• Proceedings of the KOSOMBE Conference
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• v.1993 no.05
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• pp.57-60
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• 1993

A finite element-based computer simulation of excimer laser susery was conducted to study some factors on the surgery. In particular, the radius of curvature at the apex of the cornea was examined under various surgical conditions. Corneal tissue was assumed to be a nearly incompressible, linear elastic, homogeneous, isotropic material under very small deformation. The geometry of the human cornea was taken from the experimental data[1]. The simulation utilized ANSYS(Swanson Analysis System Inc.Rev.4.4A). In this study, the major factors which affect the outcomes of the excimer laser surgery were investigated. First, two patterns of surgery with various surgery thickness(40-70micrometers) were examind. The pattern#1 describes the meridian from the apex to the edge of the surgery area to be straight. And the corresponding meridian of the pattern 2 can be expressed as a quardratic function. The results show that the pattern #2 is more realistic and effective. Then, the effects of other factors were investigated based on the pattern #2. Other factors are:various diameters of the surgical area (3-8 milimeters), Young's modules(3.5-4.5MPa), and depth of surgery at the apex(40-70micrometers). Compared with the computer simulation of the radial keratotomy surgery[2], the excimer laser surgery was proven to be more effective in treating myopia patients. In conculusion, the results of the simulation are qualitative agreement with clinical experience[3] indicating the potential of the finite element model of the surgery as a guideline to the surgeon before actual surgery.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.519-523
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• 2003

Alpha hydroxy acid (AHA) includes a group of organic acids found in natural foods such as sugarcane (glycolic acid), milk (lactic acid), apples (malic acid) and oranges (citric acid). Earlier studies demonstrated the effect of AHAs on the skin by diminishing the adhesiveness of the corneal layer and increasing the viable epidermal thickness. Recent data suggest that AHAs have some effects on the dermal component of skin and even affect the aging process of the skin. A previous study revealed increased collagen production by treatment with glycolic acid among AHAs in vitro. However, the mechanism of the regulation of collagen production by glycolic acid was unclear. In present study, we tried to demonstrate the effect of glycolic acid on human dermal fibroblasts and to unveil the mechanism of regulation of collagen production by glycolic acid in human dermal fibroblasts: proliferation of fibroblasts and collagen synthesis and degradation by collagenases in fibroblasts. Our results suggested that glycolic acid had no effect on proliferation and cytotoxicity of adult human dermal fibroblasts. However, glycolic acid not only induced the increase of the collagen synthesis in human dermal fibroblasts at lower concentration than 0.1 % but also inhibited MMP-2 activity of human dermal fibroblast in the range between 0.01 and 0.4% and MMP-9 activity of human dermal fibroblast in the range between 0.06 and 0.09%. In summary, our results suggest that glycolic acid may increase wrinkle reduction partially by both increase in collagen synthesis and decrease in collagen degradation.