LASIK治疗近视术后影响角膜非球面指数变化相关因素分析

背景 准分子激光角膜原位磨镶术（LASIK）治疗近视会改变角膜的非球面形态,进而对患者术后的视觉质量造成一定影响,但手术治疗参数,如切削深度、治疗光区直径如何影响角膜非球面形态目前国内外报道较少. 目的 探讨LASIK治疗近视术中所需切削深度及治疗光区直径大小等手术参数对角膜非球面性变化的影响.方法 采用前瞻性横断面研究方法.收集2011年3-7月在山东中医药大学附属眼科医院行飞秒制瓣LASIK治疗的近视患者89例175眼,术前等效球镜度为（-5.93±1.98）D,术前最佳矫正视力（BCVA）≥1.0.采用Orbscan-IIz角膜地形图检测患者术前和术后6个月时角膜中央6.0 mm区非球面指数（Q值）,记录每例手术治疗光区直径和切削深度,采用自身对照法比较手术前后术眼的视力和等效球镜变化,采用多元逐级回归分析法探讨切削深度和治疗光区直径与LASIK手术前后Q值变化的关系. 结果 所有术眼的术前平均球镜度为（-5.57±1.89）D,柱镜度（-0.71 ±0.55）D,等效球镜度为（-5.93±1.98）D;术后6个月的平均球镜度为（-0.25±0.30）D.平均柱镜度为（-0.14±0.22）D,平均等效球镜度为（-0.32±0.37）D,与术前比较差异均有统计学意义（=-32.39、-23.91、-35.18,均P＜0.01）.术眼术前和术后6个月角膜中央6.0mm区域Q值分别为-0.13±0.09（-0.47～0.08）和1.09±0.54（0.22～2.51）,术后Q值明显大于术前,差异有统计学意义（t=29.37,P＜0.01）.所有术眼手术切削深度平均为（95±28） μm;治疗光区直径平均为（6.32±0.26） mm.切削深度和治疗光区直径对术后Q值变化量（△Q）的多元回归公式为AQ=1.517＋0.015＆#215;切削深度-0.3＆#215;治疗光区直径,切削深度与△Q呈线性正相关（β=0.803）,而治疗光区直径与△Q呈线性负相关（β=-0.149）.结论 LASIK治疗近视术后角膜Q值有正性增大趋势,增加手术的切削深度和减小治疗光区直径可导致角膜Q值增加.

Causes of increased corneal aspherical index following LASIK for myopia

Background Laser assisted in situ keratomileusis （LASIK） for myopia will change corneal asphericity and further affect the quality of vision.However,how operating parameters such as ablation depth and optic zone diameter affect corneal asphericity is still rarely reported.Objective Aim of this study was to investigate the influence of corneal ablation depth and optic zone diameter on corneal asphericity after LASIK for myopia.Methods This prospective study comprised 175 eyes of 89 patients with the spherical equivalent of （-5.93± 1.98）D and the best corrected visual acuity （BCVA） ≥ 1.0.The flap creation with the femtosecond laser combine iris recognize guided LASIK was performed on the patients who were available for the evaluation at postoperative 6 months.Corneal aspherical index （Q value） at the central corneal 6.0 mm were measured with Orbscan IIz-corneal topography before and 6 months after operation.Corneal ablation depth and optic zone diameter were recorded in operation.The changes of visual acuity and spherical equivalent before and after surgery were compared by self-control method,and the correlations between corneal ablation depth or optic zone diameter with alteration of Q value （AQ） after LASIK were assessed using multiple regression analysis.Results The mean spherical power,cylinder diopter and spherical equivalent were （-5.57 ± 1.89） D,（-0.71 ±0.55） D and （-5.93 ± 1.98） D before surgery,and those after surgery were （-0.25 ±0.30）,（-0.14±0.22）D and （-0.32±0.37）D,showing significant differences between before and 6 months after LASIK （t=-32.39,-23.91,-35.18,all at P〈0.01）.The Q values at the central corneal 6.0 mm were -0.13 ± 0.09 （-0.47-0.08） in preoperation and 1.09 ± 0.54 （0.22-2.51） in postoperation,with a significant increase in postoperation （t=29.37,P〈0.01）.Corneal ablation depth was （95±28） μm and optic zone diameter was （6.32±0.26）mm.Ablation depth appeared to be positive correlation with AQ （β =0.803）,and optic zone diameter showed a negative correlation with AQ （β =-0.149）,with a multiple regression formula AQ =1.517＋0.015＆#215;ablation depth-0.3 ＆#215;optic zone diameter.Conclusions LASIK for myopia increase corneal Q value.The increase of corneal ablation depth and decrease of optic zone diameter contribute to enlargement of corneal Q value.