• Journal of Korean Ophthalmic Optics Society
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• v.20 no.4
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• pp.501-509
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• 2015

Purpose: To evaluate the reliability of refractive power by comparing the marked refractive power in an automatic phoropter and actually measured spherical/cylindrical refractive power. Methods: Actual refractive power of minus spherical lens and cylindrical lens in an automatic phoropter was measured by a manual lensmeter and compared with the accuracy of marked refractive power. Furthermore, combined refractive power and spherical equivalent refractive power of two overlapped lenses were compared and evaluated with the refractive power of trial lens. Results: An error of 0.125 D and more against the marked degree was observed in 70.6% of spherical refractive power of spherical lens which is built in phoropter, and the higher error was shown with increasing refractive power. Single cylindrical refractive power of cylindrical lens is almost equivalent to the marked degree. Combined spherical refractive power was equivalent to spherical refractive power of single lens when spherical lens and cylindrical lens were overlapped in a phoropter. Thus, there was no change in spherical refractive power by lens overlapping. However, there was a great difference, which suggest the effect induced by overlapping between cylindrical refractive power and the marked degree when spherical lens and cylindrical lens were overlapped. Spherical equivalent refractive power measured by using a phoropter was lower than that estimated by trial glasses frame and marked degree. The difference was bigger with higher refractive power. Conclusions: When assessment of visual acuity is made by using an automatic phoropter for high myopes or myopic astigmatism, some difference against the marked degree may be produced and they may be overcorrected which suggests that improvement is required.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.231-237
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• 2014

Purpose: This study is research of the conditions which causes difference between the refractive power of the measurement of autorefractometer and the prescription using phoropter. Methods: Autorefractometer (SR-7000) and phoroptor (AV-9000) were used to measure 60 eyes of 30 participants who had no eye diseases and wore the corrective lens due to Ametropia. To prevent the dependence of the prescription value of the refractive power on the testers, two testers measured the refractive power of the eyes of the participants at the same measuring conditions. Results: Statistically, the prescribed values of the refractive power by two testers were not significantly different. Most of the prescribed values of the refractive power were smaller than the refractive power by autorefractometer In case of myopic eyes, the difference between refractive powers by the measurement of autorefractometer and the prescription using phoropter showed the trend of increase as the spherical refractive power became larger. The result was analyzed by the range of the different cylindrical refractive power for the myopic astigmatic eyes. In this case, the difference between refractive powers showed the trend of decrease as the cylindrical refractive power became larger. Conclusions: No difference between the prescribed value by two testers was observed. In case of myopic or myopic astigmatic eyes, the difference between refractive powers by autorefractometer and the prescription were measured to be approximately proportional to the refractive powers of ametropic eyes. As the this difference become larger for the participant who needs the lens of larger refractive power, additional caution is needed in the prescription of the refractive power of the corrective lens.

• International Journal of Advanced Culture Technology
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• v.6 no.4
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• pp.71-79
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• 2018

For 299 patients who had undergone cataract surgeries we investigated the difference in visual acuity and refractive power before and after cataract surgery and the clinical change of the visual acuity and the refractive power according to age, gender, hospital visit time and specific medical history. We found the factors affecting preoperative and postoperative outcomes of the cataract patients in metropolitan hospitals by input, process, and outcome and analyzed medical characteristics and patient characteristics as the input variables. T-test and ANOVA have been performed for statistical analysis of functional status, and general status and the technical characteristic as the process variable and the outcome variable of diagnosis. Visual acuity improved significantly in patients who had undergone cataract surgery. However, the change in refractive power did not show a statistically significant difference but only a slight difference. The improvement of male patients was greater than that of female patients. The difference in age was more effective in patients under 50 years old and the effect of cataract surgery was relatively high in patients without the presence of specific medical history. Cataract surgery did not seem to help all of the patients, but it is more effective in improving visual acuity and refractive power. We conclude that simultaneous cataract surgery in both eyes is reasonable in order to have at least the better effect.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.417-421
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• 2004

We can see that two images of reflection are observed on the surface of a ophthalmic lens. These are the image reflected from front surface and back surface of lens, respectively. The reflective image shows to be affect by surface refractive power of front and back surface of lens. Total refractive power of lens is calculated by refractive power of front and back surface of lens. Accordingly, the ratio of image on the lens surface is able to measure refractive power of ophthalmic lens without helping of the lensmeter. The ratio of two reflective image measured on the lens surface is compared with the calculated ratio by the power measurement.

• 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 Digital Convergence
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• v.12 no.12
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• pp.485-490
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• 2014

The purpose of this Study investigated corneal power, corneal astigmatism and corneal axis according to spherical equivalent of refractive error. We measured spherical equivalent, corneal power and corneal astigmatism in 100 subjects from January 2014 to July 2014. Measured spherical equivalent of refractive error were $-3.01{\pm}3.79D$, corneal power of $43.79{\pm}1.60D$ and corneal astigmatism of $-1.17{\pm}0.79D$ respectively. Prevalence of spherical equivalent of refractive error were as follows : myopes (61%), emmetropes (22%), hyperopes(17%). Corneal astigmatism of refractive error greater than +0.75D was 63% and prevalence of corneal astigmatism were as follows : with-the-rlue astigmatism (84.13%), against-the-rule astigmatism(9.52%) respectively. Corneal power by spherical equivalent increased from hyperopia to myopia. Between spherical equivalent of refractive error and the mean corneal power was significant correlation(r=-0.25, p=0.01). A correlation were found between corneal power and spherical equivalent of refractive error in adults. They have the highest distribution of prevalence myopia among the refractive error. When the refractive error was increased, we found that corneal power was steeper. It is recognized that this can be refractive error factor and correct visual function is considered.

• Korean Journal of Ophthalmology
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• v.32 no.6
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• pp.497-505
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• 2018

Purpose: To evaluate and compare published methods of calculating intraocular lens (IOL) power following myopic laser refractive surgery. Methods: We performed a retrospective review of the medical records of 69 patients (69 eyes) who had undergone myopic laser refractive surgery previously and subsequently underwent cataract surgery at Samsung Medical Center in Seoul, South Korea from January 2010 to June 2016. None of the patients had pre-refractive surgery biometric data available. The Haigis-L, Shammas, Barrett True-K (no history), Wang-Koch-Maloney, Scheimpflug total corneal refractive power (TCRP) 3 and 4 mm (SRK-T and Haigis), Scheimpflug true net power, and Scheimpflug true refractive power (TRP) 3 mm, 4 mm, and 5 mm (SRK-T and Haigis) methods were employed. IOL power required for target refraction was back-calculated using stable post-cataract surgery manifest refraction, and implanted IOL power and formula accuracy were subsequently compared among calculation methods. Results: Haigis-L, Shammas, Barrett True-K (no history), Wang-Koch-Maloney, Scheimpflug TCRP 4 mm (Haigis), Scheimpflug true net power 4 mm (Haigis), and Scheimpflug TRP 4 mm (Haigis) formulae showed high predictability, with mean arithmetic prediction errors and standard deviations of $-0.25{\pm}0.59$, $-0.05{\pm}1.19$, $0.00{\pm}0.88$, $-0.26{\pm}1.17$, $0.00{\pm}1.09$, $-0.71{\pm}1.20$, and $0.03{\pm}1.25$ diopters, respectively. Conclusions: Visual outcomes within 1.0 diopter of target refraction were achieved in 85% of eyes using the calculation methods listed above. Haigis-L, Barrett True-K (no history), and Scheimpflug TCRP 4 mm (Haigis) and TRP 4 mm (Haigis) methods showed comparably low prediction errors, despite the absence of historical patient information.

• Journal of Korean Clinical Health Science
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• v.2 no.3
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• pp.203-208
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• 2014

Purpose. To analysis the refractive error in 7-9 year-old Korea children. Methods. From July 2013 to June 2014, two hundred eighty two subjects were performed in refraction test using the Auto-Refractometry. Results. The refractive error by spherical equivalent among all subjects was myopia 47.58%, emmetropia 42.35%, astigmatism 32.33%, and hyperopia 8.76%. Myopia was more common in female than males although the difference was not statically significant. The axis of astigmatism was with the rule in 65%, against the rule in 31.5%, and oblique in 3.5% There was a statistical significance between 7 year and 9 year of male in the spherical equivalent power(p=0.010). Also there was a statistical significance between 7 years and 9 years of female in the spherical equivalent power(p=0.036). However, there was not a statistical significance between male and female in spherical equivalent power(p>0.5). Conclusions. In this study, myopia was the most common refractive error. On the other hand, The prevalence of the axis of astigmatism was the with- the- rule. The spherical equivalent of refractive error was similar results between male and female. However The refractive error was different style with aging. these data suggested that the analysis of the refractive error at young children can provide the information of useful diagnosis for the correction of visual acuity.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.399-404
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• 2013

Purpose: This study was to analyse the changes of refractive error and addition in progressive eyeglasses lens wearers. Methods: Data of 244 subjects who have been prescribed progressive eyeglasses lenses were used for analysis. The range of age was between 43~69 old years and they visited the optical shop in Gwangju metropolitan city from 2003 to 2013. According to the refractive state and age, The changes of refractive error and addition was analysed respectively. Results: The changes of distance refractive power by refractive error was showed +0.10 D in emmetropia, +0.07 D in myopia, +0.23 D in hyperopia (p=0.000). The change of addition was showed +0.22 D in emmetropia, +0.29 D in myopia, +0.17 D in hyperopia (p=0.000). The changes of distance power and addition by age was +0.08 D distance refractive power, +0.30 D addition in the group of 40~49 old years, +0.17 D distance refractive power, +0.20 D addition in the group of 50~59 old years and +0.15 D distance refractive power, +0.14 D addition in the group of 60~69 old years (p=0.046, p=0.006). Conclusions: The changes of refractive error and addition of progressive eyeglasses lens wearers in all refractive state and age were gradual increase in the direction (+) diopter.

• Journal of Korean Ophthalmic Optics Society
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• v.2 no.1
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• pp.61-76
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• 1997

In this paper, we found out the objective refractive errors, the full corrective refractive powers, and the prescriptions for 64 males and 36 females aged 18 to 26 years. To increase the unaided visual acuity 0.1 to the aided visual acuity 1.0 with the glasses, we needed the spherical equivalent refractive power of -3.00D for male and -2.91D for female respectively. To increase the unaided visual acuity 0.5 to the aided visual acuity 1.0 with the glasses, we needed the spherical equivalent refractive power of -0.5D for male and -1.38D for female respectively. Comparing unaided visual acuity and corrective refractive power, the more one has refractive error the less one has unaided visual acuity but these are not linear relationships. Comparing objective refractive error figures, full corrective refractive power figures and prescriptions, objective refractive error figures are the hightest, followed by full corrective refractive power figures. Prescriptions compared with the other two are lower. The cylindrical refractive powers are less than -2.50D. In this study, with the rule astigmatism is dominant over against the rule astigmatism and oblique astigmatism. The accommodation measured by push up method is 6.75D~10.04D for male and 7.50D~9.60D for female respectively.