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Sah RP, Jaskulski M, Kollbaum PS. Modelling the refractive and imaging impact of multi-zone lenses utilised for myopia control in children's eyes. Ophthalmic Physiol Opt 2022; 42:571-585. [PMID: 35170789 PMCID: PMC9544677 DOI: 10.1111/opo.12959] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 11/27/2022]
Abstract
PURPOSE To develop an optical model of a child's eye to reveal the impact of target distance and accommodative behaviour on retinal image quality when fitted with multi-zone lenses. METHODS Pupil size, aberration levels and accommodative lag were adjusted for models viewing stimuli at 400, 100, 33 and 20 cm. Distributions of defocus across the pupil and simulated retinal images were obtained. An equivalent 16-point letter was imaged at near viewing distances, while a 0.00 logMAR (6/6) letter was imaged at 400 cm. Multi-zone lenses included those clinically utilised for myopia control (e.g., dual-focus, multi-segmented and aspherical optics). RESULTS Viewing distance adjustments to model spherical aberration (SA) and pupil radius resulted in a model eye with wider defocus distributions at closer viewing distances, especially at 20 cm. The increasing negative SA at near reduced the effective add power of dual-focus lenses, reducing the amount of myopic defocus introduced by the centre-distance, 2-zone design. The negative SA at near largely compensated for the high positive SA introduced by the aspheric lens, removing most myopic defocus when viewing at near. A 0.50 D accommodative lag had little impact on the legibility of typical text (16-point) at the closer viewing distances. CONCLUSIONS All four multi-zone lenses successfully generated myopic defocus at greater viewing distances, but two failed to introduce significant amounts of myopic defocus at the nearest viewing distance due to the combined effects of pupil miosis and negative SA. Typical 16-point type is easily legible at near even in presence of the multi-zone optics of lenses utilised for myopia control and accommodative lag.
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Affiliation(s)
- Raman Prasad Sah
- School of Optometry, Indiana University, Bloomington, Indiana, USA
| | - Matt Jaskulski
- School of Optometry, Indiana University, Bloomington, Indiana, USA
| | - Pete S Kollbaum
- School of Optometry, Indiana University, Bloomington, Indiana, USA
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Vincent M, Marin G, Legras R. Subjective Evaluation of Defocus and Astigmatism Combinations Using Image Simulation in Presbyopes. Optom Vis Sci 2021; 98:73-80. [PMID: 33394934 DOI: 10.1097/opx.0000000000001627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
SIGNIFICANCE Image simulation is a useful and efficient tool to explore the impact of defocus and astigmatism combinations on visual acuity and image quality score when accommodation is taken into account. PURPOSE The goal of this experiment was to determine if a simulation is able to predict visual acuity and image quality score (IQS) with defocus and astigmatism combinations in presbyopes. METHODS We measured visual acuity and IQS in five defocus and astigmatism combinations in either real or simulated conditions. In real conditions, the subjects viewed a stimulus through an ophthalmic lens or a deformable mirror. In simulated conditions, subjects viewed images of the same stimulus with simulated blur. The amounts of defocus and astigmatism combinations of a progressive addition lens in near vision were generated through a static correction of the subject's aberrations. We simulated three levels of accommodation: subject could not accommodate (FOC0), subject could accommodate to the less hyperopic focal point (FOC1), or subject could accommodate to the circle of least confusion (FOC2). RESULTS Visual acuity or IQS did not differ between mirror and progressive addition lens conditions. Visual acuity measured in real blur conditions differed significantly from that in FOC0 simulated blur condition but were similar to that in FOC1 and FOC2 simulated blur conditions. Image quality score obtained in real conditions were between scores measured with the FOC0 and FOC1 simulated conditions, suggesting that the subjects were able to produce a low level of accommodation. CONCLUSIONS Accommodation may play a role when comparing optical and simulated defocus and astigmatism combinations. Presbyopic subjects are able to produce a low level of accommodation that may counterbalance a part of the deleterious effect of the astigmatism on image quality. Simulation remains a useful tool if the correct accommodation state is taken into account.
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Affiliation(s)
- Marc Vincent
- Laboratoire Lumière, Matière et Interfaces, CNRS, ENS Paris-Saclay, CentraleSupelec, Université Paris-Saclay, Orsay, France
| | - Gildas Marin
- Essilor International, Research and Development, Vision Science Department, Créteil, France
| | - Richard Legras
- Laboratoire Lumière, Matière et Interfaces, CNRS, ENS Paris-Saclay, CentraleSupelec, Université Paris-Saclay, Orsay, France
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Jaskulski M, Singh NK, Bradley A, Kollbaum PS. Optical and imaging properties of a novel multi-segment spectacle lens designed to slow myopia progression. Ophthalmic Physiol Opt 2020; 40:549-556. [PMID: 32808381 DOI: 10.1111/opo.12725] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Accepted: 07/07/2020] [Indexed: 01/09/2023]
Abstract
PURPOSE High sampling density optical metrology combined with pupil- and image-plane numerical analyses were applied to evaluate a novel spectacle lens containing multiple small zones designed to slow myopia progression. METHODS High-resolution aberrometry (ClearWave, www.lumetrics.com) was used to sample wavefront slopes of a novel spectacle lens, Defocus Incorporated Multiple Segments (DIMS) (www.hoya.com), incorporating many small, positive-powered lenslets in its periphery. Using wavefront slope and error maps, custom MATLAB software ('Indiana Wavefront Analyzer') was used to compute image-plane point-spread functions (PSF), modulation transfer functions (MTF), simulated images and power distributions created by the dual-focus optic for different pupil sizes and target vergences. RESULTS Outside of a central 10 mm zone containing single distance optical power, a hexagonal array of small 1 mm lenslets with nearest-neighbour separations of 0.5 mm were distributed over the lens periphery. Sagittal and curvature-based measures of optical power imperfectly captured the consistent +3.50 D add produced by the lenslets. Image plane simulations revealed multiple PSFs and poor image quality at the lenslet focal plane. Blur at the distance optic focal plane was consistent with a combination of diffraction blur from the distance optic and the approximately +3.50 D of defocus from the 1 mm diameter near optic zones. CONCLUSION Converging the defocused beams generated by the multiple small (1 mm diameter) lenslets to a blurred image at the distance focal plane produced a blur magnitude determined by the small lenslet diameter and not the overall pupil diameter. The distance optic located in between the near-add lenslets determines the limits of the optical quality achievable by the lens. When compared to the optics of a traditional concentric-zone dual-focus contact lens, the optics of the DIMS lens generates higher-contrast images at low spatial frequencies (<7 cycles per degree), but lower-contrast at high spatial frequencies.
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Affiliation(s)
- Matt Jaskulski
- Indiana University School of Optometry, Bloomington, IN, USA
| | - Neeraj K Singh
- Indiana University School of Optometry, Bloomington, IN, USA
| | - Arthur Bradley
- Indiana University School of Optometry, Bloomington, IN, USA
| | - Pete S Kollbaum
- Indiana University School of Optometry, Bloomington, IN, USA
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Effect of Simulated and Real Spherical and Astigmatism Defocus on Visual Acuity and Image Quality Score. Optom Vis Sci 2020; 97:36-44. [PMID: 31895276 DOI: 10.1097/opx.0000000000001463] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
SIGNIFICANCE Image simulation is a useful and efficient tool to explore the impact of spherical and astigmatic blur on visual acuity (VA) and image gradation. It could help to design new optical corrections more efficiently and rapidly. PURPOSE The purpose of this study was to compare the effects of simulated (convolution by an artificial eye) and real spherical and astigmatic defocus on VA and image gradation. METHODS Experiments were performed under highly controlled conditions: dynamic correction of the subjects' aberrations at 1 Hz and application of an artificial pupil. In experiment 1, Landolt C VA was measured in various conditions of spherical and astigmatism defocus. The amounts of spherical or positive astigmatic defocus oriented at 45° that gives a Landolt C VA of 0.0, 0.2, and 0.5 logMAR were measured in experiment 2. In experiment 3, the subjects scored the quality of the perceived image (three high-contrast 0.4 logMAR letters) with a five-item continuous grading scale. RESULTS Simulated blur was always more detrimental than optical blur. We measured a difference of 0.08 ± 0.03 and 0.11 ± 0.05 logMAR between both conditions, respectively, in presence of spherical and astigmatism defocus. An average ± standard deviation difference of 0.16 ± 0.06 D (i.e., spherical defocus) and 0.24 ± 0.15 D (i.e., astigmatism defocus) was observed between simulated and real optics blur to provide a given VA. The differences of image quality score between both conditions were, respectively, 15.13 ± 9.63 and 13.33 ± 4.83 for spherical and astigmatism defocus. Most of the differences were statistically significant. CONCLUSIONS We observed a difference of about 20 and 35% between simulated and real optics blur, respectively, in presence of spherical and astigmatism blur. However, the difference between both methods remains equal to or below the clinically significant difference.
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Legras R, Rio D. Simulation of commercial vs theoretically optimised contact lenses for presbyopia. Ophthalmic Physiol Opt 2017; 37:297-304. [DOI: 10.1111/opo.12382] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Accepted: 03/11/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Richard Legras
- Laboratoire Aimé Cotton; CNRS; ENS Cachan; Université Paris-Saclay; Université Paris-Sud; Orsay France
| | - David Rio
- Laboratoire Aimé Cotton; CNRS; ENS Cachan; Université Paris-Saclay; Université Paris-Sud; Orsay France
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Rio D, Woog K, Legras R. Effect of age, decentration, aberrations and pupil size on subjective image quality with concentric bifocal optics. Ophthalmic Physiol Opt 2016; 36:411-20. [DOI: 10.1111/opo.12300] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 03/24/2016] [Indexed: 11/30/2022]
Affiliation(s)
- David Rio
- Laboratoire Aimé Cotton; CNRS; ENS Cachan; Université Paris-Sud; Université Paris-Saclay; Orsay France
| | - Kelly Woog
- Laboratoire Aimé Cotton; CNRS; ENS Cachan; Université Paris-Sud; Université Paris-Saclay; Orsay France
| | - Richard Legras
- Laboratoire Aimé Cotton; CNRS; ENS Cachan; Université Paris-Sud; Université Paris-Saclay; Orsay France
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Vandermeer G, Rio D, Gicquel JJ, Pisella PJ, Legras R. Subjective through-focus quality of vision with various versions of modified monovision. Br J Ophthalmol 2015; 99:997-1003. [DOI: 10.1136/bjophthalmol-2014-305437] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 12/26/2014] [Indexed: 11/04/2022]
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Rodriguez-Vallejo M, Benlloch J, Pons A, Monsoriu JA, Furlan WD. The effect of fractal contact lenses on peripheral refraction in myopic model eyes. Curr Eye Res 2014; 39:1151-60. [PMID: 24749733 DOI: 10.3109/02713683.2014.903498] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE To test multizone contact lenses in model eyes: Fractal Contact Lenses (FCLs), designed to induce myopic peripheral refractive error (PRE). METHODS Zemax ray-tracing software was employed to simulate myopic and accommodation-dependent model eyes fitted with FCLs. PRE, defined in terms of mean sphere M and 90°-180° astigmatism J180, was computed at different peripheral positions, ranging from 0 to 35° in steps of 5°, and for different pupil diameters (PDs). Simulated visual performance and changes in the PRE were also analyzed for contact lens decentration and model eye accommodation. For comparison purposes, the same simulations were performed with another commercially available contact lens designed for the same intended use: the Dual Focus (DF). RESULTS PRE was greater with FCL than with DF when both designs were tested for a 3.5 mm PD, and with and without decentration of the lenses. However, PRE depended on PD with both multizone lenses, with a remarkable reduction of the myopic relative effect for a PD of 5.5 mm. The myopic PRE with contact lenses decreased as the myopic refractive error increased, but this could be compensated by increasing the power of treatment zones. A peripheral myopic shift was also induced by the FCLs in the accommodated model eye. In regard to visual performance, a myopia under-correction with reference to the circle of least confusion was obtained in all cases for a 5.5 mm PD. The ghost images, generated by treatment zones of FCL, were dimmer than the ones produced with DF lens of the same power. CONCLUSIONS FCLs produce a peripheral myopic defocus without compromising central vision in photopic conditions. FCLs have several design parameters that can be varied to obtain optimum results: lens diameter, number of zones, addition and asphericity; resulting in a very promising customized lens for the treatment of myopia progression.
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Legras R, Benard Y. Measurement and prediction of subjective gradations of images in presence of monochromatic aberrations. Vision Res 2013; 86:52-8. [DOI: 10.1016/j.visres.2013.04.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 04/10/2013] [Accepted: 04/12/2013] [Indexed: 11/16/2022]
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Legras R, Benard Y, Lopez-Gil N. Effect of coma and spherical aberration on depth-of-focus measured using adaptive optics and computationally blurred images. J Cataract Refract Surg 2012; 38:458-69. [PMID: 22340606 DOI: 10.1016/j.jcrs.2011.10.032] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 09/26/2011] [Accepted: 10/04/2011] [Indexed: 11/26/2022]
Abstract
PURPOSE To compare the effect of primary spherical aberration and vertical coma on depth of focus measured with 2 methods. SETTING Laboratoire Aimé Cotton, Centre National de la Recherche Scientifique, and Université Paris-Sud, Orsay, France. DESIGN Evaluation of technology. METHODS The subjective depth of focus, defined as the interval of vision for which the target was still perceived acceptable, was evaluated using 2 methods. In the first method, the subject changed the defocus term by reshaping the mirror, which also corrected the subject's aberrations and induced a certain value of coma or primary spherical aberration. In the second procedure, the subject changed the displayed images, which were calculated for various defocuses and with the desired aberration using a numerical eye model. Depth of focus was measured using a 0.18 diopter (D) step in 4 nonpresbyopic subjects corrected for the entire eye aberrations with a 6.0 mm and 3.0 mm pupil and with the addition of 0.3 μm and 0.6 μm of positive primary spherical aberration or vertical coma. RESULTS There was good concordance between the depth of focus measured with both methods (differences within 1/3 D, r(2) = 0.88). Image-quality metrics failed to predict the subjective depth of focus (r(2) < 0.41). CONCLUSION These data confirm that defocus in the retinal image can be generated by optical or computational methods and that both can be used to assess the effect of higher-order aberrations on depth of focus. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.
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Affiliation(s)
- Richard Legras
- Centre National de Recherche Scientifique, Laboratoire Aimé Cotton, Orsay, France.
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Benard Y, Lopez-Gil N, Legras R. Optimizing the subjective depth-of-focus with combinations of fourth- and sixth-order spherical aberration. Vision Res 2011; 51:2471-7. [DOI: 10.1016/j.visres.2011.10.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 10/07/2011] [Accepted: 10/07/2011] [Indexed: 11/16/2022]
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Rouger H, Benard Y, Legras R. Effect of monochromatic induced aberrations on visual performance measured by adaptive optics technology. J Refract Surg 2011; 26:578-87. [PMID: 19731885 DOI: 10.3928/1081597x-20090901-01] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Accepted: 07/29/2009] [Indexed: 11/20/2022]
Abstract
PURPOSE The two objectives were 1) to measure visual acuity (VA) and contrast sensitivity (CS) losses induced by various amounts of individual Zernike aberrations, and 2) to examine the accuracy of image quality metrics in predicting these visual performance losses. METHODS Monocular 10 cycles/degree (cpd) and 25 cpd CS and high- and low-contrast VA were measured when introducing individual Zernike aberrations in four patients dynamically corrected using a CRX1 adaptive optics system (Imagine Eyes) and a 5.5-mm pupil. Seven levels (0, +/- 0.1, +/- 0.3, and +/- 0.9 microm) of astigmatism, spherical aberration, coma, and trefoil and four levels of defocus were induced. Several image quality metrics based on the radially averaged modulation transfer function (rMTF) and optical transfer function (rOTF) calculations were computed to attempt to predict the losses in VA and CS. RESULTS Modes near the center and at the top of the Zernike pyramid decreased VA significantly more than modes near the edge or at the bottom of the pyramid. The measured CS losses were reasonably correlated to the rMTF calculated at 10 cpd (R2 = 0.87) and 25 cpd (R2 = 0.75). The high-contrast VA degradations were also reasonably predicted (R2 = 0.85) by the intersection between the rMTF and the neural contrast threshold function. The low-contrast VA losses were also well predicted (R2 = 0.88) by three rMTF-based metrics. CONCLUSIONS Image quality metrics based on wavefront aberration measurements were able to predict the impact of individual Zernike aberrations on CS and VA.
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Affiliation(s)
- Hélène Rouger
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, Orsay, France
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Benard Y, Lopez-Gil N, Legras R. Subjective depth of field in presence of 4th-order and 6th-order Zernike spherical aberration using adaptive optics technology. J Cataract Refract Surg 2010; 36:2129-38. [DOI: 10.1016/j.jcrs.2010.07.022] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Accepted: 07/06/2010] [Indexed: 11/28/2022]
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Vera-Diaz FA, Woods RL, Peli E. Shape and individual variability of the blur adaptation curve. Vision Res 2010; 50:1452-61. [PMID: 20417657 PMCID: PMC2902630 DOI: 10.1016/j.visres.2010.04.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 04/01/2010] [Accepted: 04/09/2010] [Indexed: 10/19/2022]
Abstract
We are interested in clinical implications of adaptation to blurred and sharpened images. Therefore, we investigated repeatability, individual variability and characteristics of the adaptation curves of 39 normally-sighted individuals. The point of subjective neutrality (PSN - the slope of the spatial spectrum of the image that appears normal) following adaptation was measured for each adaptation level and was used to derive individual adaptation curves for each subject. Adaptation curves were fitted with a modified Tukey biweight function as the curves were found to be tumbled-S shaped and asymmetrical for blur and sharp in some subjects. The adaptation curve was found to be an individual characteristic as inter-subject variability exceeds test/re-test variability. The existence of individual variability may have implications for the prescription and clinical success of optical devices as well as image enhancement rehabilitation options.
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Affiliation(s)
- Fuensanta A Vera-Diaz
- Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, United States.
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Cheng X, Bradley A, Ravikumar S, Thibos LN. Visual impact of Zernike and Seidel forms of monochromatic aberrations. Optom Vis Sci 2010; 87:300-12. [PMID: 20351600 PMCID: PMC3144141 DOI: 10.1097/opx.0b013e3181d95217] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE The aim of this study was to examine the impact of different aberrations modes (e.g., coma, astigmatism, spherical aberration [SA]) and different aberration basis functions (Zernike or Seidel) on visual acuity (VA). METHODS Computational optics was used to generate retinal images degraded by either the Zernike or Seidel forms of second through fourth-order aberrations for an eye with a 5-mm pupil diameter. High contrast, photopic VA was measured using method of constant stimuli for letters displayed on a computer-controlled, linearized, quasimonochromatic (lambda = 556 nm) display. RESULTS Minimum angle of resolution (MAR) varied linearly with the magnitude (root mean square error) of all modes of aberration. The impact of individual Zernike lower- and higher-order aberrations (HOAs) varied significantly with mode, e.g., arc minutes of MAR per micrometer of root mean square slopes varied from 7 (spherical defocus) to 0.5 (quadrafoil). Seidel forms of these aberrations always had a smaller visual impact. Notably, Seidel SA had 1/17th the impact of Zernike SA with the same wavefront variance, and about 1/4th the impact of Zernike SA with matching levels of r wavefront error. With lower-order components removed, HOAs near the center of the Zernike pyramid do not have a large visual impact. CONCLUSIONS The majority of the visual impact of high levels of fourth-order Zernike aberrations can be attributed to the second-order terms within these polynomials. Therefore, the impact of SA can be minimized by balancing it with a defocus term that flattens the central wavefront (paraxial focus) or maximizes the area of the pupil with a flat wavefront. Over this wide range of aberration types and levels, image quality metrics based on the Point Spread Function (PSF) and Optical Transfer Function (OTF) can predict VA as reliably as VA measures can predict retests of VA, and, thus, such metrics may become valuable predictors of both VA and, via optimization, refractions.
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Affiliation(s)
- Xu Cheng
- School of Optometry, Indiana University, Bloomington, Indiana 47405, USA
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Through-focus visual performance measurements and predictions with multifocal contact lenses. Vision Res 2010; 50:1185-93. [PMID: 20371368 DOI: 10.1016/j.visres.2010.04.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 03/30/2010] [Accepted: 04/01/2010] [Indexed: 11/21/2022]
Abstract
We measured high-contrast visual acuity (VA) and 12c/deg contrast sensitivity (CS) through-focus functions (TFF) of four eyes of four cyclopleged subjects in three conditions: naked eye, with a center-distance and center-near Proclear(R) multifocal addition 2D contact lens. In all conditions, an adaptive optics system statically compensated the astigmatism of the subject's eye alone. Multifocal contact lenses enlarged the width of the curve of through-focus visual performance but reduced the peak performance. We investigated the ability of image quality metrics based on wave-aberration measurements to predict VA and CS TFF. CS(12) metric through-focus and measured through-focus contrast sensitivities were well correlated (r(2)=0.74). Even if visual acuity metrics were often poorer than measured ones, the shapes of the measured through-focus curves and rMTFa(5-15) through-focus were quite comparable (r(2)=0.67).
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Legras R, Rouger H. Calculations and Measurements of the Visual Benefit of Correcting the Higher-order Aberrations Using Adaptive Optics Technology. JOURNAL OF OPTOMETRY 2008. [PMCID: PMC3972647 DOI: 10.3921/joptom.2008.22] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Purpose Our goal was to examine the accuracy of metrics, calculated using a numerical eye model including the measurement of the monochromatic aberrations of the eye, to predict the contrast sensitivity (CS) and visual acuity (VA) visual benefits (VB) of correcting higher-order aberrations (HO). Methods We measured, on the right eyes of 25 subjects (10 myopes and 15 emmetropes) aged 21 to 56 years, the 16 c/deg CS and high-contrast VA in two conditions of aberration corrections: (i) when correcting only the defocus and astigmatism terms and (ii) when dynamically correcting all the monochromatic aberration terms up to the 5th order. The measured VB was defined as the ratio of the performances between these two conditions of aberration corrections. Results We measured a VB of 1.25 and 1.64 respectively in term of VA and CS. We did not find any influence of age on the VB and no statistical significant difference between the myopic and emmetropic group. The contrast sensitivity VB was well correlated (r2=0.79) with the ratio of the modulation transfer functions calculated at 16 c/deg in both conditions of aberrations corrections (i.e. MTF16c/deg HO/MTF16c/deg SC). The levels of correlation between various metrics and measured visual acuity VB were lower (r2=0.30 in the better case), however the averaged VB was correctly predicted by the ratio of the intersections between the MTF and a typically neural contrast threshold function. Conclusions Metrics based on wave aberration measurements are able to predict the impact of monochromatic aberrations on CS.
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Affiliation(s)
- Richard Legras
- Corresponding author: Laboratoire Aimé Cotton, Bât. 505, Campus d’Orsay, 91405 ORSAY Cedex, France.
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Abstract
It has been suggested that high levels of axial aberration or specific patterns of peripheral refraction could play a role in myopia development. Possible mechanisms involving high levels of retinal image blur caused by axial aberrations include form deprivation through poor retinal image quality in distance vision, enhanced accommodative lags favouring compensatory eye growth, and an absence of adequate directional cues to guide emmetropization. In addition, in initially emmetropic eyes, hyperopia in the retinal periphery may result in local compensatory eye growth, which induces axial myopia. Evidence in support of these ideas is reviewed and it is concluded that, for any fixed pupil diameter, evidence for higher levels of axial aberration in myopes in comparison with other refractive groups is weak, making involvement of axial aberrations in myopization through image degradation at the fovea unlikely. If, however, some potential myopes had unusually large pupil diameters, their effective aberration levels and associated retinal blur would be larger than those of the rest of the population. There is stronger evidence in favour of differences in patterns of peripheral refraction in both potential and existing myopes, with myopes tending to show relative hyperopia in the periphery. These differences appear to be related to a more prolate eyeball shape. Longitudinal studies are required to confirm whether the retinal defocus associated with the peripheral hyperopia can cause patterns of eyeball growth which lead to axial myopia.
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Affiliation(s)
- W N Charman
- Optometry and Neuroscience, Faculty of Life Sciences, University of Manchester, PO Box 88, Manchester M60 1QD, UK.
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Legras R, Chateau N, Charman WN. Assessment of just-noticeable differences for refractive errors and spherical aberration using visual simulation. Optom Vis Sci 2004; 81:718-28. [PMID: 15365392 DOI: 10.1097/01.opx.0000144751.11213.cd] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE The aim of this study was to evaluate the threshold levels of aberration change that a typical reference eye is able to detect. METHODS The method involved simulation of the foveal vision of a typical eye in polychromatic light through optics affected by different levels of the various chosen monochromatic aberrations. The reference eye had the following monochromatic wavefront characteristics based on the aberrations of a population of young adults: no spherical defocus, astigmatism -0.37D oriented at 0 degrees celsius, coma -0.17 D/mm oriented at 270 degrees celsius, and spherical aberration -0.12 D/mm. Average amounts of longitudinal and transverse chromatic aberration were assumed, and allowance was made for the Stiles-Crawford effect. The pupil diameter of the simulated eye was kept fixed at 6 mm. Three observers each compared, 100 times, a simulated image as seen through the standard reference eye with a variant "aberrated" image. The varying parameter was the value of a chosen additional aberration affecting the variant image in the reference eye. The test was repeated for varying amounts of spherical defocus, astigmatic defocus, and spherical aberration. For each of these aberrations and each observer, the discrimination probability as a function of the aberration level in the variant image was determined. The just-noticeable difference in aberration (JNDA) was derived from each discrimination curve as the difference between the aberrations corresponding to discrimination probabilities of 75% and 25%. The JNDA values obtained were expressed in the form of root mean square (RMS) wavefront error thresholds. RESULTS It was found that 0.04 microm of RMS aberration should be considered as the threshold of just-noticeable image change, in good agreement with the Maréchal criterion. CONCLUSIONS The results imply that in normal viewing conditions (e.g., a 3-mm pupil size), optical corrections should be in the range of +/-0.15 D in sphere and cylinder from the target prescription if perceptible change in the quality of the perceived images is to be avoided. The design of conventional soft contact lenses of high negative power or positive power should aim to produce -0.07 D/mm of spherical aberration, with a tolerated interval between -0.15 to +0.01 D/mm for a 6-mm pupil size.
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Affiliation(s)
- Richard Legras
- Université Paris Sud, Laboratoire Aimé Cotton, Orsay, France.
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