• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.353-362
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• 2014

Purpose: The present study was aimed to investigate the change of higher-order aberrations induced by aging and the effect of myopic degree on the correlation between age and higher-order aberrations. Methods: The higher-order aberrations in 931 eyes aged from 20 to 60 were measured by using a LADARWave device employing Hartmann-Shack system to analyze the effect of myopic degree measured by manifest refraction test on higher-order aberrations. Results: Coma and vertical coma aberrations were significantly decreased by the increase of myopic degree while vertical astigmatic aberration was significantly increased. The correlations of age and coma, vertical coma, spherical, vertical trefoil, horizontal trefoil, vertical astigmatic, horizontal astigmatic and vertical tetrafoil aberrations depended on the myopic degree, except for horizontal coma and horizontal tetrafoil aberrations. Conclusions: It is suggested to consider the myopic degree for the refractive correction including the laser surgery based on the present result that higher-order aberrations are affected by the myopic degree.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.199-206
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• 2014

Purpose: The present study was aimed to investigate the correlation between higher-order aberration and myopic degree by the analysis of fluctuation of high-order aberration according to the change of myopic degree in certain ranges of myopia and astigmatism. Methods: The high-order aberration in a total of 992 eyes was analyzed by using a LADARWave device employing Hartmann-Shack system, and the relation between high-order aberration and myopia by the change of myopic degree through manifest refraction test. Results: In all subjects, spherical aberration and total coma aberration were significantly increased by the increase of myopic degree, however, trefoil aberration and astigmatic aberration and tetrafoil aberration were decreased. With the group of lower myopic degree, the change of coma aberration was greater by myopic degree and its change was significantly different. The change of spherical aberration by myopic degree was greatly large in the a group of -3.00 D or more and the group of -6.00 D or more where as its change was not large in the group of lower than -3.00 D. The significant decrease of coma aberration was observed only in the group of astigmatic degree of -1.00 D or less when analyzing the correlation between the higher-order aberrations and myopia in the certain groups of astigmatic degree. In the case of spherical aberration, the significant change was shown in all astigmatic groups, however, its increase was larger with the increase of myopic degree in lower degree of astigmatism. The consistent relationship in variations of horizontal and vertical coma aberration in certain myopic and astigmatic groups was neither established nor statistically significant. Conclusions: It is concluded that the correlation between the higher-order aberration and low-order aberration obtained from the results of the present study can help the understanding related to vision quality and the improvement of vision quality.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.129-133
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• 1999

For the myopia eyes of the people which are ametropia, the classified distribution has showed % for the simple myopic, 50% for the compound myopic astigmatism, 15% for the simple myopic astigmatism and 19% for the mixed astigmatism. The myopic ametropia for the both eyes has the distribution of 35% for -0.50D~-2.00Dptr, 54% for -2.00~6.00Dptr, and 11% for over -6.00Dptr. The classifying distribution for the age for the myopic ametropia was 54% for 15~20, 22% for 21~40, 14% for 41~60 and 10% for 61. The occupational distribution for the myopic ametropia has showed 61.5% for the student(Middle, High, College), 13.5% for the office worker, and 15% for the house wives as well as the small business. The hour affecting the refraction most for a day was after P.M. 7 which recorded 45% as the highest value. The reason is that the myopia degree decreases in the morning as the cornea flats and the situation is reversed in the afternoon so that there is a difference of Sph -0.50D and as getting darker the refraction degree of the light coming through the enlarged pupil refraction around the cornea is high. For the seasons the highest myopic degree has been recorded for 68% in the summer due to the shortage of nutrition and the climination inside the body by the exhaustion of sweat. In the blood types A and B are distributed closely as 34% and more active man with O has recorded higher myopic degree than woman. However woman showed higher accommodation power than man regardless the blood types. In the characteristic factors of myopic eye, the character feels fatigue easily has showed the distribution for 42% which is the highest and it could be classified largely by two the.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.1
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• pp.85-91
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• 2013

Purpose: The purpose of this study is to investigate difference between manifest refraction (MR) and cycloplegic refraction (CR) with age and myopic value. Methods: Manifest and cycloplegic refractions were carried out on the patients of 229 myopic patients ($25.3{\pm}11.9$ years old). Results: The average results from a pre- and a postcycloplegic refraction showed a reduction of 0.19 D in myopia, 0.02 D in astigmatism and $1.85^{\circ}$ in astigmatism direction. Change of myopic value was higher in 30~40 age. Total 73 eyes of 229 patients who showed 0.50 diopter (D) in spherical, and a high degree of myopia group showed a higher discrepancy rate. Conclusions: The results found in the comparison of the value of the manifest refraction and cycloplegic refractions showed changes of myopic value was not significant with age of patient, but the group of high degree of myopia showed higher discrepancy rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1747-1754
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• 2013

We evaluate the impact of near work has on myopia and how they differ across generation. The study subjects were 201(83 males and 118 females) adults who live in Cheongju and Daejeon. Myopia was defined as more than or equal to (-)2.50D. The subjects were divided myopic and control group. The surveys and eye tests that are related to near work and refractive error were conducted and the relationship between the degree of myopia and near work was investigated. Then, the groups were divided into people in their 20s and 30s and the comparisons were made again. The survey results showed significant differences between myopic and control groups that depended on: hours spent in school and outdoor activities during high school period, degree of refractive error caused by level of exercises during the junior high school and high school years, refractive error based on the type of high schools, also hours spent in school and outdoor activities. When the same question was done on the group in their 20s and 30s, there was a different outcome in trends between the groups and refractive error depending on whether they exercised. The degree of near work is one of the environmental risk factors that affect myopia and must be considered when studying myopic progression. However, when discussing specific behavioral patterns in relations to myopia prevention, culture and visual environment of a given generation must also be considered.

• Journal of Digital Convergence
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• v.13 no.12
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• pp.285-290
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• 2015

The purpose of this study is to compare the status of eyesight according to the change of astigmatism axis in myopic astigmatism and to minimize errors in making astigmatic glasses based on accurate optometry and prescription. The subjects were 93 males and females(186 eyes) who have myopic astigmatism without any ocular disease or systemic disease. We performed comparative analysis on the status of visual acuity according to the change of astigmatism axis to 5, 10 and 15 degree in corrected eyesight 1.0. The direct astigmatism was the most common astigmatism type among the 186 eyes. After all subjects were perfectly corrected into 1.0, the change of astigmatism axis affected eyesight; The results suggested that the more change was made in astigmatism axis, the worse their eyesight would become. The main astigmatism type was changed from direct astigmatism to inverse astigmatism as age increased. The change of the astigmatism axis resulted in failing of corrected eyesight. Therefore, the convergence of examination and correction for astigmatism strength and axis is necessary when conducting refraction inspection for astigmatism.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.4
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• pp.119-125
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• 2007

The aim of the present study was to compare the contrast sensitivity of soft contact lens wearers, spectacle wearers or emmetropia. Seventy myopic eyes and thirty emmetropic eyes aged 19 to 26 years were collected. The myopic group included 48 eyes corrected with spectacle lenses and 22 eyes of them corrected with contact lenses, too: all had corrected vision acuity of 20/20 or better. Spatial contrast sensitivity was measured using the OPTEC 6500 contrast sensitivity view-in tester included the EyeView　 Functional Vision Analysis software at photopic or mesoopic condition. There was no significant difference in contrast sensitivity between spectacle lenses and emmetropes. Myopes corrected with soft contact lenses showed statistical sensitivity losses at 1.5, 12 cycle/degree spatial frequencies. In conclusion, our findings suggest that loss of contrast sensitivity in soft contact lens wearers might be interpreted as evidence for corneal disruption before corneal pathological events occur in contact lens wearers. Contrast sensitivity testing appears to be a useful method for evaluating soft contact lenses.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.443-451
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• 2018

Purpose : To find out the reliability of autorefractometer after laser refractive surgery Methods : We measured and compared spherical and cylinder powers of those undergone LASEK surgery with 1.0 of naked vision after at least 3 months of the surgery with an autorefractometer(CANON Full Auto Ref-Keratometer RK-F1, Japan) and a retinoscope(Streak Retinoscope 18200, WelchAllyn, USA), and also applied spherical equivalent powers. The refractive status before surgery was divided into high, medium, and low myopia according to the results measured using an autorefractometer, and then analyzed again the reliability of the autorefractometer after surgery according to the preoperative refractive status. The agreement of two methods was identified using Bland-Altman(Bland-Altman limits of agreement(LoA)). Results : After the surgery, when comparing spherical, cylinder and equivalent powers in the whole data measured by autorefractometry and retinoscopy significant differences were found(p<0.01). According to the degree of refractive errors, all sort of refractive errors was shown significantly different(p<0.01) except for cylinder power of the medium myopia. In general, the refractive errors especially spherical and spherical equivalent powers by autorefractometry were shown a myopic trend from -0.38 D to -0.53 D. On the other hand, it was shown a hyperopic trend of approximately +0.30 D using retinoscopy. In comparison of two objective refractions, it was shown a myopic trend as $-0.51{\pm}0.45D$(LoA +0.36 D ~ -1.39 D) and compatible. Conclusion : Even though it would be positive in terms of compatibility of the methods, it is necessary that the glasses should be prescribed by subjective refraction since autorefractometry is shown myopic in those undergone the surgery and suffering from myopic regression.

• East Asian Economic Review
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• v.25 no.3
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• pp.310-336
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• 2021

We use iterative numerical procedures combined with analytical methods due to Rapach and Wohar (2009) to solve for the dynamic asset allocation strategy for optimal portfolio demand. We compare different optimal portfolio demands when investors in each country have different access to overseas and domestic investment opportunities. The optimal dynamic asset allocation strategy without foreign investment opportunities leads domestic investors in Korea, Hong Kong, and Singapore to allocate more funds to domestic bonds than to domestic stocks. However, the U.S. investors allocate more wealth to domestic stocks than to domestic bonds. Investors in all countries short bills at a low level of risk aversion. Next, we investigate dynamic asset allocation strategy when domestic investors in Korea have access to foreign markets. The optimal portfolio demand leads investors in Korea to allocate most resources to domestic bonds and foreign stocks. On the other hand, the portfolio weights on foreign bonds and domestic stocks are relatively low. We also analyze dynamic asset allocation strategy for the investors in the U.S., Hong Kong, and Singapore when they have access to the Korean markets as overseas investment opportunities. Compared to the results when the investors only have access to domestic markets, the investors in the U.S. and Singapore increase the portfolio weights on domestic stocks in spite of the overseas investment opportunities in the Korean markets. The investors in the U.S., Hong Kong, and Singapore short domestic bills to invest more than initial funds in risky assets with a varying degree of relative risk aversion coefficients without exception.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.361-370
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• 2004

The purpose of this study was to evaluate the outcome and Factors that influence the quantity of Phoria in the low correction and perfect correction. Also the coincidence with the opticenter and the pupillary distance was a principal factor that influence the quantity of Phoria. Thereupon, this study is attributed to promote the perfect Phoria test. The subjects for this study were 120 persons(240 eye) in myopic refractive errors. ISP/WIN program was used for the data analysis. The collected data was analyzed by descriptive statistics and Spearman's correlation coefficient. The results of this study were as follows: 1. The prism pattern was difference between low correction and perfect correction in the Phoria test. The proportion of orthophoria was changed from 10.0% to 12.5%, exophoria was changed from 67.5% to 62.5%, and esophoria was changed from 22.0% to 32.5%, respectively. 2. The average of optical center distance and pupillary distance were 31.70mm and 31.49 mm, respectively. 3. Among the 120 myopic glasses wearers, the distance between optical centers was coincided with the pupillary distance in 37.5%, and discrepant in 62.5%. 4. For the patients who were coincided with the pupillary distance, the proportion of exophoria decreased 53.33%, esophoria increased 20.0%. 5. For the changing of the quantity of Phoria in the low correction, the degree of exophoria decreased 1.11 prism diopters in the perfect correction, esophoria increased 0.39 prism diopters.