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Davies LN, Biswas S, Bullimore M, Cruickshank F, Estevez JJ, Khanal S, Kollbaum P, Marcotte-Collard R, Montani G, Plainis S, Richdale K, Simard P, Wolffsohn JS. BCLA CLEAR presbyopia: Mechanism and optics. Cont Lens Anterior Eye 2024:102185. [PMID: 38796331 DOI: 10.1016/j.clae.2024.102185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2024]
Abstract
With over a billion adults worldwide currently affected, presbyopia remains a ubiquitous, global problem. Despite over a century of study, the precise mechanism of ocular accommodation and presbyopia progression remains a topic of debate. Accordingly, this narrative review outlines the lenticular and extralenticular components of accommodation together with the impact of age on the accommodative apparatus, neural control of accommodation, models of accommodation, the impact of presbyopia on retinal image quality, and both historic and contemporary theories of presbyopia.
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Affiliation(s)
- Leon N Davies
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK.
| | - Sayantan Biswas
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK
| | | | - Fiona Cruickshank
- Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, UK
| | - Jose J Estevez
- Caring Futures Institute, College of Nursing and Health Sciences, Optometry and Vision Science, Flinders University, Adelaide, Australia; Flinders Centre for Ophthalmology, Eye and Vision Research, Department of Ophthalmology, Flinders University, Adelaide, Australia
| | - Safal Khanal
- Department of Optometry and Vision Science, The University of Alabama at Birmingham, USA
| | | | | | | | - Sotiris Plainis
- Laboratory of Optics and Vision, School of Medicine, University of Crete, Greece
| | | | - Patrick Simard
- School of Optometry, Universite de Montreal, Montreal, Quebec, Canada
| | - James S Wolffsohn
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK
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Debowy F, Pierscionek B. A comparative analysis of the influence of refractive error on image acuity using three eye models. Ophthalmic Physiol Opt 2024; 44:182-190. [PMID: 38009663 DOI: 10.1111/opo.13251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 10/31/2023] [Accepted: 10/31/2023] [Indexed: 11/29/2023]
Abstract
PURPOSE To analyse and compare image acuity for different refractive errors generated by either altering axial length or corneal curvature and using three human eye models with two pupil sizes. METHODS Three different eye models, Liou-Brennan, Goncharov and Navarro, were used. Simulations were made (using Ansys Zemax OpticStudio 22.3) for real pupil sizes of 3 and 6 mm with refractive errors ranging from -2 to +2 D in 0.25 D increments. Refractive errors were simulated by varying axial length or corneal curvature. Root mean square (RMS) values were used to determine image acuity. RESULTS For the 3-mm pupil, all models gave similar results, with the Navarro model having slightly higher RMS values for the emmetropic eye. For the 6-mm pupil, the Liou-Brennan and Goncharov eye models gave similar results, with RMS values lower than for the Navarro eye model. The highest RMS value was visible in the axial length-induced refractive errors. Refractive errors generated by altering corneal curvature give smaller RMS values than those generated by altering axial length. The axial length and corneal radius simulations indicate a wide spread of results for myopic, hyperopic and emmetropic eyes. There are multiple outcomes that give the same refractive error, even within a single-eye model. The axial length/corneal curvature ratio showed a higher ratio for myopes than hyperopes for every model. CONCLUSIONS The influence of refractive error on image acuity varied depending on the simulation method of refractive error and the model used. The origins of refractive error and the influence it has on image acuity need further investigation. As models become more sophisticated, personalised and biologically relevant, they will better represent the image acuity of the eye for varying refractive errors, ethnicities, ages and pupil sizes.
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Affiliation(s)
- Fabian Debowy
- Faculty of Health, Education Medicine and Social Care, Medical Technology Research Centre, Anglia Ruskin University, Cambridge, UK
| | - Barbara Pierscionek
- Faculty of Health, Education Medicine and Social Care, Medical Technology Research Centre, Anglia Ruskin University, Cambridge, UK
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Rodriguez-Lopez V, Geisler W, Dorronsoro C. Spatiotemporal defocus sensitivity function of the human visual system. BIOMEDICAL OPTICS EXPRESS 2023; 14:3654-3670. [PMID: 37497500 PMCID: PMC10368063 DOI: 10.1364/boe.486242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 05/31/2023] [Accepted: 06/01/2023] [Indexed: 07/28/2023]
Abstract
Tunable lenses make it possible to measure visual sensitivity to rapid changes in optical power, surpassing the limits imposed by mechanical elements. Using a tunable lens system, we measured, for the first time, the spatiotemporal defocus sensitivity function (STDSF), and the limits of human defocus perception. Specifically, we measured defocus sensitivity using a QUEST adaptive psychophysical procedure for different stimuli (Gabor patches of different spatial frequencies, natural images, and edges) and we developed descriptive models of defocus perception. For Gabor patches, we found on average (across seven subjects) that the maximum sensitivity to defocus is 0.22 D at 14 cpd and 10 Hz, and that the upper limits of sensitivity are 40 cpd and 40 Hz. Our results suggest that accommodation remains fixed while performing the defocus flicker-detection task. These results have implications for new technologies whose working principles make use of fast changes to defocus.
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Affiliation(s)
- Victor Rodriguez-Lopez
- Institute of Optics, Spanish National Research Council (IO-CSIC), IO-CSIC, Serrano 121, E-28006, Madrid, Spain
| | - Wilson Geisler
- Center for Perceptual Systems, The University of Texas at Austin, 1 University Station, A8000, E-78712, Austin, Texas, USA
| | - Carlos Dorronsoro
- Institute of Optics, Spanish National Research Council (IO-CSIC), IO-CSIC, Serrano 121, E-28006, Madrid, Spain
- Center for Perceptual Systems, The University of Texas at Austin, 1 University Station, A8000, E-78712, Austin, Texas, USA
- 2EyesVision SL, Plaza de la Encina, 10, núcleo 3, planta 4ª, E-28760 Tres Cantos, Madrid, Spain
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Rodriguez-Lopez V, Hernandez-Poyatos A, Dorronsoro C. Defocus flicker of chromatic stimuli deactivates accommodation. BIOMEDICAL OPTICS EXPRESS 2023; 14:3671-3688. [PMID: 37497489 PMCID: PMC10368037 DOI: 10.1364/boe.486466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 05/20/2023] [Accepted: 05/20/2023] [Indexed: 07/28/2023]
Abstract
Tunable lenses, optical elements able to change their optical power within milliseconds, constitute an emerging technology increasingly used in ophthalmic applications. In this study, 25 subjects looked through tunable lenses at a chromatic stimulus to evaluate the perceptual response of the human visual system to periodic changes in defocus of 0.25D of amplitude and 15 Hz of temporal frequency. These defocus changes produce flicker and chromatic distortions that change with the overall level of defocus. The task in this study was to minimize the flicker by varying the average optical power, and it was performed for different myopic and hyperopic starting points. Subjects also performed a blur-minimization task in a black-and-white stimulus of the same geometry. The flicker-minimization task is more repeatable than the blur-minimization task (standard deviations ±0.17D and ±0.49D). The time per repetition of the flicker-minimization task is only 38s. Cycloplegia severely affects the blur-minimization, but not the flicker-minimization task, confirming that defocus flicker deactivates the accommodative system. This discovery can be used to develop new methods for measuring the refractive error of the eye that does not require supervision and can potentially improve existing subjective methods in terms of accuracy, precision, and measurement time.
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Affiliation(s)
- Victor Rodriguez-Lopez
- Institute of Optics, Spanish National Research Council (IO-CSIC), IO-CSIC, Serrano 121, E-28006, Madrid, Spain
| | - Alfonso Hernandez-Poyatos
- Institute of Optics, Spanish National Research Council (IO-CSIC), IO-CSIC, Serrano 121, E-28006, Madrid, Spain
| | - Carlos Dorronsoro
- Institute of Optics, Spanish National Research Council (IO-CSIC), IO-CSIC, Serrano 121, E-28006, Madrid, Spain
- 2EyesVision SL, Plaza de la Encina, 10, núcleo 3, planta 4ª, E-28760 Tres Cantos, Madrid, Spain
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The role of retinotopic cues in deciphering the direction and magnitude of monocular dynamic ocular accommodation: A review. Vision Res 2022; 196:108026. [DOI: 10.1016/j.visres.2022.108026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 02/04/2022] [Accepted: 02/10/2022] [Indexed: 12/28/2022]
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Vohnsen B. Geometrical scaling of the developing eye and photoreceptors and a possible relation to emmetropization and myopia. Vision Res 2021; 189:46-53. [PMID: 34619411 DOI: 10.1016/j.visres.2021.09.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/10/2021] [Accepted: 09/22/2021] [Indexed: 10/20/2022]
Abstract
In this study the role of vergence in relation to age-dependent scaling of eye and photoreceptor parameters is studied. The underlying hypothesis is that the size and packing of outer segments is matched to the pupil size outdoors in photopic conditions. Vergence is analysed in relation to the angular spectrum of waves being incident using age-dependent data from the literature for the actual geometry and density of photoreceptor cones and rods. This approach is used to derive simple relations for the angular confinement of light along outer segments. Only with a small photopic pupil can leakage and crosstalk for both central and peripheral photoreceptors be entirely ruled out due to the finite length of the outer segments. A limiting 3 mm pupil size is found for children in the school age. Larger pupils will increase the likelihood of leakage and crosstalk that may therefore impact on emmetropization. This study has introduced a new paradigm in myopia research by considering vergence across the 3-D retina as being matched to the angular spectrum of waves being incident from the eye pupil. Emmetropization suggests a delicate balance between photoreceptor outer segment length and density in relation to pupil size. Only when balanced will leakage and crosstalk between adjacent outer segments be effectively suppressed thereby ensuring the highest possible light capture efficiency by visual pigments in the outer segments whether an image is formed on the retina or not.
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Affiliation(s)
- Brian Vohnsen
- Advanced Optical Imaging Group, School of Physics, University College Dublin, Ireland.
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Panorgias A, Aigbe S, Jeong E, Otero C, Bex PJ, Vera-Diaz FA. Retinal Responses to Simulated Optical Blur Using a Novel Dead Leaves ERG Stimulus. Invest Ophthalmol Vis Sci 2021; 62:1. [PMID: 34338749 PMCID: PMC8340654 DOI: 10.1167/iovs.62.10.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Purpose The purpose of this study was to evaluate retinal responses to different types and magnitudes of simulated optical blur presented at specific retinal eccentricities using naturalistic images. Methods Electroretinograms (ERGs) were recorded from 27 adults using 30-degree dead leaves naturalistic images, digitally blurred with one of three types of optical blur (defocus, astigmatism, and spherical aberrations), and one of three magnitudes (0.1, 0.3, or 0.5 µm) of blur. Digitally computed blur was applied to the entire image, or on an area outside the central 6 degrees or 12 degrees of retinal eccentricity. Results ERGs were significantly affected by blur type, magnitude, and retinal eccentricity. ERGs were differentially affected by defocus and spherical aberrations; however, astigmatism had no effect on the ERGs. When blur was applied only beyond the central 12 degrees eccentricity, the ERGs were unaffected. However, when blur was applied outside the central 6 degrees, the ERG responses were significantly reduced and were no different from the ERGs recorded with entirely blurred images. Conclusions Blur type, magnitude, and location all affect the retinal responses. Our data indicate that the retinal area between 6 and 12 degrees eccentricity has the largest effect on the retinal responses to blur. In addition, certain optical blur types appear to have a more detrimental effect on the ERGs than others. These results cannot be solely explained by changes to image contrast and spatial frequency content, suggesting that retinal neurons might be sensitive to spatial cues in order to differentiate between different blur types.
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Affiliation(s)
| | - Stephanie Aigbe
- New England College of Optometry, Boston, Massachusetts, United States
| | - Emily Jeong
- New England College of Optometry, Boston, Massachusetts, United States
| | - Carles Otero
- EMEA Scientific Communications - Alcon, Barcelona, Cataluña, Spain
| | - Peter J Bex
- New England College of Optometry, Boston, Massachusetts, United States.,Psychology Department, College of Science, Northeastern University, Boston, Massachusetts, United States
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Águila-Carrasco AJD, Marín-Franch I. Predictability of sinusoidally moving stimuli does not improve the accuracy of the accommodative response. Sci Rep 2021; 11:15195. [PMID: 34312461 PMCID: PMC8313575 DOI: 10.1038/s41598-021-94642-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 07/13/2021] [Indexed: 12/31/2022] Open
Abstract
Previous research work suggests that predictable target motion such as sinusoidal movement can be anticipated by the visual system, thereby improving the accommodative response. The validity of predictable motion for studying human dynamic accommodation is sometimes put into question. The aim of this work was to assess the effect of anticipation along with learning (and motivation, etc.) and fatigue (and boredom, loss of attention, etc.) on dynamic accommodation experiments from a practical perspective. Specifically, changes in amplitude and temporal phase lag were estimated within and between trials as 9 adult observers were instructed to focus on a stimulus that oscillated sinusoidally towards and away from the eye at specific temporal frequencies. On average, amplitude decreased whereas phase increased within trials. No evidence of anticipation or learning was observed either within or between trials. Fatigue consistently dominated anticipation and learning within the course of each trial. Even if the eye is equipped by a prediction operator as it is often assumed, fatigue confounds the results from dynamic accommodation experiments more than anticipation or learning.
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Józwik A, Asejczyk-Widlicka M, Kurzynowski P, Pierscionek BK. How a dynamic optical system maintains image quality: Self-adjustment of the human eye. J Vis 2021; 21:6. [PMID: 33656560 PMCID: PMC7938001 DOI: 10.1167/jov.21.3.6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The eyeball is continually subjected to forces that cause alterations to its shape and dimensions, as well as to its optical components. Forces that induce accommodation result in an intentional change in focus; others, such as the effect of intraocular pressure fluctuations, are more subtle. Although the mechanical properties of the eyeball and its components permit mediation of such subtle forces, the concomitant optical changes are not detected by the visual system. Optical self-adjustment is postulated as the mechanism that maintains image quality. The purpose of this study was to investigate how self-adjustment occurs by using an optical model of the eyeball and to test the requisite optical and biometric conditions.
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Affiliation(s)
- Agnieszka Józwik
- Department of Optics and Photonics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.,
| | - Magdalena Asejczyk-Widlicka
- Department of Optics and Photonics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.,
| | - Piotr Kurzynowski
- Department of Optics and Photonics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.,
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