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Zhang G, Wei Q, Lu L, Lin AL, Qu C. The evolution of mechanism of accommodation and a novel hypothesis. Graefes Arch Clin Exp Ophthalmol 2023; 261:3083-3095. [PMID: 37103620 DOI: 10.1007/s00417-023-06045-w] [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: 07/11/2022] [Revised: 01/06/2023] [Accepted: 03/24/2023] [Indexed: 04/28/2023] Open
Abstract
Myopia and presbyopia are two major optometry problems facing the whole society. The mechanism of accommodation is strongly related to the treatments of myopia and presbyopia. However, the key mechanism of accommodation has puzzled us for over 400 years and is still not clear at present, leading to the stagnation of prevention and treatment of myopia and presbyopia. With the continued development of experimental technologies and equipment, the approaches to elucidate accommodation's intricacies have become more methodological and sophisticated. Fortunately, some significant progress has been made. This article is to review the evolution of the mechanism of accommodation. Helmholtz proposed a classical theory of "zonules relax during accommodation." In contrast, Schachar put forward a theory of "zonules taut during accommodation." Those hypotheses are relatively complete, but either do not fully explain everything about the accommodation mechanism or lack sufficient experimental and clinical evidence to support them. Then, some contentious issues are discussed in detail to find the truth. Finally, we proposed our hypothesis about accommodation based on the anatomy of the accommodative apparatus.
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Affiliation(s)
- Guanghong Zhang
- School of Medicine, University of Electronic Science and Technology of China, No. 2006, Xiyuan Ave West Hi-Tech Zone, Chengdu, CN611731, China
- Department of Ophthalmology, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, No. 2006, Xiyuan Ave West Hi-Tech Zone, Chengdu, CN611731, China
- Sichuan Key Laboratory for Disease Gene Study, Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, No. 32 of the West 2nd Section of First Ring Road, Chengdu, 610072, China
| | - Qian Wei
- Southwest Medical University, No. 319, Section 3, Zhongshan Road, Luzhou, 646000, China
| | - Lei Lu
- School and Hospital of Stomatology, Wenzhou Medical University, Xueyuan West Road, Wenzhou, Zhejiang, 325027, China.
| | - Andy L Lin
- Department of Internal Medicine, UC Irvine Medical Center, 333 City Blvd. West, Suite 400, Orange, CA, 92868-3298, USA.
| | - Chao Qu
- School of Medicine, University of Electronic Science and Technology of China, No. 2006, Xiyuan Ave West Hi-Tech Zone, Chengdu, CN611731, China.
- Department of Ophthalmology, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, No. 2006, Xiyuan Ave West Hi-Tech Zone, Chengdu, CN611731, China.
- Sichuan Key Laboratory for Disease Gene Study, Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, No. 32 of the West 2nd Section of First Ring Road, Chengdu, 610072, China.
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Gao R, Liu J, Zhou X, Huang L, Huang W, Xue Y, Wang F, Gong S, Wu R, Wang Y. Influence of Pilocarpine Eyedrops on the Ocular Biometric Parameters and Intraocular Lens Power Calculation. J Ophthalmol 2023; 2023:7680659. [PMID: 37455794 PMCID: PMC10348856 DOI: 10.1155/2023/7680659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 06/08/2023] [Accepted: 06/26/2023] [Indexed: 07/18/2023] Open
Abstract
Objective To evaluate the influence of pilocarpine eyedrops on the ocular biometric parameters and whether these parameter changes affect the intraocular lens (IOL) power calculation in patients with primary angle-closure glaucoma (PACG). Methods Twenty-two PACG patients and fifteen normal subjects were enrolled. Ocular biometric parameters including the axial length (AL), anterior chamber depth (ACD), lens thickness (LT), mean keratometry (Km), and white-to-white distance (WTW) were measured by using a Lenstar LS 900 device before and at least 30 minutes after instillation of 2% pilocarpine eyedrops. Lens position (LP) was calculated, and the IOL power prediction based on the ocular biometric parameters was performed using the Barrett Universal II, Haigis, Hoffer Q, Holladay I, or SRK/T formulas before and after pilocarpine application. Results In both PACG and normal groups, pilocarpine eyedrops induced a slight but statistically significant increase in the mean AL (0.01 mm for both groups) and mean LT (0.02 mm and 0.03 mm, respectively) but a significant decrease in the mean ACD (0.03 mm and 0.05 mm, respectively) and mean LP (0.02 mm and 0.04 mm, respectively). No significant changes in the mean Km and WTW were noticed in both groups. In addition, the IOL power calculation revealed insignificant changes before and after the pilocarpine instillation in both groups, regardless of the formula used. Conclusions Pilocarpine eyedrops can induce slight changes in the ocular biometric parameters including the AL, ACD, LT, and LP. However, these parameter changes will not result in a significant difference in IOL power estimation.
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Affiliation(s)
- Ruxin Gao
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
| | - Jinkun Liu
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
| | - Xiaojie Zhou
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
| | - Luping Huang
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
| | - Weiyi Huang
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
| | - Yingying Xue
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
| | - Fei Wang
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
| | - Songjian Gong
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
| | - Renyi Wu
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
| | - Yuhong Wang
- Department of Ophthalmology, Eye Institute & Affiliated Xiamen Eye Center, School of Medicine, Xiamen University, Xiamen 361001, China
- Department of Ophthalmology, Fujian Provincial Key Laboratory of Corneal & Ocular Surface Diseases, Xiamen 361001, China
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Dai C, Liu M, Lv X, Li B. Subtle changes of the crystalline lens after cycloplegia: a retrospective study. BMC Ophthalmol 2021; 21:124. [PMID: 33676428 PMCID: PMC7937324 DOI: 10.1186/s12886-021-01884-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 02/25/2021] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The purpose of this study was to evaluate the shape of the crystalline lens in terms of biometry and diopters before and after cycloplegia using the CASIA2 swept-source (SS) optical coherence tomography (OCT) system on the anterior segment. METHODS This was a retrospective study. Children and adolescents (26 males and 29 females, aged 4-21 years) with simple ametropia were selected for optometry and CASIA2 imaging at 2 separate visits before and after cycloplegia. Diopter values were derived from the spherical power (S) obtained by optometry. Biometric parameters of the crystalline lens, including the anterior chamber depth (ACD), anterior and posterior curvature of the lens (ACL and PCL), lens thickness (LTH), lens decentration (LD), lens tilt (LT), and equivalent diameter of the lens (LED), were measured by the CASIA2 system. The differences in these parameters after compared with before cycloplegia were determined, and their relationships were analyzed. RESULTS Fifty-five participants (106 eyes) were initially enrolled. There was a significant difference (P < 0.05) in the S (t=-7.026, P < 0.001), ACD (t=-8.796, P < 0.001), ACL (t=-13.263, P < 0.001) and LTH (t = 7.363, P < 0.001) after compared with before cycloplegia. The change in the PCL (t = 1.557, P = 0.122), LD (t = 0.876, P = 0.383), LT (t = 0.440, P = 0.661) and LED (t=-0.351, P = 0.726) was not statistically significant (P > 0.05). There was a significant (P < 0.05) correlation of the change in the S with that in the ACL (r = 0.466, P < 0.001), LTH (r=-0.592, P < 0.001), and LED (r = 0.223, P = 0.021) but not the PCL (r = 0.19, P = 0.051), LD (r=-0.048, P = 0.0628) or LT (r=-0.022, P = 0.822). Furthermore, the change in the ACD was closely related to the change in crystalline morphology. However, in children and adolescents, we found that the change in crystalline morphology was unrelated to age. CONCLUSIONS Changes in lens morphology after compared with before cycloplegia are mainly related to the ACL and LTH, but there is no difference in the PCL, LD, LT, or LED. In the adolescent population, change in the S is related to change in the ACL, LED and LTH. However, age is unrelated to the shape and tendency of the crystalline lens. Further research is required to determine whether the same conclusion applies to different age groups and different refractive states (myopia, hyperopia, emmetropia) .
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Affiliation(s)
- Cheng Dai
- School of Basic Medicine, North Sichuan Medical College, Sichuan Province, 637000, Nanchong, China.,Department of Ophthalmology, Affiliated Hospital of North Sichuan Medical College, Sichuan Province, 637000, Nanchong, China
| | - Meng Liu
- School of Basic Medicine, North Sichuan Medical College, Sichuan Province, 637000, Nanchong, China
| | - Xiaodong Lv
- Department of Clinical Medicine, North Sichuan Medical College, Sichuan Province, 637000, Nanchong, China
| | - Binzhong Li
- School of Basic Medicine, North Sichuan Medical College, Sichuan Province, 637000, Nanchong, China.
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Schachar RA, Schachar IH. Intralenticular Hydrostatic Pressure Increases During Ciliary Muscle Contraction: A Finding Consistent With the Schachar Mechanism of Accommodation. Invest Ophthalmol Vis Sci 2020; 61:34. [PMID: 32543663 PMCID: PMC7415311 DOI: 10.1167/iovs.61.6.34] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
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Grzybowski A, Schachar RA, Gaca-Wysocka M, Schachar IH, Pierscionek BK. Image registration of the human accommodating eye demonstrates equivalent increases in lens equatorial radius and central thickness. Int J Ophthalmol 2019; 12:1751-1757. [PMID: 31741865 PMCID: PMC6848867 DOI: 10.18240/ijo.2019.11.14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 08/03/2019] [Indexed: 11/23/2022] Open
Abstract
AIM To compare the results of in vivo human high resolution image registration studies of the eye during accommodation to the predictions of mathematical and finite element models of accommodation. METHODS Data from published high quality image registration studies of pilocarpine induced accommodative changes of equatorial lens radius (ELR) and central lens thickness (CLT) were statistically analyzed. RESULTS The mean changes in ELR and CLT were 6.76 µm/diopter and 6.51 µm/diopter, respectively. The linear regressions, reflecting the association between ELR and accommodative amplitude (AAELR) was: slope=6.58 µm/diopter, r2 =0.98, P<0.0001 and between CLT and AACLT was: slope=6.75 µm/diopter, r2 =0.83, P<0.001. On the basis of these relationships, the CLT slope and the AAELR were used to predict the measured change in ELR (ELRpredicted). There was no statistical difference between ELRpredicted and the measured ELR as demonstrated by a Student's paired t-test: P=0.96 and linear regression analysis: slope=0.97, r2 =0.98, P<0.00001. CONCLUSION Image registration with invariant positional references demonstrates that ELR and CLT equivalently minimally increase ∼7.0 µm/diopter during accommodation. The small equivalent increases in ELR and CLT are associated with a large accommodative amplitude. These findings are consistent with the predictions of mathematical and finite element models that specified the stiffness of the lens nucleus is the same or greater than the lens cortex and that accommodation involves a small force (<5 g).
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Affiliation(s)
- Andrzej Grzybowski
- Institute for Research in Ophthalmology, Poznan 60-554, Poland
- Department of Ophthalmology, University of Warmia and Mazury, Olsztyn 10-082, Poland
| | - Ronald A Schachar
- Department of Physics, University of Texas in Arlington, Arlington, Texas 76019, USA
| | | | - Ira H Schachar
- Department of Ophthalmology, Horngren Family Vitreoretinal Center, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California 94304, USA
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Wolffsohn JS, Davies LN. Presbyopia: Effectiveness of correction strategies. Prog Retin Eye Res 2018; 68:124-143. [PMID: 30244049 DOI: 10.1016/j.preteyeres.2018.09.004] [Citation(s) in RCA: 132] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 09/14/2018] [Accepted: 09/18/2018] [Indexed: 01/04/2023]
Abstract
Presbyopia is a global problem affecting over a billion people worldwide. The prevalence of unmanaged presbyopia is as high as 50% of those over 50 years of age in developing world populations, due to a lack of awareness and accessibility to affordable treatment, and is even as high as 34% in developed countries. Definitions of presbyopia are inconsistent and varied, so we propose a redefinition that states "presbyopia occurs when the physiologically normal age-related reduction in the eye's focusing range reaches a point, when optimally corrected for distance vision, that the clarity of vision at near is insufficient to satisfy an individual's requirements". Strategies for correcting presbyopia include separate optical devices located in front of the visual system (reading glasses) or a change in the direction of gaze to view through optical zones of different optical powers (bifocal, trifocal or progressive addition spectacle lenses), monovision (with contact lenses, intraocular lenses, laser refractive surgery and corneal collagen shrinkage), simultaneous images (with contact lenses, intraocular lenses and corneal inlays), pinhole depth of focus expansion (with intraocular lenses, corneal inlays and pharmaceuticals), crystalline lens softening (with lasers or pharmaceuticals) or restored dynamics (with 'accommodating' intraocular lenses, scleral expansion techniques and ciliary muscle electrostimulation); these strategies may be applied differently to the two eyes to optimise the range of clear focus for an individual's task requirements and minimise adverse visual effects. However, none fully overcome presbyopia in all patients. While the restoration of natural accommodation or an equivalent remains elusive, guidance is given on presbyopic correction evaluation techniques.
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Affiliation(s)
- James S Wolffsohn
- Ophthalmic Research Group, Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK.
| | - Leon N Davies
- Ophthalmic Research Group, Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK
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