• Journal of Korean Ophthalmic Optics Society
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• v.15 no.4
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• pp.389-397
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• 2010

Purpose: This study was to investigate the changes of refractive error and astigmatism associated with age in Korean subjects between the ages of 6 and 80 years during 10-year period. Methods: 220 normal subjects (345 eyes) who visited ophthalmic clinic was recruited and followed for 10 years between 1999 and 2009, cycloplegic manifest refraction being performed annually. Visual acuity was tested on a Han's chart. Results: The mean 10-year change in the spherical equivalent refraction (SER) of age 6 to 10 years old and 10 to 20 years was -3.649D and -2.165D respectively. There was no change of refractive error in age 21 to 40 years. The myopic shift decreased with age from 41 up to 69 years but increased slightly in patients 70 years and older; the hyperopic shift showed the opposite trend. The distribution of refractive error over the 10 years in aged 6 to 10 and 11 to 20 years was shifted myopic. The incidence of medium (> -3.01D) to high myopia at age 6 to 10 years was 4.8% and after 10 years was 62.5%. The 10-year change of astigmatism axis was in "with the rule" direction for younger age group and in a "against the rule" direction for older subjects. Conclusions: This study has documented refractive error changes in Korean subjects and confirmed reported trends of myopic shift from age 6-20 years and hyperopic shift before age 70 years and a myopic shift thereafter. The axis of astigmatism turns to "against the rule" after 40's.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.6
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• pp.53-61
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• 2014

For monitoring the flight trajectory and the status of a launch vehicle, the mission control system in NARO space center process data acquired from the ground tracking system, which consists of two tracking radars, four telemetry stations, and one electro-optical tracking system. Each tracking unit exhibits its own tracking error mainly due to multi-path, clutter and radio refraction, and by utilizing only one among transmitted informations, it is not possible to determine the actual vehicle trajectory. This paper presents a way of generating flight trajectory via post-processing the data received from the ground tracking system. The post-processing algorithm is divided into two parts: compensation for atmosphere radio refraction and multi-sensor fusion, for which a decentralized Kalman filter was adopted and implemented based on constant acceleration model. Applications of the present scheme to real data resulted in the flight trajectory where the tracking errors were minimized than done by any one sensor.

• Journal of Korean Clinical Health Science
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• v.7 no.2
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• pp.1337-1344
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• 2019

Purpose. This study was the analyze the refractive status of presbyopia in Korea. Methods. The subjects was from November 2018 to October 2019, two hundred thirty four subjects( 117 male subjects, 117 female subjects; from 40-year old to 88-year old ) were performed in refraction test using the Auto-Refraction(Speed -K model, Japan). The myopia, hyperopia, astigmatism, and anisometropia were defined as spherical equivalent(SE)≤-0.50 diopters, SE ≥+1.00 D, cylinder error ≥0.75 D and SE difference≥1.00 D between binocular eyes, respectively. Results. The refractive status by spherical equivalent among all subjects was myopia 61.43%, astigmatism 86.86%, emmetropia 19.18%, anisometropia 12.07%, and hyperopia 18.54. The prevalence of myopia and astigmatism were much more common in male. However, The hyperopia and astigmatism were much more common in female. The prevalence of spherical equivalent was much common from -0.50 diopter to -5.00 diopter. On the other hand, the prevalence of astigmatism and myopia was much more than hyperopia in all subjects. There was a statistical significance between OD and OS of the female and male in the spherical equivalent power(p<.000). However, there was not statical significant between female and male of OD and OS in the spherical equivalent power(p<.070). On the other hand, The prevalence of againest axis in astigmatism was more common in all subjects. In ADD power for the near vision correction, the female was much more diopter than male. Conclusions. These results suggested that the analysis of the refractive status on the presbyopia in Korea can give the useful diagnosis data for the correction of visual acuity at near distance.

• Journal of Biomedical Engineering Research
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• v.19 no.1
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• pp.9-18
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• 1998

In this paper, we present the degradation of focusing induced by velocity inhomogeneity in human tissue. For simulation, the fatty layer which is the major factor of degradation for its lower velocity, is modeled as a uniform velocity perturbation layer. And we simulate the degradation of resolution resulting from change of beam path due to refraction and the time delay due to velocity difference. We show that focusing error can be compensated for considering the velocity inhomogeneity only. The proposed compensation method can be operated in real time in the presently used digital focusing systems.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.4
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• pp.293-298
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• 2006

For this study, Clinical evaluation of the diverse Autorefractors was performed to examine validity and repeatability compared with subjective refraction. Measurements of refractive error were performed on 212 eyes of 106 subjects subjectivly noncycloplegic. Intersession repeatability of the Autorefractors were also assessed on all 106 subjects together with intersession repeatability on 7 to 14 days intervals. Spherical powers of subjective refraction and autorefractions by Autorefractors were analyzed by paired T-test.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.12
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• pp.164-175
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• 2008

Atmospheric effects on laser beam propagation can be broken down into two categories: attenuation of the laser power and fluctuation of laser power due to laser beam deformation. Attenuation consists of scattering of the laser light photons by the fog. Laser beam deformation occurs because of small-scale dynamic changes in the index of refraction of the atmosphere. This causes pointing error. In order to analyse these effect on optical wireless communication system, in this paper uses cassegrain optics as a transmitting and receiving telescope, AID as a detecting device and ill as a light source. The signal modulating and demodulating method is a IM/DD. I show the effects of fog and pointing error and calculate the possible communication distance for BER is $10^{-9}$.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.3
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• pp.201-206
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• 2006

The purpose of this study is observed effect of cycloplegia in emmetropia with use of cycloplegia. We examined the naked visual acuity, mainfest refraction, 105eyes with emmetropia(under SE ${\pm}0.50D$, Cyl ${\pm}1.00D$) after the use of cycloplegia. We used Nidek ARK-700 autorefractometer. Sexual difference of mainfest refraction error showed in male -0.67D, female -0.92D and difference of the CR and the MR male 0.5D, female 0.81D the total mean 0.69D. The naked visual acuity were in male 0.82, female 0.74, total mean 0.77. Age comparison, difference CR and MR were total mean 0.69D and 13 years group 1.1D were the highest. The naked visual acuity were in the highest 10 years group 0.86. Effect of cycloplegia was $0.69D{\pm}0.79$ in emmetropia and visual acuity was $0.77{\pm}0.21$. The optician, it will not be able to use cycloplegia, must pay attention spectacle prescription unnecessary and over correction in condition below -0.75D MR, above 0.77 visual acuity.

• Journal of Korean Clinical Health Science
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• v.5 no.1
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• pp.808-815
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• 2017

Purpose. To analyze the refractive status between urban and rural regions, of children in Korea, in the age group of 13. Methods. From October 2016 to January 2017, forty subjects( 20 male subjects, 20 female subjects; 13 years) were performed in refraction test using the Auto-Refraction. Myopia, hyperopia, astigmatism, and anisometropia were defined as spherical equivalent(SE)${\leq}-0.50$ diopters, SE ${\geq}+1.00D$, cylinder error ${\geq}0.75D$ and SE difference${\geq}1.00D$ between binocular eyes, respectively. Results. The refractive error by spherical equivalent among all subjects was myopia 76.25%, astigmatism 35%, emmetropia 16.25%, anisometropia 8.75%, and hyperopia 5%. The prevalence of myopia and astigmatism were much more common in urban than rural region although the difference was not statically significant. Emmetropia and astigmatism were much more common in rural region than urban although the difference was not statically significant. The prevalence of spherical equivalent was much common from -1.00 diopter to -4.00 diopter. On the other hand, the prevalence of myopia was much more than hyperopia. There was a statistical significance between OD and OS of rural region in the spherical equivalent power(p<.000). Also, There was a statistical significance between OD and OS of urban region in the spherical equivalent power(p<.004). Therefore, there was a significant statistical similarity between urban and rural regions on the OD and OS in the spherical equivalent power. On the other hand, There was a significant statistical similarity between urban and rural regions of the OD and OS in the astigmatism power(p<0.000). However, in the rural and urban regions there was not statistical significance in the OD and OS concerning the spherical equivalent power and astigmatism power (p>0.1). Conclusions. Myopia was the most common refractive error in Korea young children. while hyperopia was few. There was not a statistical significance as age between rural and urban at spherical equivalent power( P> 0.01). These results suggested that the analysis of the refractive status at young children can give the useful diagnosis data for the correction of visual acuity.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.201-206
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• 2010

Purpose: This study was to know the correlation among the dimensions of ocular components and refractive error on kindergarten children. Methods: The subjects were 80 preschool students who had no eye diseases. The refraction, corneal diopter, corneal radius, inter-pupillary distance, axial length, anterior chamber depth and dominant eye were measured and analysed. Results: It was shown that the highest correlation was between the axial length and the corneal diopter (r=-0.674, p=0.000). The ratio of height, weight and axial length (AL) to Corneal radius (CR) ratio were positively correlated with the axial length (r=0.351, r=0.408, r=0.488). The spherical equivalent of the refractive error and the corneal diopter were negatively correlated with the axial length (r=-0.302, r=-0.674). The anterior chamber depth and the corneal diopter were positively correlated with the AL/CR ratio (r=0.422, r=0.280). The spherical equivalent of the refractive error and the corneal radius were negatively correlated with the AL/CR ratio. Conclusions: It was shown that the AL/CR ratio was a very important indicator for diagnosing the refractive error of the preschoolers.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.1
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• pp.59-65
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• 2012

Purpose: The purpose of this study was to determine the distribution and correlation of accommodative lag with refractive error. Method: We had tested the clinical refraction and the accommodative lag in clinically normal 49 young adults (total 98 eyes) aged 18 to 25 years without abnormal binocular function. Monocular and binocular accommodative lag were tested with 0.50 D cross-cylinder lens and near vision test chart which had cross-hairs after full correction of LogMAR visual acuity over 0.05. Results: There was no statistical differences in monocular accommodative lag between right ($0.64{\pm}0.64$ D) and left eye ($0.63{\pm}0.64$)(p=0.858). The accommodative lag of male was higher than female and the range of the value was broader than female in binocular accommodative lag (p=0.015). The wider the inter-pupillary distance was, the higher the accommodative lag was (p=0.003). However, there were no differences with age (p=0.800) and dominant eye (p=0.402). The ranges of accommodative lag of low, middle, and high myopia were 0.75 ~ -0.25 D, 1.25 ~ -0.50 D, and 1.50 ~ -0.75 D, respectively, and the regression was 'y = -0.03953x+0.09205'. Conclusions: These data suggest that clinically normal young adults with high amounts of refractive error have more variable accommodative lag and increased spherical equivalent refraction.