• Journal of the Korea society of information convergence
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• v.6 no.1
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• pp.37-41
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• 2013

In this study, by using the Oculus Pentacam, we analyzed the relationship of corneal front astigmatism corneal and the radius of curvature of the rear face of the 20's to 40's. The vertical radius of curvature were man 7.94mm (${\pm}0.22$), women 7.87mm (${\pm}0.21$), the horizontal radius of the anterior corneal appeared man 7.69mm (${\pm}0.27$), women 7.63mm(${\pm}0.23$). And rear vertical radius of curvature were man 6.52mm(${\pm}0.23$), woman 6.55mm (${\pm}0.22$), the horizontal radius of the anterior corneal appeared man 6.06mm (${\pm}0.24$), woman 6.08mm(${\pm}0.24$). The results of correlation analysis between the radius of corneal posterior surface and the anterior corneal surface, it was found out that there is a significant correlation. In this study, similar results were obtained anterior surface of the cornea, the radius of curvature of the rear surface, the refractive power, and astigmatism, as other papers that have been reported. But in this paper, the cornea thickness was thicker than other previously reported paper.

• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.145-150
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• 1998

To 160 persons(90 men, 70 women) who went to the national hospital of Solok-island with Hansens's disease, I tested the objective refracts test with the product of Cannon Ltd. Co. which RK-3 Auto Ref-keratometer's auto ophthalmoscope. The results were like these. Visual acuity of above 0.7 that can live without glasses was contained 44 men's eyes(24.4%) and 19 women s eyes(13.6%). These result are indicated that men have had more good visual acuity than women. Visual acuity of below 0.6 that cannot do normal life was contained 80.3% of the total patients. And amblyopia of below 0.3 and eyes which cannot be corrected were shown 44.4%(80 men's eyes and 55.7% 78 woman's eyes). Myopia was contained 119 eyes(43), hyperopia was contained 139 eyes (50.4%) and emmetropia was 6.5%. Astigmatism was shown 136 men s eyes (86.6%) and 97 women's eyes(81.5%). These results are indicated what many people accompany with astigmatism. And these ratio had some high percentages men rather than women. Direct astigmatic was contained 37 eyes (11.6%), Indirect astigmatic 81 eyes(25.3%) and Oblique Astigmatic 115 eyes(35.9%). As a of distributed result oblique astigmatic occupied best high point as 49.4% in 233 astigmatism and distributed the opposite direction as compared with normal irregular emmetropia not patient.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.281-286
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• 2010

Purpose: This research provided basic data for refraction by comparing the corrected diopter of trial lens and phoropter. Methods: We compared the corrected diopter of trial lens and phoropter, and analyzed statistical significance and relations of the spherical lens corrected diopter and cylindrical lens corrected diopter according to the types (trial lens and phoropter) of subjective refractive instruments. Also we analyzed statistical significance and relations between cylindrical lens corrected diopter at the astigmatism and the types (trial lens and phoropter) of subjective refractory instruments. Results: When we measured the corrected diopter of simple myopia, the mean value for corrected diopter was S-2.74D using the trial lens and S-2.65D using the phoropter. So the corrected diopter was 0.09D smaller when measured by phoropter. The degree of astigmatism was measured C-0.81D using the trial lens and C-0.77D using the phoropter which showed that the measured value was 0.04D smaller using the phoropter. On correlation analysis between the refractive instruments (trial lens and phoropter) and the corrected diopter, there was significant (p<0.01) strong correlation between refractory machine and corrected spherical diopter (r=0.996) and the correlation between refractory machine and corrected cylindrical diopter was r=0.986 and was also significant (p<0.01). Conclusions: The use of phoropter than trial lens was more desirable when performing refraction on high myopia (simple refractive error, high astigmatism), and when using trial lens, you should consider the vertex distance and the gap between overlapped lenses before prescription.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.3
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• pp.271-277
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• 2013

Purpose: The purpose was to study the corneal refractive power changes associated with the wearing of everted silicone hydrogel soft lenses. Methods: The corneal refractive power and corneal astigmatism were measured using corneal topographer (CT-1000, Shin-nippon Co., Japan) for checking change of corneal refractive power and objective refractive error was measured by auto-refractometer (Natural vision-K 5001, Shin-nippon Co., Japan). We measured at baseline and 1 week after lens wearing. Results: The correcting of corneal refractive power could be effective in low myopia. It's more effective to the higher power of greatest meridian of cornea and the more corneal astigmatism. 73% of subjects' refractive error was decrease less than 1 D and 17% of the subjects had an reverse effect (increase) occurs. The reduction of objective refractive error was more effective when cornea refractive power was great or corneal astigmatism was much. Conclusions: Pressure which the everted silicone hydrogel lens to the cornea could be caused. It occurred as the degrees of corneal power, corneal astigmatism and objective refractive error differences. Selection of an appropriate subject is important considering difficulty of changing the parameters of the lens.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.3
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• pp.247-251
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• 2013

Purpose: To analyse the addition power of new wearer of progressive addition lenses. Methods: Data of 636 subjects who have been prescribed progressive addition lenses as the first time were used for analyse. The range of age for was between 41~78 years old and they visited the optical practice in Gwangju metropolitan city from 2001 to 2013Date of refractive state, gender and age were analysed. Results: The difference of addition by gender was 1.71 D in male and 1.67 D in women. The difference of addition by refractive error was 1.67 D in emmetropic patients and 1.74 D in myopic patients, 1.90 D in hyperopic patients. The difference of addition by age was1.26 D in 41~44 years old sge group, 1.48 D in 45~49 years old age group,1.72 D in 50~54 years old age group 1.84 D in 55~59 years old age group, 2.10 D in 60~64 years old age group and 2.43 D in over 65 years old age group. The difference of addition by diopter in myopic patients was 1.58 D in low myopic patients and 1.48 D in middle myopic patients, 1.67 D in high myopic patients. The difference of addition by axis of astigmatism was 1.80 D in with-the-rule astigmatism, 1.64 D in against-the-rule astigmatism and 1.65 D in oblique astigmatism. Conclusions: The Addition power of progressive lenses were different according to the types of refractive error, astigmatism axis and age.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.2
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• pp.29-36
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• 2008

Purpose: We have evaluated both the reliability and accuracy of refractive measurement from autorefractor by comparing with subjective refraction data. Methods: Measurements of refractive error were performed on 198 eyes of 99 subjects in noncycloplegic condition. Also we analyzed refraction results and evaluated repeatability and accuracy of subjective refraction and autorefraction. Furthermore we analyzed accuracy of autorefractor by Fourier analysis. Results: Reliability coefficient of the autorefraction for the right eye were determined to by 0.993, 0.974 and 0.925 respectively, in the spherical, cylinderical component and cylinderical Axis. Also, the reliability coefficient of the autorefraction for the left eye were found to be 0.991, 0.948 and 0.886, respectively, in the spherical, cylinderical component and cylinderical Axis. From the Fourier analysis no statistically significant differences in $J_{0}$ component were found between the auto and subjective refraction measurements (p>0.05) whereas difference of refractive power of $J_{45}$ component when compared with the subjective refraction were -0.019, -0.164. Conclusions: We conclude that autorefractormeter can be effectively used to measure the refractive power within the error limits.

• Journal of Biomedical Engineering Research
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• v.20 no.1
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• pp.45-51
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• 1999

The purpose of this study is to investigate the effects of various factors in keratotomy for astigmatism correction on surgical outcomes by finite element method as well as animal experiments. Three kinds of surgical techniques were mechanically investigated : arcuate, straight, and inverse arcuate keratotomy. Among the three techniques the arcuate keratotomy is the most popular one while the other two techniques are being investigated in this area. The arcuate keratotomy was found to be more controllable and effective in reducing the refractive power than the others. In arcuate keratotomy it was found most effective when the incision was located in the middle position between the apex and the edge of the cornea from the results of experiment as well as finite element study. Regarding to the range of the corneal incision in arcuate keratotomy, the incision angle of 90$^{\circ}$ was found th be most effective in reducing refractive power than other angles even it was incised up to 150$^{\circ}$. Therefore, it was concluded that 90$^{\circ}$ of incision angle results in the largest decrease in refractive power in arcuate keratotomy. However, other important findings were that the effect of the surgery decreased with time so the visco-effect of the cornea and auto-healing process. Therefore, these factors should be considered in future studies.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.169-175
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• 2003

This research reviewed that 83 male subjects. 89 female subjects of middle and high school visited D Optical shop at the downtown of Daegu more than twice from January, 1999 to January, 2003 and obtained the following results by using the visual acuity prescription of them for which D Optical shop was keeping. 1. The classification of correction power for 190 myopia eyes was examined (87 male eyes, 103 female eyes) showed 89 eyes(46.82%) between $0.25D{\leq}3.00D$, 86 eyes(45.26%) between $3.25D{\leq}6.00D$, 15 eyes(7.89%) for over 6.25D. 2. The kind of 154 astigmatism subjects(79 male eyes, 75 female eyes) was direct astigmatism 83.77%, reverse astigmatism 11.69%, oblique astigmatism 4.55%. The cylindrical correction power for astigmatic eyes was 61 eyes(39.61%) between $0.25D{\leq}0.50D$, 60 eyes(38.96%) between 0.50D<1.00D, 121 eyes(78.57%) for less than 1.06D, 6 eyes(0.65%) for over 3.00D. 3. The variation of spherical power showed 161 eyes(46.80%) between $0.00D{\leq}0.50D$, 109 eyes(31.69%) between $0.51D{\leq}1.00D$, 17 eyes(4.94%) for over 2.01D variation. 4. The variation of astigmatic power showed 92 eyes(59.74%) between $0.00D{\leq}0.50D$, 39 eyes(25.32%) between $0.26D{\leq}0.50D$, 10eyes (6.49%) between $0.51D{\leq}0.75D$, 13 eyes(8.44 %) for over 0.76D astigmatic variation. 5. The variation of equivalent spherical power showed 137 eyes(39.83%) between $0.00D{\leq}0.50D$, 126 eyes(36.63%) between $0.51D{\leq}1.00D$, 40 eyes(11.63%) between $1.01D{\leq}1.50D$, 21 eyes(6.10%) between $1.51D{\leq}2.00D$, 20 eyes(5.81%) for over 2.01D variation.

• Journal of Korean Ophthalmic Optics Society
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• v.2 no.1
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• pp.133-143
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• 1997

A population-based study of people aged above 20 years showed that 32% had emmetropia and 68% had ammetropia(myopia 56.6%. hyperopia 11.4%) city in Korea. The percentage of ammetropia in population based study is higher than that of clinic(O.P.D.) based. A 83.3% of the ammetropia had myopia. which is higher than 76.3% of 1968 and 76.9% of 1975 years. A 16.7% of the ammetropia had hyperopia. which is lower than 19.4% of 1968 and 17.3% of 1975 years. In the kind of refractive error. 32.1% of 985 eyes examined had compound myopic astigmatism. 18.2% had simple myopic astigmatism. 14.2% had simple myopia. 6.8% had simple hyperopic astigmatism, 5.0% had mixed astigmatism, 4.7% had compound hyperopic astigmatism and 3.6% had simple hyperopia. In the difference of binocular refractive error, 29% had 0.50~2.00 Dptr difference and 3.6% had difference above 2.00 Dptr. In age related myopic refractive error, 76.7% of people aged 20~29 years and 74.0% of 30~39 years had myopia. It is due to overstudy for entrance into a university that the percentage of myopia is higher than that of abroad. In age related hyperopic refractive error, 2.9% of people aged 20~29 years, 0.6% of 30~39 years. 6.3% of 40~49 years, 16.0% of 50~59 years and 63.9% of 60~69 years had hyperopia. It shows that the age related hyperopic refractive error was significantly increased at aged 40~49 years. The right eye had more myopic refractive error than left eye.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.357-363
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• 2013

Purpose: To investigate the visual function with prescription swimming goggles. Methods: 15 university students (mean age: $22{\pm}1.54$ years) participated, with a mean distance refractive error of RE: S-1.67 D/C-0.40 D, LE: S-1.70D/C-0.37 D. Inclusion criteria were no ocular pathology, able to wear soft contact lenses to correct their refractive error to emmetropia and able to swim. Participants were fitted with contact lenses to correct all ametropia. Subjective evaluation for satisfaction of visual acuity, asthenopia and balance were also measured using a questionnaire while wearing swimming goggles with cylinder (C+1.50 D, Ax $90^{\circ}$) compared with plano sphere outside the swimming pool area. Visual acuity was assessed using the same ETDRS chart. The prescription swimming goggles powers were assessed in random order and ranged in power from S+3.00 D to S-3.00 D in 0.50 D steps. Results: Subjective evaluation was significantly worse for the swimming goggles with cylinder than for the plano powered goggles for all 3 questions, visual acuity, asthenopia and balance. Visual acuity were significantly affected by the different power of the swimming goggles (p<0.05), but there was no significant difference between the in-air in-clinic and underwater in-swimming pool measures (p=0.173). However, visual acuity measured in the clinic was significantly better than underwater for some swimming goggle powers (+3.00, +1.00, +0.50, 0, -1.00 and -2.00 D). Conclusions: Wearing swimming goggles underwater may degrade the visual acuity compared to within air but as the difference is less than 1 line of Snellen acuity, and it is unlikely to result in significant real-life effects. Having an incorrect cylinder correction was found to be detrimental resulting in lower score of satisfaction. Considering slippery floor of swimming pool area, it can be a potential risk factor. Therefore, it is important to correct any refractive error in addition to astigmatism for swimming goggle.