This study proposed a mechanical model of the excimer laser photorefractive keratectomy(PRK) for myopia patients utilizing finite element method, which is a simulation technique widely used in engineering fields. The outcomes of the surgery depends on many factors, which are also dependent on each other. In this study, some mechanical factors are selected and the effects of the selected factors on the surgical results were analyzed. One of the important factors in the finite element analysis is the mechanical properties of the object. The representative characteristic of the human cornea is that it shows highly nonlinear property in the stress-strain relationship like most soft tissues in the human body. Therefore, the nonliear property was adopted in this study. Other important mechanical properties which affect the outcomes of the surgery are: a preoperative thickness, intraocular pressure, diameter of ablation zone and the depth of ablation. With various changes of the those mechanical factors, the outcomes of the surgery were predicted using the finite element method. The results show the qualitative agreement with clinical outcomes also promising agreement quantitatively. Therefore, this study shows a potential of the finite element method in clinical application of excimer laser PRK.
Cornea ; Finite Element Analysis ; Human Body ; Humans ; Intraocular Pressure ; Lasers, Excimer* ; Myopia ; Photorefractive Keratectomy*

BACKGROUND: The purpose of this study was to investigate the clinical and electro physiologic characteristics of patients with multiple accessory pathways. Recently as endocardial mapping has become more and more accurate, multiple accessory pathways which were considered to be rare in the past, have become more commonly reported in patients with Wolff-Parkinson-White syndrome. METHODS: From February 1993 to June 2000, there were a total of 452 patients, who were confirmed to have accessary pathway mediated-tachyarrhythmias diagnosed by electrophysiologic study. Among those, 19 patients had multiple accessory pathways, and were enrolled in this study. RESULTS: Among the 19 patients, thirteen patients were male and six were female, and their mean age was 36.5+/-16.17 years. All patients had 2 accessory pathways. The distribution of the location of the accessory pathways was at the left free wall (71.1%), right free wall (18.4%) and posteroseptal wall (10.5%). The most common combination pattern was the left free wall and left free wall (57.9%) and the most common anatomical areas were the left lateral wall and left posterior wall (36.8%). The success rate of the catheter ablation was 84.2% (16/19). The recurrence rate after the radiofrequency catheter ablation was 31.3% (5/16) and the most common recurrence site was left free wall (60.0%, 3/5). CONCLUSION: These results indicated that the clinical and electrophysiologic characteristics of the multiple accessory pathway patients with WPW syndrome in our study were similar to those of western countries.
Catheter Ablation ; Female ; Humans ; Male ; Recurrence ; Wolff-Parkinson-White Syndrome