• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.103-113
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• 1998

Until now, the study of eye refractive error examination for high school students are a few report that in Korea. In particular, there is few report about the visual power for same group during several years. We compared the study of refractive error done this year with that reported three years ago at the same high school. From the these data, the distribution of ammetropia was investigated. The study of refractive error for high school students was also compared with those reported before for the Adults and the middle school student. When the visual power is refered to spherical equivalent, the 36% of the whole students examined above had emmetropia and the other part of them fumed out to be ammetropia which is classify to 60.6% belonged to myopia and 4.4% belonged to hyperpia. The ratio of myopia for this year students is increased in comparision with the students in 1995. The ratio of emmetropia for this year students is 7.4% higher, and the ratio of myopia for this year students is 4% higher, but the ratio of hyperopia is very lower than that for the adults in 1997. In the kind of refractive error, it is classified that a simple myopia is shown to highest ratio as a 28.6% of 1212 eyes examined, a compound myopic astigmatism to the next high ratio as a 22.4%, a simple myopic astigmatism as 14.4%, a simple hyperopic astigmatism as 3.1%, a mixed astigmatism as a 1.7%, a simple astigmatism as 1.2%, a compound hyperopic astigmatism as 1.2%, respectively. The percentage of an astigmatism is a 76.7% of total eyes examined if Cyl-0.25 Dptr is included to an astigmatism. On the other hand, The percentage of an astigmatism is a 45.6% of total eyes examined if Cyl-0.25 Dptr is excluded to an astigmatism. In the kind of astigmatism, the number of students had an astigmatism with the rule is about 4.5 times than that of astigmatism against the rule. From the result of comparision the right eye with the left eye, the right eye of the students had more a myopic refractive error than the left eye, which is same as adults' case, there is no difference in a refractive error between the boy students and the girl students.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.455-462
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• 2004

In this paper, we measured and analysised the power change of tear lens for 85 patients - 170 myopia eyes - who are fitted using RGP lens, considering the BGR of RGP lens, the corneal astigmatism power, and corneal curvature. We got the following results from these experiments; 1. When the BCR of RGP lens changes, the diopters of tear lens of "on-k", 0.05Pt, 01.0Ft, 0.05St, and 0.10St are -0.25D, -0.46D, -0.63D, +0.07D, and +0.26D, respectively. 2. When the corneal astigmatism power changes, the diopters of tear lens of group below 0.75D, group of 1.00D~1.25D, group of 1.50D~1.75D, and group over 2.00D in "on-k" state, are -0.25D, -0.18D, -0.09D, and -0.39D, respectively. 3. When the corneal astigmatism power changes and the BCR of test lens is changed by 0.05mm step, the change values of tear lens diopter for 0.05St and 0.05Ft approximate to ${\pm}0.25D$, while these for 0.10St and 0.10Ft don't approximate to the value below ${\pm}0.25D$.[are irregular value below ${\pm}0.25D$.] 4. When the corneal curvature and the HCR of RGP lens change, the diopters of tear lens of group below 7.50mm, group of 7.55~7.80mm, group of 7.85~8.20mm, and group over 8.25mm in "on-k" state, are -0.40D, -0.11D, -0.20D, and -0.19D, respectively. 5. When the BCR of test lens is changed by 0.05mm step and the corneal curvature increases, the change values of tear lens diopter decrease, while these over 8.25mm are mean value ${\pm}0.17D$ and the value below ${\pm}0.25D$.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.2
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• pp.165-171
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• 2013

Purpose: This study are to analyze and to compare between pupillary size, reaction time, refractive error, corrected vision, dominant eye, static visual angle (SVA) and kinetic visual acuity (KVA) of male and female college students, to measure KVA of them in full correction and to identify changes of KVA by +0.50 D and -0.50 D spherical power addition respectively in full correction condition. Methods: KVA, SVA, pupillary size, reaction time, refractive error, corrected vision and dominant eye of 40 male and 40 female optical science students were measured by utilizing KOWA AS-4A, reaction time measurement program, subjective refractometer, and objective refractometer, and KVAs were measured when +0.50 D/-0.50 D were added in both eyes respectively. Results: Binocular KVA of whole subjects was $0.45{\pm}0.22$, and in monocular KVAs were $0.36{\pm}0.19$ for right eye and $0.34{\pm}0.19$ for left eye, and binocular KVA was significantly higher than monocular KVA. It appeared that the better SVA was, the better KVA was in significant way, and in terms of refractive error the less myopia amount was, the better KVA was, but it was not significant statistically. The lower astigmatism was, the slightly and significantly higher KVA was when dividing between equal or less than -1.00 D astigmatism group and over -1.00 D astigmatism group. In resulting from correction condition of refractive error KVAs were $0.45{\pm}0.22$ for full correction, $0.26{\pm}0.15$ for +0.50 D addition, $0.48{\pm}0.22$ for -0.50 D addition which indicates that KVA in over myopia correction was significantly the highest and followed by full correction and under correction. Similar findings were revealed in both male and female, and KVA of male was better than female in comparing between male and female. There was no significantly different KVA between dominant eye and non-dominant eye. Conclusions: Accordingly, it is concluded that KVA is related with far distance SVA, astigmatism amount, and refractive error amount except a dominant eye. Through this research, it was found that prescription for enhancing KVA is to make full correction or to overcorrect slightly myopia.

• Journal of Broadcast Engineering
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• v.17 no.2
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• pp.237-251
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• 2012

Recently, the direct terrestrial broadcasting reception has been reduced rapidly and not been improved even in digital broadcast environment. The distribution plan of 700MHz frequency band(Ch.52~69) will make the problem worse because the spectrum might be allocated to mobile communication use. In this paper, we investigated the efficient frequency usage for DTV signal reception improvement and next generation broadcasting. The frequency amount required for reception improvement and for next generation broadcasting service is presented. We estimated the beneficial effect when the spectrum(108MHz Frequency Width) is used for SFN transmission technology, UHDTV and Full-HD 3DTV.

• Electronics and Telecommunications Trends
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• v.30 no.3
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• pp.9-20
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• 2015

케이블방송망은 광대역을 가진 유선망이라는 매체 특성으로 동일한 망을 이용하여 방송뿐만 아니라 통신까지 제공할 수 있는 양방향 방송서비스를 가능케 하는 방송통신 융합을 위한 최적의 망으로 거론되고 있다. 서비스 관점에서 케이블방송망은 도입초기 단순히 지상파 방송의 난시청 해소를 위한 수단이었으나 프로그램 공급업자와 종합 유선 방송국의 등장으로 독립적인 방송 매체로 발전하였으며, 북미 주도하에 1990년대 중반 통신법이 개정된 이후 양방향 고속 데이터서비스를 제공할 수 있는 방안으로 케이블 모뎀(CM: Cable Modem)을 개발하여 방송과 통신을 동시에 수용하는 통합망으로 발전시켜왔다. 최근 케이블방송은 전송 효율 고도화, 망 구조적 진화 및 대용량 콘텐츠 전송으로 크게 3개의 방향으로 발전을 거듭하고 있다. 본고에서는 각 발전 방향에서 제시하는 차세대 케이블방송의 기술개발 및 표준화 동향에 대해 살펴보고자 한다.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.469-476
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• 2012

Purpose: The purpose of this study is to investigate the changes of asphericity according to diameter and direction of the cornea. Methods: The changes of asphericity according to diameter and direction of cornea is measured by using Pentacam(Oculus Co., Germany), as targeting 57 adults (average $27.0{\pm}4.8$, 20 men, 37 women) without any ophthalmic diseases, which may be effective in eyesight, and refractive surgery. Results: As diameter increases in every direction based on the corneal vertex, asphericity has attentively increased (p<0.05), and the size of asphericity in each direction from every measured diameter showed as superior > nasal > inferior > temporal. In group comparison by nearsightness and astigmatism level, asphericity measured high when nearsightness and astigmatism levels were higher, and this appears to be statistically attentive.(p<0.05). Conclusions: Asphericity of cornea significantly increased according to increase of diameter of cornea, and as measured figure or increased quantity appeared differently in all directions based on corneal vertex, so it helps to understand shape of cornea, and considered that is the part to be considered during manufacturing and fitting of RGP lenses.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.449-456
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• 2013

Purpose: The present study aimed to investigate the effects of corneal eccentricity and shape on the rotational pattern of toric soft lens by the postural change of lens wearers. Methods: The corneal eccentricity of 41 eyes (aged 20s) having -1.0 D with-the-rule corneal astigmatism (WRCA) was measured, and then toric soft lenses were fitted with the amount of total astigmatism. In lying and straight postures, the rotation of toric soft lenses was recorded by a camera attached to slitlamp and analyzed. Results: Most toric soft lens designed with accelerated stabilization rotated to the temporal direction, which was the lying position direction, regardless of corneal eccentricity, and some lenses rotated to the nasal direction for high corneal eccentricity and corneal type of asymmetric bowtie. There was no correlation between the amount of rotation and corneal eccentricity right after of contact lens wearing in straight and lying posture, however, the amount of rotation was the greater for the cornea with the higher eccentricity after the subjects laying down for some period. The speed of lens rotation started to decrease after the subjects laying down, but the speed was not different according to corneal eccentricity difference. The amount of lens rotation for symmetric and asymmetric bowtie-typed corneas increased more than it for oval-typed cornea, and it was same even with time elapsing. The speed of lens rotation in lying posture was the slowest in asymmetric bowtie-typed cornea compared with other corneal types. Conclusions: From the present study, it was revealed that the rotational pattern of toric soft lens was affected by corneal eccentricity and corneal shape when the wearer's posture changed. Thus, it should be considered for the development of the fitting guideline and the design of toric soft lens.

• 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 Sericultural and Entomological Science
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• v.2
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• pp.41-47
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• 1962

This work was carried out to investigate the phenotypic, genotypic, and environmental correlations between the number of the egg markings and other metric characters, and their heritability, with eight varieties in Bombyx mori L. Five European varieties, ten Chinese varieties and ten Japanese varieties were used to know the average number of the egg markings and their variabilities for each strains. The results may be summarized as follows: 1) there were highly negatively phenotypic and genotypic correlations between the number of the egg markings and total cocoon weight, weight of cocoon layer, or denier, but not an environmental correlation. 2) The average number of the egg markings in Chinese strain was more than that in other strains. 3) The correlation between the motality and the number of egg markings seemed not to be found. 4) The heritability of the weight of cocoon layer and the bave length was less than that of total cocoon weight, denier and number of egg markings. 5) The more the number of the polyhedral particles in an egg marking group became, the more the total number of egg markings increased. 6) The variation of the number of the egg markings in European strain was larger than that in any other strains. 7) It is expected that the selection for the number of the egg markings may have genetic advances of total cocoon weight, weight of cocoon layer, or denier. Especially the selection for the number of the egg markings before rearing will save the silkworm rearing cost.