• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.95-100
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• 1995

This study investigated the effects of mechanical factors involved in several corneal refractive surgeries on the surgical outcomes. Then we proposed possible new techniques from the mechanical point of a view utilizing finite element method. The models studied are: circumferential keratetomy, combination of excimer laser photorefractive keratectomy and circumferential keratotomy for myopia treatment, arcuate keratotomy for astigmatism treatment. The cornea was assumed to be nonlinear elastic and almost incompressible material as the most soft tissue in the human body. In the circumferential keratotomy the effect of the incision location was investigated. The angle and location of the incision were varied to predict the surgical outcomes in the arcuate keratotomy. The finite element analysis results showed that the location of incision was a critical factor affecting the surgical outcomes in the circumferential keratotomy. In the combination of the excimer laser photorefractive keratectomy and circumferential keratotomy, it was predicted that the circumferential can increase or decrease the refractive power depending on the incision location or it can be used to adjust the overcorrection of undercorrection. In the arcuate keratotomy for astigmatism, the most diopter changes were predicted when the location and the angle of the incision were 3.0mm from the apex and $90^{\circ}$, respectively. In the arcuate keratotomy, the effects of an incision were studied within the incision area as well as outside the incision area. Also, the arcuate keratotomy with two incisions located on the opposite area of the cornea was also studied. As a conclusion, the finite element method is a useful technique in the area of corneal refractive surgeries to develop new techinques.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.7
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• pp.10-16
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• 2012

In this paper, we tried to realize a next generation MILES detection system which is robust to optical noise using a narrow band interference optical filter. Applying a narrow band interference optical filter which has the wavelength range of 895~915nm to the LASER wavelength of 900nm, we could obtain detection characteristics robust to strong optical noise which can be occurred in street battles. However, the MILES detection system has the blind range of detection in the incident angle range of $30^{\circ}{\sim}90^{\circ}$. To solve this problem we proposed a method of incident angle scatter using refractors. Applying a concave meniscus lens refractor which has diopter of 5.4 to the MILES detection system, we could eliminate the blind angle of detection.

• 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.

• 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 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.12 no.3
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• pp.39-48
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• 2007

The stimulus of accommodation A, the stimulus of convergence C and the prism diopter ${\Delta}$ are reviewed and redefined more obviously. How the A and C are managed in the practice are reviewed and summarized. As a result, the common practical process of the binocular vision findings is most suitable in the case of the $l_c=26.67mm$, where the near distance is measured from the test lens to the near target and its value is 40 cm and the average of the P.D equal to 64 mm. The $l_c$ is the distance between the test lens and the center of rotation. Those values were used at calculating the various values in this paper. The error of the stimulus of accommodation values which are evaluated by the practically used formula (5) are calculated. Where the distance between lens and the principle point of eye is 15.07 mm ($=l_H$). The incremental stimulus of convergence values P' caused by the addition prism $P_m$ are evaluated by the recursion computation method. The P' are varied with the $P_m$, the distance $p_c$ between the prism and the center of rotation, the initial convergence value (or inverse target distance) $C_o$ and the refractive index n of the prism material. The recursion computation method and the other formulas are described in detail. In this paper n=1.7 is used. The two factors by which the P' is increased are exist. The one which is major is the property by which the values of convergence whose unit is ${\Delta}$ are not added in the generally way. The other is the that the actual power of the prism is varied with the angle of incidence light. And the P' is decreased remarkably by an increase in the $p_c$ and $C_o$. The $P^{\prime}/P_m$ are calculated and graphed which are varied with the $p_c$ and $C_o$, where the $P_m=20{\Delta}$, P.D=64 mm and n=1.7. The index n dependence of the $P^{\prime}/P_m$ is negligible (refer to fig. 6). The $p_c$ are evaluated at which the P' equal to the $P_m$ for various $P_m$ (refer to table 1). The actual values of the stimulus of convergence and accommodation which are manipulated simply in the practice are calculated. Two graphical forms are suggested. The one is like as the commonly used one. But the stimulus of convergence and of accommodation values in the practice are positioned at the exact positions when the graphic is made (refer to fig. 9). The other is the form that the incremental stimulus of convergence values caused by the addition prisms are represented at actual positions (refer to fig. 11).

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.65-71
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• 2008

Purpose: This paper studied the effect of eyes on the comparison between the distance optical centers problem of dispensing reading glasses made by optician and finished reading glasses in the current market. Methods: The method of this study has been measured by eleven different categories from +1.00D to +4.00D. This study also separated into three groups by their optical frame size and measured optical center point (O.C) and optical center height (O.H) with 200 peoples of man and females over 40 years old without ocular disease living in Gwang-san gu, Gwang-Ju city. Results: As a result, optical center point ranged from 57 mm to 80 mm and it turned to be most common range is from 61 mm to 65 mm (64.6%). Moreover, the optical center height ranged from 1 mm to 8mm and most common ranged (23%) were 4 mm. In other words, finished reading glasses have irregular optical ranges. After observing 200 people who are over 40 years old men and women, result shows that more than 75.5% (151 people) currently use finished reading glasses. Survey of 151 people, most common error between the finished reading glasses's O.C and the wearers P.D were 4 mm (45%). Furthermore, the most common error between the finished reading glassses's O.H and the wearers O.H ranged from 3 mm to 4 mm. Astonishingly, the entire 151 people who wear finished reading glasses appeal that they feel tiredness on their eyes when they wear finished reading glasses. 53 people (35%) claimed that they feel tiredness on their eyes after 10 to 20 minutes wearing finished reading glasses. Base on the research, We conducted more experiment to find the value of prism of optical centers err because it will tell us whether the finished reading glasses are good enough to wear or not. We multiplied diopter by the difference between finished reading glasses's O.C. and wearer's P.D. Consequently, We found out that the finished reading glasses counter to the German RAL-RG 915 policy. And We also found that it is relative to the diopter of lenses. In conclusion, based on the researched that wearing finished reading glasses have a dangerous factor for our vision. Therefore optician must need to recommend correctly made dispensing reading glasses based on the optical center point.

• Journal of The Korean Ophthalmological Society
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• v.59 no.11
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• pp.1009-1016
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• 2018

Purpose: To assess the effect on axial elongation and associated factors between spectacles and of orthokeratology lens (OK) wearing in children with mild to moderate myopia. Methods: A total of one hundred subjects, ranging in age from 6 to 13 years, and with mild to moderate myopia no more than -4.50 diopters in spherical equivalent, visited our clinic from 2013 to 2015. The OK group (75 eyes) and the spectacles group (64 eyes) were compared and analyzed on the axial elongation and associated factors. Results: In the OK group, axial length was elongated in 1 year period with a mean increase of $0.24{\pm}0.29mm$. In spectacles group, axial length was elongated in 1 year period with a mean increase of $0.42{\pm}0.20mm$. The statistically significant suppression of axial elongation was observed in OK group compared to the spectacles group (Mann-Whitney U test, p < 0.05). For OK group, the age of starting OK (Pearson's correlation, r = -0.481, p < 0.05) was the only influencing factor on axial elongation, which had negative correlation with axial elongation. In spectacles group, the age of starting spectacles had negative correlation with axial elongation (Pearson's correlation, r = -0.462, p < 0.05) and baseline spherical equivalent, spherical diopter, cylindrical diopter from manifest refraction had positive correlation with axial elongation. Comparison of axial elongation in orthokeratology lens group and spectacles group by age groups (6 to 9 years [28 eyes], 9 to 13 years [47 eyes]), 9 to 13 years of orthokeratology lens group had the stronger suppression of axial elongation (Mann-Whitney U test, p < 0.05). Conclusions: The OK effectively suppresses axial elongation compared to the spectacles. Although the patients are in age from 9 to 13 years, the axial elongation was effectively suppressed.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.2
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• pp.41-46
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• 2009

Purpose: Stereopsis is one of primary characteristics for assessment of binocular function. The purpose of this study was to determine the possible relationship between the degree of exophoria and stereoacuity at near. Methods: 110 exophores (male n=71, female n=39, mean $age{\pm}SD=11.30{\pm}1.47$ years) without amblyopia, strabismus, and ocular and systemic pathology were studied. Subjects were also excluded if they had visual acuity poorer than 0.8 in either eye or vertical phoria greater than 1 prism diopter. Clinical tests were performed for near phorias by von Graefe technique using a Digital Refractor (CDR-3100, Huvitz, Korea) with chart (Predio CDC-4000, Huvitz, Korea), and for stereoacuity using the Titmus fly. Results: A one-way analysis of variance revealed that mean values of the stereoacuity classified according to the degrees of the exophoria were not significantly different (p>0.05). Conclusions: Based on the result of this study, it was found that there was no relationship between the degree of exophoria and stereoacuity.

• Journal of Preventive Medicine and Public Health
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• v.44 no.1
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• pp.56-64
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• 2011

Objectives: The purpose of this study was to estimate the prevalence and correlated factors of high myopia in 19 year-old men in Southeast Korea. Methods: This retrospective study was based on the medical checkup data of conscription during 2005. The study subjects were 19 years old men in Busan, Ulsan and Gyeongsangnam-do. The health checkup data of the conscripts consisted of noncycloplegic autorefraction test, the biometric data and social factors. To analyze the social and biometric effects, we classified the biometric factors into 4 or 5 groups and the social factors into 3 groups. High myopia was defined as a spherical equivalent of under -6.0 diopter. Data analysis was performed using the chi square test for trends and multiple logistic regression analysis. The SAS(version 9.1) program was used for all the analyses. Results: The prevalence of high myopia was 12.39% (6256 / 50 508). The factors correlated with high myopia were the residence area (OR, 2.07; 95% CI, 1.77 to 2.4 for small city; OR, 2.01; 95% CI, 1.72 to 2.34 for metropolis; the reference group was rural area), academic achievement (OR, 1.43; 95% CI, 1.34 to 1.53 for students of 4-and 6-year-course university; the reference group was high school graduates & under) and blood pressure (OR, 1.54; 95% CI, 1.10 to 2.16 for hypertension; OR, 1.09; 95% CI, 1.02 to 1.17 for prehypertension; OR, 1.10; 95% CI, 1.01 to 1.20 for hypotension; the reference group was normal blood pressure). Conclusions: More than one tenth of the young men were high myopia as one of the risk factor for visual loss. Further studies on high myopia and its complications are needed to improve eye health in Southeast Korea.