• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.77-83
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• 2003

To investigate the influence of the variation of conic coefficient of the front surface on the RMS SD(Root Mean Square Spot Diameter) in a back focal plane, we use programs which are Cove V and LOSA 2.0. We consider a spectacle lens with back vertex power of -4.00D, diameter of 70 mm, the front surface powers which are 2.00D, 4.00D, 6.00D, and 8.00D, and the indices which are $n_d$=1.498, 1.523, 1.586, and 1.660, respectively. The RMS SD in the back focal plane and the thickness of an aspherical tens having the optimized conic constant are smaller than those of a spherical lens. The RMS SD in the back focal plane decreases as the front surface power decreases. From these results, we determine the optimized conic constant to improve the optical image quality and decrease RMS SD in the back focal plane.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.65-73
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• 2008

Purpose: The purpose of this study is to investigate the effect of age in the response to long-term overnight orthokeratology (OK) lens wearing. Methods: Among volunteers, ninety-five healthy subjects who had no eye diseases and could wear OK contact lens at least for 8 hours every day were divided into three groups children, youngsters and young adults. Unaided logMAR visual acuity, refractive error, apical corneal radius, corneal asphericity and central corneal thickness were measured with different period; before and after one day, one week, two weeks, one month, three months and six months of OK lens wear. Paired student t-test, ANOVA analysis and Pearson correlation were used with a critical p value of 0.05 for statistical analysis. Results: All groups showed statistically significant (p<0.001) improvement in unaided visual acuity, a trend for flattening in the apical corneal radius, decrease in central corneal thickness and less prolate after OK lens wear. The child group showed significantly rapid change (p<0.001) in visual acuity, and apical corneal radius showed that they reached the targeted refractive change earlier compared with youngster and adult groups. The visual effect of OK lens was significantly related with the change in central corneal thickness after long-term OK lens wear, especially in child and youngster group, and central corneal thickness were highly correlated with the targeted refractive change. Conclusions: Visual acuity change is statistically correlated with the central corneal thickness change, which is highly correlated with targeted refractive change in the long-term orthokeratology and younger lens wearers showed a rapid response to OK lens wear, suggesting a reduced epithelial response with increasing age. The results found this study extends our understanding and development in the long-term orthokeratology.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.119-124
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• 2008

Purpose: To determine whether the accommodation of amplitude (AA) was changed by the color of the spectacle lens or object. Methods: AA was measured in forty subjects in their 20s when they viewed different targeton-background color combination with achromatic, gray, brown or green lens. Minus-lens procedures were used for the estimation of AA. Results: When subjects viewed the black-on-white, red-on-white and green-on-white targets, AA under tinted lens tended to be increased compared with AA under achromatic lens. Especially, the green lens significantly increased AA whatever the color of target was. Furthermore, as subjects viewed the green target, AA was the highest irrespective of the color of lens. AA was also changed depending on the color of background, so AA on the red background was lower than on the white background. On the contrary, AA on the green background was higher than on the red or white backgrounds. Of tinted lens, the gray lens increased AA the lowest, but the green lens did the highest. The number of subjects, whose AA were measured more than 9 D, reached to 12.5% with the gray lens, 21.3% with the brown lens, 22.5% with the green lens on the green background, but 5%, 6.5% and 6.5% on the red background, respectively. Conclusions: This results showed that AA varied depending on the color of spectacle lens, objects or background, and the eye fatigue could be decreased with proper color of spectacle lens accordingly.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.3
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• pp.221-228
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• 2005

In order to analyze the difference of lenses production, we measured the refractive power and the thickness of their optical centers using ophthalmic lenses which were distributed at home country and abroad. The home products were manufactured to be next to foreign goods, but there were several cases to exceed acceptable limits and we need to reduce the deviation from measuring values in the same lenses. To get a beat on advanced countries, rearing technical expert, hard quality test and process control and standardization of lenses are essential to home lens industrials.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.1
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• pp.19-26
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• 2012

Purpose: This paper was to study the clinical effects of moderating myopia by comparing the myopia control lens, which was being recently recognized as a method of inhibiting the progression of myopia, with the wearers of single vision lens. Methods: Using 56 subjects between the ages of 8-15 years (112 eyes) with myopia in the areas of City of Daegu and Gyeongsangbuk Province as study subjects, refractive error, axial length, near point of convergence and accommodative near point were measured and compared a total of 3 times at the baseline, after 1-month and after 6-months. Results: For refractive error, suppression and mitigation were seen in the progression of spherical equivalent when MC lens was worn, as compared to using SV lens, and, when axial length MC lens was worn, the axial progression was significantly suppressed and delayed (p < 0.05). The near point of convergence became shorter with the use of MC lens, and the amplitude of convergence was improved when MC lens was worn. Accommodative near point became shorter with the use of MC lens, and focus ability was significantly improved (p <0.05). Conclusions: It was shown that MC lens, compared to SV lens, could alleviate myopia progression in school-age children and youth. It is considered that MC lens can be used as a useful therapy for the inhibition of myopia progression in the increasing number of myopic children and adolescents.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.349-354
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• 2015

Purpose: To investigate the changes of corrective values of astigmatism caused by the position of circle of least confusion on retina in refining astigmatic test using cross cylinder. Methods: 62 subjects (115 eyes) aged $22.24{\pm}2.48$ years participated for this study. After astigmatic test using a radial chart, refining test was performed using a cross cylinder in a condition of maximum plus to maximum visual acuity (MPMVA). Astigmatic refining test was repeatedly performed in each condition of which S+0.75 D, S+0.50 D, S+0.25 D, S-0.25 D, S-0.50 D, and S-0.75 D are added to spherical lenses of MPMVA. The measured values were compared with the values in MPMVA condition. Results: As compared with values in condition of MPMVA, change of astigmatic axis was increased with add the power of (+) spherical lenses and (-) spherical lenses. In same spherical condition, change of astigmatic axis was decreased with increment of astigmatic power (p<0.05). The corrective power of astigmatism was reduced with increment of (+) spherical lenses (p<0.05), and was raised with increment of (-) spherical lenses compared with the power in MPMVA condition. In case of adding (+) spherical lenses, difference of astigmatic power increased with increment of corrective astigmatism power in same test condition. Conclusions: In order to obtain a proper values for corrective astigmatism, position of circle of least confusion should be accurately adjusted before the performing an astigmatism's refining test.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.3
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• pp.247-253
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• 2011

Purpose: The changes in properties of plastic lens due to heating was investigated. Methods: Plastic lenses of -2.00 diopter were heated at 60-100$^{\circ}C$, and then changes of refractive power, surface condition and transmittance were examined. Results: It was shown that the changes of lens surface due to heating happened at 70$^{\circ}C$ for 1h, 75$^{\circ}C$ for 10 min and 100$^{\circ}C$ 10 sec, respectively. More serious crack was occurred in high index lens and at higher heating temperature, respectively, and transmittance decreased depending on the extent of the damage on the surface of lens. Conclusions: Heating at temperatures above 70$^{\circ}C$ drives cracks on the surface of lens. Optician should recommend an appropriate lens considering the wearer's working conditions and guide for paying attention when they use eyeglasses.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.341-347
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• 2015

Purpose : This study was to examine a correlation of response AC/A ratio by additional spherical powers with PD(Pupilary distance) and relative accommodation, and was to investigate correlation of CA/C ratio by prism powers. The mean differences between a reciprocal response AC/A ratio and a CA/C ratio were compared, and were suggested to be used as data in the refractive power and prism prescriptions in the clinical. Methods: The open field autorefractometer (Nvision-K 5001, Shin nippon) and Howell target at 40 cm fixation distance to 62 persons with average $22.62{\pm}2.84$ ages were used to measure the response AC/A ratio according to additional Spherical powers. The CA/C ratios were measured using the DOG card at 40cm according to prism powers. Results: When the response accommodation according to Additional Spherical power changes and the response accommodation according to prism power changes were compared, it was larger than the response accommodation according prism power change. These were significant differences statistically. The correlation of response AC/A ratio and PD is showed as r = -0.158, the CA / C ratio is shown as r = 0.093. The correlation of response AC/A ratio and relative accommodation showed as r = -0.253, the CA/C ratio showed as r = 0.566 that is predictable correlation. The correlation of response AC/A ratio and CA/C ratio showed as r = -0.355 that is low minus correlation (p = 0.000). The difference between a reciprocal response AC/A ratio and a CA/C ratio showed $0.12{\pm}0.06D/{\Delta}$ with a significant difference statistically (p=0.000). Conclusions: The correlation of relative accommodation and CA/C ratio showed that depend on the individual, The more a relative accommodation is, the higher a response accommodation of convergence by convergence stimulus is. The reciprocal response AC/A and CA/C ratio showed significant differences statistically. This can have higher CA/C ratio in patients with low AC/A ratio in clinical as an independent variable. Thus when the abnormal binocular vision was prescribed in the clinical, it is necessary to consider the accommodative response even if the AC/A ratio is a normal range.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.405-411
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• 2013

Purpose: In this study, the mounting status of trial case lens was investigated. Methods: We measured distances between geometric center of lens mount and optical center of lens and angle deviations between axis mark on lens and real axis using arbitrary trial case lens sets distributed in Korea, and then, compared those results with international standards. Results: In some of lenses, the prismatic power on geometric center of lens mount and the angle deviations between axis mark and real axis of cylindrical lens were out of tolerance according international standards. Conclusions: The more precise control of the manufacturing process and more thorough quality control for trial case lenses will be required to offer an accurate vision test.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.2
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• pp.119-126
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• 2012

Purpose: To study changes in coating and lens materials after chemically etched different polymer based glass lenses in short-term and ambient condition using hydrofluoric acid. Methods: Vinyl ester polymer (Lens A) and thiourethane polymer (Lens B), both dyed in gray 70%, were etched in hydrofluoric acid solution for 5, 10, or 15 min. The mechanical properties, degrees of damages in hard coating, anti-reflection coating, and other coatings, rates of refractive index and light transmission of both polymer types were evaluated. Results: Rates of refractive index of both lens types were not changed significantly after chemical etching. However, anti-reflection coatings and hard coatings were removed and lens surfaces were damaged. As a results, UV light transmission of lenses increased and mechanical properties decreased. Chemical etching notably changed various properties of thiourethane polymer materials. Conclusions: Depending on types of polymer materials, chemical reactions by hydrofluoric acid were dissimilar. Thus, various properties of les materials were altered differently.