• 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.17 no.4
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• pp.477-482
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• 2012

Purpose: This study is aimed at finding the conditions of ametropia of adults in the Philippines and the South Korean. Methods: The study objects were 7,695(15,390 eyes) Koreans and 2,256(4,512 eyes) Philippines who visited optic clinics and took refraction test. The distributions of their hypermetropias and myopias about astigmatisms were examined, using the method of equivalent spherical power. When astigmatisms were marked in S-C, cylinder lens diopter and astigmatism axis, presbyopic additions and pupillary distances were analyzed by comparison respectively. Results: Among ametropias of Koreans myopias and hypermetropias were 93.69% and 6.31% respectively and about ametropias of Philippines myopia and hypermetropias were 73.43% and 26.57% respectively. As for spherical equivalent power about Koreans, the results showed that Koreans marked -3.352 D about myopia and Philippines marked -2.213 D about it. There is a gap of -1.139 D between them. About hypermetropia Koreans marked 1.147 D and Philippines, 1.251 D and their gap is 0.104 D. As for ametropia of Koreans there is 49.86% in middle myopia, 32.28% about low myopia, 11.55% about high myopia, and 5.54% about low hypermetropia, 0.75% about middle hypermetropia. As for it about Philippines there is 44.53% in low myopia, 25.11% about middle myopia, 3.79% high myopia and 23.03% low hypermetropia, and 3.51% low hypermetropia respectively. As for cylinder lens there is differences of 0.194 D and 0.22 D between Korean and Philippine for both sexes. Totally Koreans have higher cylinders of 0.175 D than Philippines. As for astigmatism, Koreans have direct astigmatism, inverse astigmatism, and oblique astigmatism in their suffering sequence. As for Philippines, they have direct astigmatism, inverse stigmatism, and oblique astigmatism in their abnormal sequence, and they have higher oblique stigmatism than Koreans. As for presbyopic addition, Philippines have higher distributions than Koreans, and 0.296 D is higher in average. As for pupillary distance, Koreans have longer distance of 0.97 mm in man and 0.63 mm in women than Philippines. Conclusions: As for ametropia, Koreans and Philippines have more myopias than hypermetropias, but Philippines have more rates of hypermetropias than Koreans. And Philippines have more presbyopic additions. Koreans have higher morbidity of inverse astigmatism, and Philippines have higher morbidity of oblique astigmatism comparatively. As for pupillary distance, Koreans have longer length in the body characteristics. This shows that geographical circumstances have much to do with refraction conditions of eyes.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.1
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• pp.67-71
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• 2010

Purpose: The effect of two different levels of illumination and the effect of three letter chart types on subjective refraction findings were investigated. Methods: This study involved thirty Malay university students aged between 19 to 23 years old (7 males, 23 females), with their spherical refractive error ranged between plano to -7.75D astigmatism ranged from plano to -1.75D, anisometropia less than 1D and with no history of ocular injury and pathology. Monocular subjective refraction was measured under two levels of illumination (with and without room light) and with three different letter charts (Snellen letter chart, wall mounted letter chart and projected letter chart). Subjective refraction finding was calculated in spherical equivalent in unit diopter (D). Results: There was no significant effect in the subjective refraction findings with Snellen letter chart (t-test=0.15, p-value=0.88), projected letter chart (t-test=-0.19, p-value=0.85) as well as wall mounted letter chart (t-test=0.12, p-value=0.94). One Way ANOVA also revealed when the subjective refractive measures were compared under two different level of room illumination (with and without room light), no significant effect of letter chart types on subjective refraction readings with room light ($F_{2.185}$=0.11, p-value=0.89) and without room light ($F_{2.185}$=0.02, p-value=0.98). Conclusions: Subjective refraction findings were not affected whether the room light was on or off. They were also not affected by the types of letter chart used.

• Tribology and Lubricants
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• v.30 no.6
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• pp.350-355
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• 2014

This study proposes a sustainable bearing remanufacturing process using the ultrasonic nanocrystal surface modification (UNSM) technique. The UNSM technique is a newly developed and sophisticated surface modification technique that can increase the mechanical properties and improve the friction and wear performance of materials. Taking advantage of the bearing manufacturing process is the most significant way of optimizing the life of a bearing. The proper maintenance and usage of repaired bearings can increase their life to be equal to or greater than that of new bearings. This paper discusses the restoration of certain mechanical properties of worn, damaged, and discarded bearings, and suggests a remanufacturing process for used bearings, which can impart them with a lifespan equivalent to that of new bearings. The most damaged part of the discarded bearings is the raceway, which is the site of accumulated fatigue. The existing polishing or barrel finishing processes can recover the accumulated fatigue only partially. Rolling contact fatigue tests performed on UNSM-treated new and used specimens polished after $4{\times}10^6$ cycles reveal that UNSM-treated new specimens exhibit the longest fatigue life compared to other specimens. This study verifies the proposed complete fatigue recovery process, which can increase the fatigue life of used bearings to a level greater than that of new bearings.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.1
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• pp.99-104
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• 2010

Purpose: Difference of refraction result from the method of autorefraction and iTrace were investigaged for the children of elementary school in Asan City. In iTrace method. exclusion of accommodation without cycloplegia was used. Methods: Manifest refractive stale of 42 eyes of 12~13 years old were measured using autorefractor and iTrace. Refractions of far (more than 5 m) and ncar (30 cm) vision were measured using iTrace. All data showed that the spherical equivalent were classified as being in the group 1 (-0.50D < ~ < +1.00D) and 2 (below -0.50D) according 10 refractive errors. Results: Mean spherical equivalent using autorefractor and iTrace (far and near vision) were -1.08D, -0.29D and -2.34D, respectively (p<0.01). Compared with the far vision using iTrace, autorefraction was measured the myopia with -0.50D ~ -1.00D in 52.4% of total eyes. Autorefraction also statistical significant were measured a more myopia than the far vision using iTrace in group I and 2. Conclusions: The difference of refractive errors between autorefraction and iTrace, objective refraction were measured with far vision of more than 5 m were -0.79D. Autoreftaction showed statistically decreased refraction errors than iTrace with far vision.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.201-206
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• 2010

Purpose: This study was to know the correlation among the dimensions of ocular components and refractive error on kindergarten children. Methods: The subjects were 80 preschool students who had no eye diseases. The refraction, corneal diopter, corneal radius, inter-pupillary distance, axial length, anterior chamber depth and dominant eye were measured and analysed. Results: It was shown that the highest correlation was between the axial length and the corneal diopter (r=-0.674, p=0.000). The ratio of height, weight and axial length (AL) to Corneal radius (CR) ratio were positively correlated with the axial length (r=0.351, r=0.408, r=0.488). The spherical equivalent of the refractive error and the corneal diopter were negatively correlated with the axial length (r=-0.302, r=-0.674). The anterior chamber depth and the corneal diopter were positively correlated with the AL/CR ratio (r=0.422, r=0.280). The spherical equivalent of the refractive error and the corneal radius were negatively correlated with the AL/CR ratio. Conclusions: It was shown that the AL/CR ratio was a very important indicator for diagnosing the refractive error of the preschoolers.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.1
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• pp.77-82
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• 1999

To have a fine understand the refractive error eye of Korean adult male, This study was researched visual acuity test using objuctive and subjective methods. The results are as follows: 1. The eye types were 93.3% positive for myopia, 5.4% for emmetropia, and 1.7 forhyperopia, respectively. 2. The refractive error eye was positive for compound myoptic astigmatism for a percntage of 62.6%, simple myopia(32.4%), simple myoptic astigmatism(1.6%), simple hyperopia(l.4%) simple hyperopia astigmatism(0.5%), and mixed astigmatism(1.6%). 3. The axis of astigmatism was 59.7% for regular astigmatism, 25.3% for oblique astigmatism, and 15% for reverse regular astigmatism, respectively. 4. on the total myoptic spheric power, the -2.00

• 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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.6
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• pp.283-288
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• 2010

Nanosized NiO powder was prepared by mixing an acid nickel salt and a base nickel salt and their reduction behavior was studied. Ni formate was employed as an acid salt and nickel hydroxide and basic nickel carbonate as base salts. One equivalent acid salt was mixed with 9 equivalent base salt. The mixture of the formate and the carbonate produced ~100 run spherical NiO powder by heat treatment at $750^{\circ}C$/2 h, but the mixture of the formate and the hydroxide gave rise to ~100 nm pseudo spherical NiO powder by heat treatment at $600^{\circ}C$/2 h and grew fast to give pseudo cubic crystals of 100~600 run by heat treatment at $750^{\circ}C$/2 h. Reduction by hydrogen gas proceeded much faster for the one with the hydroxide than that with the carbonate to give porous body with well grown necks. Their behavior was studied by analysis of TG/DSC, XRD, and SEM.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.1
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• pp.35-40
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• 2005

Subjective and objective visions were measured on young adults(mean 21 yrs, 126 eyes) who were free of any ocular diseases and laser surgery and none wore contact lenses. The aim of this study was to investigate the diurnal variation of vision through subjective and objective measurements. Subjective visual acuity were measured at 5 m three times a day, morning(8:00 AM-10:00 AM), noon(12:00 PM-2:00 PM) and afternoon(4:00 PM-6:00 PM). The instrument used for objective refraction right after visual acuity measurement was Nvision-K 5001(shin-nippon) which unique in being able to disregard subject's accommodation because of its unrestricted viewing conditions. Also, we measured that three times and then calculated the average values. The result showed that an average subjective visual acuity in the morning, noon, afternoon were 0.256(${\pm}0.263$), 0.266(${\pm}0.276$), 0.242(${\pm}0.249$) respectively. Average spherical equivalent power in objective refraction of right eyes showed -3.416 D(${\pm}2.907$), -3.359 D(${\pm}2.735$), -3.297 D(${\pm}2.709$) respectively and dioptric power was decreased from morning to afternoon. Vision changed throughout the day in both subjective and objective measurements nevertheless its variations were statistically insignificant(p<0.05). Therefore it does not seem to matter of time for either visual acuity test or refraction.