角膜曲率对飞秒激光小切口角膜基质透镜取出术后患者屈光状态影响的临床研究

Observational study on the impact of corneal power on refractive status of patients after small incision lenticule extraction surgery

目的 观察飞秒激光小切口角膜基质透镜取出术（SMILE）对不同曲率的近视眼患者的临床疗效及其影响因素.方法 前瞻性队列研究.观察2016年1至8月在陆军军医大学大坪医院行SMILE的近视眼患者,根据术前角膜曲率分为3个组：低曲率组（K1≤41.00 D）、常见曲率组（K1＞41.00D且K2＜46.00 D）和高曲率组（K2≥46.00 D）,记录患者术前及术后1d、1周及1、3、6个月的裸眼远视力（UCDVA）、屈光状态、眼前节、眼压等检查结果,并在术后6个月时行主观验光和Pentacam HR眼前节分析检查,观察术中、术后并发症的发生情况,采用基于Ray Tracing技术的角膜总屈光力（TCRP）评价手术前后角膜曲率的变化及采用矢量分析对手术前后主观验光和角膜地形图所显示的屈光状态进行分析.术后6个月时各组间屈光状态的比较采用Hotellingt2检验,并采用多元线性回归方法分析欠矫或过矫的可能影响因素.结果 共纳入患者54例（108只眼）,其中男性34例,女性20例.高曲率组、常见曲率组和低曲率组各18例（36只眼）,其中低曲率组平均年龄[（22.1±4.2）岁]显著低于其他组（x2=8.94,P＜0.05）,且男性患者比例（15/18）更高（x2=11.20,P＜0.01）,平均瞳孔直径[（3.27±0.36）mm]更大（F=4.83,P＜0.05）.术中高曲率组患者发生重度不透明气泡层（OBL）比例（25/36）,显著高于其他组（0/36,x2=65.06,P＜O.01）.术后6个月时所有患者无一发生视力下降,UCDVA平均为5.1,但低曲率患者在角膜1和2 mm直径范围略显“欠矫”（即Error值均＜0）.6 mm直径范围内术前等效球镜度数和术后球差（正）是影响角膜曲率与屈光状态相互间关系的重要因素（r=0.392,2.745;P＜0.05）.结论 SMILE对不同角膜曲率的近视眼患者矫正均安全、有效;高曲率患者术中重度OBL发生比例明显高于其他患者;低曲率患者在角膜1和2 mm直径范围表现为轻度“欠矫”,提示SMILE术中微透镜设计可能存在非球面化以及低龄患者术后角膜重塑过程存在一定特殊性.

Objective To observe the change of refractive status and possible influencing factors for patients with different corneal power who underwent small incision lenticule extraction （SMILE） surgery.Methods Prospective cohort study was performed for patients who underwent small incision lenticule extraction （SMILE） surgery at Daping Hospital and Research Institute of Surgery of Third Military Medical University between January and August 2016.The patients were divided into 3 groups according to their corneal power：low curvature group （K1≤41.00 D）,common curvature group （41.00 D＜K1 and K2＜ 46.00 D）,and high curvature group （K2 ≥ 46.00 D）.Preoperative and postoperative （1 day,1 week,1,3 and 6 month） ophthalmic examination results of the patients including uncorrected distance visual acuity （UCDVA）,refractive status,intraocular pressure （IOP） and slip lamp microscope examination were recorded.Subjective refraction and Pentacam HR were detected at 6 month after operation so as to monitor the incidence of intraoperative and postoperative complications.The total corneal refractive power （TCRP） based on Ray Tracing technique was applied to evaluate the changes of corneal curvature before and after the surgery.Power vector analysis was applied to evaluate the refraction status based on preoperative and postoperative corneal topography.At 6 months postoperatively,Hotelling t2 test was applied to compare the refractive status among the groups,and multiple linear regression was applied to analyze the potential influencing factors of under-correction / over-correction.Results Fifty-four patients （108 eyes） were enrolled,among which 34 were male （68 eyes） and 20 were female （40 eyes）.The 3 groups had the same sample size （18 patients and 36 eyes）.The low curvature group was featured with youngest average age [（22±4） years,x2=8.94,P＜0.05],largest male patients proportion （15/18,x2=11.20,P＜0.01） and largest average pupil diameter [（3.26±0.36） mm,F=4.83,P＜0.05],as compared to the other 2 groups.The incidence of severe OBL （25/36） was significantly higher in the high curvature group （x2=65.06,P＜0.01）.All patients showed no diminution of vision and their UCDVA averaged 5.1 at 6 months postoperatively,however patients with low curvature were slightly ＂under-corrected＂ in 1-mm and 2-mm zones （Error values＜0）.The preoperative spherical equivalent （SE） and postoperative spherical aberration in 6-mm zone were the significant factors affecting the relationship between preoperative corneal curvature and postoperative refractive status （r=0.392,2.745,P＜0.05）.Conclusions SMILE is safe and effective for patients with both low and high curvature,but the incidence of intraoperative OBL is significantly higher in high curvature group.Patients with low curvature were slightly ＂under-corrected＂ in 1-mm and 2-mm zones,which may imply that the design of the lenticule may be aspheric and that the cornea reshaping process of younger patients may be of particular characteristics.