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Schachar RA, Schachar IH, Kumar S, Feldman EI, Pierscionek BK, Cosman PC. Model of zonular forces on the lens capsule during accommodation. Sci Rep 2024; 14:5896. [PMID: 38467700 PMCID: PMC10928188 DOI: 10.1038/s41598-024-56563-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 03/08/2024] [Indexed: 03/13/2024] Open
Abstract
How the human eye focuses for near; i.e. accommodates, is still being evaluated after more than 165 years. The mechanism of accommodation is essential for understanding the etiology and potential treatments for myopia, glaucoma and presbyopia. Presbyopia affects 100% of the population in the fifth decade of life. The lens is encased in a semi-elastic capsule with attached ligaments called zonules that mediate ciliary muscle forces to alter lens shape. The zonules are attached at the lens capsule equator. The fundamental issue is whether during accommodation all the zonules relax causing the central and peripheral lens surfaces to steepen, or the equatorial zonules are under increased tension while the anterior and posterior zonules relax causing the lens surface to peripherally flatten and centrally steepen while maintaining lens stability. Here we show with a balloon capsule zonular force model that increased equatorial zonular tension with relaxation of the anterior and posterior zonules replicates the topographical changes observed during in vivo rhesus and human accommodation of the lens capsule without lens stroma. The zonular forces required to simulate lens capsule configuration during in vivo accommodation are inconsistent with the general belief that all the zonules relax during accommodation.
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Affiliation(s)
- Ronald A Schachar
- Department of Physics, University of Texas at Arlington, Arlington, TX, USA.
| | - Ira H Schachar
- North Bay Vitreoretinal Consultants, Santa Rosa, CA, USA
| | - Shubham Kumar
- Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA, USA
| | | | - Barbara K Pierscionek
- Faculty of Health, Medicine and Social Care, Medical Technology Research Centre, Anglia Ruskin University, Chelmsford, UK
| | - Pamela C Cosman
- Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA, USA
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2
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Schachar RA, Schachar IH, Pu Y, Kumar S, Cosman PC, Pierscionek BK, Wang K. Finite element analysis of zonular forces. Exp Eye Res 2023; 237:109709. [PMID: 37923162 DOI: 10.1016/j.exer.2023.109709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 10/28/2023] [Accepted: 10/30/2023] [Indexed: 11/07/2023]
Abstract
To determine the effect of zonular forces on lens capsule topography, a finite element (FE) analyses of lens capsules with no lens stroma and constant and variable thickness with anterior capsulotomies of 1.5 mm-6.5 mm were evaluated when subjected to equatorial (Ez), anterior (Az) and posterior (Pz) zonular forces. The lens capsule was considered in the unaccommodated state when the total initial zonular force was 0.00075 N or 0.3 N. From the total 0.00075 N zonular force, the Ez force was increased in 0.000125 N steps for a maximum force of 0.03 N and simultaneously the Az plus Pz force was reduced in 0.000125 N steps to zero. In addition, the force of all the zonules was reduced from 0.00075 N and separately from 0.3 N in 0.000125 N steps to zero. Only when Ez force was increased as Az and Pz force was reduced did the capsule topography simulate in vivo observations with the posterior capsule pole bowing posteriorly. The posterior bowing was directly related to Ez force and capsulotomy size. Whether the total force of all the zonules in the unaccommodated state was 0.00075 N or 0.3 N and reduced in steps to zero, the lens capsule topography did not emulate the in vivo observations. The FE analysis demonstrated that Ez tension increases while the Az and Pz tension decreases and that all the zonules do not relax during ciliary muscle contraction.
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Affiliation(s)
- Ronald A Schachar
- Department of Physics, University of Texas at Arlington, Arlington, TX, 76019, USA.
| | - Ira H Schachar
- North Bay Vitreoretinal Consultants, Santa Rosa, CA, 95403, USA
| | - Yutian Pu
- Beijing Advanced Innovation Center for Biomedical Engineering, School of Engineering Medicine, Beihang University, Beijing, 100191, China
| | - Shubham Kumar
- Department of Electrical and Computer Engineering, University of California San Diego, San Diego, CA, 92093, USA
| | - Pamela C Cosman
- Department of Electrical and Computer Engineering, University of California San Diego, San Diego, CA, 92093, USA
| | - Barbara K Pierscionek
- Faculty of Health, Medicine and Social Care, Medical Technology Research Centre, Anglia Ruskin University, Chelmsford, CM1 1SQ, UK
| | - Kehao Wang
- Beijing Advanced Innovation Center for Biomedical Engineering, School of Engineering Medicine, Beihang University, Beijing, 100191, China
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Pan Y, Liu Z, Zhang H. Research progress of lens zonules. ADVANCES IN OPHTHALMOLOGY PRACTICE AND RESEARCH 2023; 3:80-85. [PMID: 37846380 PMCID: PMC10577871 DOI: 10.1016/j.aopr.2023.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 02/23/2023] [Accepted: 02/23/2023] [Indexed: 10/18/2023]
Abstract
Background The lens zonule, a circumferential system of fibres connecting the ciliary body to the lens, is responsible for centration of the lens. The structural, functional, and positional abnormalities of the zonular apparatus can lead to the abnormality of the intraocular structure, presenting a significant challenge to cataract surgery. Main text The lens zonule is the elaborate system of extracellular fibers, which not only centers the lens in the eye but also plays an important role in accommodation and lens immunity, maintains the shape of the lens, and corrects spherical aberration. The zonules may directly participate in the formation of cataract via the immune mechanism. Abnormal zonular fibers that affect the position and shape of the lens may play an important role in the pathogenesis of angle closure disease and increase the complexity of the surgery. Capsular tension rings and related endocapsular devices are used to provide sufficient capsular bag stabilization and ensure the safety of cataract surgery procedures. Better preoperative and intraoperative evaluation methods for zonules are needed for clinicians. Conclusions The microstructure, biomechanical properties, and physiological functions of the lens zonules help us to better understand the pathogenesis of cataract and glaucoma, facilitating the development of safer surgical procedures for cataract. Further studies are needed to carefully analyze the structure-function relationship of the zonular apparatus to explore new treatment strategies for cataract and glaucoma.
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Affiliation(s)
- Yingying Pan
- Department of Ophthalmology, Shandong Provincial Hospital, Shandong University, Jinan, China
| | - Zhaoqiang Liu
- Department of Ophthalmology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Han Zhang
- Department of Ophthalmology, Shandong Provincial Hospital, Shandong University, Jinan, China
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Jia WN, Wang QY, Niu LL, Chen ZX, Jiang YX. Morphometric assessment of the ciliary body in patients with Marfan syndrome and ectopia lentis: A quantitative study using ultrasound biomicroscopy: Ciliary body morphology in Marfan syndrome and ectopia lentis. Am J Ophthalmol 2023; 251:24-31. [PMID: 36948371 DOI: 10.1016/j.ajo.2023.03.003] [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: 11/08/2022] [Revised: 02/28/2023] [Accepted: 03/05/2023] [Indexed: 03/24/2023]
Abstract
PURPOSE To explore the biometric characteristics of the ciliary body in patients with Marfan syndrome (MFS) and ectopia lentis (EL). DESIGN Cross-sectional study. METHODS Seventy-two consecutive MFS patients with EL and 72 non-disease controls were recruited. Ciliary body biometric parameters such as ciliary muscle cross-sectional area at 2000 μm from the scleral spur (CMA2000), ciliary muscle thickness at 1000 μm from the scleral spur (CMT1000), and maximum ciliary body thickness (CBTmax) were measured from multiple directions with ultrasound biomicroscopy (UBM). The relationship between ciliary body parameters and other ocular characteristics was also evaluated. RESULTS Average CMA2000, CMT1000, and CBTmax were 0.692 ± 0.015 mm2, 0.405 ± 0.010 mm, and 0.855±0.023 mm in MFS eyes, respectively, and were significantly smaller than controls (all p < 0.001). The prevalence of ciliary body thinning was 22.2% in the MFS group versus 0 in controls (p < 0.001); eyes with more severe EL had smaller CMA2000 (p = 0.050), thinner CMT1000 (p = 0.022) and shorter CBTmax (p = 0.015). Patients with microspherophakia (MSP) had even smaller CMA2000 (p = 0.033) and CMT1000 (p = 0.044) than those without MSP. The most common subluxation direction was in the superonasal quadrant (25, 39.7%), which probably correlates with the thinnest CMT1000 in the inferotemporal quadrant (p = 0.005). CONCLUSIONS MFS patients with EL had thinner ciliary muscles, shorter ciliary processes, and a higher prevalence of ciliary body thinning, especially those with MSP. Both the extent and direction of subluxation were associated with ciliary body biometry.
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Affiliation(s)
- Wan-Nan Jia
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai 200031, China; NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai 200031, China
| | - Qian-Yi Wang
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai 200031, China; NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai 200031, China
| | - Ling-Ling Niu
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai 200031, China; NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai 200031, China
| | - Ze-Xu Chen
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai 200031, China; NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai 200031, China.
| | - Yong-Xiang Jiang
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai 200031, China; NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai 200031, China.
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Croft MA, Peterson J, Smith C, Kiland J, Nork TM, Mcdonald JP, Katz A, Hetzel S, Lütjen-Drecoll E, Kaufman PL. Accommodative movements of the choroid in the optic nerve head region of human eyes, and their relationship to the lens. Exp Eye Res 2022; 222:109124. [PMID: 35688214 PMCID: PMC9783760 DOI: 10.1016/j.exer.2022.109124] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 04/30/2022] [Accepted: 05/18/2022] [Indexed: 12/27/2022]
Abstract
The ciliary muscle (CM) powers the accommodative response, and during accommodation the CM pulls the choroid forward in the region of the ora serrata. Our goal was to elucidate the accommodative movements of the choroid in the optic nerve region in humans and to determine whether these movements are related to changes in the lens dimensions that occur with aging, in the unaccommodated and accommodated state. Both eyes of 12 human subjects (aged 18-51 yrs) were studied. Homatropine (1 drop/5%) was used to relax the ciliary muscle (unaccommodated or "resting" eye) and pilocarpine was used to induce the maximum accommodative response (2 drops/4%) (accommodated eye). Images of the fundus and choroid were collected in the region of the optic nerve (ON) via Spectralis OCT (infrared and EDI mode), and choroidal thickness was determined. Ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz) images were collected in the region of the lens/capsule and ciliary body. OCT and UBM images were collected in the resting and accommodated state. The unaccommodated choroidal thickness declined significantly with age (p = 0.0073, r = 0.73) over the entire age range of the subjects studied (18-51 years old). The choroidal thickness was significantly negatively correlated with lens thickness in the accommodated (p = 0.01) and the unaccommodated states (p = 0.005); the thicker the lens the thinner the choroid. Choroid movements around the optic nerve during accommodation were statistically significant; during accommodation the choroid both thinned and moved centrifugally (outward/away from the optic nerve head). The accommodative choroid movements did not decline significantly with age and were not correlated with accommodative amplitude. Measurement of the choroidal thickness is possible with the Spectralis OCT instrument using EDI mode and can be used to determine the accommodative changes in choroidal thickness. The choroidal thickness decreased with age and during accommodation. It may be that age-related choroidal thinning is due to changes in the geometry of the accommodative apparatus to which it is attached (i.e., ciliary muscle/lens complex) such that when the lens is thicker, the choroid is thinner. Accommodative decrease in choroidal thickness and stretch of the retina/choroid may indicate stress/strain forces in the region of the optic nerve during accommodation and may have implications for glaucoma.
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Affiliation(s)
- Mary Ann Croft
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, 53792, USA.
| | - John Peterson
- Diagnostic Imaging Services Lead, UCSF Health, Wayne and Gladys Valley Center for Vision, 490 Illinois St., San Francisco, CA, 94158, USA
| | - Christopher Smith
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, 53792, USA
| | - Julie Kiland
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, 53792, USA
| | - T Michael Nork
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, 53792, USA
| | - Jared P Mcdonald
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, 53792, USA
| | - Alexander Katz
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, 53792, USA
| | - Scott Hetzel
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, USA
| | | | - Paul L Kaufman
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, 53792, USA; Wisconsin National Primate Research Center, USA
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Yin R, Xu J, Wang H, Zhou S, Zhang M, Cai G. Effect of physical activity combined with extra ciliary-muscle training on visual acuity of children aged 10-11. Front Public Health 2022; 10:949130. [PMID: 36111187 PMCID: PMC9468474 DOI: 10.3389/fpubh.2022.949130] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 08/15/2022] [Indexed: 01/21/2023] Open
Abstract
This study is intended for exploring the effects of the physical activity combined with extra ciliary-muscle training with different frequencies on children's kinetic visual acuity and uncorrected distance visual acuity, and eventually figuring out the optimal frequency of ciliary-muscle training for each physical education class. To do the present research, A total of 160 students aged 10-11 from a school in Suzhou (a major city located in southeastern Jiangsu Province, East China) were randomly selected and divided into control group (n = 33), 15-frequency group (n = 44), 30-frequency group (n = 40) and 60-frequency group (n = 43), and the latter three experimental groups participated in a specially designed physical activity plan based on the training principles of ciliary muscle, while the control group participated in normal physical activity as usual. The experimental intervention period was 16 weeks, and all students' kinetic visual acuity and uncorrected distance visual acuity were measured before and after the experiment. The result showed that the kinetic visual acuity of the students in the 30 and 60-frequency groups got improved significantly after the experiment (p < 0.05), with the highest improvement occurring in the 30-frequency group, while there was no significant change in the 15-frequency group and the control group; The uncorrected distance visual acuity of the students in the 30 and 60-frequency groups was significantly improved after the experiment (p < 0.05), and the improvement range in these two groups was similar. In contrast, there was no significant change in the 15-frequency group, while the control group showed a significant decrease (p < 0.05). Physical activity combined with extra ciliary-muscle training has a positive effect on improving children's vision; at the same time, ciliary-muscle training with different frequencies bring out different outcomes on children's vision improvement, among which ciliary-muscle training with frequency of 30 in each physical education class is the best choice to enhance children's kinetic visual acuity and uncorrected distance visual acuity.
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Affiliation(s)
| | | | | | | | | | - Geng Cai
- School of Physical Education, Soochow University, Suzhou, China
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7
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Shen Y, Zhao H, Niu J, Guo W. The “Hand as Foot” teaching method in eye accommodation mechanism. Asian J Surg 2022; 45:2296-2297. [DOI: 10.1016/j.asjsur.2022.05.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 05/06/2022] [Indexed: 11/02/2022] Open
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8
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Zhang X, Wu Q, Wen T, Zhao H, Tian Q, Xu J, Tang G, Li R, Guo X, Song J, Bi H. In vivo analysis of ciliary muscle in myopic Chinese young adults using ArcScan Insight ® 100. Ophthalmic Physiol Opt 2022; 42:559-570. [PMID: 35261043 DOI: 10.1111/opo.12965] [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: 08/15/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To analyse the morphological characteristics of the ciliary muscle (CM) and to explore its relationship with different ocular biometric parameters in myopic young Chinese adults. METHODS This observational, cross-sectional study included 50 right eyes from 50 myopic adults. The CM area (CMA), CM thickness (CMT) and CM length (CML) were measured using the ArcScan Insight® 100. CMT was determined at three points: 1.0 mm (CMT-1), 2.0 mm (CMT-2) and 3.0 mm (CMT-3) posterior to the scleral spur. CML was measured on the scleral (CMLs) and vitreous (CMLv) aspects. The spherical equivalent refraction (SER), axial length (AL) and subfoveal choroidal thickness (SFCT) were examined to determine their associations with CM parameters (CMA, CML and CMT). RESULTS The mean SER and AL were -4.39 ± 2.29 D and 25.61 ± 1.15 mm, respectively. Compared with the nasal CMA, CML and CMT (CMT-1, CMT-2 and CMT-3) findings, the temporal CM parameters (CMA, CMLs, CMLv, CMT-1, CMT-2 and CMT-3) were found to be significantly thicker (all p < 0.001, except CMLv and CMT-1; p < 0.01). The nasal CMA was associated with the average corneal curvature (r = 0.30, p = 0.03) and SER (r = -0.30, p = 0.04). Nasal and temporal CMT-2 were negatively correlated with SER (r = -0.33 and -0.32, respectively, both p < 0.05). There was no correlation between CM parameters (except nasal CMLs, r = 0.31, p = 0.03) and SFCT, or between CM parameters and either the AL or anterior chamber depth (all p > 0.05). CONCLUSION These results suggest that there is temporal versus nasal asymmetry of the CM. CMA, CMT or CML did not vary with axial growth of the eye. The CM is not simply stretched as the eye elongates in myopic young adults.
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Affiliation(s)
- Xiuyan Zhang
- Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Qiuxin Wu
- Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Tiancai Wen
- Institute of Basic Research in Clinical Medicine, China Academy of Chinese Medical Sciences, Beijing, China
| | - Haiqiang Zhao
- Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Qingmei Tian
- Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Jing Xu
- Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Guodong Tang
- Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Runkuan Li
- Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Xiaoxiao Guo
- Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Jike Song
- Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Hongsheng Bi
- Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China.,Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, China
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Abstract
The Zonule of Zinn, or ciliary zonule, is the elaborate system of extracellular fibers that centers the lens in the eye. In humans, the fibers transmit forces that flatten the lens during the process of disaccommodation, thereby bringing distant objects into focus. Zonular fibers are composed almost entirely of 10-12 nm-wide microfibrils, of which polymerized fibrillin is the most abundant component. The thickest fibers have a fascicular organization, where hundreds or thousands of microfibrils are gathered into micrometer-wide bundles. Many such bundles are aggregated to form a fiber. Dozens of proteins comprise the zonule. Most are derived from cells of the non-pigmented ciliary epithelium in the pars plana region, although some are probably contributed by the lens and perhaps other tissues of the anterior segment. Zonular fibers are viscoelastic cables but their component microfibrils are rather stiff structures. Thus, the elastic properties of the fibers likely stem from lateral interactions between microfibrils. Rupture of zonular fibers and subsequent lens dislocation (ectopia lentis) can result from blunt force trauma or be a sequela of other eye diseases, notably exfoliation syndrome. Ectopia lentis is also a feature of syndromic conditions caused typically by mutations in microfibril-associated genes. The resulting ocular phenotypes raise the possibility that the zonule regulates lens size and shape, globe size, and even corneal topology, in addition to its well-recognized role in accommodation.
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Affiliation(s)
- Steven Bassnett
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8096, St. Louis, MO 63110, USA.
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10
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Charman WN. Virtual Issue Editorial: Presbyopia - grappling with an age-old problem. Ophthalmic Physiol Opt 2018; 37:655-660. [PMID: 29044672 DOI: 10.1111/opo.12416] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- W Neil Charman
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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11
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Hipsley A, Hall B, Rocha KM. Scleral surgery for the treatment of presbyopia: where are we today? EYE AND VISION (LONDON, ENGLAND) 2018; 5:4. [PMID: 29497624 PMCID: PMC5827891 DOI: 10.1186/s40662-018-0098-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 01/28/2018] [Indexed: 11/28/2022]
Abstract
Presbyopia corrections traditionally have been approached with attempts to exchange power, either at the cornea or the lens planes, inducing multifocality, or altering asphericity to impact the optical system. Treatments that affect the visual axis, such as spectacle and contact lens correction, refractive surgeries, corneal onlays and inlays, and intraocular lenses are typically unable to restore true accommodation to the presbyopic eye. Their aim is instead to enhance 'pseudoaccommodation' by facilitating an extended depth-of-focus for which vision is sufficient. There is a true lack of technology that approaches presbyopia from a treatment based or therapy based solution, rather than a 'vision correction' solution that compromises other components of the optical system. Scleral surgical procedures seek to restore true accommodation combined with pseudoaccommodation and have several advantages over other more invasive options to treat presbyopia. While the theoretical justification of scleral surgical procedures remains controversial, there has nevertheless been increasing interest and evidence to support scleral surgical and therapeutic approaches to treat presbyopia. Enormous progress in scleral surgery techniques and understanding of the mechanisms of action have been achieved since the 1970s, and this remains an active area of research. In this article, we discuss the historic scleral surgical procedures, the two scleral procedures currently available, as well as an outlook of the future for the scleral surgical space for treating presbyopia.
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Affiliation(s)
| | | | - Karolinne M. Rocha
- Storm Eye Institute, Medical University of South Carolina, Charleston, SC USA
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12
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Hipsley A, Ma DHK, Sun CC, Jackson MA, Goldberg D, Hall B. Visual outcomes 24 months after LaserACE. EYE AND VISION 2017; 4:15. [PMID: 28812042 PMCID: PMC5473977 DOI: 10.1186/s40662-017-0081-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 06/01/2017] [Indexed: 12/04/2022]
Abstract
Background To evaluate the effects on near and intermediate visual performance after bilateral Laser Anterior Ciliary Excision (LaserACE) procedure. Methods LaserACE surgery was performed using the VisioLite 2.94 μm erbium: yttrium–aluminum–garnet (Er:YAG) ophthalmic laser system in 4 oblique quadrants on the sclera over the ciliary muscle in 3 critical zones of physiological importance (over the ciliary muscles and posterior zonules) with the aim to improve natural dynamic accommodative forces. LaserACE was performed on 26 patients (52 eyes). Outcomes were analyzed using visual acuity testing, Randot stereopsis, and the CatQuest 9SF patient survey. Results Binocular uncorrected near visual acuity (UNVA) improved from +0.20 ± 0.16 logMAR preoperatively, to +0.12 ± 0.14 logMAR at 24 months postoperatively (p = 0.0014). There was no statistically significant loss in distance corrected near visual acuity (DCNVA). Binocular DCNVA improved from +0.21 ± 0.17 logMAR preoperatively, to +0.11 ± 0.12 logMAR at 24 months postoperatively (p = 0.00026). Stereoacuity improved from 74.8 ± 30.3 s of arc preoperatively, to 58.8 ± 22.9 s of arc at 24 months postoperatively (p = 0.012). There were no complications such as persistent hypotony, cystoid macular edema, or loss of best-corrected visual acuity (BCVA). Patients surveyed indicated reduced difficulty in areas of near vision, and were overall satisfied with the procedure. Conclusions Preliminary results of the LaserACE procedure show promising results for restoring visual performance for near and intermediate visual tasks without compromising distance vision and without touching the visual axis. The visual function and visual acuity improvements had clinical significance. Patient satisfaction was high postoperatively and sustained over 24 months. Trial registration NCT01491360 (https://clinicaltrials.gov/ct2/show/NCT01491360). Registered 22 November 2011.
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Affiliation(s)
| | - David Hui-Kang Ma
- Department of Ophthalmology, Chang Gung Memorial Hospital, Kweishan, Taoyuan Taiwan.,Department of Chinese Medicine, Chang Gung University, Kweishan, Taoyuan Taiwan.,Center for Tissue Engineering, Chang Gung Memorial Hospital, Kweishan, Taoyuan Taiwan
| | - Chi-Chin Sun
- Department of Ophthalmology, Chang Gung Memorial Hospital, Kweishan, Taoyuan Taiwan.,Department of Ophthalmology, Chang Gung Memorial Hospital, Keelung, Taiwan
| | - Mitchell A Jackson
- Ace Vision Group Inc, 39655 Eureka Drive, Newark, CA 94560 USA.,Jackson Eye, Lake Villa, IL USA
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Davies LN, Croft MA, Papas E, Charman WN. Presbyopia: physiology, prevention and pathways to correction. Ophthalmic Physiol Opt 2015; 36:1-4. [DOI: 10.1111/opo.12272] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Leon N. Davies
- Ophthalmic Research Group; Life and Health Sciences; Aston University; Birmingham UK
| | - Mary Ann Croft
- Department of Ophthalmology and Visual Sciences; University of Wisconsin Clinical Sciences Center; Madison USA
| | - Eric Papas
- School of Optometry and Vision Science; University of New South Wales; Sydney Australia
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