1
|
Heilman BM, Durkee H, Rowaan CJ, Arrieta E, Kelly SP, Ehrmann K, Manns F, Parel JM. Temperature affects the biomechanical response of in vitro non-human primate lenses during lens stretching. Exp Eye Res 2022; 216:108951. [DOI: 10.1016/j.exer.2022.108951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 12/31/2021] [Accepted: 01/10/2022] [Indexed: 11/25/2022]
|
2
|
de Castro A, Birkenfeld J, Heilman BM, Ruggeri M, Arrieta E, Parel JM, Manns F, Marcos S. Off-axis optical coherence tomography imaging of the crystalline lens to reconstruct the gradient refractive index using optical methods. BIOMEDICAL OPTICS EXPRESS 2019; 10:3622-3634. [PMID: 31360608 PMCID: PMC6640821 DOI: 10.1364/boe.10.003622] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 05/24/2019] [Accepted: 05/31/2019] [Indexed: 06/10/2023]
Abstract
Earlier studies have shown that the gradient index of refraction (GRIN) of the crystalline lens can be reconstructed in vitro using Optical Coherence Tomography (OCT) images. However, the methodology cannot be extended in vivo because it requires accurate measurements of the external geometry of the lens. Specifically, the posterior surface is measured by flipping the lens so that the posterior lens surface faces the OCT beam, a method that cannot be implemented in vivo. When the posterior surface is imaged through the lens in its natural position, it appears distorted by the unknown GRIN. In this study, we demonstrate a method to reconstruct both the GRIN and the posterior surface shape without the need to flip the lens by applying optimization routines using both on-axis and off-axis OCT images of cynomolgous monkey crystalline lenses, obtained by rotating the OCT delivery probe from -45 to +45 degrees in 5 degree steps. We found that the GRIN profile parameters can be reconstructed with precisions up to 0.009, 0.004, 1.7 and 1.1 (nucleus and surface refractive indices, and axial and meridional power law, respectively), the radius of curvature within 0.089 mm and the conic constant within 0.3. While the method was applied on isolated crystalline lenses, it paves the way to in vivo lens GRIN and posterior lens surface reconstruction.
Collapse
Affiliation(s)
- Alberto de Castro
- Instituto de Óptica Daza de Valdés, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Judith Birkenfeld
- Instituto de Óptica Daza de Valdés, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Bianca Maceo Heilman
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Miami, FL, USA
| | - Marco Ruggeri
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Esdras Arrieta
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Jean-Marie Parel
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Miami, FL, USA
- Brien Holden Vision Institute, Sydney, NSW, Australia
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Miami, FL, USA
| | - Susana Marcos
- Instituto de Óptica Daza de Valdés, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| |
Collapse
|
3
|
Maceo Heilman B, Manns F, Ruggeri M, Ho A, Gonzalez A, Rowaan C, Bernal A, Arrieta E, Parel JM. Peripheral Defocus of the Monkey Crystalline Lens With Accommodation in a Lens Stretcher. Invest Ophthalmol Vis Sci 2019; 59:2177-2186. [PMID: 29801154 PMCID: PMC5916546 DOI: 10.1167/iovs.17-23273] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Purpose To characterize the peripheral defocus of the monkey crystalline lens and its changes with accommodation. Methods Experiments were performed on 15 lenses from 11 cynomolgus monkey eyes (age: 3.8–12.4 years, postmortem time: 33.5 ± 15.3 hours). The tissue was mounted in a motorized lens stretcher to allow for measurements of the lens in the accommodated (unstretched) and unaccommodated (stretched) states. A custom-built combined laser ray tracing and optical coherence tomography system was used to measure the paraxial on-axis and off-axis lens power for delivery angles ranging from −20° to +20° (in air). For each delivery angle, peripheral defocus was quantified as the difference between paraxial off-axis and on-axis power. The peripheral defocus of the lens was compared in the unstretched and stretched states. Results On average, the paraxial on-axis lens power was 52.0 ± 3.4 D in the unstretched state and 32.5 ± 5.1 D in the stretched state. In both states, the lens power increased with increasing delivery angle. From 0° to +20°, the relative peripheral lens power increased by 10.7 ± 1.4 D in the unstretched state and 7.5 ± 1.6 D in the stretched state. The change in field curvature with accommodation was statistically significant (P < 0.001), indicating that the unstretched (accommodated) lens has greater curvature or relative peripheral power. Conclusions The cynomolgus monkey lens has significant accommodation-dependent curvature of field, which suggests that the lens asserts a significant contribution to the peripheral optical performance of the eye that also varies with the state of accommodation.
Collapse
Affiliation(s)
- Bianca Maceo Heilman
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Miami, Florida, United States.,Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Miami, Florida, United States.,Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States
| | - Marco Ruggeri
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Miami, Florida, United States
| | - Arthur Ho
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Miami, Florida, United States.,Brien Holden Vision Institute, Sydney, New South Wales, Australia.,School of Optometry and Vision Science, University of New South Wales, Australia
| | - Alex Gonzalez
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Miami, Florida, United States
| | - Cor Rowaan
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Miami, Florida, United States
| | - Andres Bernal
- Bioniko Consulting LLC, Sunny Isles Beach, Florida, United States
| | - Esdras Arrieta
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Miami, Florida, United States
| | - Jean-Marie Parel
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Miami, Florida, United States.,Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States.,Vision Cooperative Research Centre, Sydney, New South Wales, Australia
| |
Collapse
|
4
|
Ruggeri M, Williams S, Heilman BM, Yao Y, Chang YC, Mohamed A, Sravani NG, Durkee H, Rowaan C, Gonzalez A, Ho A, Parel JM, Manns F. System for on- and off-axis volumetric OCT imaging and ray tracing aberrometry of the crystalline lens. BIOMEDICAL OPTICS EXPRESS 2018; 9:3834-3851. [PMID: 30338159 PMCID: PMC6191619 DOI: 10.1364/boe.9.003834] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 07/17/2018] [Accepted: 07/17/2018] [Indexed: 05/22/2023]
Abstract
We present a new in vitro instrument for measuring shape and wavefront aberrations of the primate crystalline lens, both on- and off-axis, while simulating accommodation with a motorized lens stretching system. The instrument merges spectral domain optical coherence tomography (SD-OCT) imaging and ray tracing aberrometry using an approach that senses wavefront aberrations of the lens with the OCT probing beam. Accuracy and repeatability of aberration measurements were quantified. Preliminary experiments on two human and four cynomolgus monkey lenses demonstrate the ability of the system to measure the lens shape, spherical aberration and peripheral defocus, and their changes during simulated accommodation.
Collapse
Affiliation(s)
- Marco Ruggeri
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Siobhan Williams
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Bianca Maceo Heilman
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Yue Yao
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Yu-Cherng Chang
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Ashik Mohamed
- Ophthalmic Biophysics, L V Prasad Eye Institute, Hyderabad, India
- Brien Holden Vision Institute, Sydney, NSW, Australia
- School of Optometry and Vision Science, University of New South Wales, Sydney NSW, Australia
| | | | - Heather Durkee
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| | - Cornelis Rowaan
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Alex Gonzalez
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Arthur Ho
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Brien Holden Vision Institute, Sydney, NSW, Australia
- School of Optometry and Vision Science, University of New South Wales, Sydney NSW, Australia
| | - Jean-Marie Parel
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
- Brien Holden Vision Institute, Sydney, NSW, Australia
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL, USA
| |
Collapse
|
5
|
Abstract
PURPOSE To examine ocular growth in nonhuman primates (NHPs) from measurements on ex vivo eyes. METHODS We obtained NHP eyes from animals that had been killed as part of other studies or because of health-related issues. Digital calipers were used to measure the horizontal, vertical, and anteroposterior globe diameters as well as corneal horizontal and vertical diameters of excised globes from 98 hamadryas baboons, 551 cynomolgus monkeys, and 112 rhesus monkeys, at ages ranging from 23 to 360 months. Isolated lens sagittal thickness and equatorial diameter were measured by shadowphotogrammetry. Wet and fixed dry weights were obtained for lenses. RESULTS Nonhuman primate globe growth continues throughout life, slowing toward an asymptotic maximum. The final globe size scales with negative allometry to adult body size. Corneal growth ceases at around 20 months. Lens diameter increases but thickness decreases with increasing age. Nonhuman primate lens wet and dry weight accumulation is monophasic, continuing throughout life toward asymptotic maxima. The dry/wet weight ratio reaches a maximum of 0.33. CONCLUSIONS Nonhuman primate ocular globe and lens growth differ in several respects from those in humans. Although age-related losses of lens power and accommodative amplitude are similar, lens growth and properties are different indicating care should be taken in extrapolating NHP observations to the study of human accommodation.
Collapse
Affiliation(s)
- Robert C Augusteyn
- Vision Cooperative Research Centre, Sydney, Australia 2School of Optometry and Vision Science, University of New South Wales, Sydney, Australia 3Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miam
| | - Bianca Maceo Heilman
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States 4Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States
| | - Arthur Ho
- Vision Cooperative Research Centre, Sydney, Australia 2School of Optometry and Vision Science, University of New South Wales, Sydney, Australia 3Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miam
| | - Jean-Marie Parel
- Vision Cooperative Research Centre, Sydney, Australia 3Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States 4Department of Biomedical Engineering, University of Miami Colle
| |
Collapse
|
6
|
Pour HM, Kanapathipillai S, Zarrabi K, Manns F, Ho A. Stretch-dependent changes in surface profiles of the human crystalline lens during accommodation: a finite element study. Clin Exp Optom 2015; 98:126-37. [PMID: 25727940 DOI: 10.1111/cxo.12263] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 07/10/2014] [Accepted: 09/08/2014] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND A non-linear isotropic finite element (FE) model of a 29-year-old human crystalline lens was constructed to study the effects of various geometrical parameters on lens accommodation. METHODS The model simulates dis-accommodation by stretching of the lens and predicts the change in surface profiles of the lens capsule, cortex and nucleus at select states of stretching/accommodation. Multiple regression analysis (MRA) is used to develop a stretch-dependent mathematical model relating the lens sagittal height to the radial position of the lens surface as a function of dis-accommodative stretch. A load analysis is performed to compare the finite element results to empirical results from lens stretcher studies. Using the predicted geometrical changes, the optical response of the whole eye during accommodation was analysed by ray-tracing. RESULTS Aspects of lens shape change relative to stretch were evaluated, including change in diameter, central thickness and accommodation. Maximum accommodation achieved was 10.29 D. From the multiple regression analysis, the stretch-dependent mathematical model of the lens shape related lens curvatures as a function of lens ciliary stretch well (maximum mean-square residual error 2.5 × 10(-3 ) μm, p < 0.001). The results are compared with those from in vitro studies. CONCLUSIONS The finite element and ray-tracing predictions are consistent with Ex Vivo Accommodation Simulator (EVAS) studies in terms of load and power change versus change in thickness. The mathematical stretch-dependent model of accommodation presented may have utility in investigating lens behaviour at states other than the relaxed or fully accommodated states.
Collapse
Affiliation(s)
- Hooman Mohammad Pour
- School of Mechanical and Manufacturing Engineering, The University of New South Wales, Kensington, NSW, Australia; Brien Holden Vision Institute, Kensington, NSW, Australia.
| | | | | | | | | |
Collapse
|
7
|
Nankivil D, Maceo Heilman B, Durkee H, Manns F, Ehrmann K, Kelly S, Arrieta-Quintero E, Parel JM. The zonules selectively alter the shape of the lens during accommodation based on the location of their anchorage points. Invest Ophthalmol Vis Sci 2015; 56:1751-60. [PMID: 25698707 DOI: 10.1167/iovs.14-16082] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine the role of anterior and posterior zonular tension on the optomechanical lens response during accommodation simulation. METHODS Ten eyes from nine hamadryas baboons (4.9 ± 0.7 years) and 20 eyes from 18 cynomolgus monkeys (5.4 ± 0.3 years) were dissected, leaving the lens, zonules, ciliary body, hyaloid membrane, anterior vitreous, and a segmented scleral rim intact. The lens preparation was mounted in a lens stretcher, and the outer scleral shell was displaced radially in a stepwise fashion. The load, lens, and ciliary body diameters, lens power, lens thickness, and the anterior and posterior radius of curvature were measured during stretching. The zonular fibers attached to either the posterior or anterior lens surface were then carefully transected and the experiment was repeated. Zonular transection was confirmed in four eyes via laser scanning confocal microscopy after immunostaining. The effect of zonular transection on the tissue response to stretching was quantified. RESULTS Without anterior zonules, 48% and 97% of the changes in anterior and posterior radii are retained. Without posterior zonules, 81% and 67% of the changes in anterior and posterior radii are retained. The changes in lens shape were reduced after transecting either the anterior or posterior zonules; however, both surfaces still changed shape. CONCLUSIONS While either the anterior or posterior zonules alone are capable of changing the shape of both lens surfaces, the anterior zonules have a greater effect on the anterior lens surface, and the posterior zonules have a greater effect on the posterior lens surface.
Collapse
Affiliation(s)
- Derek Nankivil
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, Florida, United States
| | - Bianca Maceo Heilman
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, Florida, United States Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami, Coral Gables, Florida, United States
| | - Heather Durkee
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, Florida, United States Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami, Coral Gables, Florida, United States
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, Florida, United States Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami, Coral Gables, Florida, United States
| | - Klaus Ehrmann
- Vision Cooperative Research Centre, Brien Holden Vision Institute, University of New South Wales, Sydney, Australia
| | - Shawn Kelly
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, Florida, United States
| | - Esdras Arrieta-Quintero
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, Florida, United States
| | - Jean-Marie Parel
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, Florida, United States
| |
Collapse
|
8
|
Iribarren R. Crystalline lens and refractive development. Prog Retin Eye Res 2015; 47:86-106. [PMID: 25683786 DOI: 10.1016/j.preteyeres.2015.02.002] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 01/30/2015] [Accepted: 02/02/2015] [Indexed: 10/24/2022]
Abstract
Individual refractive errors usually change along lifespan. Most children are hyperopic in early life. This hyperopia is usually lost during growth years, leading to emmetropia in adults, but myopia also develops in children during school years or during early adult life. Those subjects who remain emmetropic are prone to have hyperopic shifts in middle life. And even later, at older ages, myopic shifts are developed with nuclear cataract. The eye grows from 15 mm in premature newborns to approximately 24 mm in early adult years, but, in most cases, refractions are maintained stable in a clustered distribution. This growth in axial length would represent a refractive change of more than 40 diopters, which is compensated by changes in corneal and lens powers. The process which maintains the balance between the ocular components of refraction during growth is still under study. As the lens power cannot be measured in vivo, but can only be calculated based on the other ocular components, there have not been many studies of lens power in humans. Yet, recent studies have confirmed that the lens loses power during growth in children, and that hyperopic and myopic shifts in adulthood may be also produced by changes in the lens. These studies in children and adults give a picture of the changing power of the lens along lifespan. Other recent studies about the growth of the lens and the complexity of its internal structure give clues about how these changes in lens power are produced along life.
Collapse
Affiliation(s)
- Rafael Iribarren
- Department of Ophthalmology, San Luis Medical Center, Buenos Aires, Argentina.
| |
Collapse
|
9
|
del Rosario RCH, Rayan NA, Prabhakar S. Noncoding origins of anthropoid traits and a new null model of transposon functionalization. Genome Res 2014; 24:1469-84. [PMID: 25043600 PMCID: PMC4158753 DOI: 10.1101/gr.168963.113] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Little is known about novel genetic elements that drove the emergence of anthropoid primates. We exploited the sequencing of the marmoset genome to identify 23,849 anthropoid-specific constrained (ASC) regions and confirmed their robust functional signatures. Of the ASC base pairs, 99.7% were noncoding, suggesting that novel anthropoid functional elements were overwhelmingly cis-regulatory. ASCs were highly enriched in loci associated with fetal brain development, motor coordination, neurotransmission, and vision, thus providing a large set of candidate elements for exploring the molecular basis of hallmark primate traits. We validated ASC192 as a primate-specific enhancer in proliferative zones of the developing brain. Unexpectedly, transposable elements (TEs) contributed to >56% of ASCs, and almost all TE families showed functional potential similar to that of nonrepetitive DNA. Three L1PA repeat-derived ASCs displayed coherent eye-enhancer function, thus demonstrating that the "gene-battery" model of TE functionalization applies to enhancers in vivo. Our study provides fundamental insights into genome evolution and the origins of anthropoid phenotypes and supports an elegantly simple new null model of TE exaptation.
Collapse
Affiliation(s)
- Ricardo C H del Rosario
- Computational and Systems Biology, Genome Institute of Singapore, #02-01 Genome, Singapore 138672
| | - Nirmala Arul Rayan
- Computational and Systems Biology, Genome Institute of Singapore, #02-01 Genome, Singapore 138672
| | - Shyam Prabhakar
- Computational and Systems Biology, Genome Institute of Singapore, #02-01 Genome, Singapore 138672
| |
Collapse
|
10
|
de Castro A, Birkenfeld J, Maceo B, Manns F, Arrieta E, Parel JM, Marcos S. Influence of shape and gradient refractive index in the accommodative changes of spherical aberration in nonhuman primate crystalline lenses. Invest Ophthalmol Vis Sci 2013; 54:6197-207. [PMID: 23927893 PMCID: PMC3771709 DOI: 10.1167/iovs.13-11996] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 07/17/2013] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To estimate changes in surface shape and gradient refractive index (GRIN) profile in primate lenses as a function of accommodation. To quantify the contribution of surface shape and GRIN to spherical aberration changes with accommodation. METHODS Crystalline lenses from 15 cynomolgus monkeys were studied in vitro under different levels of accommodation produced by a stretching system. Lens shape was obtained from optical coherence tomography (OCT) cross-sectional images. The GRIN was reconstructed with a search algorithm using the optical path measured from OCT images and the measured back focal length. The spherical aberration of the lens was estimated as a function of accommodation using the reconstructed GRIN and a homogeneous refractive index. RESULTS The lens anterior and posterior radii of curvature decreased with increasing lens power. Both surfaces exhibited negative asphericities in the unaccommodated state. The anterior surface conic constant shifted toward less negative values with accommodation, while the value of the posterior remained constant. GRIN parameters remained constant with accommodation. The lens spherical aberration with GRIN distribution was negative and higher in magnitude than that with a homogeneous equivalent refractive index (by 29% and 53% in the unaccommodated and fully accommodated states, respectively). Spherical aberration with the equivalent refractive index shifted with accommodation toward negative values (-0.070 μm/diopter [D]), but the reconstructed GRIN shifted it farther (-0.124 μm/D). CONCLUSIONS When compared with the lens with the homogeneous equivalent refractive index, the reconstructed GRIN lens has more negative spherical aberration and a larger shift toward more negative values with accommodation.
Collapse
Affiliation(s)
- Alberto de Castro
- Instituto de Óptica “Daza de Valdés,” Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Judith Birkenfeld
- Instituto de Óptica “Daza de Valdés,” Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Bianca Maceo
- Ophthalmic and Biophysics Center, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida
- Biomedical Optics Laboratory, Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida
| | - Fabrice Manns
- Ophthalmic and Biophysics Center, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida
- Biomedical Optics Laboratory, Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida
| | - Esdras Arrieta
- Ophthalmic and Biophysics Center, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida
| | - Jean-Marie Parel
- Ophthalmic and Biophysics Center, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida
| | - Susana Marcos
- Instituto de Óptica “Daza de Valdés,” Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| |
Collapse
|
11
|
Distortion correction of OCT images of the crystalline lens: gradient index approach. Optom Vis Sci 2012; 89:E709-18. [PMID: 22466105 DOI: 10.1097/opx.0b013e3182508344] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
PURPOSE To propose a method to correct optical coherence tomography (OCT) images of posterior surface of the crystalline lens incorporating its gradient index (GRIN) distribution and explore its possibilities for posterior surface shape reconstruction in comparison to existing methods of correction. METHODS Two-dimensional images of nine human lenses were obtained with a time-domain OCT system. The shape of the posterior lens surface was corrected using the proposed iterative correction method. The parameters defining the GRIN distribution used for the correction were taken from a previous publication. The results of correction were evaluated relative to the nominal surface shape (accessible in vitro) and compared with the performance of two other existing methods (simple division, refraction correction: assuming a homogeneous index). Comparisons were made in terms of posterior surface radius, conic constant, root mean square, peak to valley, and lens thickness shifts from the nominal data. RESULTS Differences in the retrieved radius and conic constant were not statistically significant across methods. However, GRIN distortion correction with optimal shape GRIN parameters provided more accurate estimates of the posterior lens surface in terms of root mean square and peak values, with errors <6 and 13 μm, respectively, on average. Thickness was also more accurately estimated with the new method, with a mean discrepancy of 8 μm. CONCLUSIONS The posterior surface of the crystalline lens and lens thickness can be accurately reconstructed from OCT images, with the accuracy improving with an accurate model of the GRIN distribution. The algorithm can be used to improve quantitative knowledge of the crystalline lens from OCT imaging in vivo. Although the improvements over other methods are modest in two dimension, it is expected that three-dimensional imaging will fully exploit the potential of the technique. The method will also benefit from increasing experimental data of GRIN distribution in the lens of larger populations.
Collapse
|
12
|
Maceo BM, Manns F, Borja D, Nankivil D, Uhlhorn S, Arrieta E, Ho A, Augusteyn RC, Parel JM. Contribution of the crystalline lens gradient refractive index to the accommodation amplitude in non-human primates: in vitro studies. J Vis 2011; 11:23. [PMID: 22131444 PMCID: PMC3310215 DOI: 10.1167/11.13.23] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The purpose of this study was to determine the contribution of the gradient refractive index to the change in lens power in hamadryas baboon and cynomolgus monkey lenses during simulated accommodation in a lens stretcher. Thirty-six monkey lenses (1.4-14.1 years) and twenty-five baboon lenses (1.8-28.0 years) were stretched in discrete steps. At each stretching step, the lens back vertex power was measured and the lens cross-section was imaged with optical coherence tomography. The radii of curvature for the lens anterior and posterior surfaces were calculated for each step. The power of each lens surface was determined using refractive indices of 1.365 for the outer cortex and 1.336 for the aqueous. The gradient contribution was calculated by subtracting the power of the surfaces from the measured lens power. In all lenses, the contribution of the surfaces and gradient increased linearly with the amplitude of accommodation. The gradient contributes on average 65 ± 3% for monkeys and 66 ± 3% for baboons to the total power change during accommodation. When expressed in percent of the total power change, the relative contribution of the gradient remains constant with accommodation and age in both species. These findings are consistent with Gullstrand's intracapsular theory of accommodation.
Collapse
Affiliation(s)
- Bianca M Maceo
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Wendt M, Bockhorst K, He L, Glasser A. Accuracy and resolution of in vitro imaging based porcine lens volumetric measurements. Exp Eye Res 2011; 93:741-52. [PMID: 21963717 DOI: 10.1016/j.exer.2011.09.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 08/30/2011] [Accepted: 09/16/2011] [Indexed: 11/24/2022]
Abstract
There is considerable interest in determining lens volume in the living eye. Lens volume is of interest to understand accommodative changes in the lens and to size accommodative IOLs (A-IOLs) to fit the capsular bag. Some studies have suggested lens volume change during accommodation. Magnetic Resonance Imaging (MRI) is the only method available to determine lens volume in vivo. MRI is, by its nature, relatively low in temporal and spatial resolution. Therefore analysis often requires determining lens volume from single image slices with relatively low resolution on which only simple image analysis methods can be used and without repeated measures. In this study, 7 T MRI scans encompassing the full lens volume were performed on 19 enucleated pig eyes. The eyes were then dissected to isolate and photograph the lens in profile and the lens volumes were measured empirically using a fluid displacement method. Lens volumes were calculated from two- and three-dimensional (2D and 3D) MR and 2D photographic profile images of the isolated lenses using several different analysis methods. Image based and actual measured lens volumes were compared. The average image-based volume of all lenses varied from the average measured volume of all lenses by 0.6%-6.4% depending on the image analysis method. Image analysis methods that use gradient based edge detection showed higher precision with actual volumes (r(2): 0.957-0.990), while threshold based segmentation had poorer correlations (r(2): 0.759-0.828). The root-mean-square (RMS) difference between image analysis based volumes and fluid displacement measured volumes ranged from 8.51 μl to 25.79 μl. This provides an estimate of the error of previously published methods used to calculate lens volume. Immobilized, enucleated porcine eyes permit improved MR image resolution relative to living eyes and therefore improved image analysis methods to calculate lens volume. The results show that some of the accommodative changes in lens volume reported in the literature are likely below the resolution limits of imaging methods used. MRI, even with detailed image analysis methods used here, is unlikely to achieve the resolution required to accurately size an A-IOL to the capsular bag.
Collapse
Affiliation(s)
- Mark Wendt
- College of Optometry, University of Houston, 505 J. Davis Armistead Building, Houston, TX 77204, USA.
| | | | | | | |
Collapse
|
14
|
Primate lens capsule elasticity assessed using Atomic Force Microscopy. Exp Eye Res 2011; 92:490-4. [PMID: 21420953 DOI: 10.1016/j.exer.2011.03.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 03/01/2011] [Accepted: 03/11/2011] [Indexed: 11/22/2022]
Abstract
The purpose of this project is to measure the elasticity of the human and non-human primate lens capsule at the microscopic scale using Atomic Force Microscopy (AFM). Elasticity measurements were performed using AFM on the excised anterior lens capsule from 9 cynomolgus monkey (5.9-8.0 years), 8 hamadryas baboon (2.8-10.1 years), and 18 human lenses (33-79 years). Anterior capsule specimens were obtained by performing a 5 mm continuous curvilinear capsulorhexis and collecting the resulting disk of capsular tissue. To remove the lens epithelial cells the specimen was soaked in 0.1% trypsin and 0.02% EDTA for 5 min, washed, and placed on a Petri dish and immersed in DMEM. Elasticity measurements of the capsule were performed with a laboratory-built AFM system custom designed for force measurements of ophthalmic tissues. The capsular specimens were probed with an AFM cantilever tip to produce force-indentation curves for each specimen. Young's modulus was calculated from the force-indentation curves using the model of Sneddon for a conical indenter. Young's modulus of elasticity was 20.1-131 kPa for the human lens capsule, 9.19-117 kPa for the cynomolgus lens capsule, and 13.1-62.4 kPa for the baboon lens capsule. Young's modulus increased significantly with age in humans (p = 0.03). The age range of the monkey and baboon samples was not sufficient to justify an analysis of age dependence. The capsule elasticity of young humans (<45 years) was not statistically different from that of the monkey and baboon. In humans, there is an increase in lens capsule stiffness at the microscale that could be responsible for an increase in lens capsule bulk stiffness.
Collapse
|