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Modrzejewska M, Durajczyk M. The Relationship between Selected Parameters and the Occurrence of Premyopia in a Group of 1155 Children Aged 8 in Northwestern Poland. J Clin Med 2024; 13:1977. [PMID: 38610742 PMCID: PMC11012722 DOI: 10.3390/jcm13071977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 03/17/2024] [Accepted: 03/26/2024] [Indexed: 04/14/2024] Open
Abstract
Background: Determination of the number of pupils at risk of developing pre-myopia and selected ophthalmic parameters in a group of 1155 children aged 8. Material: Ophthalmic examinations were performed in Polish 8-year-old, /1518 individuals/; 1155 of whom presented complete data for analysis. There was a total of 554 (47.9%) girls and 602 (52.1%) boys. Examination of the anterior and posterior segment of the eye, evaluation of accommodation, convergence, heterophoria, alignment of the eyeball, muscular balance with ocular mobility in 9 directions of gaze, and spatial vision were tested. Refraction was obtained under cycloplegia. Refractions (spherical equivalent, SE). were categorized as pre-myopia (-0.50 D-+0.75 D), myopia (≤-0.5 D), emmetropia (>-0.5 D to ≤+0.5 D), mildly hyperopia (>+0.5 D to ≤+2.0 D) and hyperopia (>+2.0 D). Data analysis was performed using Statistica 13.5 software: chi-squared, Pearson's, t-Student, and U Mann-Whitney tests. p-values of <0.05 were considered statistically significant. Results: Pre-myopia was diagnosed in as many as 704 subjects (60.9%) with a similar frequency among both girls-328 (46.6%)-and boys with 376 (53.4%). Conclusions: Current data indicates that the growing group of myopic individuals in many industrialized countries is the sixth most common cause of blindness. Further research is crucial to understand the factors underlying accommodative and binocular mechanisms for myopia development and progression and to make recommendations for targeted interventions to slow the progression of myopia in a group of early school children.
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Mahmood M, Day M, Seidel D, Cameron LA. The effect of multifocal contact lenses on the dynamic accommodation step response. Ophthalmic Physiol Opt 2024; 44:321-333. [PMID: 38303152 DOI: 10.1111/opo.13275] [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: 07/26/2023] [Revised: 12/19/2023] [Accepted: 12/26/2023] [Indexed: 02/03/2024]
Abstract
PURPOSE To measure the dynamic accommodation response (AR) to step stimuli with and without multifocal contact lenses (MFCLs), in emmetropes and myopes. METHODS Twenty-two adult subjects viewed alternating distance (0.25D) and near (3D) Maltese crosses placed in free space, through two contact lens types: single vision (SVCL) or centre-distance multifocal (MFCL; +2.50D add). The AR level was measured along with near to far (N-F) and far to near (F-N) step response characteristics: percentage of correct responses, magnitude, latency, peak velocity and duration of step response. RESULTS There was no difference between N-F and F-N responses, or between refractive groups in any aspect of the accommodation step response dynamics. The percentage of correct responses was unaffected by contact lens type. Through MFCLs, subjects demonstrated smaller magnitude, longer latency, shorter duration and slower peak velocity steps than through SVCLs. When viewing the near target, the AR through MFCLs was significantly lower than through SVCLs. When viewing the distance target with the MFCL, the focal points from rays travelling through the distance and near zones were approximately 0.004D behind and 2.50D in front of the retina, respectively. When viewing the near target, the respective values were approximately 1.89D behind and 0.61D in front of the retina. CONCLUSION The defocus error required for accommodation control appears not to be solely derived from the distance zone of the MFCL. This results in reduced performance in response to abruptly changing vergence stimuli; however, these errors were small and unlikely to impact everyday visual tasks. There was a decrease in ocular accommodation during near tasks, which has previously been correlated with a reduced myopic treatment response through these lenses. With MFCLs, the estimated dioptric myopic defocus was the largest when viewing a distant stimulus, supporting the hypothesis that the outdoors provides a beneficial visual environment to reduce myopia progression.
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Affiliation(s)
- Mubeen Mahmood
- Department of Vision Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Mhairi Day
- Department of Vision Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Dirk Seidel
- Department of Vision Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Lorraine A Cameron
- Department of Vision Sciences, Glasgow Caledonian University, Glasgow, UK
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Hughes RPJ, Read SA, Collins MJ, Vincent SJ. Higher order aberrations and retinal image quality during short-term accommodation in myopic and non-myopic children. Ophthalmic Physiol Opt 2023. [PMID: 37140840 DOI: 10.1111/opo.13146] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Revised: 03/31/2023] [Accepted: 04/03/2023] [Indexed: 05/05/2023]
Abstract
INTRODUCTION Despite the known associations between near work and myopia, and retinal image quality and eye growth, accommodation-induced changes in higher order aberrations (HOA's) and retinal image quality in children with different refractive errors are poorly understood. METHODS Ocular HOA's were measured using a Hartmann-Shack wavefront sensor (COAS-HD, Wavefront Sciences) in 18 myopic and 18 age- and sex-matched non-myopic children during short-term accommodation tasks (four demands of 0, 3, 6 and 9 D) presented using a Badal optometer. Eighth order Zernike polynomials were fitted across a 2.3 mm pupil diameter to determine refractive power vectors (M, J180 and J45 ) and the accommodation error, and a 4 mm pupil was used for HOA analyses. Retinal image quality was examined using the visual Strehl ratio based on the optical transfer function (VSOTF) for third to eighth radial orders only. RESULTS Most refractive error group differences were observed for the 6 and 9 D demands. Myopic children underwent greater changes in with-the-rule astigmatism (J180 ), higher order and third order RMS values, primary vertical ( C 3 - 1 $$ {C}_3^{-1} $$ ) and horizontal coma ( C 3 1 $$ {C}_3^1 $$ ), and several other individual Zernike coefficients compared with non-myopic children (all refractive error group by demand interaction p-values of ≤0.02). Non-myopic children exhibited a greater negative shift in primary ( C 4 0 $$ {C}_4^0 $$ ) and positive shift in secondary spherical aberration ( C 6 0 $$ {C}_6^0 $$ ) (both refractive error group by demand interaction p-values of ≤0.002). The VSOTF degraded for the 6 and 9 D demands in both groups, but the myopic children underwent a greater mean (SE) reduction from 0 D of -0.274 (0.048) for the 9 D demand, compared with -0.131 (0.052) for the non-myopic children (p = 0.001). CONCLUSION These results may have implications for the association between near work, accommodation and myopia development, particularly related to the use of short working distances during near tasks.
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Affiliation(s)
- Rohan P J Hughes
- Contact Lens and Visual Optics Laboratory, Centre for Vision and Eye Research, School of Optometry and Vision Science, Queensland University of Technology, Queensland, Brisbane, Australia
| | - 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, Queensland, Brisbane, Australia
| | - Michael J Collins
- Contact Lens and Visual Optics Laboratory, Centre for Vision and Eye Research, School of Optometry and Vision Science, Queensland University of Technology, Queensland, Brisbane, Australia
| | - Stephen J Vincent
- Contact Lens and Visual Optics Laboratory, Centre for Vision and Eye Research, School of Optometry and Vision Science, Queensland University of Technology, Queensland, Brisbane, Australia
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Przekoracka K, Michalak KP, Olszewski J, Michalski A, Przekoracka‐Krawczyk A. Computerised dynamic posturography for postural control assessment in subjects wearing multifocal contact lenses dedicated for myopia control. Ophthalmic Physiol Opt 2021; 41:486-495. [DOI: 10.1111/opo.12818] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Accepted: 03/05/2021] [Indexed: 12/11/2022]
Affiliation(s)
- Katarzyna Przekoracka
- Laboratory of Bionics and Experimental Medical Biology Department of Bionics and Bioimpendance University of Medical Sciences Poznań Poland
- Laboratory of Vision and Neuroscience NanoBioMedical Centre Adam Mickiewicz University of Poznań Poznań Poland
| | - Krzysztof Piotr Michalak
- Laboratory of Vision and Neuroscience NanoBioMedical Centre Adam Mickiewicz University of Poznań Poznań Poland
- Laboratory of Vision Science and Optometry Faculty of Physics Adam Mickiewicz University of Poznań Poznań Poland
| | - Jan Olszewski
- Laboratory of Bionics and Experimental Medical Biology Department of Bionics and Bioimpendance University of Medical Sciences Poznań Poland
| | - Andrzej Michalski
- Department of Ophthalmology University of Medical Sciences Poznań Poland
| | - Anna Przekoracka‐Krawczyk
- Laboratory of Vision and Neuroscience NanoBioMedical Centre Adam Mickiewicz University of Poznań Poznań Poland
- Laboratory of Vision Science and Optometry Faculty of Physics Adam Mickiewicz University of Poznań Poznań Poland
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Logan NS, Radhakrishnan H, Cruickshank FE, Allen PM, Bandela PK, Davies LN, Hasebe S, Khanal S, Schmid KL, Vera-Diaz FA, Wolffsohn JS. IMI Accommodation and Binocular Vision in Myopia Development and Progression. Invest Ophthalmol Vis Sci 2021; 62:4. [PMID: 33909034 PMCID: PMC8083074 DOI: 10.1167/iovs.62.5.4] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in accommodation and the consequent alterations in ocular parameters has expanded. This International Myopia Institute white paper reviews the variations in ocular parameters that occur with accommodation and the mechanisms involved in accommodation and myopia development and progression. Convergence is synergistically linked with accommodation and the impact of this on myopia has also been critiqued. Specific topics reviewed included accommodation and myopia, role of spatial frequency, and contrast of the task of objects in the near environment, color cues to accommodation, lag of accommodation, accommodative-convergence ratio, and near phoria status. Aspects of retinal blur from the lag of accommodation, the impact of spatial frequency at near and a short working distance may all be implicated in myopia development and progression. The response of the ciliary body and its links with changes in the choroid remain to be explored. Further research is critical to understanding the factors underlying accommodative and binocular mechanisms for myopia development and its progression and to guide recommendations for targeted interventions to slow myopia progression.
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Affiliation(s)
- Nicola S Logan
- School of Optometry, Aston University, Birmingham, United Kingdom
| | - Hema Radhakrishnan
- Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
| | - Fiona E Cruickshank
- Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
| | - Peter M Allen
- Vision and Hearing Sciences Research Centre, School of Psychology and Sports Sciences, Anglia Ruskin University, Cambridge, United Kingdom
| | - Praveen K Bandela
- Brien Holden Vision Institute, Sydney, New South Wales, Australia.,School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia
| | - Leon N Davies
- School of Optometry, Aston University, Birmingham, United Kingdom
| | - Satoshi Hasebe
- Department of Ophthalmology, Kawasaki Medical School, Kurashiki, Okayama, Japan
| | - Safal Khanal
- School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Katrina L Schmid
- School of Optometry and Vision Science, Queensland University of Technology, Brisbane, Australia
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Effect of Vision Therapy on Accommodative Lag in Myopic Children: A Randomized Clinical Trial. Optom Vis Sci 2019; 96:17-26. [PMID: 30575616 DOI: 10.1097/opx.0000000000001316] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
SIGNIFICANCE Accommodative dysfunction has been suggested to be related to the development and progression of myopia. Office-based accommodative/vergence therapy (OBAVT) improved accommodative facility in Chinese myopic children, but it is unclear if such improvement has a role in decreasing myopic progression. PURPOSE The purpose of this study was to compare the effects of OBAVT with home reinforcement and office-based placebo therapy (OBPT) as a treatment to improve accommodative functions (i.e., lag, amplitude, and facility) in myopic children with poor accommodative accuracy. METHODS This was a prospective, single-masked, randomized clinical trial. Thirty-four Chinese children 8 to 12 years old with myopia and at least 1 diopter of lag of accommodation measured by autorefraction were enrolled. The participants were randomly assigned to the OBAVT or OBPT group. The primary outcome measure was the change in the monocular lag of accommodation from the baseline visit to the 13-week visit measured by a Shin-Nippon open-field autorefractor. Secondary outcome measures were changes in accommodative amplitude and monocular accommodative facility. RESULTS A total of 33 participants completed the study. After 12 weeks of treatment, there were significant improvements in the lag of accommodation in both the OBAVT and OBPT groups (OBAVT: -0.30 ± 0.29 diopters [P < .001; Cohen's d effect size, 1.29]; OBPT: -0.24 ± 0.30 diopters [P = .005; Cohen's d effect size, 1.24]). There was no statistically significant difference between the improvements in the two groups (P = .50). There was statistically significant improvement in monocular accommodative facility only in the OBAVT group (OBAVT: 7.7 ± 4.7 cycles per minute [P < .001; Cohen's d effect size, 2.20]; OBPT: 1.9 ± 4.4 cycles per minute [P = .072]). The change in the OBAVT group was statistically significantly larger than that in the OBPT group (P < .001). CONCLUSIONS Office-based accommodative/vergence therapy was no more effective than OBPT in reducing the lag of accommodation in children 8 to 12 years old with low to moderate myopia. It did improve accommodative facility in Chinese myopic children, but it is unclear if such an improvement has a role in decreasing myopic progression.
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Przekoracka K, Michalak K, Olszewski J, Zeri F, Michalski A, Paluch J, Przekoracka-Krawczyk A. Contrast sensitivity and visual acuity in subjects wearing multifocal contact lenses with high additions designed for myopia progression control. Cont Lens Anterior Eye 2019; 43:33-39. [PMID: 31843372 DOI: 10.1016/j.clae.2019.12.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Revised: 11/30/2019] [Accepted: 12/02/2019] [Indexed: 10/25/2022]
Abstract
OBJECTIVES To assess the visual performance of multifocal contact lenses (MFCLs) with high addition powers designed for myopia control. METHODS Twenty-four non-presbyopic adults (mean age 24 years, range 18-36 years) were fitted with soft MFCLs with add powers of +2.0 D (Add2) and +4.0 D (Add4) (RELAX, SwissLens) and single vision lenses (SVCL; Add0) in a counterbalanced order. In this double-masked study, half of the participants were randomly fitted with 3 mm-distance central zone MFCLs while the other half received 4.5 mm-distance central zone MFCLs. Visual acuity was measured at distance (3.0 m) and at near (0.4 m). Central and peripheral contrast sensitivity was evaluated at distance using the Gabor patch test. The area under the logarithmic contrast sensitivity function curve (ALCSF) was calculated and compared between the groups (i.e. different additions powers used). RESULTS Near and distance visual acuities were not affected by the lenses, neither Add2 nor Add4, when compared to Add0, however, CZ3 significantly reduced distance visual acuity with Add4 when compared to CZ4.5 (-0.08 logMAR vs. for CZ3 and -0.18 logMAR for CZ4.5, p = 0.013). MFCLs impaired central ALCSF only when Add2 was used (15.99 logCS for Add2 and 16.36 logCS for SVCLs, p = 0.021). Peripheral ALCSF was statistically lower for both addition powers of the MFCLs when compared to SVCLs (12.70 for Add2 and Add4, 13.73 for SVCLs, p = 0.009). The above effects were the same for both central zones used. CONCLUSIONS MFCLs with CZ3 diameter and high add power (Add4) slightly reduced distance visual acuity when compared to CZ4.5 but no reduction in this parameter was found with medium add power (Add2). Central contrast sensitivity was impaired only by MFCLs with the lower add power (Add2). Both add powers in the MFCLs reduced peripheral contrast sensitivity to a similar extent.
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Affiliation(s)
- Katarzyna Przekoracka
- Laboratory of Bionics and Experimental Medical Biology, Department of Bionics and Bioimpendance, Poznań University of Medical Sciences, Parkowa 2, 60-775, Poznań, Poland; Laboratory of Vision and Neuroscience, NanoBioMedical Center, Adam Mickiewicz University of Poznań, Umultowska 85, 61-614 Poznań, Poland.
| | - Krzysztof Michalak
- Laboratory of Vision and Neuroscience, NanoBioMedical Center, Adam Mickiewicz University of Poznań, Umultowska 85, 61-614 Poznań, Poland; Laboratory of Vision Science and Optometry, Faculty of Physics, Adam Mickiewicz University of Poznań, Umultowska 85, 61-614 Poznań, Poland.
| | - Jan Olszewski
- Laboratory of Bionics and Experimental Medical Biology, Department of Bionics and Bioimpendance, Poznań University of Medical Sciences, Parkowa 2, 60-775, Poznań, Poland.
| | - Fabrizio Zeri
- University of Milano Bicocca, Department of Materials Science, R. Cozzi 55, I-20125 Milan, Italy; School of Life and Health Sciences, Aston University, Aston Triangle, B4 7ET, Birmingham, UK.
| | - Andrzej Michalski
- Department of Ophthalmology, Chair of Ophthalmology and Optometry, Poznan University of Medical Sciences, Rokietnicka 5D, 60-806 Poznań, Poznań, Poland.
| | - Joanna Paluch
- Laboratory of Vision Science and Optometry, Faculty of Physics, Adam Mickiewicz University of Poznań, Umultowska 85, 61-614 Poznań, Poland.
| | - Anna Przekoracka-Krawczyk
- Laboratory of Vision and Neuroscience, NanoBioMedical Center, Adam Mickiewicz University of Poznań, Umultowska 85, 61-614 Poznań, Poland; Laboratory of Vision Science and Optometry, Faculty of Physics, Adam Mickiewicz University of Poznań, Umultowska 85, 61-614 Poznań, Poland.
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Roberts TL, Manny RE, Anderson HA. Impact of Visual Cues on the Magnitude and Variability of the Accommodative Response in Children With Emmetropia and Uncorrected Hyperopia and Adults. Invest Ophthalmol Vis Sci 2019; 60:1527-1537. [PMID: 30994863 PMCID: PMC6736278 DOI: 10.1167/iovs.18-25256] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Purpose We investigated the effect of blur and disparity cues on accommodative accuracy (lag) and variability (time [RMS] and frequency domain [LFC]) in the developing visual system. Methods A total of 59 children (3–9 years, spherical equivalent refractive error [RE] = −0.3– +4.91 diopters [D]) and 10 adults (23–31 years, RE = −0.37–+1.15D) participated. Accommodation was measured in the right eye for 1 minute at 100 and 33 cm using photorefraction (25 Hz) for three conditions: blur + disparity (binocular, 20/50 optotypes), blur-only (monocular, 20/50 optotypes), disparity-only (binocular, difference-of-Gaussian stimulus). The effect blur and disparity cues have on accommodative accuracy, RMS, and LFC was assessed. Results Lag, RMS, and LFC increased (P < 0.001) from 100 to 33 cm for each condition in children and adults. In children, accommodation was most accurate and stable when blur and disparity cues remained in the stimulus and became significantly less accurate and more variable (P < 0.001) when blur or disparity cues were removed at 33 cm. In adults, accommodation was significantly less accurate and more variable only when blur was removed from the stimulus (P < 0.022). Children with RE matched to adults had less accurate and more variable accommodative responses at near than adults when cues were removed (P ≤ 0.02). Conclusions In children and adults, an increase in RMS and LFC is related to an increase in accommodative lag. Children's accommodative systems do not compensate as efficiently as adults when blur and disparity cues are removed, suggesting children <10 years old do not have a mature afferent visual pathway.
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Affiliation(s)
- Tawna L Roberts
- Byers Eye Institute, Stanford University, Palo Alto, California, United States
| | - Ruth E Manny
- University of Houston, College of Optometry, Houston, Texas, United States
| | - Heather A Anderson
- University of Houston, College of Optometry, Houston, Texas, United States
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Zapata-Díaz JF, Radhakrishnan H, Charman WN, López-Gil N. Accommodation and age-dependent eye model based on in vivo measurements. JOURNAL OF OPTOMETRY 2019; 12:3-13. [PMID: 29573985 PMCID: PMC6318498 DOI: 10.1016/j.optom.2018.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 01/09/2018] [Accepted: 01/20/2018] [Indexed: 06/02/2023]
Abstract
PURPOSE To develop a flexible model of the average eye that incorporates changes with age and accommodation in all optical parameters, including entrance pupil diameter, under photopic, natural, environmental conditions. METHODS We collated retrospective in vivo measurements of all optical parameters, including entrance pupil diameter. Ray-tracing was used to calculate the wavefront aberrations of the eye model as a function of age, stimulus vergence and pupil diameter. These aberrations were used to calculate objective refraction using paraxial curvature matching. This was also done for several stimulus positions to calculate the accommodation response/stimulus curve. RESULTS The model predicts a hyperopic change in distance refraction as the eye ages (+0.22D every 10 years) between 20 and 65 years. The slope of the accommodation response/stimulus curve was 0.72 for a 25 years-old subject, with little change between 20 and 45 years. A trend to a more negative value of primary spherical aberration as the eye accommodates is predicted for all ages (20-50 years). When accommodation is relaxed, a slight increase in primary spherical aberration (0.008μm every 10 years) between 20 and 65 years is predicted, for an age-dependent entrance pupil diameter ranging between 3.58mm (20 years) and 3.05mm (65 years). Results match reasonably well with studies performed in real eyes, except that spherical aberration is systematically slightly negative as compared with the practical data. CONCLUSIONS The proposed eye model is able to predict changes in objective refraction and accommodation response. It has the potential to be a useful design and testing tool for devices (e.g. intraocular lenses or contact lenses) designed to correct the eye's optical errors.
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Affiliation(s)
- Juan F Zapata-Díaz
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Hema Radhakrishnan
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, United Kingdom
| | - W Neil Charman
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Norberto López-Gil
- Facultad de Óptica y Optometría, Universidad de Murcia, 30100 Murcia, Spain.
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Labhishetty V, Chakraborty A, Bobier WR. Is blur sensitivity altered in children with progressive myopia? Vision Res 2018; 154:142-153. [PMID: 30472331 DOI: 10.1016/j.visres.2018.11.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 11/07/2018] [Accepted: 11/13/2018] [Indexed: 12/25/2022]
Abstract
School aged children with progressive myopia show large accommodative lags to blur only cue which is suggestive of a large depth of focus (DOF). While DOF measures are lacking in this age group, their blur detection and discrimination capacities appear to be similar to their non-myopic peers. Accordingly, the current study quantified DOF and blur detection ability in progressive myopic children showing large accommodative lags compared to their non-myopic peers and adults. Blur sensitivity measures were taken from 12 children (8-13 years, 6 myopes and 6 emmetropes) and 6 adults (20-35 years). DOF was quantified using step changes in the lens induced defocus while the subjects viewed a high contrast target through a Badal lens at either 2 or 4D demand. Blur detection thresholds (BDT) were tested using a similar high contrast target in a 2-alternate forced-choice paradigm (2AFC) at both the demands. In addition to the large accommodative lags, micro fluctuations and DOF were significantly larger in myopic children compared to the other groups. However, BDTs were similar across the three groups. When limited to blur cues, the findings of a large DOF coupled with large response lags suggests that myopes are less sensitive to retinal defocus. However, in agreement to a previous study, refractive error had no influence on their BDTs suggesting that the reduced sensitivity to the defocus in a myopic eye appears to be compensated by some form of an adjustment in the higher visual processes to preserve the subjective percept even with a poor retinal image quality.
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Affiliation(s)
- Vivek Labhishetty
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON N2L3G1, Canada.
| | - Arijit Chakraborty
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON N2L3G1, Canada
| | - William R Bobier
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON N2L3G1, Canada
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Abstract
Blur occurs naturally when the eye is focused at one distance and an object is presented at another distance. Computer-graphics engineers and vision scientists often wish to create display images that reproduce such depth-dependent blur, but their methods are incorrect for that purpose. They take into account the scene geometry, pupil size, and focal distances, but do not properly take into account the optical aberrations of the human eye. We developed a method that, by incorporating the viewer's optics, yields displayed images that produce retinal images close to the ones that occur in natural viewing. We concentrated on the effects of defocus, chromatic aberration, astigmatism, and spherical aberration and evaluated their effectiveness by conducting experiments in which we attempted to drive the eye's focusing response (accommodation) through the rendering of these aberrations. We found that accommodation is not driven at all by conventional rendering methods, but that it is driven surprisingly quickly and accurately by our method with defocus and chromatic aberration incorporated. We found some effect of astigmatism but none of spherical aberration. We discuss how the rendering approach can be used in vision science experiments and in the development of ophthalmic/optometric devices and augmented- and virtual-reality displays.
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Affiliation(s)
- Steven A Cholewiak
- Optometry & Vision Science, University of California, Berkeley, Berkeley, CA, USA
| | - Gordon D Love
- Computer Science & Physics, Durham University, Durham, UK
| | - Martin S Banks
- Optometry & Vision Science, University of California, Berkeley, Berkeley, CA, USA
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Altoaimi BH, Kollbaum P, Meyer D, Bradley A. Experimental investigation of accommodation in eyes fit with multifocal contact lenses using a clinical auto-refractor. Ophthalmic Physiol Opt 2018; 38:152-163. [DOI: 10.1111/opo.12438] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 12/06/2017] [Indexed: 11/30/2022]
Affiliation(s)
- Basal H. Altoaimi
- School of Optometry; Indiana University; Bloomington USA
- Department of Optometry; College of Applied Medical Sciences; King Saud University; Riyadh Saudi Arabia
| | - Pete Kollbaum
- School of Optometry; Indiana University; Bloomington USA
| | - Dawn Meyer
- School of Optometry; Indiana University; Bloomington USA
| | - Arthur Bradley
- School of Optometry; Indiana University; Bloomington USA
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Maiello G, Kerber KL, Thorn F, Bex PJ, Vera-Diaz FA. Vergence driven accommodation with simulated disparity in myopia and emmetropia. Exp Eye Res 2017; 166:96-105. [PMID: 29051012 DOI: 10.1016/j.exer.2017.10.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 08/25/2017] [Accepted: 10/08/2017] [Indexed: 11/24/2022]
Abstract
The formation of focused and corresponding foveal images requires a close synergy between the accommodation and vergence systems. This linkage is usually decoupled in virtual reality systems and may be dysfunctional in people who are at risk of developing myopia. We study how refractive error affects vergence-accommodation interactions in stereoscopic displays. Vergence and accommodative responses were measured in 21 young healthy adults (n=9 myopes, 22-31 years) while subjects viewed naturalistic stimuli on a 3D display. In Step 1, vergence was driven behind the monitor using a blurred, non-accommodative, uncrossed disparity target. In Step 2, vergence and accommodation were driven back to the monitor plane using naturalistic images that contained structured depth and focus information from size, blur and/or disparity. In Step 1, both refractive groups converged towards the stereoscopic target depth plane, but the vergence-driven accommodative change was smaller in emmetropes than in myopes (F1,19=5.13, p=0.036). In Step 2, there was little effect of peripheral depth cues on accommodation or vergence in either refractive group. However, vergence responses were significantly slower (F1,19=4.55, p=0.046) and accommodation variability was higher (F1,19=12.9, p=0.0019) in myopes. Vergence and accommodation responses are disrupted in virtual reality displays in both refractive groups. Accommodation responses are less stable in myopes, perhaps due to a lower sensitivity to dioptric blur. Such inaccuracies of accommodation may cause long-term blur on the retina, which has been associated with a failure of emmetropization.
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Affiliation(s)
- Guido Maiello
- UCL Institute of Ophthalmology, University College London, London, UK; Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
| | - Kristen L Kerber
- New England College of Optometry, 424 Beacon Street, Boston, MA 02115, USA
| | - Frank Thorn
- New England College of Optometry, 424 Beacon Street, Boston, MA 02115, USA
| | - Peter J Bex
- Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
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Effects of Near Addition Lenses and Prisms on Accommodative Microfluctuations in Chinese Children. Optom Vis Sci 2017; 93:488-96. [PMID: 26808382 DOI: 10.1097/opx.0000000000000816] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
PURPOSE To investigate the effects of different near addition lenses and prisms on accommodative microfluctuations (AMFs) in Chinese early-onset myopic (EOM) and emmetropic (EMM) children. METHODS Twenty-one EMM and 27 EOM children aged between 9 and 14years participated in the study. At near, 23 children were exophoric (exo, <0 Δ), and 25 were esophoric (eso, ≥0 Δ). The AMFs and phoria through multiple addition lenses (-1.00, 0, +1.00, +2.00, and +3.00D on each eye) and prisms (base-in prism power: 3 Δ, 2 Δ, 1 Δ; and base-out prism power: 1 Δ and 2 Δ on each eye) were measured at 25cm under binocular viewing conditions with a Grand Seiko WAM-5500 auto-refractor and a modified Thorington card. RESULTS Higher AMFs were found in EOM than in EMM (EOM, 0.19±0.06D; EMM, 0.16±0.03D; p=0.035). Plus additions from +1.00 to +3.00D reduced the AMFs in both EMM and EOM, except +3.00D for EMM. In both refractive groups, -1.00D additions increased AMFs. Esophores showed greater AMFs compared with exophores (esophores, 0.20±0.01D; exophores, 0.16±0.01D; p=0.012). Prisms increased the AMFs in EMM and did not alter the AMFs in EOM. CONCLUSIONS Microfluctuations of accommodation decreased with plus addition lenses and increased with negative addition lenses. Plus addition lenses of +2.00 to +3.00D for EOM and +2.00D for EMM decreased AMFs the least at a 25-cm working distance. Esophores had higher AMFs than exophores, indicating that phoria status influences AMFs.
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Hampson KM, Cufflin MP, Mallen EAH. Sensitivity of Chaos Measures in Detecting Stress in the Focusing Control Mechanism of the Short-Sighted Eye. Bull Math Biol 2017. [PMID: 28639168 PMCID: PMC5517597 DOI: 10.1007/s11538-017-0310-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
When fixating on a stationary object, the power of the eye’s lens fluctuates. Studies have suggested that changes in these so-called microfluctuations in accommodation may be a factor in the onset and progression of short-sightedness. Like many physiological signals, the fluctuations in the power of the lens exhibit chaotic behaviour. A breakdown or reduction in chaos in physiological systems indicates stress to the system or pathology. The purpose of this study was to determine whether the chaos in fluctuations of the power of the lens changes with refractive error, i.e. how short-sighted a subject is, and/or accommodative demand, i.e. the effective distance of the object that is being viewed. Six emmetropes (EMMs, non-short-sighted), six early-onset myopes (EOMs, onset of short-sightedness before the age of 15), and six late-onset myopes (LOMs, onset of short-sightedness after the age of 15) took part in the study. Accommodative microfluctuations were measured at 22 Hz using an SRW-5000 autorefractor at accommodative demands of 1 D (dioptres), 2 D, and 3 D. Chaos theory analysis was used to determine the embedding lag, embedding dimension, limit of predictability, and Lyapunov exponent. Topological transitivity was also tested for. For comparison, the power spectrum and standard deviation were calculated for each time record. The EMMs had a statistically significant higher Lyapunov exponent than the LOMs (\documentclass[12pt]{minimal}
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\begin{document}$$0.64\pm 0.33$$\end{document}0.64±0.33 vs. \documentclass[12pt]{minimal}
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\begin{document}$$0.39\pm 0.20~\hbox {D}/\hbox {s}$$\end{document}0.39±0.20D/s) and a lower embedding dimension than the LOMs (\documentclass[12pt]{minimal}
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\begin{document}$$3.28\pm 0.46$$\end{document}3.28±0.46 vs. \documentclass[12pt]{minimal}
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\begin{document}$$3.67\pm 0.49$$\end{document}3.67±0.49). There was insufficient evidence (non-significant p value) of a difference between EOMs and EMMs or EOMs and LOMs. The majority of time records were topologically transitive. There was insufficient evidence of accommodative demand having an effect. Power spectrum analysis and assessment of the standard deviation of the fluctuations failed to discern differences based on refractive error. Chaos differences in accommodation microfluctuations indicate that the control system for LOMs is under stress in comparison to EMMs. Chaos theory analysis is a more sensitive marker of changes in accommodation microfluctuations than traditional analysis methods.
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Affiliation(s)
- Karen M Hampson
- School of Optometry and Vision Science, University of Bradford, Bradford, BD7 1DP, UK.
| | - Matthew P Cufflin
- School of Optometry and Vision Science, University of Bradford, Bradford, BD7 1DP, UK
| | - Edward A H Mallen
- School of Optometry and Vision Science, University of Bradford, Bradford, BD7 1DP, UK
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Almutairi MS, Altoaimi BH, Bradley A. Accommodation and pupil behaviour of binocularly viewing early presbyopes. Ophthalmic Physiol Opt 2017; 37:128-140. [DOI: 10.1111/opo.12356] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 01/04/2017] [Indexed: 11/29/2022]
Affiliation(s)
| | | | - Arthur Bradley
- School of Optometry; Indiana University; Bloomington USA
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17
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Aldaba M, Otero C, Pujol J, Atchison DA. Does the Badal optometer stimulate accommodation accurately? Ophthalmic Physiol Opt 2016; 37:88-95. [DOI: 10.1111/opo.12334] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/26/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Mikel Aldaba
- Davalor Research Center (DRC); Universitat Politècnica de Catalunya; Terrassa Spain
- Centre for Sensors, Instruments, and Systems Development (CD6); Universitat Politecnica de Catalunya (UPC); Terrassa Spain
| | - Carles Otero
- Davalor Research Center (DRC); Universitat Politècnica de Catalunya; Terrassa Spain
- Centre for Sensors, Instruments, and Systems Development (CD6); Universitat Politecnica de Catalunya (UPC); Terrassa Spain
| | - Jaume Pujol
- Davalor Research Center (DRC); Universitat Politècnica de Catalunya; Terrassa Spain
- Centre for Sensors, Instruments, and Systems Development (CD6); Universitat Politecnica de Catalunya (UPC); Terrassa Spain
| | - David A. Atchison
- Institute of Health & Biomedical Innovation and School of Optometry & Vision Science; Queensland University of Technology; Kelvin Grove Australia
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Abstract
The effects of signal and noise on contrast discrimination are difficult to separate because of a singularity in the signal-detection-theory model of two-alternative forced-choice contrast discrimination (Katkov, Tsodyks, & Sagi, 2006). In this article, we show that it is possible to eliminate the singularity by combining that model with a binocular combination model to fit monocular, dichoptic, and binocular contrast discrimination. We performed three experiments using identical stimuli to measure the perceived phase, perceived contrast, and contrast discrimination of a cyclopean sine wave. In the absence of a fixation point, we found a binocular advantage in contrast discrimination both at low contrasts (<4%), consistent with previous studies, and at high contrasts (≥34%), which has not been previously reported. However, control experiments showed no binocular advantage at high contrasts in the presence of a fixation point or for observers without accommodation. We evaluated two putative contrast-discrimination mechanisms: a nonlinear contrast transducer and multiplicative noise (MN). A binocular combination model (the DSKL model; Ding, Klein, & Levi, 2013b) was first fitted to both the perceived-phase and the perceived-contrast data sets, then combined with either the nonlinear contrast transducer or the MN mechanism to fit the contrast-discrimination data. We found that the best model combined the DSKL model with early MN. Model simulations showed that, after going through interocular suppression, the uncorrelated noise in the two eyes became anticorrelated, resulting in less binocular noise and therefore a binocular advantage in the discrimination task. Combining a nonlinear contrast transducer or MN with a binocular combination model (DSKL) provides a powerful method for evaluating the two putative contrast-discrimination mechanisms.
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Peripheral contrast sensitivity and attention in myopia. Vision Res 2016; 125:49-54. [PMID: 27264028 DOI: 10.1016/j.visres.2016.05.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 05/27/2016] [Accepted: 05/30/2016] [Indexed: 11/20/2022]
Abstract
Disruption of normal visual experience or changes in the normal interaction between central and peripheral retinal input may lead to the development of myopia. In order to examine the relationship between peripheral contrast sensitivity and myopia, we manipulated attentional load for foveal vision in emmetropes and myopes while observers detected targets with peripheral vision. Peripheral contrast detection thresholds were measured binocularly using vertical Gabor stimuli presented at three eccentricities (±8°, 17°, 30°) in a spatial 2 alternative forced choice task. Contrast thresholds were measured in young adult (mean age 24.5±2.6years) emmetropes (n=17; group SE: +0.19±0.32D) and myopes (n=25; group SE: -3.74±1.99D). Attention at central fixation was manipulated with: (1) a low attention task, requiring simple fixation; or (2) a high attention task, which required subjects to perform a mathematical task. We found that at 30° all subjects exhibited lower contrast sensitivity (higher thresholds). In addition, myopes (Wilcoxon, p<0.01), but not emmetropes (Wilcoxon, p=0.1), had a significant decrease in sensitivity at 30° during the high attention task. However, the attention dependent threshold increase for myopes was not significantly greater than for emmetropes (Wilcoxon, p=0.27). Attentional load did not increase thresholds at 8° or 17° for either refractive group. These data indicate that myopes experience a greater decrease in contrast sensitivity in the far periphery than emmetropes when attention is deployed in central vision.
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Abstract
PURPOSE The purpose of this study is to determine the relationship between target clarity and the magnitude of accommodative lag using the metric accommodative gain (AG). METHODS Monocular accommodative responses were measured with Grand Seiko autorefraction using both proximal and minus lens techniques in 139 subjects aged 5 to 35 years. Subjects viewed a 1.5-mm letter at 13 discrete distances (range, 40 to 3.33 cm) for the proximal technique and fixed at 33 cm through minus lenses of increasing power for the lens technique. Subjects were instructed to keep the target clear and report when it blurred. The AG was calculated (accommodative response/accommodative demand) for the four greatest consecutive demands perceived clear (termed conditions 1 to 4) and the first demand perceived blurry (termed condition 5). RESULTS Multivariate planned contrast, including age as a predictor, revealed that mean AG was significantly larger when the target was clear (range, 0.71 to 0.77 for conditions 1 to 4 across techniques) versus blurry (0.59 and 0.68 for condition 5 across techniques) (p < 0.001 for proximal and p < 0.036 for lens). Age was only a contributing factor for the proximal technique, with the youngest subjects having the largest decrease in AG when the target changed from clear to blurry (p = 0.017). CONCLUSIONS These data suggest that across age and technique, the AG is relatively constant when the target is perceived clear but drops below approximately 70%, on average, once the target is perceived as blurry for subjects aged 5 to 35 years. The AG may be a useful metric to compare accommodative responses across a range of demands and to identify accommodative responses that may not be sufficient to perceive a clear target.
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Radhakrishnan H, Hartwig A, Charman WN, Llorente L. Accommodation response to Chinese and Latin characters in Chinese-illiterate young adults. Clin Exp Optom 2015; 98:527-34. [PMID: 26450168 DOI: 10.1111/cxo.12296] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 03/09/2015] [Accepted: 03/12/2015] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Differences in accommodation when reading Chinese, as compared to Latin, characters have been suggested to have a role in the higher prevalence of myopia in some Asian countries. Yeo and colleagues (Optom Vis Sci 2013; 90: 156-163) found that, in Chinese-literate children, accommodation was marginally more accurate (by less than 0.05 D), when reading Chinese text. This was attributed to the additional cognitive demand associated with interpreting the more complex Chinese symbols. The present study compared responses to single Chinese and Latin characters, while controlling for cognitive demand. METHODS The monocular accommodative response was measured in Chinese-illiterate adults (10 emmetropes, mean spherical equivalent: -0.07 ± 0.42 D, age: 29.9 ± 4.2 years; 11 myopes, mean spherical equivalent: -4.28 ± 2.84 D, age: 31.7 ± 4.6 years) with an open-field autorefractor. Four Chinese and three Latin characters (approximately 1.15 degrees subtense) were individually presented on a display screen one metre away from the subject, while their vergence was varied over the range zero to 5.00 D using spectacle trial lenses. The slope and the accommodative error index (AEI) were calculated from the accommodative stimulus/response curves (ASRC). RESULTS No statistically significant differences were found between refractive groups or among characters within the same refractive group in ARSC slopes (Latin: 0.87 ± 0.14 for myopes versus 0.81 ± 0.12 for emmetropes; Chinese: 0.84 ± 0.12 for myopes versus 0.85 ± 0.12 for emmetropes). No significant differences were found between characters in accommodative error index either (Latin, 0.78 ± 0.42 D for myopes versus 1.15 ± 0.72 D for emmetropes; Chinese, 0.74 ± 0.37 D for myopes versus 1.17 ± 0.83 D for emmetropes). However, accommodative error indices and accommodative errors were significantly higher for emmetropes. CONCLUSION Under controlled cognitive demand, Chinese and Latin characters elicited similar responses in both individual refractive groups. This study fails to support the hypothesis that development of myopia in some Asian populations is associated with larger lags of accommodation when reading or viewing Chinese characters.
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Affiliation(s)
- Hema Radhakrishnan
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Andreas Hartwig
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - W Neil Charman
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Lourdes Llorente
- Faculty of Health Science, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia. .,Faculty of Health, Deakin University, Waurn Ponds, Australia.
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22
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Charman WN, Heron G. Microfluctuations in accommodation: an update on their characteristics and possible role. Ophthalmic Physiol Opt 2015; 35:476-99. [DOI: 10.1111/opo.12234] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 07/23/2015] [Indexed: 11/30/2022]
Affiliation(s)
- W Neil Charman
- Faculty of Life Sciences; University of Manchester; Manchester UK
| | - Gordon Heron
- Vision Sciences; Glasgow Caledonian University; Glasgow UK
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Efficacy of Chinese eye exercises on reducing accommodative lag in school-aged children: a randomized controlled trial. PLoS One 2015; 10:e0117552. [PMID: 25742161 PMCID: PMC4350838 DOI: 10.1371/journal.pone.0117552] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 12/24/2014] [Indexed: 02/05/2023] Open
Abstract
Purpose To evaluate the efficacy of Chinese eye exercises on reducing accommodative lag in children by a randomized, double-blinded controlled trial. Methods A total of 190 children aged 10 to 14 years with emmetropia to moderate myopia were included. They were randomly allocated to three groups: standard Chinese eye exercises group (trained for eye exercises by doctors of traditional Chinese medicine); sham point eye exercises group (instructed to massage on non-acupoints); and eyes closed group (asked to close their eyes without massage). Primary outcome was change in accommodative lag immediately after intervention. Secondary outcomes included changes in corrected near and distant visual acuity, and visual discomfort score. Results Children in the standard Chinese eye exercises group had significantly greater alleviation of accommodative lag (-0.10D) than those in sham point eye exercises group (-0.03D) and eyes closed group (0.07D) (P = 0.04). The proportion of children with alleviation of accommodative lag was significantly higher in the standard Chinese eye exercises group (54.0%) than in the sham point eye exercises group (32.8%) and the eyes closed group (34.9%) (P = 0.03). No significant differences were found in secondary outcomes. Conclusion Chinese eye exercises as performed daily in primary and middle schools in China have statistically but probably clinically insignificant effect in reducing accommodative lag of school-aged children in the short-term. Considering the higher amounts of near work load of Chinese children, the efficacy of eye exercises may be insufficient in preventing myopia progression in the long-term. Trial Registration ClinicalTrials.gov NCT01756287
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Abstract
PURPOSE To identify variables associated with myopia progression and to identify any interaction between accommodative function, myopia progression, age, and treatment effect in the Cambridge Anti-Myopia Study. METHODS Contact lenses were used to improve static accommodation by altering ocular spherical aberration, and vision training was performed to improve dynamic accommodation. One hundred forty-two subjects, aged 14-21 years, were recruited who had a minimum of -0.75D of myopia. Subjects were assigned to contact lens treatment only, vision training only, contact lens treatment and vision training, or control group. Spherical aberration, lag of accommodation, accommodative convergence/accommodation (AC/A) ratio, accommodative facility, ocular biometry, and refractive error were measured at regular intervals throughout the 2-year trial. RESULTS Ninety-five subjects completed the 24-month trial period. There was no significant difference in myopia progression between the four treatment groups at 24 months. Age, lag of accommodation, and AC/A ratio were significantly associated with myopia progression. There was a significant treatment effect at 12 months in the contact lens treatment group in younger subjects, based on a median split, aged under 16.9 years (p = 0.005). This treatment effect was not maintained over the second year of the trial. Younger subjects experienced a greater reduction in lag of accommodation with the treatment contact lens at 3 months (p = 0.03), compared to older contact lens treatment and control groups. There was no interaction between AC/A ratio and contact lens treatment effect. CONCLUSIONS Age, lag of accommodation, and AC/A ratio were significantly associated with myopia progression. Although there was no significant treatment effect at 24 months, an interaction between age and contact lens treatment suggests younger subjects may be more amenable, at least in the short term, to alteration of the visual system using optical treatments.
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Repeatability of Relative Peripheral Refraction in Untreated and Orthokeratology-Treated Eyes. Optom Vis Sci 2012; 89:1477-86. [DOI: 10.1097/opx.0b013e31826912cd] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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Flitcroft DI. The complex interactions of retinal, optical and environmental factors in myopia aetiology. Prog Retin Eye Res 2012; 31:622-60. [PMID: 22772022 DOI: 10.1016/j.preteyeres.2012.06.004] [Citation(s) in RCA: 456] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 06/10/2012] [Accepted: 06/21/2012] [Indexed: 02/09/2023]
Abstract
Myopia is the commonest ocular abnormality but as a research topic remains at the margins of mainstream ophthalmology. The concept that most myopes fall into the category of 'physiological myopia' undoubtedly contributes to this position. Yet detailed analysis of epidemiological data linking myopia with a range of ocular pathologies from glaucoma to retinal detachment demonstrates statistically significant disease association in the 0 to -6 D range of 'physiological myopia'. The calculated risks from myopia are comparable to those between hypertension, smoking and cardiovascular disease. In the case of myopic maculopathy and retinal detachment the risks are an order of magnitude greater. This finding highlights the potential benefits of interventions that can limit or prevent myopia progression. Our understanding of the regulatory processes that guide an eye to emmetropia and, conversely how the failure of such mechanisms can lead to refractive errors, is certainly incomplete but has grown enormously in the last few decades. Animal studies, observational clinical studies and more recently randomized clinical trials have demonstrated that the retinal image can influence the eye's growth. To date human intervention trials in myopia progression using optical means have had limited success but have been designed on the basis of simple hypotheses regarding the amount of defocus at the fovea. Recent animal studies, backed by observational clinical studies, have revealed that the mechanisms of optically guided eye growth are influenced by the retinal image across a wide area of the retina and not solely the fovea. Such results necessitate a fundamental shift in how refractive errors are defined. In the context of understanding eye growth a single sphero-cylindrical definition of foveal refraction is insufficient. Instead refractive error must be considered across the curved surface of the retina. This carries the consequence that local retinal image defocus can only be determined once the 3D structure of the viewed scene, off axis performance of the eye and eye shape has been accurately defined. This, in turn, introduces an under-appreciated level of complexity and interaction between the environment, ocular optics and eye shape that needs to be considered when planning and interpreting the results of clinical trials on myopia prevention.
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Affiliation(s)
- D I Flitcroft
- Children's University Hospital, Temple Street, Dublin, Ireland.
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Effect of heterophoria type and myopia on accommodative and vergence responses during sustained near activity in children. Vision Res 2012; 57:9-17. [DOI: 10.1016/j.visres.2012.01.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/16/2012] [Accepted: 01/17/2012] [Indexed: 11/18/2022]
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Langaas T, Riddell PM. Accommodative instability: relationship to progression of early onset myopia. Clin Exp Optom 2012; 95:153-9. [PMID: 22283788 DOI: 10.1111/j.1444-0938.2011.00699.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND In a previous study, we demonstrated that children with early onset myopia had greater instability of accommodation than a group of emmetropic children. Since that study was correlational, we were unable to determine the causal relationship between this and myopic progression. To address this, we examined the children two years later. We predicted that if accommodative instability was causing the myopic progression, instability at Visit 1 should predict the refractive error at Visit 2. Additionally, instability at Visit 1 should predict myopic progression. METHODS Thirteen myopic and 16 emmetropic children were included in the analysis. Dynamic measures of accommodation were made using eccentric photorefraction (PowerRefractor) while children viewed targets set at three distances (accommodative demands), namely, 0.25 metres (4.00 D demand), 0.5 metres (2.00 D demand) and 4.00 metres (0.25 D demand). RESULTS Both refractive error and accommodative instability at Visit 1 were highly correlated with the same measures at Visit 2. Children with myopia showed greater instability of accommodation (0.38 D) than children with emmetropia (0.26 D) at the 4.00 D target on Visit 1 and this instability of accommodation weakly predicted myopic progression. CONCLUSIONS The results presented in the present study suggest that instability of accommodation accompanies myopic progression, although a casual relationship cannot be established.
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Affiliation(s)
- Trine Langaas
- Department of Optometry and Visual Science, Buskerud University College, Kongsberg, Norway.
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Wu Y, Jiang BC. The effects of spherical aberration on static accommodative responses in emmetropes and myopes. Ophthalmic Physiol Opt 2011; 31:595-602. [PMID: 21943364 DOI: 10.1111/j.1475-1313.2011.00870.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE To compare the effects of spherical aberration (SA) on accommodative responses between emmetropes (EMs), stable myopes (SMs), and progressing myopes (PMs). METHODS The accommodative responses (AR) induced by negative lenses from 0 to -5 D in 1 D steps were measured with a Complete Ophthalmic Analysis System (COAS) for 10 emmetropes (EMs), 13 stable myopes (SMs), and 9 progressing myopes (PMs). Three types of AR were calculated from wavefront aberration data based on ocular foci within a paraxial area, natural pupil area, and a 3.5 mm-diameter annular pupil area. The accommodative stimulus response curves (ASRCs) were compared between the three groups and between the three AR conditions. RESULTS The difference in the slope of ASRC was significant between the three AR conditions (p < 0.0001) but it was not significant between the three refractive groups. In each group, the slope of ASRC for the accommodative response measured within the paraxial area of the pupil (paraxial AR) was significantly steeper than that measured for the natural pupil (total AR) and also for that estimated for the 3.5 mm-diameter annular pupil (p < 0.01). The difference in the y-intercept of ASRC between the three AR conditions was also significant (p = 0.02) but not between the three refractive groups. The y-intercept of ASRC for paraxial AR was more positive than that for total AR in SMs (p < 0.01) and in PMs (p < 0.05); the y-intercept of ASRC for the 3.5 mm peripheral AR was more positive than that for total AR in SMs (p < 0.05). CONCLUSIONS The spherical aberration of the eye has a significant effect on the slope of ASRC and is less in PMs than in EMs and SMs.
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Affiliation(s)
- Ying Wu
- Eye and ENT Hospital, Fudan University, Shanghai, China College of Optometry, Nova South Eastern University, Fort Lauderdale, Florida, USA
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Strang NC, Day M, Gray LS, Seidel D. Accommodation steps, target spatial frequency and refractive error. Ophthalmic Physiol Opt 2011; 31:444-55. [PMID: 21651598 DOI: 10.1111/j.1475-1313.2011.00855.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE Errors in the accommodation response of myopes have been reported in many studies although questions remain about the exact differences in accommodation steps when compared with emmetropic individuals. METHODS The characteristics of the accommodation step response to large (4/1D) and small (3/2D) steps in targets with low (0.5 cpd), mid (4 cpd) and high (16 cpd) spatial frequency (SF) information was measured in myopes (MYOs) and emmetropes (EMMs). RESULTS In terms of step size, the larger steps showed a greater response in the 4 cpd condition than the 0.5 and 16 cpd conditions and an improved percentage correct response in the 4 cpd compared to the 16 cpd steps. In small step conditions target SF had less effect upon the magnitude of the response. In terms of refractive group differences, MYOs had a lower proportion of correct accommodation responses compared to EMMs during the small steps only, however, when correct steps were performed there were no differences in the characteristics of both large and small step responses between MYOs and EMMs. CONCLUSIONS These findings suggest that MYOs have some difficulty interpreting small changes in defocus to initiate or possibly fine tune a small accommodation response, however, when a correct accommodation step response is made, the MYOs accommodation plant responds in a similar manner to EMMs.
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Affiliation(s)
- Niall C Strang
- Department of Vision Sciences, Glasgow Caledonian University, Glasgow, UK
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Accommodative lag and juvenile-onset myopia progression in children wearing refractive correction. Vision Res 2011; 51:1039-46. [PMID: 21342658 DOI: 10.1016/j.visres.2011.02.016] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2010] [Revised: 12/23/2010] [Accepted: 02/17/2011] [Indexed: 11/20/2022]
Abstract
The relationship between accommodative lag and annual myopia progression was investigated using linear models in 592 myopic children wearing a full refractive correction in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study. The mean (± SD) age and spherical equivalent refractive error at baseline were 10.4 ± 1.8 years and -2.13 ± 1.24 D, respectively. The mean annual progression of myopia was -0.45 ± 0.32 D, and the mean accommodative lag (for a 4-D Badal stimulus) was 1.59 ± 0.63 D. Neither lag at the beginning nor at the end of a yearly progression interval was associated with annual myopia progression (all p ≥ 0.12). These data suggest that foveal hyperopic retinal blur during near viewing may not drive juvenile-onset myopia progression.
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Effect of near adds on the variability of accommodative response in myopic children. Ophthalmic Physiol Opt 2011; 31:145-54. [DOI: 10.1111/j.1475-1313.2010.00818.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Berntsen DA, Mutti DO, Zadnik K. The effect of bifocal add on accommodative lag in myopic children with high accommodative lag. Invest Ophthalmol Vis Sci 2010; 51:6104-10. [PMID: 20688729 DOI: 10.1167/iovs.09-4417] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine the effect of a bifocal add and manifest correction on accommodative lag in myopic children with high accommodative lag, who have been reported to have the greatest reduction in myopia progression with progressive addition lenses (PALs). METHODS Monocular accommodative lag to a 4-D Badal stimulus was measured on two occasions 6 months apart in 83 children (mean ± SD age, 9.9 ± 1.3 years) with high lag randomized to wearing single-vision lenses (SVLs) or PALs. Accommodative lag was measured with the following corrections: habitual, manifest, manifest with +2.00-D add, and habitual with +2.00-D add (6-month visit only). RESULTS At baseline, accommodative lag was higher (1.72 ± 0.37 D; mean ± SD) when measured with manifest correction than with habitual correction (1.51 ± 0.50; P < 0.05). This higher lag with manifest correction correlated with a larger amount of habitual undercorrection at baseline (r = -0.29, P = 0.009). A +2.00-D add over the manifest correction reduced lag by 0.45 ± 0.34 D at baseline and 0.33 ± 0.38 D at the 6-month visit. Lag results at 6 months were not different between PAL and SVL wearers (P = 0.92). CONCLUSIONS A +2.00-D bifocal add did not eliminate accommodative lag and reduced lag by less than 25% of the bifocal power, indicating that children mainly responded to a bifocal by decreasing accommodation. If myopic progression is substantial, measuring lag with full correction can overestimate the hyperopic retinal blur that a child most recently experienced. (ClinicalTrials.gov number, NCT00335049.).
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Affiliation(s)
- David A Berntsen
- Ohio State University College of Optometry, Columbus, Ohio, USA.
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Mira-Agudelo A, Lundström L, Artal P. Temporal dynamics of ocular aberrations: monocular vs binocular vision. Ophthalmic Physiol Opt 2010; 29:256-63. [PMID: 19422556 DOI: 10.1111/j.1475-1313.2009.00655.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The temporal dynamics of ocular aberrations are important for the evaluation of, e.g. the accuracy of aberration estimates, the correlation to visual performance, and the requirements for real-time correction with adaptive optics. Traditionally, studies on the eye's dynamic behavior have been performed monocularly, which might have affected the results. In this study we measured aberrations and their temporal dynamics both monocularly and binocularly in the relaxed and accommodated state for six healthy subjects. Temporal frequencies up to 100 Hz were measured with a fast-acquisition Hartmann-Shack wavefront sensor having an open field-of-view configuration which allowed fixation to real targets. Wavefront aberrations were collected in temporal series of 5 s duration during binocular and monocular vision with fixation targets at 5 m and 25 cm distance. As expected, a larger temporal variability was found in the root-mean-square wavefront error when the eye accommodated, mainly for frequencies lower than 30 Hz. A statistically-significant difference in temporal behavior between monocular and binocular viewing conditions was found. However, on average it was too small to be of practical importance, although some subjects showed a notably higher variability for the monocular case during near vision. We did find differences in pupil size with mono- and binocular vision but the pupil size temporal dynamics did not behave in the same way as the aberrations' dynamics.
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Affiliation(s)
- A Mira-Agudelo
- Laboratorio de Optica, Centro de Investigación en Optica y Nanofísica (CiOyN), Universidad de Murcia, Campus de Espinardo Murcia, Murcia 30100, Spain.
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Vasudevan B, Ciuffreda KJ, Ludlam DP. Accommodative Training to Reduce Nearwork-Induced Transient Myopia. Optom Vis Sci 2009; 86:1287-94. [DOI: 10.1097/opx.0b013e3181bb44cf] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Abstract
PURPOSE To investigate the relationship among microfluctuations in accommodation, resting tension on the crystalline lens, ciliary body thickness, and refractive error in children. METHODS Subjects were 49 children, aged 8 to 15 years. Subjects wore habitual correction over their left eye and an infrared filter over the right eye during accommodative measurements. Monocular accommodation was measured continuously for two, 30-second periods using a PowerRef I at a sampling rate of 25 Hz while subjects viewed a high-contrast target at 0.25 m. The high (1.0 to 2.3 Hz) and low- (0 to 0.6 Hz) frequency components of the power spectrum from a fast Fourier transform of the accommodative response were used in analysis. Resting tension on the crystalline lens was assessed by measuring the amplitude of the oscillations of the crystalline lens after a rightward 20 degrees saccadic eye movement. Ciliary body thickness was measured 2 mm posterior to the scleral spur from images obtained with a Zeiss Visante optical coherence tomography (OCT). Cycloplegic spherical equivalent refractive error was obtained with the Grand Seiko autorefractor. RESULTS The mean +/- SD spherical equivalent refractive error was -1.00 D +/- 2.25 (range, -6.00 D to +3.44 D). Greater power in the log of the high-frequency component of accommodative microfluctuations was associated with thinner ciliary bodies (p = 0.03) and lower ages (p = 0.0004). More hyperopic refractive errors with greater power in the high-frequency component (p = 0.0005) and the low-frequency component (p = 0.02). No statistically significant relationship was found for the low-frequency component or root mean square of accommodative microfluctuations and refractive error. CONCLUSIONS High-frequency microfluctuations of accommodation appear to be suppressed with thicker ciliary bodies. These variations in accommodation need to be observed in a longitudinal study to better assess the functional significance of their relationship to ciliary body size and refractive error.
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Abstract
PURPOSE Adaptation to defocus is known to influence the subjective sensitivity to blur in both emmetropes and myopes. Blur is a major contributing factor in the closed-loop dynamic accommodation response. Previous investigations have examined the magnitude of the accommodation response following blur adaptation. We have investigated whether a period of blur adaptation influences the dynamic accommodation response to step and sinusoidal changes in target vergence. METHOD Eighteen subjects (six emmetropes, six early onset myopes, and six late onset myopes) underwent 30 min of adaptation to 0.00 D (control), +1.00 D or +3.00 D myopic defocus. Following this adaptation period, accommodation responses to a 2.00 D step change and 2.00 D sinusoidal change (0.2 Hz) in target vergence were recorded continuously using an autorefractor. RESULTS Adaptation to defocus failed to influence accommodation latency times, but did influence response times to a step change in target vergence. Adaptation to both +1.00 and +3.00 D induced significant increases in response times (p = 0.002 and p = 0.012, respectively) and adaptation to +3.00 D increased the change in accommodation response magnitude (p = 0.014) for a 2.00 D step change in demand. Blur adaptation also significantly increased the peak-to-peak phase lag for accommodation responses to a sinusoidally oscillating target, although failed to influence the accommodation gain. These changes in accommodative response were equivalent across all refractive groups. CONCLUSION Adaptation to a degraded stimulus causes an increased level of accommodation for dynamic targets moving towards an observer and increases response times and phase lags. It is suggested that the contrast constancy theory may explain these changes in dynamic behavior.
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The effect of modulating ocular depth of focus upon accommodation microfluctuations in myopic and emmetropic subjects. Vision Res 2008; 49:211-8. [PMID: 18992269 DOI: 10.1016/j.visres.2008.10.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Revised: 09/22/2008] [Accepted: 10/08/2008] [Indexed: 11/22/2022]
Abstract
The magnitude of accommodation microfluctuations increases in emmetropic subjects viewing low luminance targets or viewing a target through small artificial pupils. Larger microfluctuations reported in myopia may result from an abnormally large depth of focus (DoF). The effect of modulating the size of the DoF has not been investigated in myopic subjects and may help to explain the cause of the increased DoF. Accommodation microfluctuations were recorded under two experimental conditions. Firstly, 12 emmetropes (EMMs), and 24 myopes (MYOs) viewed a Maltese Cross target with luminance levels of 0.002, 0.2, 6 and 600cd/m(2) and in darkness, and second, 14 EMMs and 16 MYOs viewed a Maltese Cross target through pupil diameters of 0.5, 1, 2, 3, 4 and 5mm presented in Maxwellian view. The magnitude of the accommodation microfluctuations increased significantly with a target luminance of 0.002cd/m(2) (p<.03) and pinhole diameters of <2mm (p<.05). For all other luminance levels and pupil diameters the magnitude was constant. For both conditions, MYOs had significantly larger microfluctuations than EMMs (p<.01). Considerable inter-subject variability was observed in the degree to which the magnitude of the microfluctuations increased, for both the 0.002cd/m(2) luminance and 0.5mm pupils, however, this was not correlated with refractive error. The increase in the magnitude of the microfluctuations while viewing a low luminance target (0.002cd/m(2)) may be due to a shallower contrast gradient in the cortical image, with a consequent increase in DoF. The microfluctuations also increase when viewing through small pupils (<2mm), which increases the DoF without altering the contrast gradient. The larger microfluctuations found in the MYOs consolidates the theory that MYOs have a larger DoF than EMMs and therefore have a higher threshold for retinal image blur.
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Chin SS, Hampson KM, Mallen EAH. Binocular correlation of ocular aberration dynamics. OPTICS EXPRESS 2008; 16:14731-45. [PMID: 18795011 DOI: 10.1364/oe.16.014731] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Fluctuations in accommodation have been shown to be correlated in the two eyes of the same subject. However, the dynamic correlation of higher-order aberrations in the frequency domain has not been studied previously. A binocular Shack-Hartmann wavefront sensor is used to measure the ocular wavefront aberrations concurrently in both eyes of six subjects at a sampling rate of 20.5 Hz. Coherence function analysis shows that the inter-ocular correlation between aberrations depends on subject, Zernike mode and frequency. For each subject, the coherence values are generally low across the resolvable frequency range (mean 0.11), indicating poor dynamic correlation between the aberrations of the two eyes. Further analysis showed that phase consistency dominates the coherence values. Monocular and binocular viewing conditions showed similar power spectral density functions.
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Affiliation(s)
- S S Chin
- Bradford School of Optometry and Vision Science, University of Bradford, Bradford, UK.
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Tarrant J, Severson H, Wildsoet CF. Accommodation in emmetropic and myopic young adults wearing bifocal soft contact lenses. Ophthalmic Physiol Opt 2008; 28:62-72. [PMID: 18201337 DOI: 10.1111/j.1475-1313.2007.00529.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To assess the effect of bifocal soft contact lenses on the accommodative errors (lags) of young adults. Recent studies suggest that bifocal soft contact lenses are an effective myopia control treatment although the underlying mechanism is not understood. METHODS Accommodation responses were measured for four target distances: 100, 50, 33 and 25 cm in 35 young adult subjects (10 emmetropes and 25 myopes; mean age, 22.8 +/- 2.5 years). Measurements were made under both monocular and binocular conditions with three types of lenses: single vision distance soft contact lenses (SVD), single vision near soft contact lenses (SVN; +1.50 D added to the distance prescription) and bifocal soft contact lenses (BF; +1.50 D add). RESULTS For the SVD lenses, all subjects exhibited lags of accommodation, with myopes accommodating significantly less than emmetropes for the 100 and 50 cm target distances (p < 0.05). With the SVN lenses, there was no significant difference in accommodative responses between emmetropes and myopes. With the BF lenses, both emmetropic and myopic groups exhibited leads in accommodation for all target distances, with emmetropes showing significantly greater leads for all distances (p < 0.005). CONCLUSIONS Overall, myopes tended to accommodate less than emmetropes, irrespective of the contact lens type, which significantly affected accommodation for both groups. The apparent over-accommodation of myopes when wearing the BF contact lenses may explain the reported efficacy as a myopia control treatment, although further studies are required to elucidate the mechanism underlying this accommodative effect.
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Affiliation(s)
- Janice Tarrant
- School of Optometry, 592 Minor Hall, University of California, Berkeley, CA 94720-2020, USA.
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Weizhong L, Zhikuan Y, Wen L, Xiang C, Jian G. A longitudinal study on the relationship between myopia development and near accommodation lag in myopic children. Ophthalmic Physiol Opt 2008; 28:57-61. [PMID: 18201336 DOI: 10.1111/j.1475-1313.2007.00536.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE To investigate the possible relationship between myopia progression and near accommodative lag. METHODS A 1-year longitudinal study was carried out to measure the accommodative response and myopia progression in 62 children with mild and progressing myopia at two visits: they were 10.81 +/- 1.60 years old with refractive error -1.70 +/- 0.76 D on entry. Repeated measurements included refractive error, ocular biometry and accommodative response at 33 cm. The refractive error was determined by autorefraction after cycloplegia; ocular biometry by A-scan ultrasonography; and accommodative response by an open-field autorefractor. Results were based on the right eye and analysed by paired t-test and Pearson's correlation coefficient. RESULTS Myopia progression in the year was -0.72 +/- 0.37 D (p < 0.001) with a range from -0.06 to -1.96 D. The change of axial length and vitreous depth were 0.41 +/- 0.25 mm (p < 0.001) and 0.36 +/- 0.24 mm (p < 0.001), respectively. The near lag was 0.76 +/- 0.29 D on entry and 0.72 +/- 0.38 D 1 year later (p = 0.79). No statistically significant correlations were found between near lag vs myopia progression and the change of ocular biometry as a whole (p > 0.10 for all). There was no significant difference in myopia progression between myopic children with greater than, compared to less than the mean amount of near lag (p = 0.36). CONCLUSIONS This study demonstrates no statistically significant relationship between myopia progression and near accommodation lag in children with mild and progressing myopia. There is no evidence that near lag provides a stimulus to progression in this stage of myopia.
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Affiliation(s)
- Lan Weizhong
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, China
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Day M, Strang NC, Seidel D, Gray LS. Technical note: effect of contact lenses on measurement of the accommodation microfluctuations. Ophthalmic Physiol Opt 2008; 28:91-5. [PMID: 18201340 DOI: 10.1111/j.1475-1313.2007.00522.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM Dynamic measurement of accommodation in subjects with myopia usually involves recording through soft contact lenses (CLs) to correct the refractive error. Conversely, dynamic accommodation measurement in emmetropic control subjects is generally undertaken without any corrective lenses. The aim of this experiment was to determine whether CL correction affects the measurement of accommodation microfluctuations using infrared refractometry, and whether this needs to be considered in studies which attempt to compare accommodation responses between the two groups. METHODS Ten young emmetropic subjects viewed a high contrast Maltese cross target monocularly using the right eye at a target vergence of 0 D. The subjects viewed the target under two conditions: with CL condition and without CL condition, where the subjects viewed the target with the eye only. Accommodation responses of the right eye were recorded continuously for 2 min at a sampling rate of 52 Hz using the Shin-Nippon SRW-5000 autorefractor. RESULTS No significant difference (two-tailed paired t-test, t(9) = -1.499, p = 0.168) was found in mean accommodation response between the with CL (mean +/- S.D. = -0.02 +/- 0.24 D) and without CL conditions (mean +/- S.D. = +0.01 +/- 0.25 D). No significant (two-tailed paired t-test, t(9) = 0.151, p = 0.883) difference in the magnitude of the accommodation microfluctuations was found between the with CL (mean +/- S.D. = 0.162 +/- 0.04 D) and without CL condition (mean +/- S.D. = 0.169 +/- 0.04 D). Power spectrum analysis revealed no differences in the characteristics of the microfluctuations waveform between the two conditions. A control experiment carried out on a subgroup of five subjects using a negative (-3 D) CL demonstrated that there was no significant effect of the dioptric power of the CL on the magnitude of the accommodation microfluctuations (anova: F(3,15) = 0.254, p = 0.782). CONCLUSION Thin soft CLs do not affect the magnitude or frequency characteristics of accommodation microfluctuations when measured using the Shin-Nippon SRW-5000.
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Affiliation(s)
- Mhairi Day
- Department of Vision Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA, UK.
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Abstract
PURPOSE Hyperopic retinal defocus (blur) is thought to be a cause of myopia. If the retinal image of an object is not clearly focused, the resulting blur is thought to cause the continuing lengthening of the eyeball during development causing a permanent refractive error. Both lag of accommodation, especially for near targets, and greater variability in the accommodative response, have been suggested as causes of increased hyperopic retinal blur. Previous studies of lag of accommodation show variable findings. In comparison, greater variability in the accommodative response has been demonstrated in adults with late onset myopia but has not been tested in children. This study looked at the lag and variability of accommodation in children with early onset myopia. METHODS Twenty-one myopic and 18 emmetropic children were tested. Dynamic measures of accommodation and pupil size were made using eccentric photorefraction (PowerRefractor) while children viewed targets set at three different accommodative demands (0.25, 2, and 4 D). RESULTS We found no difference in accommodative lag between groups. However, the accommodative response was more variable in the myopes than emmetropes when viewing both the near (4 D) and far (0.25 D) targets. Since pupil size and variability also varied, we analyzed the data to determine whether this could account for the inter-group differences in accommodation variability. Variation in these factors was not found to be sufficient to explain these differences. Changes in the accommodative response variability with target distance were similar to patterns reported previously in adult emmetropes and late onset myopes. CONCLUSIONS Children with early onset myopia demonstrate greater accommodative variability than emmetropic children, and have similar patterns of response to adult late onset myopes. This increased variability could result in an increase in retinal blur for both near and far targets. The role of accommodative variability in the etiology of myopia is discussed.
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Cufflin MP, Hazel CA, Mallen EAH. Static accommodative responses following adaptation to differential levels of blur. Ophthalmic Physiol Opt 2007; 27:353-60. [PMID: 17584286 DOI: 10.1111/j.1475-1313.2007.00491.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE To investigate the effects of two levels of blur adaptation on visual resolution and steady-state accommodation responses in emmetropes and myopes. METHODS Eleven emmetropes (mean refractive error +0.01 +/- 0.31 DS) and 11 early-onset myopes (EOM, mean refractive error -4.44 +/- 1.64 DS) fixated monocularly at 4 m in three trials of 45 min duration with either: optimal refractive correction, +1 DS defocus, or +3 DS defocus. Monocular logMAR visual acuity (VA) was measured at 10 min intervals during each trial, and immediately following completion of the trial. Accommodative stimulus-response function (ASRF), refractive error and pupil size were measured before and after each trial. RESULTS Blur adaptation was found to have no effect on pupil size or baseline refraction, irrespective of the power of the blurring lens. Adaptation to +1 DS of defocus yielded an improvement in VA of -0.16 +/- 0.07 logMAR and -0.17 +/- 0.11 logMAR in the emmetropes and myopes respectively. An improvement in VA of -0.20 +/- 0.18 logMAR in the emmetropes and -0.26 +/- 0.17 logMAR in the myopes was observed following adaptation to +3 DS of defocus. The changes in acuity became significant following 30 min of exposure to defocus. Blur adaptation was found to have no effect on the ASRF gradient or individual steady-state accommodative responses. CONCLUSIONS Following blur adaptation, visual resolution was found to increase in both emmetropes and myopes. The magnitude of the blur level did not produce significantly different increases in resolution. Blur adaptation failed to affect either the steady-state responses to an accommodative stimulus or ASRF gradient.
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Affiliation(s)
- Matthew P Cufflin
- Department of Optometry, University of Bradford, Richmond Road, Bradford, West Yorkshire BD7 1DP, UK
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Troilo D, Quinn N, Baker K. Accommodation and induced myopia in marmosets. Vision Res 2007; 47:1228-44. [PMID: 17360018 PMCID: PMC1892168 DOI: 10.1016/j.visres.2007.01.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2006] [Revised: 01/25/2007] [Accepted: 01/29/2007] [Indexed: 11/20/2022]
Abstract
Accommodation may indirectly influence visually guided eye growth by affecting the retinal defocus signal used to guide growth. Specifically, increased lags of accommodation associated with low stimulus-response (S-R) function slopes will impose increased hyperopic blur on the retina and may induce axial elongation and myopia. The purpose of this study was (1) to measure accommodation in awake, free viewing marmosets and (2) compare accommodation behavior in marmosets before and after inducing different amounts of myopia with binocular spectacle lenses. In untreated marmosets, the average accommodation S-R slope approached one, but showed considerable inter-individual variability (mean+/-SD: 0.964+/-0.249 for monocular viewing; 0.895+/-0.235 for binocular viewing; monocular and binocular measures not significantly different). The monocular S-R slopes were significantly reduced following a period of lens rearing that produced axial myopia (change in slope=-0.30+/-0.30, p<.01) and the reduction in slope was proportional to the amount of myopia induced (p<.01). The S-R slopes measured either under monocular or binocular conditions before induction of myopia were not well correlated with the degree of myopia induced (monocular: r=-.240, p=.453; binocular: r=-.060, p=.824). These results support the hypothesis that the reduction in S-R slope in myopes is a consequence of the myopia induced. The alternative hypothesis-that low S-R slope increases susceptibility to the development of myopia--is not supported by the weak correlation between the pre-manipulation S-R slopes and the magnitude of the myopic shift.
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Affiliation(s)
- David Troilo
- The New England College of Optometry, 424 Beacon Street, Boston, MA 02115, USA.
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IN THE NEWS. Optom Vis Sci 2005. [DOI: 10.1097/00006324-200504000-00002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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