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Schaeffel F, Swiatczak B. Mechanisms of emmetropization and what might go wrong in myopia. Vision Res 2024; 220:108402. [PMID: 38705024 DOI: 10.1016/j.visres.2024.108402] [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: 10/17/2023] [Revised: 03/25/2024] [Accepted: 03/25/2024] [Indexed: 05/07/2024]
Abstract
Studies in animal models and humans have shown that refractive state is optimized during postnatal development by a closed-loop negative feedback system that uses retinal image defocus as an error signal, a mechanism called emmetropization. The sensor to detect defocus and its sign resides in the retina itself. The retina and/or the retinal pigment epithelium (RPE) presumably releases biochemical messengers to change choroidal thickness and modulate the growth rates of the underlying sclera. A central question arises: if emmetropization operates as a closed-loop system, why does it not stop myopia development? Recent experiments in young human subjects have shown that (1) the emmetropic retina can perfectly distinguish between real positive defocus and simulated defocus, and trigger transient axial eye shortening or elongation, respectively. (2) Strikingly, the myopic retina has reduced ability to inhibit eye growth when positive defocus is imposed. (3) The bi-directional response of the emmetropic retina is elicited with low spatial frequency information below 8 cyc/deg, which makes it unlikely that optical higher-order aberrations play a role. (4) The retinal mechanism for the detection of the sign of defocus involves a comparison of defocus blur in the blue (S-cone) and red end of the spectrum (L + M-cones) but, again, the myopic retina is not responsive, at least not in short-term experiments. This suggests that it cannot fully trigger the inhibitory arm of the emmetropization feedback loop. As a result, with an open feedback loop, myopia development becomes "open-loop".
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Affiliation(s)
- Frank Schaeffel
- Myopia Research Group, Institute of Molecular and Clinical Ophthalmology Basel (IOB), Switzerland; Section Neurobiology of the Eye, Institute of Ophthalmic Research, University of Tübingen, Germany; Zeiss Vision Lab, Institute of Ophthalmic Research, University of Tübingen, Germany.
| | - Barbara Swiatczak
- Myopia Research Group, Institute of Molecular and Clinical Ophthalmology Basel (IOB), Switzerland
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Huang Y, Li X, Zhuo Z, Zhang J, Que T, Yang A, Drobe B, Chen H, Bao J. Effect of spectacle lenses with aspherical lenslets on choroidal thickness in myopic children: a 3-year follow-up study. EYE AND VISION (LONDON, ENGLAND) 2024; 11:16. [PMID: 38659078 PMCID: PMC11044302 DOI: 10.1186/s40662-024-00383-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 04/04/2024] [Indexed: 04/26/2024]
Abstract
BACKGROUND To investigate the impact of wearing spectacle lenses with highly aspherical lenslets (HAL) for 3 years and the impact of switching from single-vision lenses (SVL) to HAL on choroidal thickness (ChT). METHODS Fifty-one participants who had already worn HAL for 2 years continued wearing them for an additional year (HAL group). Further, 50 and 41 participants who had worn spectacle lenses with slightly aspherical lenslets (SAL) and SVL for 2 years, respectively, switched to wearing HAL for another year (SAL-HAL and SVL-HAL groups). Additionally, 48 new participants aged 10-15 years were enrolled to wear SVL at the third year (new-SVL group). ChT was measured every 6 months throughout the study. RESULTS Significant differences were observed in the changes in ChT among the four groups at the third year (all P < 0.05 except for the outer nasal region: P = 0.09), with the new-SVL group showing larger reductions compared with the other three groups. However, none of the three HAL-wearing groups showed significant changes in ChT at the third year (all P > 0.05). When comparing the changes in ChT for 3 years among the HAL, SAL-HAL, and SVL-HAL groups, significant differences were found before switching to HAL, but these differences were abolished after all participants switched to HAL. CONCLUSIONS Compared to those in the SVL group, choroid thinning was significantly inhibited in all the HAL groups. Wearing HAL for 3 years no longer had a choroidal thickening effect but could still inhibit choroidal thinning compared to wearing SVL. TRIAL REGISTRATION The study was registered at the Chinese Clinical Trial Registry (ChiCTR1800017683), http://www.chictr.org.cn/showproj.aspx?proj=29789 .
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Affiliation(s)
- Yingying Huang
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China
- Wenzhou Medical University - Essilor International Research Center (WEIRC), Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xue Li
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China
- Wenzhou Medical University - Essilor International Research Center (WEIRC), Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zuopao Zhuo
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China
- Wenzhou Medical University - Essilor International Research Center (WEIRC), Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jiali Zhang
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China
| | - Tianxing Que
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China
- School of Biomedical Engineering, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Adeline Yang
- Wenzhou Medical University - Essilor International Research Center (WEIRC), Wenzhou Medical University, Wenzhou, Zhejiang, China
- R&D Singapore, Essilor International, Singapore, Singapore
| | - Björn Drobe
- Wenzhou Medical University - Essilor International Research Center (WEIRC), Wenzhou Medical University, Wenzhou, Zhejiang, China
- R&D Singapore, Essilor International, Singapore, Singapore
| | - Hao Chen
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China.
- Wenzhou Medical University - Essilor International Research Center (WEIRC), Wenzhou Medical University, Wenzhou, Zhejiang, China.
- School of Biomedical Engineering, Wenzhou Medical University, Wenzhou, Zhejiang, China.
| | - Jinhua Bao
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China.
- Wenzhou Medical University - Essilor International Research Center (WEIRC), Wenzhou Medical University, Wenzhou, Zhejiang, China.
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Chiu YC, Tsai PC, Lee SH, Wang JH, Chiu CJ. Systematic Review of Myopia Progression after Cessation of Optical Interventions for Myopia Control. J Clin Med 2023; 13:53. [PMID: 38202060 PMCID: PMC10779574 DOI: 10.3390/jcm13010053] [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: 11/20/2023] [Revised: 12/12/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024] Open
Abstract
Despite high discontinuation rates for myopia optical interventions, limited attention has been given to the potential rebound effects post-discontinuation. This systematic review aims to assess the extent of the rebound effects following the cessation of common clinical optical myopia-control interventions in children. A comprehensive search of PubMed, Embase, Cochrane CENTRAL, and ClinicalTrials.gov was conducted from inception to October 2023. The rebound effects, defined as changes in the axial length or spherical equivalent during and after treatment cessation, were categorized into four levels. These studies encompassed 703 participants and spanned from 2019 to 2023, with durations of treatment and cessation ranging from 6 months to 3.5 years and from 2 weeks to 5 years, respectively. This review, encompassing 14 studies, revealed a predominant strong rebound effect in orthokeratology (8 studies), a weak rebound effect in multifocal soft contact lenses (4 studies), and a variable rebound effect in peripheral-plus spectacle lenses (2 studies). Notably, with the increasing cessation duration, the rebound effects diminished, potentially linked to the reversal of choroidal thickening and the disappearance of peripheral myopic defocus. In conclusion, a temporal trend of rebound effects exists in all three myopia optical interventions, possibly contributing to their myopia control mechanisms.
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Affiliation(s)
- Yu-Chieh Chiu
- School of Medicine, Tzu Chi University, Hualien 970, Taiwan; (Y.-C.C.); (P.-C.T.); (S.-H.L.)
| | - Ping-Chiao Tsai
- School of Medicine, Tzu Chi University, Hualien 970, Taiwan; (Y.-C.C.); (P.-C.T.); (S.-H.L.)
| | - Ssu-Hsien Lee
- School of Medicine, Tzu Chi University, Hualien 970, Taiwan; (Y.-C.C.); (P.-C.T.); (S.-H.L.)
| | - Jen-Hung Wang
- Department of Medical Research, Buddhist Tzu Chi General Hospital, Hualien 970, Taiwan;
| | - Cheng-Jen Chiu
- Department of Ophthalmology and Visual Science, Tzu Chi University, Hualien 970, Taiwan
- Department of Ophthalmology, Hualien Tzu Chi Hospital, the Buddhist Tzu Chi Medical Foundation, Hualien 970, Taiwan
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Guggenheim JA, Walline JJ. Identifying non-responders to treatments for myopia. Ophthalmic Physiol Opt 2023; 43:945-946. [PMID: 37162175 DOI: 10.1111/opo.13162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 04/27/2023] [Accepted: 04/28/2023] [Indexed: 05/11/2023]
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Xuan M, Zhu Z, Jiang Y, Wang W, Zhang J, Xiong R, Shi D, Bulloch G, Zeng J, He M. Longitudinal Changes in Choroidal Structure Following Repeated Low-Level Red-Light Therapy for Myopia Control: Secondary Analysis of a Randomized Controlled Trial. Asia Pac J Ophthalmol (Phila) 2023; 12:377-383. [PMID: 37523429 DOI: 10.1097/apo.0000000000000618] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 05/05/2023] [Indexed: 08/02/2023] Open
Abstract
PURPOSE Repeated low-level red-light (RLRL) therapy has been confirmed as a novel intervention for myopia control in children. This study aims to investigate longitudinal changes in choroidal structure in myopic children following 12-month RLRL treatment. MATERIALS AND METHODS The current study is a secondary analysis from a multicenter, randomized controlled trial (NCT04073238). Choroidal parameters were derived from baseline and follow-up swept-source optical coherence tomography scans taken at 1, 3, 6, and 12 months. These parameters included the luminal area (LA), stromal area (SA), total choroidal area (TCA; a combination of LA and SA), and choroidal vascularity index (CVI; ratio of LA to TCA), which were automatically measured by a validated custom choroidal structure assessment tool. RESULTS A total of 143 children (88.3% of all participants) with sufficient image quality were included in the analysis (n=67 in the RLRL and n=76 in the control groups). At the 12-month visit, all choroidal parameters increased in the RLRL group, with changes from baseline of 11.70×10 3 μm 2 (95% CI: 4.14-19.26×10 3 μm 2 ), 3.92×10 3 μm 2 (95% CI: 0.56-7.27×10 3 μm 2 ), 15.61×10 3 μm 2 (95% CI: 5.02-26.20×10 3 μm 2 ), and 0.21% (95% CI: -0.09% to 0.51%) for LA, SA, TCA, and CVI, respectively, whereas these parameters reduced in the control group. CONCLUSIONS Following RLRL therapy, the choroidal thickening was found to be accompanied by increases in both the vessel LA and SA, with the increase in LA being greater than that of SA. In the control group, with myopia progression, both the LA and SA decreased over time.
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Affiliation(s)
- Meng Xuan
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong Province, China
| | - Zhuoting Zhu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong Province, China
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
| | - Yu Jiang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong Province, China
| | - Wei Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong Province, China
| | - Jian Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong Province, China
| | - Ruilin Xiong
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong Province, China
| | - Danli Shi
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong Province, China
| | - Gabriella Bulloch
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
- Faculty of Science, Medicine and Health, University of Melbourne, Melbourne, Victoria, Australia
| | - Junwen Zeng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong Province, China
| | - Mingguang He
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, Guangdong Province, China
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
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Sankaridurg P, Berntsen DA, Bullimore MA, Cho P, Flitcroft I, Gawne TJ, Gifford KL, Jong M, Kang P, Ostrin LA, Santodomingo-Rubido J, Wildsoet C, Wolffsohn JS. IMI 2023 Digest. Invest Ophthalmol Vis Sci 2023; 64:7. [PMID: 37126356 PMCID: PMC10155872 DOI: 10.1167/iovs.64.6.7] [Citation(s) in RCA: 28] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Myopia is a dynamic and rapidly moving field, with ongoing research providing a better understanding of the etiology leading to novel myopia control strategies. In 2019, the International Myopia Institute (IMI) assembled and published a series of white papers across relevant topics and updated the evidence with a digest in 2021. Here, we summarize findings across key topics from the previous 2 years. Studies in animal models have continued to explore how wavelength and intensity of light influence eye growth and have examined new pharmacologic agents and scleral cross-linking as potential strategies for slowing myopia. In children, the term premyopia is gaining interest with increased attention to early implementation of myopia control. Most studies use the IMI definitions of ≤-0.5 diopters (D) for myopia and ≤-6.0 D for high myopia, although categorization and definitions for structural consequences of high myopia remain an issue. Clinical trials have demonstrated that newer spectacle lens designs incorporating multiple segments, lenslets, or diffusion optics exhibit good efficacy. Clinical considerations and factors influencing efficacy for soft multifocal contact lenses and orthokeratology are discussed. Topical atropine remains the only widely accessible pharmacologic treatment. Rebound observed with higher concentration of atropine is not evident with lower concentrations or optical interventions. Overall, myopia control treatments show little adverse effect on visual function and appear generally safe, with longer wear times and combination therapies maximizing outcomes. An emerging category of light-based therapies for children requires comprehensive safety data to enable risk versus benefit analysis. Given the success of myopia control strategies, the ethics of including a control arm in clinical trials is heavily debated. IMI recommendations for clinical trial protocols are discussed.
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Affiliation(s)
- Padmaja Sankaridurg
- Brien Holden Vision Institute, Sydney, Australia
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia
| | - David A Berntsen
- University of Houston, College of Optometry, Houston, Texas, United States
| | - Mark A Bullimore
- University of Houston, College of Optometry, Houston, Texas, United States
| | - Pauline Cho
- West China Hospital, Sichuan University, Sichuan, China
- Eye & ENT Hospital of Fudan University, Shanghai, China
- Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou, China
| | - Ian Flitcroft
- Centre for Eye Research Ireland, School of Physics and Clinical and Optometric Sciences, Technological University Dublin, Dublin, Ireland
- Department of Ophthalmology, Children's Health Ireland at Temple Street Hospital, Dublin, Ireland
| | - Timothy J Gawne
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Kate L Gifford
- Queensland University of Technology, Brisbane, Australia
| | - Monica Jong
- Johnson & Johnson Vision, Jacksonville, Florida, United States
| | - Pauline Kang
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia
| | - Lisa A Ostrin
- University of Houston, College of Optometry, Houston, Texas, United States
| | | | - Christine Wildsoet
- UC Berkeley Wertheim School Optometry & Vision Science, Berkeley, California, United States
| | - James S Wolffsohn
- College of Health & Life Sciences, Aston University, Birmingham, United Kingdom
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Ostrin LA, Harb E, Nickla DL, Read SA, Alonso-Caneiro D, Schroedl F, Kaser-Eichberger A, Zhou X, Wildsoet CF. IMI-The Dynamic Choroid: New Insights, Challenges, and Potential Significance for Human Myopia. Invest Ophthalmol Vis Sci 2023; 64:4. [PMID: 37126359 PMCID: PMC10153586 DOI: 10.1167/iovs.64.6.4] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
The choroid is the richly vascular layer of the eye located between the sclera and Bruch's membrane. Early studies in animals, as well as more recent studies in humans, have demonstrated that the choroid is a dynamic, multifunctional structure, with its thickness directly and indirectly subject to modulation by a variety of physiologic and visual stimuli. In this review, the anatomy and function of the choroid are summarized and links between the choroid, eye growth regulation, and myopia, as demonstrated in animal models, discussed. Methods for quantifying choroidal thickness in the human eye and associated challenges are described, the literature examining choroidal changes in response to various visual stimuli and refractive error-related differences are summarized, and the potential implications of the latter for myopia are considered. This review also allowed for the reexamination of the hypothesis that short-term changes in choroidal thickness induced by pharmacologic, optical, or environmental stimuli are predictive of future long-term changes in axial elongation, and the speculation that short-term choroidal thickening can be used as a biomarker of treatment efficacy for myopia control therapies, with the general conclusion that current evidence is not sufficient.
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Affiliation(s)
- Lisa A Ostrin
- University of Houston College of Optometry, Houston, Texas, United States
| | - Elise Harb
- Herbert Wertheim School of Optometry and Vision Science, University of California Berkeley, Berkeley, California, United States
| | - Debora L Nickla
- Department of Biomedical Sciences and Disease, New England College of Optometry, Boston, Massachusetts, United States
| | - Scott A Read
- Contact Lens and Visual Optics Laboratory, Centre for Vision and Eye Research, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - David Alonso-Caneiro
- Contact Lens and Visual Optics Laboratory, Centre for Vision and Eye Research, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Falk Schroedl
- Center for Anatomy and Cell Biology, Institute of Anatomy and Cell Biology-Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Alexandra Kaser-Eichberger
- Center for Anatomy and Cell Biology, Institute of Anatomy and Cell Biology-Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Xiangtian Zhou
- Eye Hospital and School of Optometry and Ophthalmology, National Clinical Research Center for Ocular Diseases, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Christine F Wildsoet
- Herbert Wertheim School of Optometry and Vision Science, University of California Berkeley, Berkeley, California, United States
- Centre for Vision and Eye Research, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, Queensland, Australia
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Alrasheed SH, Aldakhil S. Corneal Curvature, Anterior Chamber Depth, Lens Thickness, And Vitreous Chamber Depth: Their Intercorrelations With Refractive Error In Saudi Adults. Open Ophthalmol J 2022. [DOI: 10.2174/18743641-v16-e2209300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Background:
Ocular biometrics, such as corneal curvature, axial length, anterior chamber depth, and lens thickness, play a significant role in the development of refractive error and are essential in many clinical and research applications.
Objective:
To determine means and ranges for corneal curvature, axial length, anterior chamber depth, lens thickness, vitreous chamber depth, and their intercorrelations with refractive error in Saudi adults.
Methods:
A total of 120 eyes of 60 hyperopic and 60 myopic subjects aged 19-26 years old were enrolled in this comparative cross-sectional study. Axial Length (AL), Anterior Chamber Depth (ACD), Lens Thickness (LT), and Vitreous Chamber Depth (VCD) were measured by the SONOMED ultrasound E-Z SCAN AB5500+, A-scan, with a contact technique. An ophthalmometer measured the refractive status objectively by auto-refraction and the corneal radius of curvature.
Results:
The findings showed that the myopic eyes had a deeper ACD(3.70±0.27mm) than hyperopic eyes (3.28±0.32mm), P=0.0001. However, the hyperopic eyes had a thicker LT (3.84±0.24mm) than the myopic eyes (3.81±0.19mm), P=0.640. The mean of the corneal radius of curvature for the myopic eyes was slightly more curved (7.87±0.23mm) than for the hyperopic eyes (7.95±0.27mm), P=0.602. The myopic eyes had a higher axial length/corneal radius AL/CR ratio (3.12±0.11) than hyperopic eyes (2.89±0.06), with P=0.0001. Myopic spherical equivalent (SPH) positively correlated with VCD and AL/CR ratio, P=0.0001. Vitreous chamber depth/Axial length ratio (VCD/AL) in the myopic eyes was higher (0.693±0.041) than in the hyperopic eyes (0.677±0.018), P=0.000. Hyperopic SPH was positively associated with the VCD/AL ratio, P=0.0001.
Conclusion:
Myopic eyes had a deeper VCD than hyperopic eyes; there was a strong positive correlation between VCD and myopic SPH. There was a strong positive correlation between the AL/CR ratio and myopic SPH and a VCD/AL ratio and the hyperopic SPH. Thus, the study suggests the possible utility of the AL/CR ratio while assessing the development of myopic refractive error and the VCD/AL ratio when evaluating hyperopic eyes and their associated complications.
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