• 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 Biomedical Engineering Research
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• v.20 no.1
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• pp.45-51
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• 1999

The purpose of this study is to investigate the effects of various factors in keratotomy for astigmatism correction on surgical outcomes by finite element method as well as animal experiments. Three kinds of surgical techniques were mechanically investigated : arcuate, straight, and inverse arcuate keratotomy. Among the three techniques the arcuate keratotomy is the most popular one while the other two techniques are being investigated in this area. The arcuate keratotomy was found to be more controllable and effective in reducing the refractive power than the others. In arcuate keratotomy it was found most effective when the incision was located in the middle position between the apex and the edge of the cornea from the results of experiment as well as finite element study. Regarding to the range of the corneal incision in arcuate keratotomy, the incision angle of 90$^{\circ}$ was found th be most effective in reducing refractive power than other angles even it was incised up to 150$^{\circ}$. Therefore, it was concluded that 90$^{\circ}$ of incision angle results in the largest decrease in refractive power in arcuate keratotomy. However, other important findings were that the effect of the surgery decreased with time so the visco-effect of the cornea and auto-healing process. Therefore, these factors should be considered in future studies.

• Journal of Veterinary Clinics
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• v.28 no.6
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• pp.562-565
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• 2011

A total of 29 eyes (25 dogs: one eye, 2 dogs: both eyes) with indolent corneal ulcer were treated with grid keratotomy from January 2008 to March 2010. The corneal lesions were reevaluated at 7-14 day intervals. The treatments had been repeated until fluorescein dye was not retained on the cornea and the epithelium did not appear to be loosely attached to the stromal layer. The healing rate of the corneal ulcers was 86.2%. The mean healing time ($mean{\pm}SD$) was $15.92{\pm}9.19$ days, ranged from 7 to 39 days. The lesions of remaining 4 eyes had deteriorated or not improved for more than 6 weeks. In those cases, $3^{rd}$ eyelid flap following grid keratotomy was applied. After 2 weeks, all of the eyes healed by the treatment. The results in this study suggest that grid keratotomy could be an excellent choice as an initial treatment for superficial corneal ulcers in dogs. In the cases of recurrence or to promote healing of the lesions, however, $3^{rd}$ eyelid flap following grid keratotomy is recommended.

• Korean Journal of Veterinary Research
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• v.63 no.2
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• pp.20.1-20.4
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• 2023

A 10-year-old, spayed female, Maltese dog presented with a 2-day history of severe left eye squint. Slit-lamp biomicroscopy showed a deep corneal defect stained into a doughnut shape together with hypopyon in the anterior chamber. Based on these results, a diagnosis of descemetocele and uveitis in the left eye was made. Deep keratotomy combined with a nictitating membrane flap effectively resolved the descemetocele without complications. The surgical procedures performed on this patient were easy and effective, and could be used as an alternative to graft surgery for descemetocele treatment.

• 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.