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이상범,최병훈,Sang-Bumm Lee,M,D,Ph,D,Byeung-Hun Choi,M,D 대한안과학회 2005 대한안과학회지 Vol.46 No.9
Purpose: To investigate the preoperative characteristics and postoperative change of the higher-order wavefront aberrations (HOAs) in myopic photorefractive keratectomy (PRK). Methods: Standard PRK was performed in 39 eyes (spherical equivalent -4.71±1.56D) using the VISX? STAR S4TM excimer laser system. Wavefront analysis was performed preoperatively and 6 months postoperatively using the VISX? WaveScanTM aberrometer. Statistical analysis was performed to assess the preoperative characteristics of the HOAs and the PRK-induced aberrations. Results: The preoperative root mean square (RMS) value of the total HOAs was 0.291 ㎛: coma 0.159 ㎛, trefoil 0.157 ㎛, spherical aberration 0.093 ㎛. Among the 3 HOAs, only the spherical aberration showed moderate magnitude negative correlation with the spherical equivalent (p=0.012) and sphere (p=0.005). The magnitude of all of the HOAs, except trefoil, were significantly increased at postoperative 6 months: total HOAs 183% (0.533 ㎛, p<0.001), spherical aberration 341% (0.317 ㎛, p<0.001), coma 185% (0.294 ㎛, p<0.001), trefoil 104% (0.163 ㎛, p=0.681). In the postoperative correlation analysis, only the PRK-induced spherical aberration showed the increase of magnitude with increasing preoperative spherical equivalent (p=0.036) and sphere (p=0.019). Conclusions: The HOAs, especially spherical aberration and coma, were increased after PRK. Among the 3 HOAs, the spherical aberration showed the greatest increase of magnitude and percent change; it also showed a positive correlation with increasing preoperative spherical equivalent and sphere. Further software improvements in the wavefront-guided surface ablations need to have a diminution of PRK-induced spherical aberration.
눈추적장치를 이용한 고등각막표면굴절교정레이저절제술에서 수술자 지정 연마중심의 정확도
이상범,조명진.Sang Bumm Lee. M.D.. Ph.D.. Myung Jin Cho. M.D. 대한안과학회 2007 대한안과학회지 Vol.48 No.9
Purpose: To evaluate the accuracy of the surgeon-selected ablation center in active eye-tracker-assisted ASA-PRK and to identify factors influencing the ablation center. Methods: This retrospective study included 109 eyes of 62 patients who underwent active eye-tracker-assisted ASA-PRK (VISX STARTM S4 with ActiveTrakTM System). The location the surgeon-selected ablation center and its distance from the center of the entrance pupil were analyzed by corneal topography (EyeSys Corneal Analysis SystemTM with pupil finding software). The factors influencing centration were investigated. Results: The mean decentration was 0.24±0.13 mm (range 0.04 to 0.83 mm). One-hundred and five eyes (96%) were within 0.5 mm of the pupillary center. Supero-nasal displacement of the ablation center occurred most frequently in 44 eyes (40%) after ASA-PRK. The decentration amount was not dependant on factors related to the patient, the surgeon, or the surgery. There was no significant correlation between the amount of decentration and the vertical scale bar of the ActiveTrakTM icon on the screen representing the distance from the pupil center determined by the tracking system, to the surgeon-selected ablation center. Conclusions: This method of tracking the ablation center, which was selected by the surgeon according to each patient`s specific pupil decentration with the active eye tracking system, was highly accurate and effective in avoiding severe decentration in ASA-PRK.
Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK): 각막두께가 얇은 경중등도 근시안에서의 수술 효과 및 안전성
이상범,정민수,Sang Bumm Lee,Min Su Chung 대한안과학회 2006 대한안과학회지 Vol.47 No.8
Purpose: To evaluate the safety, clinical outcome, and change in higher-order wavefront aberrations (HOAs) of Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK) for the correction of mild to moderate myopia in cases with a thin cornea. Methods: ASA-PRK was performed, using a rotary epithelial scrubber, post-laser chilled BSS? irrigation, and bandage contact lens, in 127 eyes of 70 patients who had a preoperative spherical equivalent within -7.0 D and who were followed-up for more than six months. The patients were divided into two groups, according to their central corneal thickness (CCT), by ultrasonic pachymetry (Group Ⅰ: CCT≤520 ?m, 32 eyes, mean 506.6±8.6 ?m; Group Ⅱ: CCT>520 ?m, 95 eyes, mean 552.3±24.8 ?m). The clinical outcomes of Group Ⅰ and Ⅱ were compared. Results: At six months, 100% of Group I (32/32 eyes) and 93.7% of Group II (89/95 eyes) had an UCVA of 1.0 or better (p>0.05). At six months, a spherical equivalent within 0.5 D of emmetropia was observed in 100% (32/32) of the eyes in Group I and in 94.7% (90/95) of the eyes in Group II (p>0.05). At the 12-month follow-up, all eyes showed good stability of the refractive errors, and none showed corneal haze of grade 1 or more, loss of two or more lines of BSCVA, or serious iatrogenic keratectasia. The magnitude of total HOAs, spherical ablation, and coma were significantly higher six and 12 months after surgery in both groups (p<0.05). The postoperative changes in the HOAs at six and 12 months were similar in both groups (p>0.05). Conclusions: ASA-PRK performed on patients with mild to moderate myopia and a thin cornea (≥ 490 ?m) showed a high level of efficacy, predictability, stability, and safety. There was no statistically significant difference in surgically induced HOAs between Groups I and II. The authors suggest that ASA-PRK be used for the correction of mild to moderate myopia, especially in cases with a thin cornea. Further study will be needed to determine the safety of this procedure for thinner corneas in surface keratorefractive surgery.