Objectives: To investigate angle Kappa and diopter distribution in myopic patients and the changes of angle Kappa and corneal morphology after Sub-Bowman-Keratomileusis (SBK), and to analyze the effects of the surgery on corneal morphologic changes and the patients' near fixation characteristics.
Methods: The clinical data of 134 myopic patients (268 eyes) undergoing SBK from August 2015 to August 2016 were retrospectively analyzed. Angle Kappa, corneal curvature in the central corneal region of 3 mm, and post-corneal Diff value were measured by Orbscan IIz Corneal Topography System before operation, 1 month and 6 months after operation. According to the values of angle Kappa before SBK, the patients were divided into 2 groups: the large K group (angle Kappa≥5°, 71 eyes) and the small K group (angle Kappa<5°, 197 eyes). Correlation analysis of the factors influencing angle Kappa at 6 months after operation was performed.
Results: In the large K group, angle Kappa was (5.67±0.65)°, spherical equivalent was (-4.84±2.32) D, and angle Kappa was decreased after operation (both P<0.05) with the increased decreasing range over time. In the small K group, angle Kappa was (3.51±1.08)°, spherical equivalent was (-5.78±2.63) D, angle Kappa was increased after operation with decreased increasing range over time, and the difference was statistically significant between 6 months after operation and before operation (P<0.05).The post-corneal Diff value of the 2 groups was increased after operation (all P<0.001), and was decreased from 1 month to 6 months after surgery. The corneal curvature in the central corneal region of 3 mm of the 2 groups 1 month after operation was decreased significantly (both P<0.001). From 1 month to 6 months after operation, the corneal curvature of the large K group tended to be stable, while the corneal curvature of the small K group tended to increase. There was no significant correlation between the changes of angle Kappa 6 months after operation and the changes of the corneal central curvature or the post-corneal Diff value (both P>0.05), but the changes of angle Kappa 6 months after operation was positively correlated with corneal cutting thickness (rlarge K group=0.398, rsmall K group=0.218, both P<0.05) and it was negatively correlated with preoperative diopter (rlarge K group=-0.283, rsmall K group=-0.233, both P<0.05).
Conclusions: The angle Kappa is decreased in low-moderate myopia patients with large angle Kappa, while is increased in high myopia patients with small angle Kappa after SBK. Myopia patients after SBK will look for the new balance of the binocular accommodation and vergence function for improving the comfort in the near-work situations.
目的: 研究近视患者Kappa角与屈光度的分布情况及前弹力层下激光角膜磨削术(Sub-Bowman-Keratomileusis，SBK)后患者Kappa角与角膜形态的变化规律，分析手术对角膜形态及双眼视近功能的影响。方法: 回顾性分析2015年8月至2016年8月在中南大学湘雅医院行SBK治疗的134例(268只眼)近视患者的临床资料。患者在术前、术后1个月、术后6个月均采用Orbscan IIz角膜地形图行Kappa角、角膜中央3 mm区曲率、角膜后表面Diff值检测。根据术前Kappa角的大小分为大K组(Kappa角≥5°，71只眼)和小K组(Kappa角<5°，197只眼)。对影响术后6个月Kappa角变化的因素进行相关性分析。结果: 大K组Kappa角为(5.67±0.65)°，等效球镜度为(-4.84±2.32) D，术后Kappa角较术前减小(均P<0.01)，且随着时间的推移减小的幅度增大；小K组Kappa角为(3.51±1.08)°，等效球镜度为(-5.78±2.63) D，术后Kappa角较术前增大，术后6个月与术前相比差异具有统计学意义(P<0.05)，且随着时间的推移增大的幅度减小。2组术后角膜后表面Diff值均变大(均P<0.001)，术后1个月至6个月Diff值呈减小趋势。2组术后1个月角膜中央3 mm区曲率均明显变小(均P<0.001)，术后1个月至术后6个月，大K组曲率趋于稳定，小K组曲率呈增大趋势。2组患者术后6个月Kappa角的变化与角膜中央3 mm区曲率及角膜后表面Diff值的变化均无明显相关性(均P>0.05)，而均与角膜切削厚度呈正相关(r大K组=0.398，r小K组=0.218，均P<0.05)，与术前屈光度呈负相关(r大K组=-0.283，r小K组=-0.233，均P<0.05)。结论: 大Kappa角多出现在中低度近视患者中，术后Kappa角明显减小，而小Kappa角多出现在中高度近视患者中，术后Kappa角增大。近视患者经SBK后视近时双眼调节与集合功能重新调整以达到平衡，视近功能可能获得一定程度的改善。.
Keywords: Sub-Bowman-Keratomileusis; angle Kappa; corneal curvature; myopia; post-corneal Diff value.