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Liu ESF, Cudia MKET, Wong GKY, Ko CN, Lam DSC. The concept of cone opponency may extend beyond accommodation, to myopiagenesis and emmetropization, for a better peripheral defocus lens. Asia Pac J Ophthalmol (Phila) 2024; 13:100125. [PMID: 39662699 DOI: 10.1016/j.apjo.2024.100125] [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: 11/20/2024] [Revised: 11/29/2024] [Accepted: 12/06/2024] [Indexed: 12/13/2024] Open
Abstract
Myopia has ever-rising prevalence in the past few decades globally. Its pathogenesis is still not adequately elucidated especially at the signal transduction level. For the environmental risk factors, there is a large body of fragmented knowledge about the visual inputs for accommodation, myopiagenesis and emmetropization, with the latter two being essentially local processes. The red-green and yellow-blue chromatic pathways, together with the underlying L-M and S-(L+M) cone opponency, seem to be the common denominator amongst them. In this review, experimental and observational evidence are summarized to delineate the interplay of them. This review may establish the pivotal role of longitudinal chromatic aberration (LCA) for a mechanistic approach to future research in myopia control. This review looks into the mechanistic processes underlying myopiagenesis and emmetropization, specifically focusing on chromatic aberration and cone opponency in vision as pivotal components. The roles of longitudinal chromatic aberration (LCA) and cone contrast in myopia onset and development are intriguing. How visual input and chromatic pathways (specifically, red-green and blue-yellow cone opponency) contribute to accommodation that may trigger emmetropization mechanisms, thereby influencing eye growth patterns are explored and discussed. In brief, this manuscript delves into the physiology of visual processing and highlights a foundational aspect of visual science that may account for a "Go" or "Stop" signaling in axial eye growth. It further proposes a metric to gauge myopia-inhibiting optical devices such as the peripheral defocus lenses, for its best iteration. Future research in the above-mentioned areas is warranted.
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Affiliation(s)
- Edward S F Liu
- The Primasia International Eye Research Institute of The Chinese University of Hong Kong (Shenzhen), Shenzhen, China.
| | | | - Graham K Y Wong
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Chung-Nga Ko
- The Primasia International Eye Research Institute of The Chinese University of Hong Kong (Shenzhen), Shenzhen, China
| | - Dennis S C Lam
- The Primasia International Eye Research Institute of The Chinese University of Hong Kong (Shenzhen), Shenzhen, China.
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2
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Höfling L, Szatko KP, Behrens C, Deng Y, Qiu Y, Klindt DA, Jessen Z, Schwartz GW, Bethge M, Berens P, Franke K, Ecker AS, Euler T. A chromatic feature detector in the retina signals visual context changes. eLife 2024; 13:e86860. [PMID: 39365730 PMCID: PMC11452179 DOI: 10.7554/elife.86860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 08/25/2024] [Indexed: 10/06/2024] Open
Abstract
The retina transforms patterns of light into visual feature representations supporting behaviour. These representations are distributed across various types of retinal ganglion cells (RGCs), whose spatial and temporal tuning properties have been studied extensively in many model organisms, including the mouse. However, it has been difficult to link the potentially nonlinear retinal transformations of natural visual inputs to specific ethological purposes. Here, we discover a nonlinear selectivity to chromatic contrast in an RGC type that allows the detection of changes in visual context. We trained a convolutional neural network (CNN) model on large-scale functional recordings of RGC responses to natural mouse movies, and then used this model to search in silico for stimuli that maximally excite distinct types of RGCs. This procedure predicted centre colour opponency in transient suppressed-by-contrast (tSbC) RGCs, a cell type whose function is being debated. We confirmed experimentally that these cells indeed responded very selectively to Green-OFF, UV-ON contrasts. This type of chromatic contrast was characteristic of transitions from ground to sky in the visual scene, as might be elicited by head or eye movements across the horizon. Because tSbC cells performed best among all RGC types at reliably detecting these transitions, we suggest a role for this RGC type in providing contextual information (i.e. sky or ground) necessary for the selection of appropriate behavioural responses to other stimuli, such as looming objects. Our work showcases how a combination of experiments with natural stimuli and computational modelling allows discovering novel types of stimulus selectivity and identifying their potential ethological relevance.
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Affiliation(s)
- Larissa Höfling
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
- Centre for Integrative Neuroscience, University of TübingenTübingenGermany
| | - Klaudia P Szatko
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
- Centre for Integrative Neuroscience, University of TübingenTübingenGermany
| | - Christian Behrens
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
| | - Yuyao Deng
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
- Centre for Integrative Neuroscience, University of TübingenTübingenGermany
| | - Yongrong Qiu
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
- Centre for Integrative Neuroscience, University of TübingenTübingenGermany
| | | | - Zachary Jessen
- Feinberg School of Medicine, Department of Ophthalmology, Northwestern UniversityChicagoUnited States
| | - Gregory W Schwartz
- Feinberg School of Medicine, Department of Ophthalmology, Northwestern UniversityChicagoUnited States
| | - Matthias Bethge
- Centre for Integrative Neuroscience, University of TübingenTübingenGermany
- Tübingen AI Center, University of TübingenTübingenGermany
| | - Philipp Berens
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
- Centre for Integrative Neuroscience, University of TübingenTübingenGermany
- Tübingen AI Center, University of TübingenTübingenGermany
- Hertie Institute for AI in Brain HealthTübingenGermany
| | - Katrin Franke
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
| | - Alexander S Ecker
- Institute of Computer Science and Campus Institute Data Science, University of GöttingenGöttingenGermany
- Max Planck Institute for Dynamics and Self-OrganizationGöttingenGermany
| | - Thomas Euler
- Institute for Ophthalmic Research, University of TübingenTübingenGermany
- Centre for Integrative Neuroscience, University of TübingenTübingenGermany
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Zheleznyak L, Liu C, Winter S. Chromatic cues for the sign of defocus in the peripheral retina. BIOMEDICAL OPTICS EXPRESS 2024; 15:5098-5114. [PMID: 39296412 PMCID: PMC11407258 DOI: 10.1364/boe.537268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2024] [Accepted: 07/28/2024] [Indexed: 09/21/2024]
Abstract
Detecting optical defocus at the retina is crucial for accurate accommodation and emmetropization. However, the optical characteristics of ocular defocus are not fully understood. To bridge this knowledge gap, we simulated polychromatic retinal image quality by considering both the monochromatic wavefront aberrations and chromatic aberrations of the eye, both in the fovea and the periphery (nasal visual field). Our study revealed two main findings: (1) chromatic and monochromatic aberrations interact to provide a signal to the retina (chromatic optical anisotropy) to discern positive from negative defocus and (2) that chromatic optical anisotropy exhibited notable differences among refractive error groups (myopes, emmetropes and hyperopes). These findings could enhance our understanding of the underlying mechanisms of defocus detection and their subsequent implications for myopia control therapies. Further research is needed to explore the retinal architecture's ability to utilize the optical signals identified in this study.
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Affiliation(s)
- Len Zheleznyak
- Clerio Vision, Inc., Rochester NY, USA
- Center for Visual Science, University of Rochester, Rochester, New York, USA
| | - Chang Liu
- The Institute of Optics, University of Rochester, Rochester, New York, USA
| | - Simon Winter
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
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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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She Z, Gawne TJ. The Parameters Governing the Anti-Myopia Efficacy of Chromatically Simulated Myopic Defocus in Tree Shrews. Transl Vis Sci Technol 2024; 13:6. [PMID: 38722277 PMCID: PMC11090138 DOI: 10.1167/tvst.13.5.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 03/21/2024] [Indexed: 05/15/2024] Open
Abstract
Purpose We previously showed that exposing tree shrews (Tupaia belangeri, small diurnal mammals closely related to primates) to chromatically simulated myopic defocus (CSMD) counteracted small-cage myopia and instead induced hyperopia (approximately +4 diopters [D]). Here, we explored the parameters of this effect. Methods Tree shrews were exposed to the following interventions for 11 days: (1) rearing in closed (n = 7) or open (n = 6) small cages; (2) exposed to a video display of Maltese cross images with CSMD combined with overhead lighting (n = 4); (3) exposed to a video display of Maltese cross images with zero blue contrast ("flat blue," n = 8); and (4) exposed to a video display of black and white grayscale tree images with different spatial filtering (blue pixels lowpass <1 and <2 cycles per degree [CPD]) for the CSMD. Results (1) Tree shrews kept in closed cages, but not open cages, developed myopia. (2) Overhead illumination reduced the hyperopia induced by CSMD. (3) Zero-blue contrast produced hyperopia but slightly less than the CSMD. (4) Both of the CSMD tree images counteracted small cage myopia, but the one low pass filtering blue <1 CPD was more effective at inducing hyperopia. Conclusions Any pattern with reduced blue contrast at and below approximately 1 CPD counteracts myopia/promotes hyperopia, but maximal effectiveness may require that the video display be the brightest object in the environment. Translational Relevance Chromatically simulated myopic blur might be a powerful anti-myopia therapy in children, but the parameter selection could be critical. Issues for translation to humans are discussed.
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Affiliation(s)
- Zhihui She
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Timothy J. Gawne
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, USA
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Clement SP, Breher K, Domdei N, Dolata J, Wahl S. Influence of Aberration-Free, Narrowband Light on the Choroidal Thickness and Eye Length. Transl Vis Sci Technol 2024; 13:30. [PMID: 38662401 PMCID: PMC11055502 DOI: 10.1167/tvst.13.4.30] [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: 12/07/2023] [Accepted: 02/26/2024] [Indexed: 04/26/2024] Open
Abstract
Purpose To determine whether light chromaticity without defocus induced by longitudinal chromatic aberration (LCA) is sufficient to regulate eye growth. Methods An interferometric setup based on a spatial light modulator was used to illuminate the dominant eyes of 23 participants for 30 minutes with three aberration-free stimulation conditions: (1) short wavelength (450 nm), (2) long wavelength (638 nm), and (3) broadband light (450-700 nm), covering a retinal area of 12°. The non-dominant eye was occluded and remained as the control eye. Axial length and choroidal thickness were measured before and after the illumination period. Results Axial length increased significantly from baseline for short-wavelength (P < 0.01, 7.4 ± 2.2 µm) and long-wavelength (P = 0.01, 4.8 ± 1.7 µm) light. The broadband condition also showed an increase in axial length with no significance (P = 0.08, 5.1 ± 3.5 µm). The choroidal thickness significantly decreased in the case of long-wavelength light (P < 0.01, -5.7 ± 2.2 µm), but there was no significant change after short-wavelength and broadband illumination. The axial length and choroidal thickness did not differ significantly between the test and control eyes or between the illumination conditions (all P > 0.05). Also, the illuminated versus non-illuminated choroidal zone did not show a significant difference (all P > 0.05). Conclusions All stimulation conditions with short- and long-wavelength light and broadband light led to axial elongation and choroidal thinning. Therefore, light chromaticity without defocus induced by LCA is suggested to be insufficient to regulate eye growth. Translational Relevance This study helps in understanding if light chromaticity alone is a sufficient regulator of eye growth.
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Affiliation(s)
- Susanna P. Clement
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | | | - Niklas Domdei
- Carl Zeiss Vision International GmbH, Aalen, Germany
| | | | - Siegfried Wahl
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany
- Carl Zeiss Vision International GmbH, Aalen, Germany
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7
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Chen YY, Tsai TH, Liu YL, Lin HJ, Wang IJ. The impact of light properties on ocular growth and myopia development. Taiwan J Ophthalmol 2024; 14:143-150. [PMID: 39027063 PMCID: PMC11253990 DOI: 10.4103/tjo.tjo-d-24-00031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Accepted: 04/03/2024] [Indexed: 07/20/2024] Open
Abstract
The objective of this article is to comprehensively review the effect of environmental lighting on ocular growth and refractive status in both animal and clinical studies, with an emphasis on the underlying mechanisms. This review was performed by searching research articles and reviews utilizing the terms "myopia," "light therapy," "axial length," "refractive error," and "emmetropization" in PubMed datasets. The review was finalized in December 2023. In the animal studies, high lighting brightness, illumination periods aligning with circadian rhythm, and color contrast signals including multiple wavelengths all help regulate ocular growth against myopia. Long wavelengths have been found to induce myopia in chicks, mice, fish, and guinea pigs, whereas shorter wavelengths lead to hyperopia. In contrast, red light has been observed to have a protective effect against myopia in tree shrews and rhesus monkeys. Apart from wavelength, flicker status also showed inconsistent effects on ocular growth, which could be attributed to differences in ocular refractive status, evolutionary disparities in retinal cone cells across species, and the selection of myopia induction models in experiments. In the clinical studies, current evidence suggests a control effect with red light therapy. Although the lighting conditions diverge from those in animal experiments, further reports are needed to assess the long-term effects. In conclusion, this review encompasses research related to the impact of light exposure on myopia and further explores the retinoscleral signaling pathway in refractive development. The aim is to establish a theoretical foundation for optimizing environmental factors in lighting design to address the epidemic of childhood myopia.
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Affiliation(s)
- Ying-Yi Chen
- Department of Ophthalmology, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan
- Department of Ophthalmology, Cathay General Hospital, Taipei, Taiwan
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan
- Department of Ophthalmology, Sijhih Cathay General Hospital, New Taipei City, Taiwan
| | - Tzu-Hsun Tsai
- Department of Ophthalmology, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan
- College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Yao-Lin Liu
- Department of Ophthalmology, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan
- Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Hui-Ju Lin
- Department of Ophthalmology, China Medical University Hospital, Taichung, Taiwan
- School of Chinese Medicine, China Medical University, Taichung, Taiwan
| | - I-Jong Wang
- Department of Ophthalmology, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan
- College of Medicine, National Taiwan University, Taipei, Taiwan
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8
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Salzano AD, Khanal S, Cheung NL, Weise KK, Jenewein EC, Horn DM, Mutti DO, Gawne TJ. Repeated Low-level Red-light Therapy: The Next Wave in Myopia Management? Optom Vis Sci 2023; 100:812-822. [PMID: 37890098 DOI: 10.1097/opx.0000000000002083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/29/2023] Open
Abstract
SIGNIFICANCE Exposure to long-wavelength light has been proposed as a potential intervention to slow myopia progression in children. This article provides an evidence-based review of the safety and myopia control efficacy of red light and discusses the potential mechanisms by which red light may work to slow childhood myopia progression.The spectral composition of the ambient light in the visual environment has powerful effects on eye growth and refractive development. Studies in mammalian and primate animal models (macaque monkeys and tree shrews) have shown that daily exposure to long-wavelength (red or amber) light promotes slower eye growth and hyperopia development and inhibits myopia induced by form deprivation or minus lens wear. Consistent with these results, several recent randomized controlled clinical trials in Chinese children have demonstrated that exposure to red light for 3 minutes twice a day significantly reduces myopia progression and axial elongation. These findings have collectively provided strong evidence for the potential of using red light as a myopia control intervention in clinical practice. However, several questions remain unanswered. In this article, we review the current evidence on the safety and efficacy of red light as a myopia control intervention, describe potential mechanisms, and discuss some key unresolved issues that require consideration before red light can be broadly translated into myopia control in children.
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Affiliation(s)
| | - Safal Khanal
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, Alabama
| | - Nathan L Cheung
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina
| | - Katherine K Weise
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, Alabama
| | - Erin C Jenewein
- Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania
| | - Darryl M Horn
- Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania
| | - Donald O Mutti
- The Ohio State University College of Optometry, Columbus, Ohio
| | - Timothy J Gawne
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, Alabama
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She Z, Ward AH, Gawne TJ. The effects of ambient narrowband long-wavelength light on lens-induced myopia and form-deprivation myopia in tree shrews. Exp Eye Res 2023; 234:109593. [PMID: 37482282 PMCID: PMC10529043 DOI: 10.1016/j.exer.2023.109593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Revised: 06/21/2023] [Accepted: 07/11/2023] [Indexed: 07/25/2023]
Abstract
Here we examine the effects of ambient red light on lens-induced myopia and diffuser-induced myopia in tree shrews, small diurnal mammals closely related to primates. Starting at 24 days of visual experience (DVE), seventeen tree shrews were reared in red light (624 ± 10 or 634 ± 10 nm, 527-749 human lux) for 12-14 days wearing either a -5D lens (RL-5D, n = 5) or a diffuser (RLFD, n = 5) monocularly, or without visual restriction (RL-Control, n = 7). Refractive errors and ocular dimensions were compared to those obtained from tree shrews raised in broad-spectrum white light (WL-5D, n = 5; WLFD, n = 10; WL Control, n = 7). The RL-5D tree shrews developed less myopia in their lens-treated eyes than WL-5D tree shrews at the end of the experiment (-1.1 ± 0.9D vs. -3.8 ± 0.3D, p = 0.007). The diffuser-treated eyes of the RLFD tree shrews were near-emmetropic (-0.3 ± 0.6D, vs. -5.4 ± 0.7D in the WLFD group). Red light induced hyperopia in control animals (RL-vs. WL-Control, +3.0 ± 0.7 vs. +1.0 ± 0.2D, p = 0.02), the no-lens eyes of the RL-5D animals, and the no-diffuser eyes of the RLFD animals (+2.5 ± 0.5D and +2.3 ± 0.3D, respectively). The refractive alterations were consistent with the alterations in vitreous chamber depth. The lens-induced myopia developed in red light suggests that a non-chromatic cue could signal defocus to a less accurate extent, although it could also be a result of "form-deprivation" caused by defocus blur. As with previous studies in rhesus monkeys, the ability of red light to promote hyperopia appears to correlate with its ability to retard lens-induced myopia and form-deprivation myopia, the latter of which might be related to non-visual ocular mechanisms.
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Affiliation(s)
- Zhihui She
- Department of Optometry and Vision Science, University of Alabama at Birmingham, 1716 University Blvd, HPB 528, Birmingham, AL, 35294, UK
| | - Alexander H Ward
- Georgia Cancer Center, Augusta University. Dr. Ward Contributed to This Work During His Graduate Training at the University of Alabama at Birmingham, UK
| | - Timothy J Gawne
- Department of Optometry and Vision Science, University of Alabama at Birmingham, 1716 University Blvd, HPB 528, Birmingham, AL, 35294, UK.
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Zhang P, Zhang X, Zhu H. Photobiomodulation at 660 nm promotes collagen synthesis via downregulation of HIF-1α expression without photodamage in human scleral fibroblasts in vitro in a hypoxic environment. Graefes Arch Clin Exp Ophthalmol 2023; 261:2535-2545. [PMID: 37074407 DOI: 10.1007/s00417-023-06066-5] [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: 02/06/2023] [Revised: 03/29/2023] [Accepted: 04/10/2023] [Indexed: 04/20/2023] Open
Abstract
PURPOSE The increasing prevalence of myopia is a global public health issue. Because of the complexity of myopia pathogenesis, current control methods for myopia have great limitations. The aim of this study was to explore the effect of photobiomodulation (PBM) on human sclera fibroblasts (HSFs) under hypoxia, in the hope of providing new ideas for myopia prevention and control. METHODS Hypoxic cell model was established at 0, 6, 12, and 24 h time points to simulate myopia microenvironment and explore the optimal time point. Control, hypoxia, hypoxia plus light, and normal plus light cell models were set up for the experiments, and cells were incubated for 24 or 48 h after PBM (660 nm, 5 J/cm2), followed by evaluation of hypoxia-inducible factor 1α (HIF-1α) and collagen I a1 (COL1A1) proteins using Western blotting and immunofluorescence, and photo damage was detected by CCK-8, scratch test, and flow cytometry assays. We also used transfection technology to further elucidate the regulatory mechanism. RESULTS The change of target proteins is most obvious when hypoxia lasts for 24 h (p < 0.01). PBM at 660 nm increased extracellular collagen content (p < 0.001) and downregulated expression of HIF-1α (p < 0.05). This treatment did not affect the migration and proliferation of cells (p > 0.05), and effectively inhibited apoptosis under hypoxia (p < 0.0001). After overexpression of HIF-1α, the effect of PBM was attenuated (p > 0.05). CONCLUSIONS Photobiomodulation at 660 nm promotes collagen synthesis via downregulation of HIF-1α expression without photodamage.
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Affiliation(s)
- Pengbo Zhang
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China
| | - Xibo Zhang
- Department of Ophthalmology, Affiliated Hospital of Southwest Medical University, Luzhou, 646000, Sichuan, China.
| | - Huang Zhu
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China.
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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: 36] [Impact Index Per Article: 36.0] [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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12
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Khanal S, Norton TT, Gawne TJ. Limited bandwidth short-wavelength light produces slowly-developing myopia in tree shrews similar to human juvenile-onset myopia. Vision Res 2023; 204:108161. [PMID: 36529048 PMCID: PMC9974583 DOI: 10.1016/j.visres.2022.108161] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 11/30/2022] [Accepted: 12/01/2022] [Indexed: 12/23/2022]
Abstract
During postnatal development, an emmetropization feedback mechanism uses visual cues to modulate the axial growth of eyes so that, with maturation, images of distant objects are in focus on the retina. If the visual cues indicate that the eye has become too long, it generates STOP signals that slow eye elongation. Myopia is a failure of this process where the eye becomes too long. The existing animal models of myopia have been essential in understanding the mechanics of emmetropization but use visual cues that lead to rapidly progressing myopia and don't match the stimuli that lead to human myopia. Form deprivation removes esssentially all spatial contrast. Minus lens wear accurately guides axial elongation to restore sharp focus: technically it is not a model of myopia! In contrast, childhood myopia involves a slow drift into myopia, even with the presence of clear images. We hypothesize that, in the modern visual environment, STOP signals are present but often are not quite strong enough to prevent myopic progression. Using tree shrews, small diurnal mammals closely related to primates, we have developed an animal model that we propose better represents this situation. We used limited bandwidth light to provide limited chromatic cues for emmetropization that are not quite enough to produce fully effective STOP signaling, resulting in a slow drift into myopia as seen in children. We hypothesize that this animal model of myopia may prove useful in evaluating anti-myopia therapies where form deprivation and minus lens wear would be too powerful.
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Affiliation(s)
- Safal Khanal
- Dept. of Optometry and Vision Science, University of Alabama at Birmingham (UAB), Birmingham, AL, United States
| | - Thomas T Norton
- Dept. of Optometry and Vision Science, University of Alabama at Birmingham (UAB), Birmingham, AL, United States
| | - Timothy J Gawne
- Dept. of Optometry and Vision Science, University of Alabama at Birmingham (UAB), Birmingham, AL, United States.
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13
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Myopia: why the retina stops inhibiting eye growth. Sci Rep 2022; 12:21704. [PMID: 36522540 PMCID: PMC9755470 DOI: 10.1038/s41598-022-26323-7] [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: 08/29/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
In myopia, the eye grows too long, and the image projected on the retina is poorly focused when subjects look at a distance. While the retina normally controls eye growth by visual processing, it seems to give up during myopia development. But what has changed? To determine whether the sharp image is in front or behind the retinal plane, a comparison of image sharpness in red and blue would provide a reliable cue because focal planes are about 1.3 D apart due to longitudinal chromatic aberration (LCA). However, up to now, it could not be demonstrated that the retina does, in fact, such a comparison. We used a new approach: movies were digitally filtered in real time to present either the blue channel of the RGB color format unfiltered while green and red were blurred ("blue in focus"), or the red channel was unfiltered while green and blue were blurred ("red in focus") accordingly to the human LCA function. Here we show that, even though filtered movies looked similar, eyes became significantly shorter when the movie was sharp in the red plane but became longer when it was presented sharp in the blue plane. Strikingly, the eyes of young subjects who were already myopic did not respond at all-showing that their retina could no longer decode the sign of defocus based on LCA. Our findings resolve a long-standing question as to how the human retina detects the sign of defocus. It also suggests a new non-invasive strategy to inhibit early myopia development: keeping the red image plane on a computer screen sharp but low pass filtering the blue.
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14
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Gawne TJ, She Z, Norton TT. Chromatically simulated myopic blur counteracts a myopiagenic environment. Exp Eye Res 2022; 222:109187. [PMID: 35843288 DOI: 10.1016/j.exer.2022.109187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 06/03/2022] [Accepted: 07/05/2022] [Indexed: 02/09/2023]
Abstract
There is a world-wide epidemic of myopia (nearsightedness), produced largely by human-made environmental visual cues that disrupt the emmetropization feedback mechanism that normally uses defocus cues to produce and maintain eyes in good focus. Previous studies have shown that the wavelength of light affects this process and that myopic defocus can slow the progression of myopia in children. We first asked if continuous exposure to a small cage with restricted viewing distance would produce an environmentally-induced myopia in tree shrews, small diurnal mammals closely related to primates. A group (n = 7) spent 11 days in a small cage with restricted viewing distance; one wall was a video display covered with Maltese crosses that included low-to-high spatial frequencies in the range visible to tree shrews. This group developed myopia (-1.2 ± 0.4 [stderr] D) that was significant relative to a colony group of seven animals (+1.0 ± 0.2 D) raised in mesh cages allowing more distant viewing. We then asked if chromatically-simulated myopic defocus, produced by blurring just the blue channel of the video display, would counteract this environmentally-induced myopia in a group of eight tree shrews. This group instead became significantly hyperopic (+4.0 ± 0.4 D) due to slowed axial elongation. These results demonstrate the high potency of chromatic cues in refractive regulation and may provide the basis for an anti-myopia treatment in humans.
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Affiliation(s)
- Timothy J Gawne
- Department of Optometry and Vision Science, University of Alabama at Birmingham (UAB), USA.
| | - Zhihui She
- Department of Optometry and Vision Science, University of Alabama at Birmingham (UAB), USA
| | - Thomas T Norton
- Department of Optometry and Vision Science, University of Alabama at Birmingham (UAB), USA
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15
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Huang Z, He T, Zhang J, Du C. Red light irradiation as an intervention for myopia. Indian J Ophthalmol 2022; 70:3198-3201. [PMID: 36018087 DOI: 10.4103/ijo.ijo_15_22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Myopia is one of the main causes of visual impairment worldwide. Preventing myopia and providing myopia-related interventions are of paramount importance. Based on a thorough review of the available literature, we conclude that red light irradiation can produce hyperopia, resulting in myopia prevention and control. Further, we suggest that red light irradiation may be a powerful tool for myopia prevention and control in the future. At the same time, red light has a protective effect on the cornea and retina at the cellular level, suggesting that red light irradiation may be a safe and effective modality for delaying myopia. Therefore, this form of irradiation is expected to play an important role in the prevention and control of myopia. However, more studies are needed to enhance the current state of knowledge and inform medical guidelines more comprehensively.
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Affiliation(s)
- Zhu Huang
- Department of Ophthalmology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Ting He
- Department of Ophthalmology, The Forth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Junna Zhang
- Department of Ophthalmology, The Forth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Chixin Du
- Department of Ophthalmology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
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16
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Ji S, Ye L, Zhang L, Xu D, Dai J. Retinal neurodegeneration in a mouse model of green-light-induced myopia. Exp Eye Res 2022; 223:109208. [DOI: 10.1016/j.exer.2022.109208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 07/23/2022] [Accepted: 07/31/2022] [Indexed: 11/15/2022]
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17
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Myopia: Mechanisms, Interventional Strategies, and Clinical Evidence. Optom Vis Sci 2022; 99:321. [PMID: 35383730 DOI: 10.1097/opx.0000000000001895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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18
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Thakur S, Dhakal R, Verkicharla PK. Short-Term Exposure to Blue Light Shows an Inhibitory Effect on Axial Elongation in Human Eyes Independent of Defocus. Invest Ophthalmol Vis Sci 2021; 62:22. [PMID: 34935883 PMCID: PMC8711007 DOI: 10.1167/iovs.62.15.22] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Given the potential role of light and its wavelength on ocular growth, we investigated the effect of short-term exposure to the red, green, and blue light on ocular biometry in the presence and absence of lens-induced defocus in humans. Methods Twenty-five young adults were exposed to blue (460 nm), green (521 nm), red (623 nm), and white light conditions for 1-hour each on 4 separate experimental sessions conducted on 4 different days. In each light condition, hyperopic defocus (3D) was induced to the right eye with the fellow eye experiencing no defocus. Axial length and choroidal thickness were measured before and immediately after the light exposure with a non-contact biometer. Results Axial length increased from baseline after red light (mean difference ± standard error in the defocussed eye and non-defocussed eye = 11.2 ± 2 µm and 6.4 ± 2.3 µm, P < 0.001 and P < 0.01, respectively) and green light exposure (9.2 ± 3 µm and 7.0 ± 2.5 µm, P < 0.001 and P < 0.001) with a significant decrease in choroidal thickness (P < 0.05, both red and green light) after 1-hour of exposure. Blue light exposure resulted in a reduction in axial length in both the eyes (−8.0 ± 3 µm, P < 0.001 in the defocussed eye and −6.0 ± 3 µm, P = 0.11 in the non-defocused eye) with no significant changes in the choroidal thickness. Conclusions Exposure to red and green light resulted in axial elongation, and blue light resulted in inhibition of axial elongation in human eyes. Impact of such specific wavelength exposure on children and its application in myopia control need to be explored.
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Affiliation(s)
- Swapnil Thakur
- Myopia Research Lab - Prof. Brien Holden Eye Research Centre, L V Prasad Eye Institute, Hyderabad, India and Brien Holden Institute of Optometry and Vision Sciences, L V Prasad Eye Institute, Hyderabad, India
| | - Rohit Dhakal
- Myopia Research Lab - Prof. Brien Holden Eye Research Centre, L V Prasad Eye Institute, Hyderabad, India and Brien Holden Institute of Optometry and Vision Sciences, L V Prasad Eye Institute, Hyderabad, India
| | - Pavan K Verkicharla
- Myopia Research Lab - Prof. Brien Holden Eye Research Centre, L V Prasad Eye Institute, Hyderabad, India and Brien Holden Institute of Optometry and Vision Sciences, L V Prasad Eye Institute, Hyderabad, India
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19
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Khanal S, Norton TT, Gawne TJ. Amber light treatment produces hyperopia in tree shrews. Ophthalmic Physiol Opt 2021; 41:1076-1086. [PMID: 34382245 DOI: 10.1111/opo.12853] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 05/27/2021] [Accepted: 05/28/2021] [Indexed: 11/29/2022]
Abstract
PURPOSE Exposure to narrow-band red light, which stimulates only the long-wavelength sensitive (LWS) cones, slows axial eye growth and produces hyperopia in tree shrews and macaque monkeys. We asked whether exposure to amber light, which also stimulates only the LWS cones but with a greater effective illuminance than red light, has a similar hyperopia-inducing effect in tree shrews. METHODS Starting at 24 ± 1 days of visual experience, 15 tree shrews (dichromatic mammals closely related to primates) received light treatment through amber filters (BPI 500/550 dyed acrylic) either atop the cage (Filter group, n = 8, 300-400 human lux) or fitted into goggles in front of both eyes (Goggle group, n = 7). Non-cycloplegic refractive error and axial ocular dimensions were measured daily. Treatment groups were compared with age-matched animals (Colony group, n = 7) raised in standard colony fluorescent lighting (100-300 lux). RESULTS At the start of treatment, mean refractive errors were well-matched across the three groups (p = 0.35). During treatment, the Filter group became progressively more hyperopic with age (p < 0.001). By contrast, the Goggle and Colony groups showed continued normal emmetropization. When the treatment ended, the Filter group exhibited significantly greater hyperopia (mean [SE] = 3.5 [0.6] D) compared with the Goggle (0.2 [0.8] D, p = 0.01) and Colony groups (1.0 [0.2] D, p = 0.01). However, the refractive error in the Goggle group was not different from that in the Colony group (p = 0.35). Changes in the vitreous chamber were consistent with the refractive error changes. CONCLUSIONS Exposure to ambient amber light produced substantial hyperopia in the Filter group but had no effect on refractive error in the Goggle group. The lack of effect in the Goggle group could be due to the simultaneous activation of the short-wavelength sensitive (SWS) and LWS cones caused by the scattering of the broad-band light from the periphery of the goggles.
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Affiliation(s)
- Safal Khanal
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Thomas T Norton
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Timothy J Gawne
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, Alabama, USA
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20
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The effects of reduced ambient lighting on lens compensation in infant rhesus monkeys. Vision Res 2021; 187:14-26. [PMID: 34144362 DOI: 10.1016/j.visres.2021.05.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Revised: 05/21/2021] [Accepted: 05/31/2021] [Indexed: 11/22/2022]
Abstract
Although reduced ambient lighting (~50 lx) does not increase the degree of form-deprivation myopia (FDM) in chickens or infant monkeys, it does reduce the probability that monkeys will recover from FDM and that the normal age-dependent reduction in hyperopia will occur in monkeys reared with unrestricted vision. These findings suggest that low ambient lighting levels affect the regulatory mechanism responsible for emmetropization. To study this issue, infant rhesus monkeys (age ~ 24 days) were reared under dim light (55 ± 9 lx) with monocular -3D (dim-light lens-induced myopia, DL-LIM, n = 8) or +3D spectacle lenses (dim-light lens-induced hyperopia, DL-LIH, n = 7) until approximately 150 days of age. Refractive errors, ocular parameters and sub-foveal choroidal thickness were measured periodically and compared with normal-light-reared, lens-control monkeys (NL-LIM, n = 16; NL-LIH, n = 7). Dim light rearing significantly attenuated the degree of compensatory anisometropias in both the DL-LIM (-0.63 ± 0.77D vs. -2.11 ± 1.10D in NL-LIM) and DL-LIH treatment groups (-0.18 ± 1.93D vs. +1.71 ± 0.39D in NL-LIH). These effects came about because the treated and fellow control eyes had a lower probability of responding appropriately to the eye's effective refractive state. Vision-induced interocular differences in choroidal thickness were only observed in monkeys that exhibited compensating refractive changes, suggesting that failures in detecting the relative magnitude of optical errors underlay the abnormal refractive responses. Our findings suggest that low ambient lighting levels reduce the efficacy of the vision-dependent mechanisms that regulate refractive development.
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21
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Yoon H, Taylor CP, Rucker F. Spectral composition of artificial illuminants and their effect on eye growth in chicks. Exp Eye Res 2021; 207:108602. [PMID: 33930397 DOI: 10.1016/j.exer.2021.108602] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 04/16/2021] [Accepted: 04/19/2021] [Indexed: 01/04/2023]
Abstract
In broadband light, longitudinal chromatic aberration (LCA) provides emmetropization signals from both wavelength defocus and the resulting chromatic cues. Indoor illuminants vary in their spectral output, potentially limiting the signals from LCA. Our aim is to investigate the effect that artificial illuminants with different spectral outputs have on chick emmetropization with and without low temporal frequency modulation. In Experiment 1, two-week-old chicks were exposed to 0.2 Hz, square-wave luminance modulation for 3 days. There were 4 spectral conditions: LED strips that simulated General Electric (GE) LED "Soft" (n = 13), GE LED "Daylight" (n = 12), a novel "Equal" condition (n = 12), and a novel "High S" condition (n = 10). These conditions were all tested at a mean level of 985 lux. In Experiment 2, the effect of intensity on the "Equal" condition was tested at two other light levels (70 lux: n = 10; 680 lux: n = 7). In Experiment 3, the effect of temporal modulation on the "Equal" condition was tested by comparing the 0.2 Hz condition with 0 Hz (steady). Significant differences were found in axial growth across lighting conditions. At 985 lux, birds exposed to the "Equal" condition showed a greater reduction in axial growth (both p < 0.01) and a greater hyperopic shift compared to "Soft" and "Daylight" (both p < 0.01). The "High S" birds experienced more axial growth compared to "Equal" (p < 0.01) but less than in "Soft" and "Daylight" (p < 0.01). Axial changes in "Equal" were only observed at 985 lux with 0.2 Hz temporal modulation, and not with lower light levels or steady light. We conclude that axial growth and refraction were dependent on the lighting condition in a manner predicted by wavelength defocus signals arising from LCA.
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Affiliation(s)
- Hannah Yoon
- New England College of Optometry, Department of Biomedical Science and Disease, Boston, MA, United States
| | - Christopher P Taylor
- New England College of Optometry, Department of Biomedical Science and Disease, Boston, MA, United States
| | - Frances Rucker
- New England College of Optometry, Department of Biomedical Science and Disease, Boston, MA, United States.
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22
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Tree shrews do not maintain emmetropia in initially-focused narrow-band cyan light. Exp Eye Res 2021; 206:108525. [PMID: 33711339 DOI: 10.1016/j.exer.2021.108525] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 02/07/2021] [Accepted: 02/24/2021] [Indexed: 02/06/2023]
Abstract
We asked if emmetropia, achieved in broadband colony lighting, is maintained in narrow-band cyan light that is well focused in the emmetropic eye, but does not allow for guidance from longitudinal chromatic aberrations (LCA) and offers minimal perceptual color cues. In addition, we examined the response to a -5 D lens in this lighting. Seven tree shrews from different litters were initially housed in broad-spectrum colony lighting. At 24 ± 1 days after eye opening (Days of Visual Experience, DVE) they were housed for 11 days in ambient narrow-band cyan light (peak wavelength 505 ± 17 nm) selected because it is in focus in an emmetropic eye. Perceptually, monochromatic light at 505 nm cannot be distinguished from white by tree shrews. While in cyan light, each animal wore a monocular -5 D lens (Cyan -5 D eyes). The fellow eye was the Cyan no-lens eye. Daily awake non-cycloplegic measures were taken with an autorefractor (refractive state) and with optical low-coherence optical interferometry (axial component dimensions). These measures were compared with the values of animals raised in standard colony fluorescent lighting: an untreated group (n = 7), groups with monocular form deprivation (n = 7) or monocular -5 D lens treatment (n = 5), or that experienced 10 days in total darkness (n = 5). Refractive state at the onset of cyan light treatment was low hyperopia, (mean ± SEM) 1.4 ± 0.4 diopters. During treatment, the Cyan no-lens eyes became myopic (-2.9 ± 0.3 D) whereas colony lighting animals remained slightly hyperopic (1.0 ± 0.2 D). Initially, refractions of the Cyan -5 D eyes paralleled the Cyan no-lens eyes. After six days, they gradually became more myopic than the Cyan no-lens eyes; at the end of treatment, the refractions were -5.4 ± 0.3 D, a difference of -2.5 D from the Cyan no-lens eyes. When returned to colony lighting at 35 ± 1 DVE, the no-lens eye refractions rapidly recovered towards emmetropia but, as expected, the refraction of the -5 D eyes remained near -5 D. Vitreous chamber depth in both eyes was consistent with the refractive changes. In narrow-band cyan lighting the emmetropization mechanism did not maintain emmetropia even though the light initially was well focused. We suggest that, as the eyes diverged from emmetropia, there were insufficient LCA cues for the emmetropization mechanism to utilize the developing myopic refractive error in order to guide the eyes back to emmetropia. However, the increased myopia in the Cyan -5 D eyes in the narrow-band light indicates that the emmetropization mechanism nonetheless detected the presence of the lens-induced refractive error and responded with increased axial elongation that partly compensated for the negative-power lens. These data support the conclusion that the emmetropization mechanism cannot maintain emmetropia in narrow-band lighting. The additional myopia produced in eyes with the -5 D lens shows that the emmetropization mechanism responds to multiple defocus-related cues, even under conditions where it is unable to use them to maintain emmetropia.
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23
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Watts NS, Taylor C, Rucker FJ. Temporal color contrast guides emmetropization in chick. Exp Eye Res 2020; 202:108331. [PMID: 33152390 DOI: 10.1016/j.exer.2020.108331] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 10/20/2020] [Accepted: 10/22/2020] [Indexed: 12/27/2022]
Abstract
As a result of longitudinal chromatic aberration (LCA), longer wavelengths are blurred when shorter wavelengths are in focus, and vice versa. As a result, LCA affects the color and temporal aspects of the retinal image with hyperopic defocus. In this experiment, we investigated how the sensitivity to temporal color contrast affects emmetropization. Ten-day-old chicks were exposed for three days to sinusoidal color modulation. The modulation was either blue/yellow flicker (BY) (n = 57) or red/green flicker (RG) (n = 60) simulating hyperopic defocus with and without a blue light component. The color contrasts tested were 0.1, 0.2, 0.3, 0.4, 0.6, and 0.8 Michelson contrast. The mean illuminance of all stimuli was 680 lux. Temporal modulation was either of a high (10 Hz) or low (0.2 Hz) temporal frequency. To test the role of short- and double-cone stimulation, an additional condition silenced these cones in RG_0.4 (D-) and was compared with RG_0.4 (D+) (n = 14). Changes in ocular components and refractive error were measured using Lenstar and a photorefractometer. With high temporal frequency BY representing an in-focus condition for shorter-wavelengths, we found that high temporal frequency BY contrast was positively correlated with vitreous expansion (R2 = 0.87, p < 0.01), expanding the vitreous to compensate for hyperopic defocus. This expansion was offset by low temporal frequency RG, which represented blurred longer wavelengths. The reduction in vitreous expansion in RG_0.4, was enhanced in D+ compared to D- (p < 0.001), indicating a role for short- and/or double-cones. With high temporal frequency RG representing an in-focus condition for longer-wavelengths, we found that high temporal frequency RG contrast was also positively correlated with a linear increase in vitreous chamber depth (R2 = 0.84, p < 0.01) and eye length (R2 = 0.30, p ≤ 0.05), required to compensate for hyperopic defocus, but also with RG sensitive choroidal thickening (R2 = 0.18: p < 0.0001). These increases in the vitreous and eye length were enhanced with D+ compared to D- (p = 0.003) showing the role of short- and double-cones in finessing the vitreous response to hyperopic defocus. Overall, the increase in vitreous chamber depth in RG was offset by reduced expansion in BY, indicating sensitivity to the shorter focal length of blue light and wavelength defocus. Predictable changes in cone contrast and temporal frequency of the retinal image that occur with LCA and defocus result in homeostatic control of emmetropization.
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Affiliation(s)
- Nathaniel S Watts
- New England College of Optometry, 424 Beacon Street, Boston, MA, 02115, USA
| | - Christopher Taylor
- New England College of Optometry, 424 Beacon Street, Boston, MA, 02115, USA
| | - Frances J Rucker
- New England College of Optometry, 424 Beacon Street, Boston, MA, 02115, USA.
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24
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Buch J, Hammond B. Photobiomodulation of the Visual System and Human Health. Int J Mol Sci 2020; 21:ijms21218020. [PMID: 33126530 PMCID: PMC7662260 DOI: 10.3390/ijms21218020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 10/25/2020] [Accepted: 10/27/2020] [Indexed: 12/24/2022] Open
Abstract
Humans express an expansive and detailed response to wavelength differences within the electromagnetic (EM) spectrum. This is most clearly manifest, and most studied, with respect to a relatively small range of electromagnetic radiation that includes the visible wavelengths with abutting ultraviolet and infrared, and mostly with respect to the visual system. Many aspects of our biology, however, respond to wavelength differences over a wide range of the EM spectrum. Further, humans are now exposed to a variety of modern lighting situations that has, effectively, increased our exposure to wavelengths that were once likely minimal (e.g., “blue” light from devices at night). This paper reviews some of those biological effects with a focus on visual function and to a lesser extent, other body systems.
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Affiliation(s)
- John Buch
- Johnson & Johnson Vision, Research & Development, Jacksonville, FL 32256, USA
- Correspondence: ; Tel.: +1-904-443-1707
| | - Billy Hammond
- Department of Psychology, University of Georgia, Athens, GA 30602, USA;
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25
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Rucker FJ, Eskew RT, Taylor C. Signals for defocus arise from longitudinal chromatic aberration in chick. Exp Eye Res 2020; 198:108126. [PMID: 32717338 DOI: 10.1016/j.exer.2020.108126] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 06/16/2020] [Accepted: 06/19/2020] [Indexed: 02/06/2023]
Abstract
Chicks respond to two signals from longitudinal chromatic aberration (LCA): a wavelength defocus signal and a chromatic signal. Wavelength defocus predicts reduced axial eye growth in monochromatic short-wavelength light, compared to monochromatic long-wavelength light. Wavelength defocus may also influence growth in broadband light. In contrast, a chromatic signal predicts increased growth when short-wavelength contrast > long-wavelength contrast, but only when light is broadband. We aimed to investigate the influence of blue light, temporal frequency and contrast on these signals under broadband conditions. Starting at 12 to 13 days-old, 587 chicks were exposed to the experimental illumination conditions for three days for 8h/day and spent the remainder of their day in the dark. The stimuli were flickering lights, with a temporal frequency of 0.2 or 10 Hz, low (30%) or high contrast (80%), and a variety of ratios of cone contrast simulating the effects of defocus with LCA. There were two color conditions, with blue contrast (bPlus) and without (bMinus). Stimuli in the "bPlus" condition varied the amounts of long- (L), middle- (M_) and double (D-) cone contrast, relative to short- (S-) and (UV-) cone contrast, to simulate defocus. Stimuli in the "bMinus" condition only varied the relative modulations of the L + D vs. M cones. In all cases, the average of the stimuli was white, with an illuminance of 777 lux, with cone contrast created through temporal modulation. A Lenstar LS 900 and a Hartinger refractometer were used to measure ocular components and refraction. Wavelength defocus signals with relatively high S-cone contrast resulted in reduced axial growth, and more hyperopic refractions, under low-frequency conditions (p = 0.002), in response to the myopic defocus of blue light. Chromatic signals with relatively high S-cone contrast resulted in increased axial growth and more myopic refractions, under high frequency, low contrast, conditions (p < 0.001). We conclude that the chromatic signals from LCA are dependent on the temporal frequency, phase, and relative contrast of S-cone temporal modulation, and recommend broadband spectral and temporal environments, such as the outdoor environment, to optimize the signals-for-defocus in chick.
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Affiliation(s)
- Frances J Rucker
- New England College of Optometry, 424 Beacon Street, Boston, MA, 02115, United States.
| | - Rhea T Eskew
- Northeastern University, 360 Huntington Ave, Boston, MA, 02115, United States
| | - Christopher Taylor
- New England College of Optometry, 424 Beacon Street, Boston, MA, 02115, United States
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