굴절교정레이저각막절제술에서 파면고위수차의 분석

Analysis of Higher-Order Wavefront Aberrations in Standard PRK

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.