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Wang K, Xia Y, Wang X, Pu Y, Zhao Y, Chang P, Pierscionek BK, Fan Y. Influence of design parameters and capsulorhexis on intraocular lens stabilities: A 3D finite element analysis. Comput Biol Med 2023; 160:106972. [PMID: 37120989 DOI: 10.1016/j.compbiomed.2023.106972] [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: 01/20/2023] [Revised: 03/17/2023] [Accepted: 04/22/2023] [Indexed: 05/02/2023]
Abstract
BACKGROUND Current treatment of cataract widely used in clinics is by removal of the opacified content from the lens capsule which is followed by insertion of an artificial intraocular lens (IOL). The IOL needs to remain stabilized in the capsular bag for the eye to achieve desired optical quality. The present study aims to investigate how different design parameters of the IOL can influence the axial and rotational stabilities of IOLs using Finite Element Analysis. METHODS Eight designs of IOL with variations in types of optics surface, types of haptics and haptic angulation were constructed using parameters obtained from an online IOL databank (IOLs.eu). Each IOL was subjected to compressional simulations both by two clamps and by a collapsed natural lens capsule with an anterior rhexis. Comparisons were made between the two scenarios on axial displacement, rotation, and distribution of stresses. RESULTS The clamps compression method set out by ISO does not always produce the same outcome as the in-the-bag analysis. The open-loop IOLs show better axial stability while the closed-loop IOLs show better rotational stability when compressed by two clamps. Simulations of IOL in the capsular bag only demonstrate better rotational stability for closed-loop designs. CONCLUSIONS The rotational stability of an IOL is largely dependent on its haptic design whilst the axial stability is affected by the appearance of the rhexis to the anterior capsule which has a major influence on designs with a haptic angulation.
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Affiliation(s)
- Kehao Wang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry for Education, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China; School of Engineering Medicine, Beihang University, Beijing, China
| | - Yunxin Xia
- Key Laboratory for Biomechanics and Mechanobiology of Ministry for Education, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China; School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Xiaofei Wang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry for Education, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China; School of Biological Science and Medical Engineering, Beihang University, Beijing, China.
| | - Yutian Pu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry for Education, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China; School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Yune Zhao
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China
| | - Pingjun Chang
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China
| | - Barbara K Pierscionek
- Faculty of Health, Education, Medicine and Social Care, Medical Technology Research Centre, Anglia Ruskin University, Bishops Hall Lane, Chelmsford, United Kingdom
| | - Yubo Fan
- Key Laboratory for Biomechanics and Mechanobiology of Ministry for Education, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China; School of Engineering Medicine, Beihang University, Beijing, China; School of Biological Science and Medical Engineering, Beihang University, Beijing, China.
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Webb JN, Dong C, Bernal A, Scarcelli G. Simulating the Mechanics of Lens Accommodation via a Manual Lens Stretcher. J Vis Exp 2018. [PMID: 29553512 DOI: 10.3791/57162] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The goal of this protocol is to mimic the biomechanics of physiological accommodation in a cost-efficient, practical manner. Accommodation is achieved through the contraction of the ciliary body and relaxation of zonule fibers, which results in the thickening of the lens necessary for near vision. Here, we present a novel, simple method in which accommodation is replicated by tensing the zonules connected to the lens capsule via a manual lens stretcher (MLS). This method monitors the radial stretching achieved by a lens when subjected to a consistent force and allows for a comparison of accommodating lenses, which can be stretched, to non-accommodating lenses, which cannot be stretched. Importantly, the stretcher couples to the zonules directly, and not to the sclera of the eye, thus only requiring the lens, zonules, and ciliary body rather than the entire globe sample. This difference can significantly decrease the cost of acquiring donor cadaver lenses by about 62% compared to acquiring an entire globe.
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Affiliation(s)
- Joshua N Webb
- Fischell Department of Bioengineering, University of Maryland
| | - Caroline Dong
- Fischell Department of Bioengineering, University of Maryland
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Vignetting and field of view with the KAMRA corneal inlay. BIOMED RESEARCH INTERNATIONAL 2013; 2013:154593. [PMID: 24324954 PMCID: PMC3845687 DOI: 10.1155/2013/154593] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 10/10/2013] [Indexed: 11/17/2022]
Abstract
PURPOSE To evaluate the effect of the KAMRA corneal inlay on the retinal image brightness in the peripheral visual field. METHODS A KAMRA inlay was "implanted" into a theoretical eye model in a corneal depth of 200 microns. Corneal radius was varied to a steep, normal, and flat (7.37, 7.77, and 8.17 mm) version keeping the proportion of anterior to posterior radius constant. Pupil size was varied from 2.0 to 5.0 mm. Image brightness was determined for field angles from -70° to 70° with and without KAMRA and proportion of light attenuation was recorded. RESULTS In our parameter space, the attenuation in brightness ranges in between 0 and 60%. The attenuation in brightness is not affected by corneal shape. For large field angles where the incident ray bundle is passing through the peripheral cornea, brightness is not affected. For combinations of small pupil sizes (2.0 and 2.5 mm) and field angles of 20-40°, up to 60% of light may be blocked with the KAMRA. CONCLUSION For combinations of pupil sizes and field angles, the attenuation of image brightness reaches levels up to 60%. Our theoretical findings have to be clinically validated with detailed investigation of this vignetting effect.
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Gillner M, Eppig T, Langenbucher A. Automatic intraocular lens segmentation and detection in optical coherence tomography images. Z Med Phys 2013; 24:104-11. [PMID: 23928353 DOI: 10.1016/j.zemedi.2013.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 07/13/2013] [Accepted: 07/15/2013] [Indexed: 11/25/2022]
Abstract
We present a new algorithm for automatic segmentation and detection of an accommodative intraocular lens implanted in a biomechanical eye model. We extracted lens curvature and position. The algorithm contains denoising and fan correction by a multi-level calibration routine. The segmentation is realized by an adapted canny edge detection algorithm followed by a detection of lens surface with an automatic region of interest search to suppress non-optical surfaces like the lens haptic. The optical distortion of lens back surface is corrected by inverse raytracing. Lens geometry was extracted by a spherical fit. We implemented and demonstrated a powerful algorithm for automatic segmentation, detection and surface analysis of intraocular lenses in vitro. The achieved accuracy is within the expected range determined by previous studies. Future improvements will include the transfer to clinical anterior segment OCT devices.
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Affiliation(s)
- Melanie Gillner
- Institute of Medical Physics, Friedrich-Alexander University Erlangen-Nuremberg, Henkestr. 91, 91052 Erlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander University Erlangen-Nuremberg, Paul-Gordan-Str. 6, 91052 Erlangen, Germany.
| | - Timo Eppig
- Experimental Ophthalmology, Saarland University, Kirrberger Str. 100, Bldg. 22, 66421 Homburg, Germany
| | - Achim Langenbucher
- Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander University Erlangen-Nuremberg, Paul-Gordan-Str. 6, 91052 Erlangen, Germany; Experimental Ophthalmology, Saarland University, Kirrberger Str. 100, Bldg. 22, 66421 Homburg, Germany
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Speck A, Zelzer B, Kannengießer M, Langenbucher A, Eppig T. Inspection of freeform intraocular lens topography by phase measuring deflectometric methods. APPLIED OPTICS 2013; 52:4279-4286. [PMID: 23842171 DOI: 10.1364/ao.52.004279] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 05/17/2013] [Indexed: 06/02/2023]
Abstract
Manufacturing spherical, aspheric, and freeform surfaces requires testing throughout the development and production process. State-of-the-art topography measurement is limited in applicability for intraocular lenses (IOLs), and there is no dedicated commercial surface measurement system available for freeform IOLs. The purpose of this work was to validate a deflectometric setup for surface measurement, detection of defects, and shape fidelity analysis for the development and production of IOLs. The setup is based on a phase measuring deflectometer with a field-of-view of 80 mm×80 mm and a mean repetition accuracy of 1.6·10(-3) D. The technique is suitable for detection of global and local surface errors, extracted from geometry and topography analysis. For validation according to DIN ISO 5725:2002, spherical IOLs with radii of curvature of 10 and 20 mm, a commercial aspheric IOL, and single-sided freeform IOL samples were used.
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Affiliation(s)
- Alexis Speck
- Experimental Ophthalmology, Saarland University, Homburg/Saar, Germany.
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