctuations between 0 and 4 Hz. Results The amplitude of lens microfluctuations was higher in the accommodated states than in the relaxed state in both age groups. Lens microfluctuations were higher in young adult participants than in prepresbyopes, with a significant difference in relaxed and maximally accommodated states (P = 0.04 and P = 0.04). In the young participants, the amplitude of microfluctuations reached a plateau at maximum accommodation. Conclusions Lens mechanical dynamics are both age and accommodation dependent. The decrease in lens thickness microfluctuations with age is consistent with an age-related increase in lens stiffness or decrease of the ciliary muscle displacement. The lens does not contribute to the high-frequency component of ocular dioptric microfluctuations.
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Affiliation(s)
- Leana Rohman
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States
| | - Marco Ruggeri
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States
| | - Arthur Ho
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States
- Brien Holden Vision Institute, Sydney, New South Wales, Australia
- School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia
| | - Jean-Marie Parel
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States
- Brien Holden Vision Institute, Sydney, New South Wales, Australia
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States
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4
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Read JCA, Kaspiris-Rousellis C, Wood TS, Wu B, Vlaskamp BNS, Schor CM. Seeing the future: Predictive control in neural models of ocular accommodation. J Vis 2022; 22:4. [PMID: 35925580 PMCID: PMC9363677 DOI: 10.1167/jov.22.9.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Ocular accommodation is the process of adjusting the eye's crystalline lens so as to bring the retinal image into sharp focus. The major stimulus to accommodation is therefore retinal defocus, and in essence, the job of accommodative control is to send a signal to the ciliary muscle which will minimize the magnitude of defocus. In this article, we first provide a tutorial introduction to control theory to aid vision scientists without this background. We then present a unified model of accommodative control that explains properties of the accommodative response for a wide range of accommodative stimuli. Following previous work, we conclude that most aspects of accommodation are well explained by dual integral control, with a “fast” or “phasic” integrator enabling response to rapid changes in demand, which hands over control to a “slow” or “tonic” integrator which maintains the response to steady demand. Control is complicated by the sensorimotor latencies within the system, which delay both information about defocus and the accommodation changes made in response, and by the sluggish response of the motor plant. These can be overcome by incorporating a Smith predictor, whereby the system predicts the delayed sensory consequences of its own motor actions. For the first time, we show that critically-damped dual integral control with a Smith predictor accounts for adaptation effects as well as for the gain and phase for sinusoidal oscillations in demand. In addition, we propose a novel proportional-control signal to account for the power spectrum of accommodative microfluctuations during steady fixation, which may be important in hunting for optimal focus, and for the nonlinear resonance observed for low-amplitude, high-frequency input. Complete Matlab/Simulink code implementing the model is provided at https://doi.org/10.25405/data.ncl.14945550.
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Affiliation(s)
- Jenny C A Read
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom.,
| | | | - Toby S Wood
- School of Mathematics, Statistics & Physics, Newcastle University, Newcastle upon Tyne, UK.,
| | - Bing Wu
- Quantified Experience, Magic Leap Inc, Plantation, FL, USA.,
| | | | - Clifton M Schor
- Herbert Wertheim School of Optometry and Vision Science, University of California at Berkeley, Berkeley, CA, USA.,
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5
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Chakraborty R, Landis EG, Mazade R, Yang V, Strickland R, Hattar S, Stone RA, Iuvone PM, Pardue MT. Melanopsin modulates refractive development and myopia. Exp Eye Res 2022; 214:108866. [PMID: 34838844 PMCID: PMC8792255 DOI: 10.1016/j.exer.2021.108866] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 11/19/2021] [Accepted: 11/23/2021] [Indexed: 01/03/2023]
Abstract
Myopia, or nearsightedness, is the most common form of refractive abnormality and is characterized by excessive ocular elongation in relation to ocular power. Retinal neurotransmitter signaling, including dopamine, is implicated in myopic ocular growth, but the visual pathways that initiate and sustain myopia remain unclear. Melanopsin-expressing retinal ganglion cells (mRGCs), which detect light, are important for visual function, and have connections with retinal dopamine cells. Here, we investigated how mRGCs influence normal and myopic refractive development using two mutant mouse models: Opn4-/- mice that lack functional melanopsin photopigments and intrinsic mRGC responses but still receive other photoreceptor-mediated input to these cells; and Opn4DTA/DTA mice that lack intrinsic and photoreceptor-mediated mRGC responses due to mRGC cell death. In mice with intact vision or form-deprivation, we measured refractive error, ocular properties including axial length and corneal curvature, and the levels of retinal dopamine and its primary metabolite, L-3,4-dihydroxyphenylalanine (DOPAC). Myopia was measured as a myopic shift, or the difference in refractive error between the form-deprived and contralateral eyes. We found that Opn4-/- mice had altered normal refractive development compared to Opn4+/+ wildtype mice, starting ∼4D more myopic but developing ∼2D greater hyperopia by 16 weeks of age. Consistent with hyperopia at older ages, 16 week-old Opn4-/- mice also had shorter eyes compared to Opn4+/+ mice (3.34 vs 3.42 mm). Opn4DTA/DTA mice, however, were more hyperopic than both Opn4+/+ and Opn4-/- mice across development ending with even shorter axial lengths. Despite these differences, both Opn4-/- and Opn4DTA/DTA mice had ∼2D greater myopic shifts in response to form-deprivation compared to Opn4+/+ mice. Furthermore, when vision was intact, dopamine and DOPAC levels were similar between Opn4-/- and Opn4+/+ mice, but higher in Opn4DTA/DTA mice, which differed with age. However, form-deprivation reduced retinal dopamine and DOAPC by ∼20% in Opn4-/- compared to Opn4+/+ mice but did not affect retinal dopamine and DOPAC in Opn4DTA/DTA mice. Lastly, systemically treating Opn4-/- mice with the dopamine precursor L-DOPA reduced their form-deprivation myopia by half compared to non-treated mice. Collectively our findings show that disruption of retinal melanopsin signaling alters the rate and magnitude of normal refractive development, yields greater susceptibility to form-deprivation myopia, and changes dopamine signaling. Our results suggest that mRGCs participate in the eye's response to myopigenic stimuli, acting partly through dopaminergic mechanisms, and provide a potential therapeutic target underling myopia progression. We conclude that proper mRGC function is necessary for correct refractive development and protection from myopia progression.
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Affiliation(s)
- Ranjay Chakraborty
- Department of Ophthalmology, Emory University School of Medicine, 1365B Clifton Rd NE, Atlanta, GA 30322, United States,Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Health Care System, 1670 Clairmont Rd, Decatur, GA 30033, United States,College of Nursing and Health Sciences, Optometry and Vision Science, Flinders University, Bedford Park, SA 5001, Adelaide, Australia,Caring Futures Institute, Flinders University, Bedford Park, SA 5042, Adelaide, Australia
| | - Erica G. Landis
- Department of Ophthalmology, Emory University School of Medicine, 1365B Clifton Rd NE, Atlanta, GA 30322, United States,Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Health Care System, 1670 Clairmont Rd, Decatur, GA 30033, United States,Neuroscience Program, Emory University School of Medicine, 1365 Clifton Rd NE, Atlanta, GA 30322, United States
| | - Reece Mazade
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Health Care System, 1670 Clairmont Rd, Decatur, GA 30033, United States,Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Dr, Atlanta, GA 30332, United States
| | - Victoria Yang
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Health Care System, 1670 Clairmont Rd, Decatur, GA 30033, United States,Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Dr, Atlanta, GA 30332, United States
| | - Ryan Strickland
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Health Care System, 1670 Clairmont Rd, Decatur, GA 30033, United States,Neuroscience Program, Emory University School of Medicine, 1365 Clifton Rd NE, Atlanta, GA 30322, United States
| | - Samer Hattar
- Section on Light and Circadian Rhythms, NIMH, NIH, 9000 Rockville Pike, Bethesda, Maryland, USA 20892
| | - Richard A. Stone
- Department of Ophthalmology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States
| | - P. Michael Iuvone
- Department of Ophthalmology, Emory University School of Medicine, 1365B Clifton Rd NE, Atlanta, GA 30322, United States,Department of Pharmacology, Emory University School of Medicine, 1365B Clifton Rd NE, Atlanta, GA 30322, United States
| | - Machelle T. Pardue
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Health Care System, 1670 Clairmont Rd, Decatur, GA 30033, United States,Neuroscience Program, Emory University School of Medicine, 1365 Clifton Rd NE, Atlanta, GA 30322, United States,Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Dr, Atlanta, GA 30332, United States
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6
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Houston KE, McDaniel CE, Greenspan L, Tirandazi P. Case Series: Periodic Accommodative Fluctuations after Concussion. Optom Vis Sci 2021; 98:1387-1393. [PMID: 34905525 DOI: 10.1097/opx.0000000000001810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
SIGNIFICANCE This is the first report recording an accommodative disorder after concussion characterized by periodic moderately sized myopic refractive error fluctuations without measurable other features of spasm of the near reflex. PURPOSE Objectively document a class of accommodative dysfunction that may be related to concussion. CASE REPORTS Case 1 involved two sports-related concussions 2 months apart with symptoms of headache and variable blur. Refractive stability was measured 28 months after injury with a binocular open-field refractometer documenting fluctuations from -0.25 to -1.75 D occurring 10 times during 4.2 seconds of recording with no evident miosis or convergent strabismus. The symptoms resolved with 1% atropine × 3 weeks. Case 2 involved a concussive blast injury (improvised explosive device) 7 years prior with symptoms of headache behind the eyes and occasional variable blur and reduced tolerance of electronic displays and other visually intensive tasks. Refractive fluctuations from +0.50 to -2.00 D occurred seven times over 44 seconds of recording with no appreciable miosis or change of interpalpebral fissure. The signs and symptoms were unresponsive to seven occupational therapy sessions involving task modifications and accommodative vision therapy activities. CONCLUSIONS In patients complaining of blurry vision, a careful evaluation of the stability of accommodation is indicated.
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Affiliation(s)
| | | | - Lynn Greenspan
- Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania
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7
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Atchison DA. Recent advances in measurement of monochromatic aberrations of human eyes. Clin Exp Optom 2021; 88:5-27. [PMID: 15658922 DOI: 10.1111/j.1444-0938.2005.tb06659.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2004] [Revised: 11/18/2004] [Accepted: 11/27/2004] [Indexed: 11/29/2022] Open
Abstract
The field of aberrations of the human eye is moving rapidly, being driven by the desire to monitor and optimise vision following refractive surgery. It is important for ophthalmologists and optometrists to have an understanding of the magnitude of various aberrations and how these are likely to be affected by refractive surgery and other corrections. In this paper, I consider methods used to measure aberrations, the magnitude of aberrations in general populations and how these are affected by various factors (for example, age, refractive error, accommodation and refractive surgery) and how aberrations and their correction affect spatial visual performance.
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Affiliation(s)
- David A Atchison
- School of Optometry, Queensland University of Technology, Kelvin Grove, QLD 4059, Australia
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8
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Redondo B, Vera J, Luque-Casado A, García-Ramos A, Jiménez R. Associations between accommodative dynamics, heart rate variability and behavioural performance during sustained attention: A test-retest study. Vision Res 2019; 163:24-32. [PMID: 31374236 DOI: 10.1016/j.visres.2019.07.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 07/03/2019] [Accepted: 07/08/2019] [Indexed: 12/19/2022]
Abstract
This study evaluated the time-on-task effect of a sustained attention task on the accommodative response, explored the link between ocular accommodation, cardiac autonomic regulation and behavioral performance, and tested the inter-session repeatability of these results by performing the same experimental procedure on different days. The accommodative response was measured in 25 university students using a WAM-5500 autorefractor, while participants performed a 10-minute psychomotor vigilance task at 50 cm. There were no time-on-task effects for the lag of accommodation, whereas the microfluctuations of accommodation and reaction time were modulated as a function of time-on-task, observing a progressive increment of both variables over time. Multiple regression analysis revealed that the microfluctuations of accommodation were a reasonably good predictor of behavioral performance. Analysis of inter-session repeatability showed that ocular accommodation, heart rate variability and reaction time had a low to moderate level of repeatability between two measurements. The microfluctuations of accommodation were sensitive to time-on-task effects during sustained attention, with a lower stability of accommodation being linked to reduced behavioral performance. The predictive capacity of the variability of accommodation for behavioral performance might be explained by the brain mechanisms shared by the ocular dynamics and attentional state; however, future studies would be required to elucidate this association. The low to moderate inter-session repeatability indicated that results in two measurement periods cannot be considered interchangeable, and therefore, the results of this study should be interpreted cautiously in this regard.
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Affiliation(s)
- Beatriz Redondo
- Department of Optics, Faculty of Sciences, University of Granada, Granada, Spain
| | - Jesús Vera
- Department of Optics, Faculty of Sciences, University of Granada, Granada, Spain.
| | - Antonio Luque-Casado
- Center for Sport Studies, King Juan Carlos University, Madrid, Spain; Mind, Brain and Behaviour Research Center (CIMCYC), University of Granada, Granada, Spain
| | - Amador García-Ramos
- Department of Physical Education and Sport, Faculty of Sport Sciences, University of Granada, Granada, Spain; Department of Sports Sciences and Physical Conditioning, Faculty of Education, CIEDE, Catholic University of Most Holy Concepción, Concepción, Chile
| | - Raimundo Jiménez
- Department of Optics, Faculty of Sciences, University of Granada, Granada, Spain
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9
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Burns SA, Elsner AE, Sapoznik KA, Warner RL, Gast TJ. Adaptive optics imaging of the human retina. Prog Retin Eye Res 2019; 68:1-30. [PMID: 30165239 PMCID: PMC6347528 DOI: 10.1016/j.preteyeres.2018.08.002] [Citation(s) in RCA: 126] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 08/22/2018] [Accepted: 08/24/2018] [Indexed: 12/18/2022]
Abstract
Adaptive Optics (AO) retinal imaging has provided revolutionary tools to scientists and clinicians for studying retinal structure and function in the living eye. From animal models to clinical patients, AO imaging is changing the way scientists are approaching the study of the retina. By providing cellular and subcellular details without the need for histology, it is now possible to perform large scale studies as well as to understand how an individual retina changes over time. Because AO retinal imaging is non-invasive and when performed with near-IR wavelengths both safe and easily tolerated by patients, it holds promise for being incorporated into clinical trials providing cell specific approaches to monitoring diseases and therapeutic interventions. AO is being used to enhance the ability of OCT, fluorescence imaging, and reflectance imaging. By incorporating imaging that is sensitive to differences in the scattering properties of retinal tissue, it is especially sensitive to disease, which can drastically impact retinal tissue properties. This review examines human AO retinal imaging with a concentration on the use of the Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO). It first covers the background and the overall approaches to human AO retinal imaging, and the technology involved, and then concentrates on using AO retinal imaging to study the structure and function of the retina.
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Affiliation(s)
- Stephen A Burns
- 800E. Atwater S, School of Optometry, Indiana University, Bloomington, IN, United States.
| | - Ann E Elsner
- 800E. Atwater S, School of Optometry, Indiana University, Bloomington, IN, United States
| | - Kaitlyn A Sapoznik
- 800E. Atwater S, School of Optometry, Indiana University, Bloomington, IN, United States
| | - Raymond L Warner
- 800E. Atwater S, School of Optometry, Indiana University, Bloomington, IN, United States
| | - Thomas J Gast
- 800E. Atwater S, School of Optometry, Indiana University, Bloomington, IN, United States
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10
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Abstract
Blur occurs naturally when the eye is focused at one distance and an object is presented at another distance. Computer-graphics engineers and vision scientists often wish to create display images that reproduce such depth-dependent blur, but their methods are incorrect for that purpose. They take into account the scene geometry, pupil size, and focal distances, but do not properly take into account the optical aberrations of the human eye. We developed a method that, by incorporating the viewer's optics, yields displayed images that produce retinal images close to the ones that occur in natural viewing. We concentrated on the effects of defocus, chromatic aberration, astigmatism, and spherical aberration and evaluated their effectiveness by conducting experiments in which we attempted to drive the eye's focusing response (accommodation) through the rendering of these aberrations. We found that accommodation is not driven at all by conventional rendering methods, but that it is driven surprisingly quickly and accurately by our method with defocus and chromatic aberration incorporated. We found some effect of astigmatism but none of spherical aberration. We discuss how the rendering approach can be used in vision science experiments and in the development of ophthalmic/optometric devices and augmented- and virtual-reality displays.
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Affiliation(s)
- Steven A Cholewiak
- Optometry & Vision Science, University of California, Berkeley, Berkeley, CA, USA
| | - Gordon D Love
- Computer Science & Physics, Durham University, Durham, UK
| | - Martin S Banks
- Optometry & Vision Science, University of California, Berkeley, Berkeley, CA, USA
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11
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Hynes NJ, Cufflin MP, Hampson KM, Mallen EAH. Cognitive Demand and Accommodative Microfluctuations. Vision (Basel) 2018; 2:vision2030036. [PMID: 31735899 PMCID: PMC6836075 DOI: 10.3390/vision2030036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 08/31/2018] [Accepted: 09/04/2018] [Indexed: 12/29/2022] Open
Abstract
Previous studies have shown cognition to have an influence on accommodation. Temporal variation in the accommodative response occurs during the fixation on a stationary target. This constantly shifting response has been called accommodative micro-fluctuations (AMFs). The aim of this study is to determine the effects of increasing task cognitive demand on the ocular accommodation response. AMFs for 12 myopes and 12 emmetropes were measured under three conditions of varying cognitive demand and comprising reading of numbers (Num), simple arithmetic (SA), and complex arithmetic (CA). Fast Fourier transforms were used to analyze the different frequency band components of the AMFs. Other aspects of AMFs including root mean square accommodation values and chaos analysis was applied. A repeated measures ANOVA revealed a significant main effect of cognition in the mean power of the high frequency component (HFC) (F2,44 = 10.03, p < 0.005). Pairwise analyses revealed that these differences exist between SA and CA tasks (p < 0.005) and the Num and CA (p < 0.005) tasks with the HFC power being the highest for the CA condition. It appears that the difficulty of a task does affect active accommodation but to a lesser extent than other factors affecting accommodation.
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Affiliation(s)
- Niall J. Hynes
- School of Optometry & Vision Science, University of Bradford, Bradford BD7 1DP, UK
- Correspondence:
| | - Matthew P. Cufflin
- School of Optometry & Vision Science, University of Bradford, Bradford BD7 1DP, UK
| | - Karen M. Hampson
- Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK
| | - Edward A. H. Mallen
- School of Optometry & Vision Science, University of Bradford, Bradford BD7 1DP, UK
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12
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Kaido M, Kawashima M, Shigeno Y, Yamada Y, Tsubota K. Relation of accommodative microfluctuation with dry eye symptoms in short tear break-up time dry eye. PLoS One 2017; 12:e0184296. [PMID: 28886090 PMCID: PMC5590915 DOI: 10.1371/journal.pone.0184296] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 08/21/2017] [Indexed: 11/29/2022] Open
Abstract
Purpose To investigate accommodative microfluctuations (AMFs) and visual function in short tear break-up time (BUT)-type dry eye (DE) and non-DE subjects. Methods This prospective comparative study included 48 volunteers with DE symptoms (mean age 34.8 ± 5.5 years, age range 25–42 years) and 73 without DE symptoms (mean age 30.6 ± 4.7 years, age range 25–42 years). The eyes were divided into two groups: (1) DE group with DE symptoms and BUT ≤ 5 s and (2) non-DE group without DE symptoms and BUT > 5 s. We excluded eyes with Schirmer score ≤ 5 mm and positive keratoconjunctival epithelial damage. Tear evaluation, AMF, and functional visual acuity (VA) examinations were performed. AMF parameters included total high-frequency component (HFC), HFC with low accommodation for the task of staring into the distance (HFC1), and HFC with high accommodation for deskwork (HFC2). Functional VA parameters included starting VA, functional VA, visual maintenance ratio, and blink frequency. Results A total of 33 and 34 eyes were categorized in the DE and non-DE groups, respectively. Mean blink frequency and HFC1 values were significantly higher in the DE group than they were in the non-DE group. Conclusions DEs with symptoms showed abnormal AMF and visual function, which may be associated with DE symptoms.
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Affiliation(s)
- Minako Kaido
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.,Shinanozaka Clinic, Tokyo, Japan
| | - Motoko Kawashima
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Yuta Shigeno
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | | | - Kazuo Tsubota
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
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Hampson KM, Cufflin MP, Mallen EAH. Sensitivity of Chaos Measures in Detecting Stress in the Focusing Control Mechanism of the Short-Sighted Eye. Bull Math Biol 2017. [PMID: 28639168 PMCID: PMC5517597 DOI: 10.1007/s11538-017-0310-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
When fixating on a stationary object, the power of the eye’s lens fluctuates. Studies have suggested that changes in these so-called microfluctuations in accommodation may be a factor in the onset and progression of short-sightedness. Like many physiological signals, the fluctuations in the power of the lens exhibit chaotic behaviour. A breakdown or reduction in chaos in physiological systems indicates stress to the system or pathology. The purpose of this study was to determine whether the chaos in fluctuations of the power of the lens changes with refractive error, i.e. how short-sighted a subject is, and/or accommodative demand, i.e. the effective distance of the object that is being viewed. Six emmetropes (EMMs, non-short-sighted), six early-onset myopes (EOMs, onset of short-sightedness before the age of 15), and six late-onset myopes (LOMs, onset of short-sightedness after the age of 15) took part in the study. Accommodative microfluctuations were measured at 22 Hz using an SRW-5000 autorefractor at accommodative demands of 1 D (dioptres), 2 D, and 3 D. Chaos theory analysis was used to determine the embedding lag, embedding dimension, limit of predictability, and Lyapunov exponent. Topological transitivity was also tested for. For comparison, the power spectrum and standard deviation were calculated for each time record. The EMMs had a statistically significant higher Lyapunov exponent than the LOMs (\documentclass[12pt]{minimal}
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\begin{document}$$0.64\pm 0.33$$\end{document}0.64±0.33 vs. \documentclass[12pt]{minimal}
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\begin{document}$$0.39\pm 0.20~\hbox {D}/\hbox {s}$$\end{document}0.39±0.20D/s) and a lower embedding dimension than the LOMs (\documentclass[12pt]{minimal}
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\begin{document}$$3.28\pm 0.46$$\end{document}3.28±0.46 vs. \documentclass[12pt]{minimal}
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\begin{document}$$3.67\pm 0.49$$\end{document}3.67±0.49). There was insufficient evidence (non-significant p value) of a difference between EOMs and EMMs or EOMs and LOMs. The majority of time records were topologically transitive. There was insufficient evidence of accommodative demand having an effect. Power spectrum analysis and assessment of the standard deviation of the fluctuations failed to discern differences based on refractive error. Chaos differences in accommodation microfluctuations indicate that the control system for LOMs is under stress in comparison to EMMs. Chaos theory analysis is a more sensitive marker of changes in accommodation microfluctuations than traditional analysis methods.
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Affiliation(s)
- Karen M Hampson
- School of Optometry and Vision Science, University of Bradford, Bradford, BD7 1DP, UK.
| | - Matthew P Cufflin
- School of Optometry and Vision Science, University of Bradford, Bradford, BD7 1DP, UK
| | - Edward A H Mallen
- School of Optometry and Vision Science, University of Bradford, Bradford, BD7 1DP, UK
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Optical Coherence Tomography as a Tool for Ocular Dynamics Estimation. BIOMED RESEARCH INTERNATIONAL 2015; 2015:293693. [PMID: 26557659 PMCID: PMC4628777 DOI: 10.1155/2015/293693] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Revised: 06/04/2015] [Accepted: 06/11/2015] [Indexed: 12/01/2022]
Abstract
Purpose. The aim of the study is to demonstrate that the ocular dynamics of the anterior chamber of the eye can be estimated quantitatively by means of optical coherence tomography (OCT). Methods. A commercial high speed, high resolution optical coherence tomographer was used. The sequences of tomographic images of the iridocorneal angle of three subjects were captured and each image from the sequence was processed in MATLAB environment in order to detect and identify the contours of the cornea and iris. The data on pulsatile displacements of the cornea and iris and the changes of the depth of the gap between them were retrieved from the sequences. Finally, the spectral analysis of the changes of these parameters was performed. Results. The results of the temporal and spectral analysis manifest the ocular microfluctuation that might be associated with breathing (manifested by 0.25 Hz peak in the power spectra), heart rate (1–1.5 Hz peak), and ocular hemodynamics (3.75–4.5 Hz peak). Conclusions. This paper shows that the optical coherence tomography can be used as a tool for noninvasive estimation of the ocular dynamics of the anterior segment of the eye, but its usability in diagnostics of the ocular hemodynamics needs further investigations.
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15
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Charman WN, Heron G. Microfluctuations in accommodation: an update on their characteristics and possible role. Ophthalmic Physiol Opt 2015; 35:476-99. [DOI: 10.1111/opo.12234] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 07/23/2015] [Indexed: 11/30/2022]
Affiliation(s)
- W Neil Charman
- Faculty of Life Sciences; University of Manchester; Manchester UK
| | - Gordon Heron
- Vision Sciences; Glasgow Caledonian University; Glasgow UK
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16
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Jeng WD, Ouyang Y, Huang TW, Duann JR, Chiou JC, Tang YS, Ou-Yang M. Research of accommodative microfluctuations caused by visual fatigue based on liquid crystal and laser displays. APPLIED OPTICS 2014; 53:H76-H84. [PMID: 25322435 DOI: 10.1364/ao.53.000h76] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 07/13/2014] [Indexed: 06/04/2023]
Abstract
Different levels of visual fatigue in the human eye depend on different color-formation methods and image quality. This paper uses the high-frequency component of the spectral power of accommodative microfluctuations as a major objective indicator for analyzing the effects of visual fatigue based on various displays, such as color-formation displays and 3D displays. Also, a questionnaire is used as a subjective indicator. The results are that 3D videos cause greater visual fatigue than 2D videos (p<0.001), the shutter-type 3D display causes visual fatigue more than the polarized type (p=0.012), the display of the time-sharing method causes greater visual fatigue than the spatial-formation method (p=0.008), and there is no significance between various light source modules of displays (p=0.162). In general, people with normal color discrimination have more visual fatigue than those with good color discrimination (p<0.001). Therefore, this paper uses the high-frequency component of accommodative microfluctuations to evaluate the physiological stress or strain by overexerting the visual system, and can compare the level of visual fatigue between various displays.
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Ju LH, Lee DH, Lee DH, Kim JH. The Relationship between the High-Frequency Component of Accommodative Microfluctuation, Accommodative Lag and Accommodative Amplitude in Presbyopic Eyes. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2014. [DOI: 10.3341/jkos.2014.55.11.1606] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Lock Hyun Ju
- Department of Ophthalmology, Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
| | | | - Do Hyung Lee
- Department of Ophthalmology, Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
| | - Jin Hyoung Kim
- Department of Ophthalmology, Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea
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Abstract
PURPOSE To review the methods for dynamic, non-invasive, and objective assessment of tear film surface quality and to outline their current state-of-the-art and their future potential. METHODS Among the methods available, high-speed videokeratoscopy, lateral shearing interferometry, and dynamic wavefront sensing are being considered. RESULTS The principles of operations, their advantages and disadvantages, and limitations of each method are being outlined. The possible future directions of each method are also discussed. CONCLUSIONS To gain a better understanding of tear film, its structure and function, it is essential to combine macroimaging technologies with those focusing on tear film microstructure. In this way, one can envisage a clinical device that could help, in future, early diagnosis of dry eye syndrome and development of better materials for contact lenses and eye lubricants.
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Serial measurements of accommodation by open-field Hartmann–Shack wavefront aberrometer in eyes with accommodative spasm. Jpn J Ophthalmol 2012; 56:617-23. [DOI: 10.1007/s10384-012-0187-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 07/09/2012] [Indexed: 10/27/2022]
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Danielewska ME, Iskander DR, Kowalska M, Kasprzak HT. Phase dependencies between longitudinal corneal apex displacement and cardiovascular signals: is the ocular pulse influenced by the electrical activity of the heart? Clin Exp Optom 2012; 95:631-7. [PMID: 22827844 DOI: 10.1111/j.1444-0938.2012.00775.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2011] [Revised: 02/21/2012] [Accepted: 02/22/2012] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND The aim was to establish phase relationships between the principal harmonic, related to the heart rate, of synchronically registered longitudinal corneal apex displacement (LCAD), blood pulsation (BP) and electrical heart activity signals in a group of healthy subjects. METHODS Longitudinal corneal apex displacement was non-invasively measured using an ultrasonic distance sensor. Synchronously, electrocardiographic (ECG) and blood pulsation signals were acquired. As all considered signals are non-stationary (that is, their spectral characteristics vary in time), a reliable and repeatable phase estimation method was sought. For this, a range of phase estimators were tested in the windowed regime of simulated non-stationary signals. Two robust estimators that showed minimum mean square error performance, were selected for further analysis of real signals registered for seven subjects participating in the study. RESULTS The windowed cross-correlation and the windowed minimum sum of squared error method achieved the best results among the estimators considered and their outputs were averaged to arrive at a robust phase estimator. Across the subjects, it was found that an increase in the time delay between the principal harmonic of BP and ECG signals, θ(BP,ECG), corresponds to a slight time delay increase between the corresponding harmonics of longitudinal corneal apex displacement and blood pulsation signals, θ(LCAD,BP) and a decrease in the time delay between those of longitudinal corneal apex displacement and ECG signals, θ(LCAD,ECG). Significant correlation (paired t-test, p < 0.05) were found between θ(BP,ECG) and θ(LCAD,BP) as well as between θ(BP,ECG) and θ(LCAD,ECG). There was no significant correlation found between θ(LCAD,BP) and θ(LCAD,ECG). CONCLUSION The results indicate that longitudinal corneal apex displacement and correspondingly the ocular pulse phenomenon have not only a vascular origin but could also be influenced by the electrical activity of the heart.
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Hampson KM, Mallen EAH. Chaos in ocular aberration dynamics of the human eye. BIOMEDICAL OPTICS EXPRESS 2012; 3:863-77. [PMID: 22567581 PMCID: PMC3342193 DOI: 10.1364/boe.3.000863] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 03/25/2012] [Accepted: 03/30/2012] [Indexed: 05/22/2023]
Abstract
Since the characterization of the eye's monochromatic aberration fluctuations in 2001, the power spectrum has remained the most widely used method for analyzing their dynamics. However, the power spectrum does not capture the complexities of the fluctuations. We measured the monochromatic aberration dynamics of six subjects using a Shack-Hartmann sensor sampling at 21 Hz. We characterized the dynamics using techniques from chaos theory. We found that the attractor embedding dimension for all aberrations, for all subjects, was equal to three. The embedding lag averaged across aberrations and subjects was 0.31 ± 0.07 s. The Lyapunov exponent of the rms wavefront error was positive for each subject, with an average value of 0.44 ± 0.15 µm/s. This indicates that the aberration dynamics are chaotic. Implications for future modeling are discussed.
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Effect of near adds on the variability of accommodative response in myopic children. Ophthalmic Physiol Opt 2011; 31:145-54. [DOI: 10.1111/j.1475-1313.2010.00818.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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23
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Ghosh A, Collins MJ, Read SA, Davis BA, Iskander DR. Measurement of ocular aberrations in downward gaze using a modified clinical aberrometer. BIOMEDICAL OPTICS EXPRESS 2011; 2:452-463. [PMID: 21412451 PMCID: PMC3047351 DOI: 10.1364/boe.2.000452] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 01/25/2011] [Accepted: 01/26/2011] [Indexed: 05/30/2023]
Abstract
Changes in corneal optics have been measured after downward gaze. However, ocular aberrations during downward gaze have not been previously measured. A commercial Shack-Hartmann aberrometer (COAS-HD) was modified by adding a relay lens system and a rotatable beam splitter to allow on-axis aberration measurements in primary gaze and downward gaze with binocular fixation. Measurements with the modified aberrometer (COAS-HD relay system) in primary and downward gaze were validated against a conventional aberrometer. In human eyes, there were significant changes (p<0.05) in defocus C(2,0), primary astigmatism C(2,2) and vertical coma C(3,-1) in downward gaze (25 degrees) compared to primary gaze, indicating the potential influence of biomechanical forces on the optics of the eye in downward gaze. To demonstrate a further clinical application of this modified aberrometer, we measured ocular aberrations when wearing a progressive addition lens (PAL) in primary gaze (0 degree), 15 degrees downward gaze and 25 degrees downward gaze.
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Affiliation(s)
- Atanu Ghosh
- Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology, Brisbane, Australia
| | - Michael J Collins
- Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology, Brisbane, Australia
| | - Scott A Read
- Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology, Brisbane, Australia
| | - Brett A Davis
- Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology, Brisbane, Australia
| | - D. Robert Iskander
- Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Wroclaw, Poland
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Monika D, Małgorzata K, Henryk K. Application of Coherence Function for Calculating Time Shifts between Axial Corneal Displacements and Electrical Heart Activity. Biocybern Biomed Eng 2011. [DOI: 10.1016/s0208-5216(11)70002-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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25
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Szczesna DH, Alonso-Caneiro D, Iskander DR, Read SA, Collins MJ. Lateral shearing interferometry, dynamic wavefront sensing, and high-speed videokeratoscopy for noninvasive assessment of tear film surface characteristics: a comparative study. JOURNAL OF BIOMEDICAL OPTICS 2010; 15:037005. [PMID: 20615034 DOI: 10.1117/1.3431103] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
There are several noninvasive techniques for assessing the kinetics of tear film, but no comparative studies have been conducted to evaluate their efficacies. Our aim is to test and compare techniques based on high-speed videokeratoscopy (HSV), dynamic wavefront sensing (DWS), and lateral shearing interferometry (LSI). Algorithms are developed to estimate the tear film build-up time T(BLD), and the average tear film surface quality in the stable phase of the interblink interval TFSQ(Av). Moderate but significant correlations are found between T(BLD) measured with LSI and DWS based on vertical coma (Pearson's r(2)=0.34, p<0.01) and higher order rms (r(2)=0.31, p<0.01), as well as between TFSQ(Av) measured with LSI and HSV (r(2)=0.35, p<0.01), and between LSI and DWS based on the rms fit error (r(2)=0.40, p<0.01). No significant correlation is found between HSV and DWS. All three techniques estimate tear film build-up time to be below 2.5 sec, and they achieve a remarkably close median value of 0.7 sec. HSV appears to be the most precise method for measuring tear film surface quality. LSI appears to be the most sensitive method for analyzing tear film build-up.
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Affiliation(s)
- Dorota H Szczesna
- Wroclaw University of Technology, Institute of Physics, 27 Wybrzeze Wyspianskiego, Wroclaw, 50-370 Poland.
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Abstract
PURPOSE To investigate the relationship among microfluctuations in accommodation, resting tension on the crystalline lens, ciliary body thickness, and refractive error in children. METHODS Subjects were 49 children, aged 8 to 15 years. Subjects wore habitual correction over their left eye and an infrared filter over the right eye during accommodative measurements. Monocular accommodation was measured continuously for two, 30-second periods using a PowerRef I at a sampling rate of 25 Hz while subjects viewed a high-contrast target at 0.25 m. The high (1.0 to 2.3 Hz) and low- (0 to 0.6 Hz) frequency components of the power spectrum from a fast Fourier transform of the accommodative response were used in analysis. Resting tension on the crystalline lens was assessed by measuring the amplitude of the oscillations of the crystalline lens after a rightward 20 degrees saccadic eye movement. Ciliary body thickness was measured 2 mm posterior to the scleral spur from images obtained with a Zeiss Visante optical coherence tomography (OCT). Cycloplegic spherical equivalent refractive error was obtained with the Grand Seiko autorefractor. RESULTS The mean +/- SD spherical equivalent refractive error was -1.00 D +/- 2.25 (range, -6.00 D to +3.44 D). Greater power in the log of the high-frequency component of accommodative microfluctuations was associated with thinner ciliary bodies (p = 0.03) and lower ages (p = 0.0004). More hyperopic refractive errors with greater power in the high-frequency component (p = 0.0005) and the low-frequency component (p = 0.02). No statistically significant relationship was found for the low-frequency component or root mean square of accommodative microfluctuations and refractive error. CONCLUSIONS High-frequency microfluctuations of accommodation appear to be suppressed with thicker ciliary bodies. These variations in accommodation need to be observed in a longitudinal study to better assess the functional significance of their relationship to ciliary body size and refractive error.
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Davies LN, Wolffsohn JS, Gilmartin B. Autonomic correlates of ocular accommodation and cardiovascular function. Ophthalmic Physiol Opt 2009; 29:427-35. [DOI: 10.1111/j.1475-1313.2009.00635.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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The effect of modulating ocular depth of focus upon accommodation microfluctuations in myopic and emmetropic subjects. Vision Res 2008; 49:211-8. [PMID: 18992269 DOI: 10.1016/j.visres.2008.10.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Revised: 09/22/2008] [Accepted: 10/08/2008] [Indexed: 11/22/2022]
Abstract
The magnitude of accommodation microfluctuations increases in emmetropic subjects viewing low luminance targets or viewing a target through small artificial pupils. Larger microfluctuations reported in myopia may result from an abnormally large depth of focus (DoF). The effect of modulating the size of the DoF has not been investigated in myopic subjects and may help to explain the cause of the increased DoF. Accommodation microfluctuations were recorded under two experimental conditions. Firstly, 12 emmetropes (EMMs), and 24 myopes (MYOs) viewed a Maltese Cross target with luminance levels of 0.002, 0.2, 6 and 600cd/m(2) and in darkness, and second, 14 EMMs and 16 MYOs viewed a Maltese Cross target through pupil diameters of 0.5, 1, 2, 3, 4 and 5mm presented in Maxwellian view. The magnitude of the accommodation microfluctuations increased significantly with a target luminance of 0.002cd/m(2) (p<.03) and pinhole diameters of <2mm (p<.05). For all other luminance levels and pupil diameters the magnitude was constant. For both conditions, MYOs had significantly larger microfluctuations than EMMs (p<.01). Considerable inter-subject variability was observed in the degree to which the magnitude of the microfluctuations increased, for both the 0.002cd/m(2) luminance and 0.5mm pupils, however, this was not correlated with refractive error. The increase in the magnitude of the microfluctuations while viewing a low luminance target (0.002cd/m(2)) may be due to a shallower contrast gradient in the cortical image, with a consequent increase in DoF. The microfluctuations also increase when viewing through small pupils (<2mm), which increases the DoF without altering the contrast gradient. The larger microfluctuations found in the MYOs consolidates the theory that MYOs have a larger DoF than EMMs and therefore have a higher threshold for retinal image blur.
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Chin SS, Hampson KM, Mallen EAH. Binocular correlation of ocular aberration dynamics. OPTICS EXPRESS 2008; 16:14731-45. [PMID: 18795011 DOI: 10.1364/oe.16.014731] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Fluctuations in accommodation have been shown to be correlated in the two eyes of the same subject. However, the dynamic correlation of higher-order aberrations in the frequency domain has not been studied previously. A binocular Shack-Hartmann wavefront sensor is used to measure the ocular wavefront aberrations concurrently in both eyes of six subjects at a sampling rate of 20.5 Hz. Coherence function analysis shows that the inter-ocular correlation between aberrations depends on subject, Zernike mode and frequency. For each subject, the coherence values are generally low across the resolvable frequency range (mean 0.11), indicating poor dynamic correlation between the aberrations of the two eyes. Further analysis showed that phase consistency dominates the coherence values. Monocular and binocular viewing conditions showed similar power spectral density functions.
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Affiliation(s)
- S S Chin
- Bradford School of Optometry and Vision Science, University of Bradford, Bradford, UK.
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Siedlecki D, Kasprzak H, Pierscionek BK. Dynamic changes in corneal topography and its influence on the point-spread function of the eye. APPLIED OPTICS 2007; 46:1361-6. [PMID: 17318256 DOI: 10.1364/ao.46.001361] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The dynamic changes of the anterior surface of the eye are investigated. A Twyman-Green interferometer is used to record topographic images at 40 ms intervals. A method of analysis of the dynamic changes in topography by use of Zernike polynomials enables a general distinction to be made between dynamic alterations in the shape of the cornea itself and the changes in the layer of the tears. The influence of deviations in the shape of the anterior surface of the eye on the retinal image is estimated.
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Affiliation(s)
- Damian Siedlecki
- Institute of Physics, Wroclaw University of Technology, Wroclaw, Poland.
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Kasprzak HT, Iskander DR. Spectral characteristics of longitudinal corneal apex velocities and their relation to the cardiopulmonary system. Eye (Lond) 2006; 21:1212-9. [PMID: 16936640 DOI: 10.1038/sj.eye.6702578] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To study the naturally occurring kinetic characteristics of corneal surface. METHODS The right eyes of three subjects (young, early presbyope, and presbyope) were examined. Cardiac signal and longitudinal corneal apex movements were simultaneously measured with electrocardiography (ECG) and a high-speed videokeratoscope, respectively. Time, frequency, and combined time-frequency representations of the acquired signals were derived to establish their temporal and spectral contents. Coherence analysis was used to assess the correlation between the corneal apex velocities and the cardiopulmonary system. RESULTS In all measurements, longitudinal corneal apex velocity signals showed close correlation with the corresponding ECG signals. The signatures of the pulse frequency, which was inferred from the ECG spectra and their variations in time, were clearly visible in the spectral content of corneal apex velocities. For the young subject, the correlation was the strongest and all of the spectral content of the pulse signal including the harmonics was propagating to the corneal apex velocities. For the other two subjects, there was a clear propagation of the pulse signal itself but not of all pulse harmonics. CONCLUSIONS Longitudinal movements of the corneal apex are closely related to the cardiopulmonary system. The differences in propagation of pulse harmonics to the corneal apex velocities for different subjects suggest that the frequency characteristics of apex velocity could be related to pulsative variations in the intraocular pressure and biomechanical properties of the eye. These findings could potentially be used in noninvasive assessment of the hemodynamic status of the eye with high-speed videokeratoscopy.
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Affiliation(s)
- H T Kasprzak
- Faculty of Health, School of Optometry, Queensland University of Technology, Brisbane, Queensland, Australia
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Wolffsohn JS, Ukai K, Gilmartin B. Dynamic measurement of accommodation and pupil size using the portable Grand Seiko FR-5000 autorefractor. Optom Vis Sci 2006; 83:306-10. [PMID: 16699443 DOI: 10.1097/01.opx.0000216059.54932.3a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
PURPOSE The purpose of this study was to evaluate the potential of the portable Grand Seiko FR-5000 autorefractor to allow objective, continuous, open-field measurement of accommodation and pupil size for the investigation of the visual response to real-world environments and changes in the optical components of the eye. METHODS The FR-5000 projects a pair of infrared horizontal and vertical lines on either side of fixation, analyzing the separation of the bars in the reflected image. The measurement bars were turned on permanently and the video output of the FR-5000 fed into a PC for real-time analysis. The calibration between infrared bar separation and the refractive error was assessed over a range of 10.0 D with a model eye. Tolerance to longitudinal instrument head shift was investigated over a +/-15 mm range and to eye alignment away from the visual axis over eccentricities up to 25.0 degrees . The minimum pupil size for measurement was determined with a model eye. RESULTS The separation of the measurement bars changed linearly (r2 = 0.99), allowing continuous online analysis of the refractive state at 60 Hz temporal and approximately 0.01 D system resolution with pupils >2 mm. The pupil edge could be analyzed on the diagonal axes at the same rate with a system resolution of approximately 0.05 mm. The measurement of accommodation and pupil size were affected by eccentricity of viewing and instrument focusing inaccuracies. CONCLUSIONS The small size of the instrument together with its resolution and temporal properties and ability to measure through a 2 mm pupil make it useful for the measurement of dynamic accommodation and pupil responses in confined environments, although good eye alignment is important.
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Affiliation(s)
- James Stuart Wolffsohn
- Ophthalmic Research Group, Life and Health Sciences, Aston University, Birmingham, United Kingdom.
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Hampson KM, Paterson C, Dainty C, Mallen EAH. Adaptive optics system for investigation of the effect of the aberration dynamics of the human eye on steady-state accommodation control. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2006; 23:1082-8. [PMID: 16642185 DOI: 10.1364/josaa.23.001082] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
It is now known that defocus is not the only aberration in the eye that exhibits dynamic behavior during fixation. It is currently unknown what effects, if any, the dynamics of these other aberrations have on steady-state accommodation control. We constructed an adaptive optics system to serve as a tool for future investigations in this area. The system has several design features of interest, including automated precompensation of defocus and astigmatism and a method to bypass a scanner used to reduce speckle. It also has the facility to measure the eye's aberrations independent of the aberration manipulation device-a 37-actuator membrane deformable mirror. Coherence function analysis was used to assess the deformable mirror performance in terms of coupling between Zernike modes. Modes beyond third radial order showed severe coupling. Pilot data were collected on one subject to demonstrate the utility of this system in steady-state accommodation studies. The value of the system for future work in this area is discussed.
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Affiliation(s)
- Karen M Hampson
- Photonics Group, Blackett Laboratory, Imperial College London, UK.
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Abstract
PURPOSE To investigate fluctuations in the ocular surface, we used high-speed videokeratoscopy (50 Hz) to measure the dynamics of the ocular surface topography. METHODS Ocular surface height difference maps were computed to illustrate the changes in the tear film in the inter-blink interval. Topography data were used to derive the ocular surface wavefront aberrations up to the fourth radial order of the Zernike polynomial expansion. We examined the ocular surface dynamics and temporal changes in the ocular surface wavefront aberrations in the inter-blink interval. RESULTS During the first 0.5 s following a blink, the ocular surface height at the upper edge of the topography map increased by about 2 mum. Temporal changes occurred for some ocular surface wavefront aberrations and appeared to be related to changes in the distribution of tear film. CONCLUSION In the clinical measurement of ocular surface topography using videokeratoscopy or optics of the eye using wavefront sensors, care should be taken to avoid the initial tear film build-up phase following a blink to achieve more consistent results.
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Affiliation(s)
- M Zhu
- Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology, Kelvin Grove, Australia.
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Yi F, Iskander DR, Franklin R, Collins MJ. Computer simulation of visual outcomes of wavefront-only corneal ablation. J Cataract Refract Surg 2006; 32:487-94. [PMID: 16631063 DOI: 10.1016/j.jcrs.2005.12.073] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Accepted: 08/09/2005] [Indexed: 10/24/2022]
Abstract
PURPOSE To evaluate the effectiveness, predicted visual outcome, and limitations of a corneal ablation algorithm that uses wavefront aberration measurement alone without the need for corneal shape information. SETTING Contact Lens and Visual Optical Laboratory, School of Optometry, Queensland University of Technology, Brisbane, Australia. METHODS Corneal topography and wavefront error data from 22 eyes of 11 potential refractive surgery candidates were used. A computer simulation of the corneal ablation was performed, and the predicted postoperative visual outcome was assessed by calculating the resulting wavefront root-mean-square (RMS) values and visual Strehl ratios. Additionally, the effect of ablation alignment error was examined. Finally, the visual outcomes of the wavefront-only corneal ablations were compared to those in an age-matched group of 20 emmetropic patients. RESULTS Significant improvement in total and higher-order wavefront RMS was achieved postoperatively in both an ideal setting and in the case of ablation alignment errors. The predicted improvement in visual Strehl ratio in the potential refractive surgery candidates was significantly better than that in the untreated emmetropes. After additional simulated decentration of the pupil center by 150 microm, the result was slightly worse, but the change was found to not be significant when compared to the retinal image quality of emmetropes. CONCLUSIONS Wavefront-only corneal ablation algorithms could potentially lead to significantly better visual outcomes than those normally encountered in untreated emmetropes, provided that the alignment error is not large. The presented methodology may be used as a screening tool to predict patients' visual outcomes before the surgery.
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Affiliation(s)
- Fan Yi
- School of Engineering, Griffith University, Gold Coast, Australia
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Buehren T, Collins MJ. Accommodation stimulus-response function and retinal image quality. Vision Res 2005; 46:1633-45. [PMID: 16040078 DOI: 10.1016/j.visres.2005.06.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2005] [Revised: 06/07/2005] [Accepted: 06/08/2005] [Indexed: 10/25/2022]
Abstract
Accommodation stimulus-response function (ASRF) and its relationship to retinal image quality were investigated using a modified wavefront sensor. Ten subjects were presented with six vergence stimuli between 0.17 D and 5 D. For each vergence distance, ocular wavefronts and subjective visual acuity were measured. Wavefronts were analysed for a fixed 3-mm pupil diameter and for natural pupil sizes. Visual Strehl ratio computed in the frequency domain (VSOTF) and retinal images were calculated for each condition tested. Subjective visual acuity was significantly improved at intermediate vergence distances (1D and 2D; p < 0.01), and only decreased significantly at 5 D compared with 0.17 D (p < 0.05). VSOTF magnitude was associated with subjective visual acuity and VSOTF peak location correlated with accommodation error. Apparent accommodation errors due to spherical aberration were highly correlated with accommodation lead and lag for natural pupils (R(2) = 0.80) but not for fixed 3-mm pupils (R(2) < 0.00). The combination of higher-order aberrations and accommodation errors improved retinal image quality compared with accommodation errors or higher order aberrations alone. Pupil size and higher order aberrations play an important role in the ASRF.
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Affiliation(s)
- Tobias Buehren
- Contact Lens and Visual Optics Laboratory, School of Optometry, Victoria Park Road, Kelvin Grove, Queensland University of Technology, Brisbane, Qld 4059, Australia.
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Hampson KM, Munro I, Paterson C, Dainty C. Weak correlation between the aberration dynamics of the human eye and the cardiopulmonary system. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2005; 22:1241-50. [PMID: 16053145 DOI: 10.1364/josaa.22.001241] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
It is fairly well established that the higher-order aberrations of the eye fluctuate over relatively short time periods, but as yet there is no conclusive evidence regarding the origin of these fluctuations. We measured the aberrations and the pulse pressure wave simultaneously for five subjects. The aberrations were measured by using a Shack-Hartmann sensor sampling at 21.2 Hz. We decomposed the aberration data into Zernike coefficients up to and including fifth order and also calculated the rms wave-front error. From the pulse data the heart rate variability signal was also derived. Coherence function analysis showed that for all subjects there was a weak correlation between many of the aberrations and the pulse and the derived heart rate variability. The pulse and the heart rate variability can account for only 11% +/- 2% and 20% +/- 2%, respectively, of the aberration dynamics.
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Affiliation(s)
- Karen M Hampson
- Photonics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW, UK.
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Abstract
We determined the effect upon accommodative responses of tinted lenses prescribed for the relief of visual discomfort in a group of five long term lens wearers. Static and dynamic responses were measured under four viewing conditions (1) prescribed tinted lens (2) neutral density filter (3) tinted lens of complementary colour and (4) no absorptive lens. While similarity and normality of the mean stimulus-response functions between the four viewing conditions were evident, the low frequency component of the accommodation microfluctuations was significantly greater while viewing the target in the 'no lens' viewing condition. These increases in the low frequency components (LFC) of the accommodation may be a subtle indicator of visual stress in these patients. Colour specificity is not supported by this finding.
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Affiliation(s)
- A J Simmers
- Department of Academic Ophthalmology, Imperial College of Science, Technology and Medicine, Western Eye Hospital, London, UK.
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