The impact of COVID-19 home confinement on axial length in myopic children undergoing orthokeratology

Author(s):  
Huibin Lv ◽  
Yuexin Wang ◽  
Siman Sun ◽  
Shanshan Wei ◽  
Yining Guo ◽  
...  
Keyword(s):  
2019 ◽  
Vol 22 (6) ◽  
pp. 492-498
Author(s):  
Xiaohu Ding ◽  
Wei Wang ◽  
Jane Scheetz ◽  
Mingguang He

AbstractThe primary aim of the Guangzhou Twin Eye Study (GTES) is to explore the impact that genes and environmental influences have on common eye diseases. Since 2006, approximately 1300 pairs of twins, aged 7–15 years, were enrolled at baseline. Progressive phenotypes, such as cycloplegic refraction, axial length, height and weight, have been collected annually. Nonprogressive phenotypes such as parental refraction, corneal thickness, fundus photo, intraocular pressure and DNA were collected once at baseline. We are collaborating with fellow international twin researchers and psychologists to further explore links with general medical conditions. In this article, we review the history, major findings and future research directions for the GTES.


2019 ◽  
Vol 103 (11) ◽  
pp. 1571-1575 ◽  
Author(s):  
Yin Hu ◽  
Canhong Wen ◽  
Zhouyue Li ◽  
Wenchen Zhao ◽  
Xiaohu Ding ◽  
...  

BackgroundThe myopia control effect of orthokeratology (OK) varies among individuals. The variation might relate to the proposed ‘areal summation effect’ of lens-induced visual signals. The current study evaluated the areal summed corneal power shift (ASCPS) in myopic children treated with OK lenses and assessed whether the ASCPS achieved at early post-OK visit can predict the lens long-term effect on the axial length (AL) elongation.MethodsStudy participants were 130 myopic children treated with OK lenses (age range, 8 to 15 years) in a prospective study. Corneal topography and AL were measured at baseline and 1, 3, 6, 9 and 12 months after OK lens wear. The ASCPS was derived from corneal topographic measurements and defined as the change in the areal summed corneal relative refraction at the follow-up visit from baseline. The impact of the ASCPS achieved at the 1 month post-OK visit on the 12 months AL elongation was examined using multivariate linear regression analysis.ResultsBaseline age of the study participants was 11.8 ± 1.8 years and their mean spherical equivalent was −3.00±0.92 D. The ASCPS was 6.90±6.09 D*mm at the 1 month visit and remained stable throughout the follow-up period (p=0.5508, repeated-measures analysis of variance). Greater 1 month ASCPS was associated with slower AL elongation at the 12 months visit (β=−0.007, p=0.001).ConclusionsThe ASCPS achieved at early post-OK visit is predictive for the lens long-term effect on the myopic AL elongation. The parameter is potential in guiding the OK lens practice to slow down axial growth in myopic children.


2011 ◽  
Vol 2-3 ◽  
pp. 700-705
Author(s):  
Kai Yuan Hao ◽  
Wei Min Wang ◽  
Yong Qiang Shi ◽  
Sha Sha Wang

The purpose of the study described in this paper was to investigate the impact of shroud curvature on the performance of a centrifugal impeller or stage. The paper discusses a computational fluid dynamics (CFD) study done to assess the influence of shroud curvature on impeller performance. The computational fluid dynamics (CFD) and finite element analyses (FEA) methods were used to describe the various designs of the impeller. Aerodynamic and mechanical analysis results are presented for four impellers of varying cover curvature and axial length. The aerodynamic results showed there were clear aerodynamic benefits to decreasing the curvature along the impeller shroud. The mechanical analytical results showed that the impeller with the lowest curvature or longest axial length provided the highest performance; it also yielded the lowest Von Mises stress level. In closing, there are clear aerodynamic benefits to decreasing the curvature along the impeller shroud but these benefits must be weighed against the impact on the rotordynamic considerations Comments are offered regarding the rotordynamic issues that must be considered when increasing the length of impellers.


Author(s):  
Daniel Kessler ◽  
Daniel Giesecke ◽  
Jens Friedrichs ◽  
Jörg Leuschner

Abstract Axial fans used in automotive and especially in locomotive cooling systems have to follow several, partially contrary specifications. In addition to geometrical and aerodynamic specifications, acoustic limits must be taken into account for new fan stage designs. Legislation will tweak axial fan requirements in the future further and further to lower their noise emission and maximize their efficiency. The main focus of this paper is to design and test a single stage axial fan for locomotive cooling systems with high aerodynamic efficiency and low noise emissions. The fan stage is designed to be installed in a so-called tower construction. The available construction space is limited. Therefore, special attention is paid to reduce the axial length. Extensive blade sweep and dihedral are implemented in the design process. The fan stage design is validated by experimental tests including aerodynamic and acoustic studies. During the aerodynamic studies, it was found that an often used approximation about the static pressure downstream the fan cannot be applied. Downstream the fan stage no further components are installed. Therefore, the static pressure at this position must be approximated. An alternative approach is developed using the results of additional studies including a downstream pipe and scaling factors. The results of the approach are plausible. The acoustic tests were carried out at a fan test facility at TU Braunschweig. To evaluate the impact of the halls acoustic repercussion on the test results, different tests were done. Additionally, another axial fan was tested which has been investigated a few years ago in an acoustic test chamber. The studies show the positive effect of the design methodology on aerodynamic and acoustic of the fan stage. All requirements were achieved as well as a reduction of the axial length of the fan stage.


2020 ◽  
pp. bjophthalmol-2019-315636
Author(s):  
Jingjing Wang ◽  
Tianyu Cheng ◽  
Bo Zhang ◽  
Shuyu Xiong ◽  
Huijuan Zhao ◽  
...  

AimTo explore the impact of puberty on refractive development and its interaction with outdoor time in children and adolescents.MethodsIn this 2-year observational study, students aged 7–13 years were selected with cluster sampling. All participants underwent cycloplegic refraction and axial length measurements once every year. Information of related factors was acquired through proper questionnaire or inquiry. The level of testosterone/estradiol was detected from the saliva of the subjects using the ELISA kit. Multiple linear regression and generalised estimating equation (GEE) were used to analyse the relationship among puberty, outdoor activities and refractive indicators.ResultsA total of 776 children and adolescents were included, with an average baseline age of 9.64±1.54 years and 53.6% boys. There were 350 myopes (55.2% of the 634 cyclopleged subjects) at baseline. There was a significant difference in the mean axial length changes and outdoor time among different puberty groups (for axial length: p=0.017, for outdoor time: p=0.015). Myopic parents, less outdoor time and more changes in estradiol were associated with greater changes in axial length and spherical equivalent (SE) (axial length changes: parental myopia β=0.230, outdoor time β=−0.250, changes in estradiol β=0.261; SE changes: parental myopia β=−0.267, outdoor time β=0.256, changes in estradiol β=−0.297). In the GEE model, the interaction between outdoor time and puberty was significantly associated with axial length (p=0.024, β=1.199).ConclusionsThis study implies puberty may play a regulating role on the relationship between outdoor time and refractive development among Chinese children and adolescents, which provides clues for in-depth mechanism interpretation and efficient intervention strategies.


2010 ◽  
Vol 249 (5) ◽  
pp. 671-675 ◽  
Author(s):  
Roxane J. Hillier ◽  
Theodor Stappler ◽  
Rachel L. Williams ◽  
George S. Turner ◽  
David Wong

2019 ◽  
Author(s):  
Hong Kyu Kim ◽  
Tyler Hyungtaek Rim ◽  
Jong Yun Yang ◽  
Soo Han Kim ◽  
Sung Soo Kim

Abstract Background: To investigate the impact of axial length (AL) and ocular factors on axial length elongation (ALE). Methods: A retrospective chart review of patients who underwent more than two axial length examinations using a single instrument Results: The mean age of the participants was 47.21 ± 7.79 years. Eyes were classified into four groups according to their initial AL measurement. AL remained almost unchanged in the groups with AL < 26mm. On the contrary, AL increased by 0.011mm/year in the group with 26 ≤ AL < 28mm and 0.035mm/year in the group with AL ≥ 28mm (P < .001). In high myopia, ALE increased in eyes with longer axial lengths (r = 0.003, P = .024), females (r = 0.014, P = .019), eyes with larger peripapillary chorioretinal atrophic areas (r = 0.002, P = .019), and smaller vascular arcade angles (r = -0.004, P = .006). The risk of elongation 0.03mm/year in high myopia was increased in females (OR = 2.265, P = .040), and gradually increased in eyes with large peripapillary chorioretinal atrophy area (OR = 5.604, 6.939, and 7.470, respectively; P = .001, < .001, and .008, respectively) Conclusions: AL remained almost unchanged in the group with AL < 26mm. On the contrary, ALE was observed in the group with AL ≥ 26mm. AL elongated significantly in eyes with longer AL, female, and eyes with larger atrophic areas and smaller arcade angles on fundus photographs.


2021 ◽  
pp. bjophthalmol-2020-318717
Author(s):  
Philipp L Müller ◽  
Tim Treis ◽  
Abdulrahman Alsaedi ◽  
Andrew R Webster ◽  
Peng Khaw ◽  
...  

Background/aimsThe reason for visual impairment in patients with nanophthalmos and posterior microphthalmos is not completely understood. Therefore, this study aims to investigate foveal structure, and the impact of demographic, clinical and imaging parameters on best-corrected visual acuity (BCVA) in these conditions.MethodsSixty-two eyes of 33 patients with nanophthalmos (n=40) or posterior microphthalmos (n=22), and 114 eyes of healthy controls with high-resolution retinal imaging including spectral-domain or swept-source optical coherence tomography images were included in this cross-sectional case–control study. Foveal retinal layer thickness was determined by two independent readers. A mixed-effect model was used to perform structure–function correlations and predict the BCVA based on subject-specific variables.ResultsMost patients (28/33) had altered foveal structure associated with loss of foveal avascular zone and impaired BCVA. However, widening of outer nuclear layer, lengthening of photoreceptor outer segments, normal distribution of macular pigment and presence of Henle fibres were consistently found. Apart from the presence of choroidal effusion, which had significant impact on BCVA, the features age, refractive error, axial length and retinal layer thickness at the foveal centre explained 61.7% of the variability of BCVA.ConclusionThis study demonstrates that choroidal effusion, age, refractive error, axial length and retinal layer thickness are responsible for the majority of interindividual variability of BCVA as well as the morphological foveal heterogeneity in patients with nanophthalmos or posterior microphthalmos. This might give further insights into the physiology of foveal development and the process of emmetropisation, and support clinicians in the assessment of these disease entities.


Author(s):  
Dhinagaran Ramachandran ◽  
Balamurugan Mayandi ◽  
Subramani Dasappagoundenpudur Arthanarisamy ◽  
Vanamurthy Murugan ◽  
Saravanan Boolingam ◽  
...  

Abstract Increasingly stringent emission norms place tougher challenges on the efficiencies of a turbocharger. Higher efficiency requirement on turbocharger translates into tighter tolerances on the various geometrical dimensions. While this is applicable for all the components, in this study, the focus is on the compressor wheel. Compressor wheels are either cast or milled and variations are possible in either of the processes. Even small changes in the dimensions of compressor wheel (like diameter, angle distribution, thickness distribution, axial length and blade width etc.), cause the performance losses in Turbo charger. Loss in Performance of turbocharger affects Low-end torque, power rating, fuel economy as well as increasing compressor exit temperature. It is therefore important to understand and quantify the impact of the variation in blade geometry on pressure ratio, choke flow and efficiency. In this paper, a few case studies of manufacturing variations in blade thickness, blade height and axial length are shown based on gas stand tests as well as 3D CFD simulations. A process for extracting real geometry from white light scan data obtained from the manufactured wheel is shown which helps to compare the differences with the design intent geometry. Flow simulations with the real geometry show the impact on performance. Subsequently a systematic analysis of the variations is carried out to quantify the performance impact.


1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.


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