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Vyas SA, Lakshmanan Y, Chan HHL, Leung TW, Kee CS. Experimentally induced myopia and myopic astigmatism alter retinal electrophysiology in chickens. Sci Rep 2022; 12:21180. [PMID: 36477183 PMCID: PMC9729572 DOI: 10.1038/s41598-022-25075-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 11/24/2022] [Indexed: 12/12/2022] Open
Abstract
Myopia (or "short-sightedness") and astigmatism are major causes of visual impairment worldwide. Significant amounts of astigmatism are frequently observed in infants and have been associated with myopia development. Although it is well established that both myopia and astigmatism are associated with ocular structural changes from anterior to posterior segments, very little is known on how these refractive errors alter retinal functions. This study investigated the effects of experimentally induced myopia and myopic-astigmatism on retinal electrophysiology by using an image-guided, multifocal global flash stimulation in chickens, a widely used animal model for refractive error development. Myopia and myopic-astigmatism were experimentally induced, respectively, by wearing spherical (- 10 D, n = 12) and sphero-cylindrical lenses (- 6.00 DS/- 8.00 DCx90: Hyperopic With-The Rule, H-WTR, n = 15; - 6.00 DS/- 8.00 DCx180: Hyperopic Against-The-Rule, H-ATR, n = 11) monocularly for a week (post-hatching day 5 to 12). An aged-matched control group without any lens treatment provided normal data (n = 12). Multifocal electrophysiological results revealed significant regional variation in the amplitude of induced component (IC) (central greater than peripheral; both p < 0.05) in the normal and H-ATR groups, but not in the - 10 D and H-WTR groups. Most importantly, for the first time, our results showed that both H-WTR and H-ATR groups exhibited a significantly longer implicit time of the inner retinal response at the central region when compared to the normal and - 10 D groups, highlighting a significant role of astigmatism in retinal physiology.
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Affiliation(s)
- Sonal Aswin Vyas
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, SAR, China
| | - Yamunadevi Lakshmanan
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, SAR, China.,Laboratory of Experimental Optometry (Neuroscience), School of Optometry, The Hong Kong Polytechnic University, Hong Kong, SAR, China
| | - Henry Ho-Lung Chan
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, SAR, China.,Laboratory of Experimental Optometry (Neuroscience), School of Optometry, The Hong Kong Polytechnic University, Hong Kong, SAR, China.,Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Hong Kong, China
| | - Tsz-Wing Leung
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, SAR, China.,Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Hong Kong, China.,Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Kowloon, Hong Kong
| | - Chea-Su Kee
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, SAR, China. .,Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Hong Kong, China. .,Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Kowloon, Hong Kong.
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Hemodynamic and morphological changes of the central retinal artery in myopic eyes. Sci Rep 2022; 12:7104. [PMID: 35501327 PMCID: PMC9061854 DOI: 10.1038/s41598-022-11087-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 04/12/2022] [Indexed: 11/13/2022] Open
Abstract
Due to excessive elongation of the eyeball, myopia-related vascular abnormalities are frequently observed in the central retinal artery (CRA) and its intraretinal branches. In addition to inconsistency in previously reported findings, hemodynamic (reduced flow velocity, increased vascular resistance) and morphological changes (narrower vessel diameter) were usually studied separately. This cross-sectional study evaluated the hemodynamic and morphological characteristics concurrently in a large sample of healthy myopes, by using the color Doppler ultrasound and adaptive optics retinal camera. Results showed that the retrobulbar segment of CRA had a tendency of slightly reduced flow velocity in eyeballs with longer axial length, but the correlation was not significant after adjusting for the multiple correlations. Vascular resistance was not affected by the axial elongation. With respect to the intraretinal branches, no significant changes in longer eyes of total diameter or lumen diameter were observed, while both the wall thickness and the wall cross-sectional area were significantly increased, but only a marginally increase in the wall to lumen ratio was found with increasing axial length. This implies some potential small artery remodeling in the intraretinal CRA branches. Overall, blood supply of the inner retina in healthy young myopes is likely to be maintained. Additionally, morphological parameters of vascular microstructure could be potential biomarkers to monitor myopia progression and understand myopia-related vascular abnormalities in future studies.
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Gupta SK, Chakraborty R, Verkicharla PK. Electroretinogram responses in myopia: a review. Doc Ophthalmol 2021; 145:77-95. [PMID: 34787722 PMCID: PMC9470726 DOI: 10.1007/s10633-021-09857-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 10/11/2021] [Indexed: 11/02/2022]
Abstract
The stretching of a myopic eye is associated with several structural and functional changes in the retina and posterior segment of the eye. Recent research highlights the role of retinal signaling in ocular growth. Evidence from studies conducted on animal models and humans suggests that visual mechanisms regulating refractive development are primarily localized at the retina and that the visual signals from the retinal periphery are also critical for visually guided eye growth. Therefore, it is important to study the structural and functional changes in the retina in relation to refractive errors. This review will specifically focus on electroretinogram (ERG) changes in myopia and their implications in understanding the nature of retinal functioning in myopic eyes. Based on the available literature, we will discuss the fundamentals of retinal neurophysiology in the regulation of vision-dependent ocular growth, findings from various studies that investigated global and localized retinal functions in myopia using various types of ERGs.
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Affiliation(s)
- Satish Kumar Gupta
- Myopia Research Lab, Prof. Brien Holden Eye Research Centre, Brien Holden Institute of Optometry and Vision Sciences, Kallam Anji Reddy Campus, L V Prasad Eye Institute, Hyderabad, India
| | - Ranjay Chakraborty
- Caring Futures Institute, College of Nursing and Health Sciences, Optometry and Vision Science, Flinders University, Adelaide, South Australia, Australia
| | - Pavan Kumar Verkicharla
- Myopia Research Lab, Prof. Brien Holden Eye Research Centre, Brien Holden Institute of Optometry and Vision Sciences, Kallam Anji Reddy Campus, L V Prasad Eye Institute, Hyderabad, India.
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Nagra M, Patel M, Barbur J. Changes in forward light scatter parameters as a function of refractive error in young adults. Graefes Arch Clin Exp Ophthalmol 2020; 258:925-930. [PMID: 31912219 PMCID: PMC7575508 DOI: 10.1007/s00417-019-04584-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 12/10/2019] [Accepted: 12/19/2019] [Indexed: 11/04/2022] Open
Abstract
Background/aims Some aspects of visual performance worsen with increasing myopia. Whilst the underlying causes are not always clear, reduction in retinal image quality is often attributed to structural changes in the posterior myopic eye. Forward light scatter, originating principally from the cornea and lens, is known to produce veiling glare which subsequently reduces retinal image contrast. It is therefore of interest to investigate whether forward light scatter varies with refractive error. Methods Thirteen young-adult subjects (18–25 years), with mean spherical errors (MSE ± sd, D) RE, − 1.69 ± 2.02 (range 0.38 to − 4.75); LE, − 1.91 ± 1.94 (range 0.50 to − 4.63) underwent binocular assessment of forward light scatter using the AVOT light scatter test. Five glare annuli, with effective eccentricities ranging from 2 to 10°, were used to estimate parameters, k and n, which define the light scatter function of the eye. These were then used to calculate the area under the light scatter function (k′) and the total volume of light scatter (k″). Results Significant correlation was found between increasing myopia and k′ values (RE, p < 0.05; r = 0.64; LE, p < 0.05, r = 0.66). Neither the ‘volume’ of light scatter (k″), the parameter, n, which controls the angular distribution of light scatter, or the straylight parameter constant, k, were significantly correlated with refractive error (p > 0.05 for both eyes). Axial length was also not correlated with any of the light scatter parameters measured. Conclusion The preliminary data from this study provide evidence that some light scatter parameters may be correlated with refractive error. Further studies are needed to characterize how changes in the anterior media of the eye, and inclusion of a wider range of refractive errors, may affect forward light scatter.
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Affiliation(s)
- Manbir Nagra
- School of Health and Care Professions, University of Portsmouth, Portsmouth, PO1 2DT, UK.
| | - Mansi Patel
- Applied Vision Research Centre, Division of Optometry and Visual Science, City, University of London, London, EC1V 0HB, UK
| | - John Barbur
- Applied Vision Research Centre, Division of Optometry and Visual Science, City, University of London, London, EC1V 0HB, UK
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Chin MP, Chu PHW, Cheong AMY, Chan HHL. Human electroretinal responses to grating patterns and defocus changes by global flash multifocal electroretinogram. PLoS One 2015; 10:e0123480. [PMID: 25874564 PMCID: PMC4395308 DOI: 10.1371/journal.pone.0123480] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 02/19/2015] [Indexed: 11/18/2022] Open
Abstract
The electrical response of the retina was examined as a function of retinal region, using stimuli of various spatial frequencies in the first experiment. In the second experiment, the regional response of the retina to defocus at high and low spatial frequencies was investigated. Twenty three subjects were recruited for global flash multifocal electroretinogram (mfERG) in experiment 1. Black and white gratings (printed on plastic transparent sheets) of four spatial frequencies (SF), 0.24, 1.2, 2.4 and 4.8 cycle per degree were presented in front of the mfERG stimulation. The amplitudes and implicit times of the direct (DC) and induced (IC) components of mfERG responses were pooled into six concentric rings for analysis. There was low amplitude DC at low SF, which increased with increasing SF, and which decreased with increasing eccentricity. The IC was high in amplitude at all SF and reduced in amplitude with increasing eccentricity. Our findings suggested that outer and inner retina had different characteristics in processing spatial details. In experiment 2, Twenty-three young adults were recruited for mfERG measurement. The retinal electrical responses for low (0.24cpd) and high (4.8cpd) SF under fully corrected conditions of short-term negative defocus (-2D) and short term positive defocus (+2D) conditions were measured. There was a sign-dependent response to defocus in the DC response, mainly in peripheral regions. The sign dependent response at low SF was more obvious than that at high SF, and was located more peripherally. The IC response showed no clear trends for either defocus condition. The human retina seems to have a decoding system for optical defocus, which was tuned for low spatial frequency, and was located in the retinal near periphery.
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Affiliation(s)
- Man Pan Chin
- Laboratory of Experimental Optometry (Neuroscience), School of Optometry, Hong Kong Polytechnic University, Hong Kong SAR, China
| | - Patrick H. W. Chu
- Laboratory of Experimental Optometry (Neuroscience), School of Optometry, Hong Kong Polytechnic University, Hong Kong SAR, China
| | - Allen M. Y. Cheong
- Laboratory of Experimental Optometry (Neuroscience), School of Optometry, Hong Kong Polytechnic University, Hong Kong SAR, China
| | - Henry H. L. Chan
- Laboratory of Experimental Optometry (Neuroscience), School of Optometry, Hong Kong Polytechnic University, Hong Kong SAR, China
- * E-mail:
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Li Q, Guo M, Dong H, Zhang Y, Fu Y, Yin X. Voxel-based analysis of regional gray and white matter concentration in high myopia. Vision Res 2012; 58:45-50. [PMID: 22402232 DOI: 10.1016/j.visres.2012.02.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2011] [Revised: 02/17/2012] [Accepted: 02/21/2012] [Indexed: 11/25/2022]
Abstract
Structural changes of the brain have been detected in many early-onset eye diseases, whereas little is known about whether changes could occur if the onset age is after the sensitive development period. High Myopia is a prime example of neural plasticity after development, whose case history is usually long. To investigate potential morphological changes in the brain of high myopic patients, we compared a group of 30 adults with high myopia and 30 control subjects using high-resolution anatomic MRI in combination with vision tests. No difference in gray matter (GM) concentration was detected. However, increased concentration of white matter (WM) was observed in patients with high myopia, primarily in the calcarine area. Another three comparatively smaller regions were in the prefrontal and parietal lobe. It can be inferred that cortices developed normally and refractive error in high myopic patients may be compensated by strengthening the correlation between visual cortex and visual related areas. Our study suggests that besides early-onset diseases, the late-onset eye diseases can also affect the structure of brain.
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Affiliation(s)
- Qian Li
- Department of Medical Imaging, Tianjin Medical University, Tianjin, China
| | - Mingxia Guo
- Department of Medical Imaging, Tianjin Medical University, Tianjin, China
| | - Honghuan Dong
- Department of Medical Imaging, Tianjin Medical University, Tianjin, China
| | - Yunting Zhang
- Department of Radiology, Tianjin Medical University General Hospital, Tianjin, China
| | - Yue Fu
- Department of Radiology, Tianjin Medical University General Hospital, Tianjin, China
| | - Xiaohui Yin
- Department of Radiology, Tianjin Medical University General Hospital, Tianjin, China
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Chan HHL. Is the peripheral retina an important site for myopic development? [Liu Y, Wildsoet C (2011) The effectof two-zone concentric bifocal spectacle lenses on refractive error development and eye growth in young chicks. Invest Ophthalmol Vis Sci 52(2):1078-1086]. Graefes Arch Clin Exp Ophthalmol 2011; 249:955-6. [PMID: 21643721 DOI: 10.1007/s00417-011-1720-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 05/26/2011] [Accepted: 05/26/2011] [Indexed: 11/28/2022] Open
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