• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.1-7
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• 2009

Purpose: To improve the quality of Korean progressive addition lenses, we measured the optical and geometrical elements of them and evaluated their qualities. Methods: We have measured the refractive power, the thickness at optical center and prism power for home and foreign progressive addition lenses which were distributed in the domestic market, and then have done a comparative analysis according to international standards. Results: The qualities of Korean progressive addition lens were on an equal footing with famous foreign brand products, but they were out of tolerance in a few cases. Conclusions: The careful attention is required to progressive addition lens, therefore, it is considered that more precise quality control is an essential element to strength the competitiveness of Korean products in the world market.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.57-63
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• 2003

To investigate the RMS SD(Root Mean Square Spot Diameter) in a back focal plane as the front surface power, the center thickness, and the refraction index vary, we use programs which are Cove V and LOSA 2.0, and consider a spectacle lens with back vertex power of -4.00D and diameter of 70 mm. We also consider the front surface power varied from 0.00 to 10.00D, the center thickness varied from 1.1 to 2.0 mm, and the indices which are $n_d$ = 1.498, 1.523, 1.586, and 1.660, respectively. As the front surface power increases the RMS SD in the back focal plane increase rapidly. When the refraction index increases, the RMS SD in the back focal plane decrease and the variation of RMS SD in the back focal plane decreases as the front surface power increases. When the center thickness of spectacle lens increases, the RMS SD in the back focal plane is constant and the edge thickness of that increases. We know from these results that the image in the back focal plane of a spherical spectacle lens improves as the front surface power increases and the refraction index decreases.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.1
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• pp.31-35
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• 2001

We have studied the auto-lensometer for several years in order to begin korean-made production of it and then developed the auto-lensmeter using with the personal computer. We introduce the most important principal of PSD device and the optical principal of measuring the power of the refraction of the lens by auto-lensometer and also explain the fabrication of the LED optical source system and PSD optical system. Finally, we found the power constant of our auto-lensmeter to be about 30 Diopter/mm.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.1
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• pp.55-60
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• 2010

Purpose: We investigated the changes of plastic lens after etching of coating films by comparing uncoated lens. Methods: CR-39, middle index and high index lenses of 0 (zero) diopter were etched at $80^{\circ}C$ and room temperature using a coating remover, and then changes of refractive power, transmittance and surface morphology were investigated. Results: There were no differences in refractive power and transmittance between uncoated and etched lenses. The etching rate was similar in both CR-39 and middle index lens, but in the case of high index lens, it was slower and less steady than the others. From the SEM observation of lens surface, etching damage was found out on the surface of etched lens. It was shown the least damage in middle index lens but the most damage in high index lens. Conclusions: If the etching of coating films is demanded on condition that the surface of ophthalmic lenses are not damaged, a using of most adequate coating remover based on lens material should be considered, and a caution for proper etching conditions is required.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.163-169
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• 2014

Purpose: This study is for compared the change of corneal refractive power before and after wearing of rigid gas permeable contact lense with diagnostic method which is 1 D flatter than alignment fitting on right eye and alignment fitting on left eye for 2 months and investigate the preference. Methods: Twenty middle school and high school students (40 eyes) who had never worn a contact lense before for no corneal topographical change, no ocular disease, no experience of ophthalmic surgery and have normal tear amount were selected for this study and corneal refractive power were examined before wearing rigid gas permeable contact lense and adaptation status and corneal examination were performed after 10 days of wearing and after cheking up the continuation of wearing, all candidate wear contact lens 8 hours per day for 2 month and corneal refractive power were compared. Results: After 2 months of wearing with 1 D flatter than the alignment fitting on right eyes, there was significant difference in the central corneal refractive power was $43.84{\pm}1.33D$, flat K power was $43.05{\pm}1.29D$, and steep K power was $44.61{\pm}1.42D$ decreased than before wearing (p<0.001, 0.001, 0.047). The e-value of the principal meridians also shows statistically significant difference (p=0.037, 0.015). After 2 months of wearing with alignment fitting on left eyes, the central corneal refractive power was $44.40{\pm}1.26D$, flat K power was $43.57{\pm}1.23D$. and flat K e-value was $0.58{\pm}0.05$ which showed no statistically significant difference (p = 0.769, 0.614, 0.181). But steep K power was $45.25{\pm}1.36$, and steep K e-value was $0.45{\pm}0.18$ which shows statistically significant difference (p=0.018, 0.027). Conclusions: Consider the comfort, clear vision, dryness for preference fitting investment, 6 students (30%) prefer right eye which is 1 D flatter fitting, 14 students (70%) prefer left eye which is alignment fitting. For rigid gas permeable fitting needed for accurate examination and should prescribe the alignment fitting which is suitable for each cornea.

• 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.20 no.4
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• pp.455-462
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• 2015

Purpose: To develop more accurate wet measuring system combining the wet cell, automatic lensmeter and the related software for hydrophilic contact lenses and to verify the accuracy of those measuring holder system already available in the market. Methods: Refractive power measurement were done in both a conventional method which has been commonly used in optical shops and a new method which is recently developed in korea. Hydrophilic contact lens of korean brand was chosen as a test material and was tested by water content ratio and by spherical refractive power. Results: When spherical power of -3.00 D contact lens is measured in the newly developed wet cell measurement holder with automatic lensmeter, it reads -3.01 D at water content ratio of 38%. -3.00 D at 45% and -2.98 D at 58%. The same experiment with the Poster soft contact lens wet cell measurement holder maintaining other conditions same resulted in -3.60 D at the water content ratio of 38%, -3.06 D at 45% and -2.46 D at 58%. Conclusions: At the higher water content, the refractive power values measured by both of the wet cell measuring holders are shown lower, and additionally, the new method using the wet cell holder and new software program in a automatic lensmeter showed more accurate readings than conventional Poster soft contact lens wet cell measuring system.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.105-115
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• 2015

Purpose: The accuracy for measuring the refractive power of hydrogel contact lenses by spectacle lens holder and contact lens holder was evaluated. The accuracy for each sample was also analyzed with water content and diopter categories. Methods: The hydrogel contact lenses used for measurement were classified into three categories in water content (38%, 43%, 58%). Also, three diopter categories of refractive power were used such as -3.000 D, -7.000 D, -10.000 D. And also, the reliability of measurement results were evaluated by measuring refractive power with spectacle lens holder and contact lens holder using an Manual lensmeter. Results: In case of spectacle lens holder method, the average value of refractive power was -3.3273D for -3.0000 D, -7.1306 D for -7.0000 D and -10.2944 D for -10.0000 D, respectively. In case of contact lens holder method, the average value of refractive power was -3.1060 D for -3.0000 D, -7.0028 D for -7.0000 D and -10.2611 D for -10.0000 D, respectively. In measurement of all diopters, the accuracy of contact lens holder method was better than spectacle lens holder method. Conclusions: From these results, it is judged that the refractive power of soft contact lens by manual lensmeter with contact lens holder have a higher accuracy than spectacle lens holder.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.219-225
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• 2010

Purpose: Usefulness in predicting the power of spherical rigid gas-pearmeable (RGP) lenses prescription using dioptric power matrices and arithmetic calculations was evaluated in this study. Noncycloplegic refractive errors and over-refractions were performed on 110 eyes of 55 subjects (36 males and 19 females, aged $24.60{\pm}1.55$years) in twenties objectively with an auto-refractometer (with keratometer) and subjectively. Tear lenses were calculated from keratometric readings and base curves of RGP lenses, and the power of RGP lenses were computed by a dioptric power matrix and an arithmetic calculation from the manifest refraction and the tear lens, and were compared with those by over-refractions in terms of spherical (Sph), spherical quivalent (SE) and astigmatic power. Results: The mean difference (MD) and 95% limits of agreement (LOA=$MD{\pm}1.96SD$) were better for SE (0.26D, $0.26{\pm}0.70D$) than for Sph (0.61D, $0.61{\pm}0.86D$). The mean difference and agreement of the cylindrical power between matrix and arithmetic calculation (-0.13D, $-0.13{\pm}0.53D$) were better than between the others (-0.24D, $0.24{\pm}0.84D$ between matrix and over-refraction; -0.12D, $0.12{\pm}1.00D$ between arithmetic calculation and over-refraction). The fitness of spherical RGP lenses were 54.5% for matrix, 66.4% for arithmetic calculation and 91.8% for over-refraction. Arithmetic calculation was close to the over-refraction. Conclusions: In predicting indications and powers of spherical RGP lens fitting, although there are the differences of axis between total (spectacle) astigmatism and corneal astigmatism, Spherical equivalent using an arithmetic calculation provides a more useful application than using a dioptric power matrix.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.3
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• pp.217-223
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• 2006

The purpose of this study is to provide improvements and standards of trial lens, in a situation that there is a lack of standards of trial lens set that have been used for self-conscious refraction test after helm refraction test at about 5,000 opticians, ophthalmologic clinics and hospitals, and contact-lens shops, that there is a lot of discrepancies between refraction specified and the actual power, and that there is no regulation of optical tolerance error. For the study, opticians who have used Trial lens set were asked to participate in a questionnaire survey through continuing education, and divided into those who have used domestic lens and those who have used imported lens, 5 opticians each for less than 5 years, 5 to 10 years, more than 10 years. The measurement of both refraction specified and the actual diopter was compared to Japan Industrial Standards(JIS T4402). As a result of comparative analysis, more than 80% of respondents have had reliability on the refraction of trial lens they had used, indicating that they have never measured the refraction specified and the actual diopter after buying them. Besides, Korean Industrial Standards(KS P4402) has been imperfect in diopter range since it was legislated in 1979. More than 95% of respondents have been unsatisfied with optometry. Also, it has indicated that refraction error is more frequent in long-term-used trial lens. The conclusion is that it is necessary to standardize trial lens set and that it is required to add lens to lens set provided under KS P4402. Moreover, it is necessary to have supervisory agency for a standardization of trial lens. I hope that both domestic lens and imported lens, as in German and Japan, will be tested to find whether they meet optical tolerance error and standard trial lens will be distributed. Good optic inspection is required for the improvement and management of eye health and optical function, and the same standard trial lens set should be used. whoever is tested. Also, I hope that trial lens set will be specified within standards and tolerance error.