摘要：目的 分析达芬奇（LDV）飞秒激光所制作的角膜瓣横径与角膜曲率（K）值的相关性，为临床上不同角膜曲率患者选择角膜瓣的制作方法提供依据。方法 随机选取进行飞秒激光制瓣的准分子激光原位角膜磨镶术矫治近视的患者50例（100眼），根据飞秒制作角膜瓣所采用的吸引环直径分为两组，其中I组13例（26眼）采用9.0mm吸引环，II组37例（74眼）采用8.5mm吸引环。于手术台上测量并记录角膜曲率、角膜横径及瓣横径，手术由同一位医生完成。采用独立样本t检验及双变量相关分析的统计方法对数据进行分析。结果 样本的年龄范围为18～37（平均25）岁, 其中男18例（36眼）, 女性32例（64眼），均为双眼手术，且无术中并发症发生。结果显示，两组角膜横径平均值分别为10.7mm和10.6mm（t =0.04，p＞0.05）；其中Ⅰ组平均角膜瓣横径9.2 mm，K值＞44.0D、44.0D～42.0D、＜42.0D患者角膜瓣的横径分别为9.3 mm、9.1 mm、8.6 mm，K值与角膜瓣横径存在显著正相关 ( r=0.492，Ｐ=0.027) ；Ⅱ组平均角膜瓣横径8.3 mm；K值＞44.0D、44.0 D ～42.0D、＜42.0D角膜瓣的横径分别为8.4 mm、8.3 mm、8.0 mm (r=0.513，Ｐ=0.001)。结论 LDV飞秒激光制作角膜瓣的横径大小与K值有密切的相关性，K值高者角膜瓣相对偏大，K值越低则角膜瓣越小。提示角膜曲率低的患者在手术时尽量选用偏大的吸引环，而避免因选择了直径小的吸引环导致的小瓣、游离瓣。角膜曲率高的患者宜选用偏小的吸引环，避免因选择了直径大的吸引环导致的瓣过大、手术中出血、术后干眼等。
Correlation analysis of LDV femtosecond laser flap and corneal curvature
Abstract：Objective To evaluate the correlation between the diameter of corneal flap created by LDV femtosecond laser and corneal curvature (K), so as to provide clinical evidence for the choice of suction ring to satisfy patients with different corneal curvature. Methods Fifty myopic patients (100 eyes) who had femtosecond-assisted LASIK surgery from February to April 2013 in Peking Union Medical College Hospital were included in this study. Patients were divided into two groups based on the diameter of suction ring used in the creation of corneal flap. Thirteen patients (26 eyes) who used suction ring of 9.0mm were in Group I, while the other thirty-seven patients (74 eyes) who used suction ring of 8.5mm were in Group II. All the procedures were done by the same skillful surgeon, and she also measured the diameter of cornea and flap, and the corneal curvature during each procedure. An independent samples t test and bivariate correlation method were used to analyze the quantitative data. Results There were eighteen males (36 eyes) and thirty-two females (64 eyes) in this study, and they were 18～37 (average 24.6) years old. Patients all underwent binocular surgery and no intraoperative complication occurred. The average diameter of corneal in each group was 10.7mm and 10.6mm respectively (t=0.04, p<0.05). The average diameter of corneal flap in Group I was 9.2mm, and for patients whose corneal curvature were greater than 44.0D, between 42.0D and 44.0D, or less than 42.0D, their average corneal flap diameter were 9.3mm, 9.1mm, and 8.6mm respectively, which showed significant positive correlation between the corneal curvature and corneal flap diameter (r=0.492, p=0.027). The average diameter of corneal flap in Group I was 8.3mm, and for patients whose corneal curvature were greater than 44.0D, between 42.0D and 44.0D, or less than 42.0D, their average corneal flap diameter were 8.4mm, 8.3mm, and 8.0mm respectively, which also showed significant positive correlation between the corneal curvature and corneal flap diameter (r=0.513, p=0.001). Conclusion The diameter of corneal flap created by LDV femtosecond laser was strongly correlated with corneal curvature, meaning patients with a high K Value tended to have a bigger corneal flap than patients with a relatively low K Value in femtosecond-assisted LASIK surgery. It suggested that surgeons should choose suction rings that are relatively bigger for patients with a low K Value in order to prevent creation of small or even free corneal flaps. And for patients with a high K Value, suction rings that are relatively smaller were recommended, in order to prevent creation of large corneal flaps, intraoperative bleeding, and post-LASIK dry eye.
Key words： LDV femtosecond laser; corneal flap; corneal curvature; correlation