目的 探讨飞秒激光辅助准分子激光原位角膜磨镶术(FS-LASIK)术后光学区的变化及Pentacam角膜地形图各模式测量值的特点.方法 回顾性病例研究.选取于青岛眼科医院角膜屈光科行FS-LASIK且术后随访≥6个月资料完整的近视眼及近视散光患者24例(41只眼),其中男性7例,女性17例,年龄18～ 42岁.应用Pentacam眼前节分析系统角膜地形图6种不同模式(单纯角膜轴向曲率图、单纯角膜切线曲率图、角膜轴向曲率差异图、角膜切线曲率差异图、角膜前表面高度图及角膜厚度差异图)联合自主研制的透明同心圆软件对患者术后光学区进行测量.手术后1、3、6个月不同角膜地形图模式测量的光学区直径比较采用重复测量方差分析,光学区实际测量值与理论设计值的比较采用两样本t检验.FS-LASIK术后光学区测量值与可能影响因素的相关性分析采用Spearman秩相关分析.结果 FS-LASIK术后1、3、6个月,单纯角膜轴向曲率图光学区测量值分别为(6.55±0.50)、(6.50±0.53)、(6.48±0.53) mm,差异无统计学意义(F=1.60,P＞0.05);单纯角膜切线曲率图测量值分别为(5.44±0.46)、(5.46±0.52)、(5.44±0.50)mm,差异无统计学意义(F=0.17,P＞0.05);角膜前表面高度图光学区测量值分别为(5.06±0.28)、(5.12±0.32)、(5.17±0.28)mm,仅术后3、6个月相比差异无统计学意义(F=6.14,P＞0.05);角膜轴向曲率差异图光学区测量值分别为(6.51±0.37)、(6.45±0.41)、(6.41±0.40) mm,仅术后3、6个月相比差异无统计学意义(F=7.25,P＞0.05);角膜切线曲率差异图光学区测量值分别为(5.21±0.23)、(5.16±0.19)、(5.17±0.20)mm,仅术后1、3个月差异有统计学意义(F=1.75,P＜0.05);角膜厚度差异图光学区测量值分别为(6.53±0.40)、(6.39±0.43)、(6.41±0.47)mm,仅术后1、3个月差异有统计学意义(F=1.67,P＜0.05).6种模式角膜地形图的光学区测量值与理论值(7.75 mm)相比均明显减小,差异均有统计学意义(t=16.79,31.91,66.44,22.76,69.98,20.09;P＜0.01).结论 FS-LASIK术后光学区直径测量值在术后3个月趋于稳定.角膜地形图6种不同模式测量结果显示实际激光切削区与手术设计理论值相比均下降,其中单纯角膜切线曲率图、角膜切线曲率差异图、角膜前表面高度图测量值与理论设计值相差较大且边界清晰,对于偏心评估更有优势;而单纯角膜轴向曲率图、角膜轴向曲率差异图及角膜厚度差异图与理论设计值相对接近,此外角膜轴向曲率差异图边界更清晰更有利于光学区的测量.%Objective To explore the change of optical zone after femtosecond laser assisted laser in sitn keratomileusis(FS-LASIK) so as to provide the reference for measurement and design of clinical optical zone.Methods This retrospective case series study covers 41 eyes of 24 patients (7 males and 17 females,aged from 18 to 42 years old) with myopia and myopic astigmatism who have received FS-LASIK surgery at Corneal Refractive Department of Qingdao Eye Hospital and completed over 6 months of clinical follow-up.Pentacam system (with the application of 6 corneal topographic map modes including:the pure axial curvature topographic map,the pure tangential curvature topographic map,the axial curvature difference topographic map,the tangential curvature difference topographic map,the postoperative front elevation map and the corneal thickness difference topographic map),combined with transparent concentric software (a system independently developed by Qingdao Eye Hospital) was used to measure the optical zone at 1,3 and 6 months postoperatively,the optical zone diameters measurement results among different follow-up times in group were analyzed with the repeated measures analysis of variance,and the actual measured values and the theoretical design values of the optical zone were analyzed with independent-samples t-testing.Spearman correlation coefficient (rs) have been applied to evaluate the relationship between postoperative optical zone measurement values and the potential influencing factors.Results The optical zone diameters measured by pure axial curvature topographic map at 1,3 and 6 months after FS-LASIK showed (6.55± 0.50)mm,(6.50 ± 0.53)mm and (6.48 ± 0.53)mm respectively.The differences between values are of no statistical significance (F=1.60,P=0.21),the optical zone diameter measured by pure tangential curvature topographic map at 1,3 and 6 months after FS-LASIK showed (5.44±0.46)mm,(5.46 ± 0.52)mm and (5.44 ± 0.50)mm respectively,the differences between values are of no statistical significance (F=0.17,P=0.85).The optical zone diameters measured by postoperative front elevation map at 1,3 and 6 months after FS-LASIK showed (5.06±0.28)mm,(5.12±0.32)mm and (5.17±0.28)mm respectively.The differences between the values of 3 and 6 months postoperatively are of no statistical significance (F=6.14,P=0.15),the optical zone diameters measured by axial curvature difference topographic map at 1,3 and 6 months after FS-LASIK showed (6.51±0.37)mm,(6.45±0.41)mm and (6.41 ±0.40)mm respectively,and the differences between the values of 3 and 6 months postoperatively are of no statistical significance (F=7.25,P=0.05).The optical zone diameters measured by tangential curvature difference topographic map at 1,3 and 6 months after FS-LASIK showed (5.21 ± 0.23)mm,(5.16 ± 0.19)mm and (5.17 ±0.20) mm respectively,and the differences between the values of 1 and 3 months postoperatively are of statistical significance (F=1.75,P=0.04).The optical zone diameters measured by corneal thickness difference topographic map at 1,3 and 6 months after FS-LASIK showed (6.53±0.40)mm,(6.39±0.43)mm and (6.41± 0.47)mm respectively,and the differences between the values of 1 and 3 months postoperatively are of statistical significance (F=1.67,P=0.032).The actual measured optical zone values from the 6 different modes of Pentacam system are less than the theoretical design values (7.75 mm),and the differences were statistical significance (t=-15.42,-29.39,-59.27,-21.47,-81.69,-18.22,P＜0.01).Conclusions The optical zone measurement values tend to be stable at 3 months after FS-LASIK.The actual measured values from all the 6 different modes of Pentacam system were less than the theoretical design values.The results from pure tangential curvature topographic map,the tangential curvature difference topographic map and the postoperative front elevation map showed greater variation with clear border,which was beneficial for eccentric research.The results from pure axial curvature topographic map,the axial curvature difference topographic map and the corneal thickness difference topographic map were close to the theoretically designed values.Furthermore,the axial curvature difference topographic map showed clearer border and less variation thus maybe more favorable for measuring optical zone in clinical application.
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