LASIK手术前后近视散光患者角膜前、后表面Q值的变化分析

目的比较青年近视散光患者在准分子激光原位角膜磨镶术（LASIK）手术前后角膜前、后表面非球面性的分布变化以及可能的影响因素。方法前瞻性系列病例研究。用ALLEGROOculyzer眼前房诊断系统分别在术前和术后1～3个月对北京同仁眼科中心18～39岁的近视散光患者共163例（296眼）进行测量，获得角膜前、后表面20。、25。、30。、35。、40。的Q值（AQ和PQ）及其变化（AAQ和APQ），分析其与屈光参数的关系。对手术前后角膜前、后表面不同范围的Q值进行秩和检验．对术后各Q值与患者屈光度、角膜中央厚度、最大切削深度进行直线相关分析。结果术前角膜各AQ值均与术前柱镜度（CD）呈负相关（r=-．213、-0．279、-0．332、-0．363、-0．133，P〈0．05）。术后各AQ值与术前差异均有统计学意义（皓38．15、43．94、48．47、44．78、25．97，P〈0．05），术后各PQ值与术前差异均有统计学意义（u=9．10、10．18、9．77、7．75、3．30，P〈0．05，）。术后△AQ20、△AQ25、△AQ30、△AQ35、△AQ40与术前球镜度（so）呈正相关（r=0．884、0．870、0．871、0．612、0．370，P〈0．05），与术前等效球镜度（SE）呈正相关（r=0．834、0．866、0．872、0．625、0．388，P〈0．05），与最大切削深度（MD）呈正相关（r=0．779、0．823、0．842、0．634、0．403。P〈0．05）．与残留角膜基质厚度（CS）呈负相关（r=-0．332、-0．377、-0．410、-0．352、-0．168，P〈0。05）；△AQ35、△AQ40与术前CD呈正相关（r=0．124、O．120，P〈0，05）。△PQ20、△PQ25、△PQ30与术前SD呈负相关（r=-0．210、-0．185、-0．154，P〈0．05），与术前SE呈负相关（r=-0．225、-0．196、-0．169，P〈0．05），与MD呈负相关（r=：-0．210、-0．184、-0．164，P〈0．05）。另外△PQ35与术前SD和SE均呈负相关（r=-0．121、-0．124，P〈0．05），△PQ40与术前SD呈负相关（r=-0．120，P〈0．05）。结论大多数青年近视散光患者角膜形态前表面为长椭圆形，后表面中央为扁椭圆形，周边为长椭圆形，LASIK术后发生明显改变，均向扁椭圆形方向变化．前表面形态变化更为显著，可能受多种因素的影响。

Analvsis of the change in anterior and posterior corneal Q-values in myopic astigmatism patients before and after LASIK

Objective To evaluate and compare the distribution of anterior and posterior corneal asphericity in young myopic astigmatism patients before and after laser in situ keratomileusis （LASIK） surgery, and to investigate the possible factors influencing change. Methods This was a prospective case-series study. Patients with myopic astigmatism （18-39 years old） were recruited from Beijing Tongren Eye Center. The Q-values of 20°, 25°, 30°, 35°, 40° of the anterior and posterior corneal surfaces （AQ and PQ） were registered using an ALLEGRO Oculyzer before and after LASIK surgery （1-3 months）. Changes in AQ and PQ （△AQ and △PQ） were investigated. Correlations of AQ, PQ, △AQ and △PQ to the refractive index were also analyzed. Data were analyzed with a rank sum test and a Pearson correlation. Results Two hundred ninety-six eyes of 163 patients were studied. The AQ20, AQ25, AQ30, AQ35 and AQ40 of the cornea were -0.24±0.12, -0.28±0.12, -0.31±0.12, -0.35±0.12 and -0.33±0.27 before LASIK surgery, while the PQ20, PQ25, PQ30, PQ35 and PQ40 were 0.21±0.25, 0.04±0.21, -0.10±0.19, -0.20±0.16 and -0.30±0.13. AQ values were negatively correlated with the cylindrical diopter （CD） （r=-0.213, -0.279, -0.332, -0.363, -0.133, P〈0.05）. After LASIK surgery both the AQ and PQ values showed significantly changes, which were 0.96±0.55, 0.94±0.48, 0.80±0.40, 0.51±0.35, 0.25±0.36 for the AQs （U=38.15, 43.94, 48.47, 44.78, 25.97, P〈0.05） and 0.31±0.25, 0.14±0.21, -0.02±0.19, -0.16i4）.17, -0.29i4）.15 for the PQs （U=9.10, 10.18, 9.77, 7.75, 3.30, P〈O.05）. △AAQ20, △AQ25, △AQ30, △AQ35 and △AQ4o showed positive correlation with spherical diopter （SD） （r=0.884, 0.870, 0.871, 0.612, 0.370, P〈0.05）, spherical equivalent （SE） （r=0.834, 0.866, 0.872, 0.625, 0.388, P〈0.05） and the maximum ablation depth （MD） （r=0.779, 0.823, 0.842, 0.634, 0.403, P〈0.05）. They were also negatively correlated with the residual depth of cornea stroma （CS） （r=-0.332, -0.377, -0.410, -0.352, -0.168, P〈0.05）. AAQa5 and AAQ4o showed negative correlation with CD （r=0.124, 0.120, P〈0.05）. △PQ20, △PQ 25and △PQ30 showed negative correlation with SD （r=-0.210, -0.185, -0.154, P〈0.05）, SE （r=-0.225, -0.196, -0.169, P〈0.05） and MD （r=-0.210, -0.184, -0.164, P〈0.05）. △PQ35 were negatively correlated with SD （r=-0.121, P〈0.05） and SE （r=-0.124, P〈0.05）. While △PQ40 only showed negative correlation with SD （r=-0.120, P〈0.05）. Conclusion The anterior corneal surface of most young myopic astigmatic patients is prolate. The central part of posterior corneal surface is oblate, and the periphery part is prolate. They changes to oblate significantly after LASIK, especially the anterior corneal surface. Many factors affect the Q-values.