準分子雷射近視手術術後光學區大小的影響因子與變化情形: 兩種準分子雷射機之比較

Abstract

前言: 台灣接受準分子雷射近視手術(Laser In Situ Keratomileusis, LASIK)之病人有日漸增加之趨勢，根據臨床上之觀察，接受準分子雷射近視手術後一段時間，有些許病人會抱怨視力不如剛開完時清楚且夜間視力會變差，並伴隨有眩光現象。由於病人視力表現和光學區(optic zone)大小有密切的關係。而光學區的大小是否與實際設定的值相符合、是否會隨著不同的雷射機型而有所不同、影響光學區的大小之因子為何、是否會隨術後時間而變化、若會隨術後時間而變化，那影響光學區的變化之因子為何等問題很值得探討。本實驗試圖利用電腦角膜地形分析圖(computerized videokeratography)來研究不同的雷射機型削切出來之光學區(topographic optic zone)大小及其隨時間之變化情形，並試圖找出會影響光學區大小及變化之因子，期使病人術後有更佳之視力。 方法: 從2000 年10月到2004年5月，國立臺灣大學醫學院附設醫院在此3年8個月期間，停止配戴隱形眼鏡兩星期以上，無任何眼科受傷病史及其他眼科手術記錄，接受Summit或Allegretto雷射手術且同意參與研究之病人。其中使用Summit雷射機型者，追蹤至術後6個月，使用Allegretto雷射機型者，追蹤至術後3個月。45位接受Summit雷射機治療且同意參與研究之病人中，有39位，共73個眼睛符合條件，而23位接受Allegretto雷射機治療且同意參與研究之病人中，有15位，共27個眼睛符合條件。39位符合接受Summit雷射機治療且同意參與研究之病人中，有1位只追蹤了3個月後，就失去了追蹤。 在病人接受雷射近視手術後，分析病人的基本資料，包括年齡，性別，術前的屈光度，術前之電腦角膜地形分析圖，欲矯正之度數，雷射之機型，欲矯正之光學區面積之大小，術後1星期、1、3及6 (Summit)個月時的屈光度，術後1星期、1、3及6 (Summit)個月之電腦角膜地形分析圖。 先以預設之光學區面積之值為基值，比較術後1星期時光學區面積百分比是否與預設的值相符合，是否會隨著不同的機型而有所不同。方法為不同機型之雷射機應分開計算，紀錄術後1星期時之光學區面積，除以欲矯正之光學區面積之值，計算百分比後與100%相比較，用pair t-test來檢測術後1星期時光學區面積百分比與100%是否有差別；用Two-sample t-test來比較兩種雷射機之實際光學區面積百分比是否有差異。 同樣以欲矯正之光學區面積之值為基值，研究術後1星期時光學區面積百分比之影響因子。方法為不同機型之雷射機應分開計算，紀錄術後1星期時光學區之面積，除以欲矯正之光學區面積之值，計算百分比後，用線性回歸分析來檢定術後1星期時光學區的面積百分比是否與年齡、性別、欲矯正之屈光度及欲矯正之光學區面積之值有相關。 以術後1星期之光學區面積為基值，研究術後光學區面積百分比隨時間之變化情形。方法為分別計算術後1、3及6 (Summit)個月時之光學區面積，除以術後1星期之光學區面積，分別得到術後1、3及6 (Summit)個月時之光學區面積百分比。不同機型之雷射機應分開計算，分別以pair t-test測試術後1個月對1星期、3個月對1個月及6個月對3個月(Summit)的光學區之面積百分比是否有差異。 同樣以術後1星期之光學區面積為基值，研究影響術後1個月、3個月及6個月(Summit)光學區面積百分比之相關因子。方法為不同機型之雷射機應分開計算，以線性回歸方法計算術後1個月、3個月及6個月(Summit)光學區面積百分比是否與年齡、性別、欲矯正之屈光度、欲矯正之光學區面積及度數回歸之程度有相關。 結果: 光學區面積的大小與預設值並不符合，實際的光學區面積通常都比預設值小(Summit: 88.69% +/- 13.69%, p<0.0001; Allegretto: 91.24% +/- 14.51%, p=0.0042)。而此兩種雷射機之間並無統計學上之差異(p=0.4179)。 以多變數線性回歸分析方法來看，在調整了年齡及性別等相關因子後，發現兩台雷射機在欲矯正之面積及欲矯正之屈光度與實際的光學區面積百分比都有顯著相關(Summit欲矯正之面積：beta = -1.8453%, p<0.001；Summit欲矯正之屈光度：beta =2.8721%, p<0.001；Allegretto欲矯正之面積：beta =-2.3697%, p<0.001；Allegretto欲矯正之屈光度：beta =3.8348%, p = 0.001)，而且兩台雷射機都有欲矯正之光學區面積越大、欲矯正之近視度數越深時，實際之光學區面積百分比會越小之結果。 在光學區隨時間變化方面，Summit之光學區面積一直在縮小，直到術後3個月才趨穩定(術後1個月減術後1星期: -5.19% +/- 9.40%,p<0.001；術後3個月減術後1個月：-3.79% +/- 8.01%, p=0.0001；術後6個月減術後3個月：-0.73% +/- 9.12%，p=0.505) 。Allegretto之光學區面積也在縮小，但到術後1個月即趨穩定(術後1個月減術後1星期: -5.045% +/- 9.22%，p=0.0087；術後3個月減術後1個月：-1.39% +/- 7.02%，p=0.31)。 以多變數線性回歸分析方法來看，在調整了年齡及性別等相關因子後，Summit雷射機只有在術後同時期之度數回歸與術後同時期之光學區面積百分比變化有相關性(術後1個月之度數回歸：beta = 10.3191%， p<0.001；術後3個月之度數回歸：beta = 9.5676%，p<0.001；術後6個月之度數回歸：beta = 8.1963%，p<0.001)。但是Allegretto因為病例數較少，所以雖然在調整了年齡及性別等相關因子後，在術後1個月之度數回歸卻只有邊界顯著相關(beta =5.1488%, p=0.13)，但在術後3個月之度數回歸顯示有相關(beta = 8.5942%, p=0.008)。雖然Allegretto雷射機在術後1個月之度數回歸只有邊界顯著相關，但其趨勢與Summit雷射機相同，都是術後同時期之近視方向回歸越多，其光學區面積百分比會變越小。而且此兩種雷射機都有欲矯正之近視度數深淺並無法預測光學區縮減之多寡之結果。 結論: 上述兩雷射機型的實際光學區通常都比預設值小。雖然Summit實際光學區面積又比Allegretto稍小，但是並無統計學上之差異。而欲矯正之近視方向之屈光度越多或欲矯正之光學區面積越大，削切出來的光學區面積都會比預設值越小，且成相關。 但是Summit雷射機之光學區面積到達穩定之時間較Allegretto慢，可能是雷射光束之不同或是有無雷射過渡區之差異所造成。在兩台雷射機上，欲矯正之度數並無法預測光學區面積縮減之多寡。而若光學區面積持續變小，則病人之屈光度會往近視方向偏移。

Purpose To determine whether the optic zone matches what we have proposed, whether the optic zone is different with different excimer laser machines, what factors associate with the area of the optic zone, whether the optic zone changes or not as time passes and what factors associate with the change of the optic zone after myopic laser in situ keratomileusis (LASIK) surgery. Setting Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan Methods 73 eyes out of 39 patients had myopic LASIK surgery with Summit laser machine and 27 eyes out of 15 patients with Allegretto were analyzed. The data include preoperative and 1-week, 1-month, 3-month and 6-month (Summit) postoperative subjective refraction and computerized videokeratography. Statistical analysis was performed to determine the difference of the area of the optic zone between the actual and the intended, the relationship between the optic zone and factors, such as the intended correction of spherical equivalent, the intended correction of the area of the optic zone, to compare the optic zone at different post-operative time, and to determine the relationship between the change of the optic zone and factors, such as the intended correction of spherical equivalent and the change of subjective refraction as time goes on. Results The actual optic zone does not match what we have proposed no matter what laser machine is. The actual optic zone is slightly smaller than the intended. (Summit: 88.69% +/- 13.69%, p<0.0001; Allegretto: 91.24% +/- 14.51%, p=0.0042). In multiple linear regression model, there is correlation between the actual optic zone and the intended correction of the area of the optic zone (Summit : beta = -1.8453%, p<0.001；Allegretto: beta = -2.3697%, p<0.001) and the intended correction of spherical equivalent in these two laser machine (Summit : beta = 2.8721%, p<0.001；Allegretto: beta =3.8348%, p = 0.001) after adjusting age and gender. It means that the more intended correction of the area of the optic zone or the more intended correction of myopia, the less actual optic zone comparing with what we intended. The actual optic zone becomes smaller and smaller when time goes by. The actual optic zone becomes stationary at post-operative 3 month with Summit laser machine and at post-operative 1 month with Allegretto (Summit: post-operative 1 month v.s. post-operative 1 week: -5.19% +/- 9.40%, p<0.001；post-operative 3 month v.s. post-operative 1 month:-3.79% +/- 8.01%, p=0.0001；post-operative 3 month v.s. post-operative 6 month：-0.73% +/- 9.12%, p=0.505 and Allegretto : post-operative 1 month v.s. post-operative 1 week: -5.045% +/- 9.22%, p=0.0087；post-operative 3 month v.s. post-operative 1 month: -1.39% +/- 7.02%, p=0.31). In multiple linear regression model , there is no correlation between the optic zone change at different post-operative time and the intended correction of spherical equivalent in these two laser machines (Summit : post-operative 1 month : beta =0.3304%, p=0.457, post-operative 3 month : beta =0.2162%, p=0.662, post-operative 6 month : beta =0.6549%, p=0.392 and Allegretto : post-operative 1 month : beta =0.2011%, p=0.837, post-operative 3 month : beta = -0.2628%, p=0.839) after adjusting age and gender. There is correlation between the change of the optic zone and the change of subjective refraction at different post-operative time in these two laser machines. (Summit: post-operative 1-month：beta =10.3191%, p < 0.001；post-operative 3-month：beta =9.5676%, p < 0.001；post-operative 6-month：beta =8.1963%, p < 0.001 and Allegretto: post-operative 1-month：beta =5.1488%, p = 0.130；post-operative 3-month：beta =8.5942%, p = 0.008). Conclusions The actual optic zone is slightly smaller than what have proposed to treat. Though the actual optic zone with Summit is slightly smaller than that with Allegretto, there is no statistical significance. There is correlation between the size of the actual optic zone and the intended correction of spherical equivalent and the intended correction of the area of the optic zone in these two laser machines. It means that the more intended correction of the area of the optic zone or the more intended correction of myopia, the less actual area of the optic zone comparing with what we intended. The reason why the optic zone takes more time to become stationary with Summit than Allegretto may be that Allegretto has a blend zone and Summit doesn’t. There is no correlation between the optic zone change at different post-operative time and the intended correction of spherical equivalent in these two laser machines. If the optic zone becomes smaller as time goes on, the patient will be more myopic.