• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.281-290
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• 2004

The purpose of this study is to investigate the correlation between the central corneal thickness and peripheral one, and the changing aspect of corneal thickness by the refractive error through the measure of central corneal thickness and peripheral one in myopic eyes. For this study, the central thickness and the peripheral one of the 198 eyes of 99 normal subjects was measured by Orbscan Topography System(Orbtex, Inc. USA). The latter was measured in each 2mm point distance of superior, inferior, nasal and temporal from the center of left & right eye. And the revealed results was analyzed according to sex, age, left & right eyes, and refractive error of the subjects. The mean central corneal thickness of the whole subjects was shown as $530.12{\pm}43.18{\mu}m$, and the mean peripheral ones were as follows : superior(SCT) $591.91{\pm}36.88{\mu}m$, inferior(ICT) $561.04{\pm}41.82{\mu}m$, nasal(NCT) $584.23{\pm}41.97{\mu}m$ and temporal(TCT) $567.35{\pm}43.25{\mu}m$. From this, we can see that the mean central corneal thickness and the peripheral ones show significantly difference, but there is no statistically Significant difference in the corneal thickness according to refractive error, age, sex, and left & right.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.1-11
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• 2003

A mathematical model was proposed to analyze the oxygen diffusion reaching the cornea through the tear layers and contact lens based on Fick's law and the principle of continuity of the diffusion flux through the each layers. The model predicts how the parameters such as the thickness of tear layer on the cornea, both the Dk and thickness of contact lenses etc., affect the oxygen tension at cornea and oxygen flux entering the cornea. It is found that either too flat or too tightly fitted contact lenses can cause the oxygen deficiency inside the periphery of the cornea because of the reduction of oxygen flux resulted from too thickened tear layer.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.35-43
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• 2008

Purpose: This review article was written to investigate how the various factors, such as lacrimal thickness, CL's thickness and Dk, affects the influx of $O_2$ diffusion into the cornea. Methods: A mathematical model was proposed to analyze the oxygen diffusion reaching the cornea through the tear layers and contact lens based on Fick's law and the principle of continuity of the diffusion flux through the each layers. Results: The model predicts how the parameters such as the thickness of tear layer on the cornea, both the Dk and thickness of contact lenses etc., affect the oxygen tension at cornea and oxygen flux entering the cornea. Conclusions: It is found that either too flat or too tightly fitted contact lenses can cause the oxygen deficiency at/inside the periphery of the cornea because of the reduction of oxygen flux resulted from too thickened tear layer.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.107-116
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• 2011

Purpose: The review article was written to establish an excel program that could calculate minimal Dk of contact lens without $O^2$ deficiency and actual $O^2$ concentration on cornea when contact lens were being fitted by changing lens-related factors. Methods: An excel program was formulated to calculate the thickness of post-lens lacrimal layer, Dk of contact lens and $O^2$ concentration on cornea. Results: With the excel program established, minimal $O^2$ concentration needed on cornea could be calculated when the thickness of post-lens lacrimal layer was changed by varying lens-related factors. A different route in the excel program was needed to choose based on the shape of lacrimal layer. The thickness of lacrimal layer was determined by the shape of meniscus made of tear between lens edge and cornea with flat fit. Thus, the $O^2$ concentration showing negative number in calculation decreased on peripheral cornea with flatter fitting and actual $O^2$ concentration would be zero on cornea. With tight fitting, the thickness of post-lens lacrimal layer is much thicker than lens itself thus negative number in calculation by the excel program is shown indicating zero oxygen on cornea. It can cause $O^2$ deficiency regardless of Dk of contact lens. Conclusions: The calculation of thickness of post-lens lacrimal layer and $O^2$ concentration on cornea by the established excel program is suggested to avoid $O^2$ deficiency when fitting state is varied by changing lens-related factors.

• Journal of IKEEE
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• v.18 no.2
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• pp.240-247
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• 2014

Intraocular pressure is measured after a cornea air puff by observing biomechanical properties such as thickness or displacement of the cornea. In this paper, we deal with a frequency domain analysis of corneal deformation in the air puff tonometry that is used to diagnose glaucoma or lasik. We distinguish the patient from the normal by measuring the oscillation frequency in the neighborhood of the central cornea section. A binary image was obtained from the video images, and cornea vertical oscillation profile was extracted from the difference between the vertical displacement data and the curve fitting. In terms of Fourier transform, a vibration frequency of 479.2Hz for the patient was obtained as well as more higher 702.8Hz for the normal due to stiffness. Hilbert-Huang transform's empirical mode decomposition generally describes local, nonlinear, and nonstationary data. After the data were decomposed into intrinsic mode functions, a spectrum and power were analysed. Finally, we confirm that the patient has 6 times more higher power ratio for the specific intrinsic mode function between the patient and the normal.