采用不同术式和切削比的准分子激光角膜屈光手术后角膜地形图参数变化

Influence of Different Surgery Types and Ablation Ratios on the Change of Corneal Topography After Excimer Laser Refractive Surgery

目的探讨准分子激光角膜屈光手术中采用不同术式和切削比对术后角膜地形图参数变化的影响。方法选择2008年8月至2009年2月间在北京协和医院眼科接受准分子激光屈光手术治疗的患者52例(103眼),按手术方式将患者分为准分子激光原位角膜磨镶术组(L组)27例53眼和新型表层屈光手术组(A组)25例50眼。两组中,再按切削比分为亚组1(切削比≤0.15)和亚组2(切削比>0.15)。术前及术后第1周、1个月和3个月进行常规眼科检查,包括角膜地形图检查,测定指标包括角膜表面不规则指数(surface asymmetry index,SAI)、角膜表面规则指数(surface regularity index,SRI)、垂直子午线的角膜镜度数及其差值(Δsimulated keratoscopy reading,ΔSimK)和最大模拟角膜镜度数(simulated keratoscopy reading,SimK)等效值。分析不同术式组、不同切削比组之间术后角膜地形图参数变化的特点。结果在L2和A2组术后各时期SAI与术前比较差异均存在统计学意义(P均=0.000),而L1和A1组与术前比较差异无统计学意义(P>0.05)。在L2组,术后1周SRI较术前明显增加(P=0.010),而术后1个月及3个月差异无统计学意义(P>0.05);在A2组,术后1周及1个月SRI均较术前明显增加(P=0.000,P=0.005),而术后3个月差异无统计学意义(P>0.05);在L1和A1组术后各时期与术前比较差异均无统计学意义(P>0.05)。在各组中,术后各时期ΔSimK及SimK等效值较术前均明显下降(P均=0.000)。术后SAI和ΔSimK的变化受手术方式和切削比的共同影响(P均<0.05),而SRI和SimK等效值的变化仅受切削比的影响(P均<0.05)。结论准分子激光角膜屈光手术后角膜地形图参数均发生一定程度的变化,准分子激光原位角膜磨镶术后的变化程度大于新型表层屈光手术,且切削比越大,变化程度越大。

Objective To analyze the change of corneal topography after excimer laser photorefractive keratectomy and the influence of surgery types and ablation ratios. Methods A total of 52 myopic patients （ 103 eyes） underwent excimer laser refractive surgery in our hospital from August 2008 to February 2009. The patients were grouped by the type of surgery： laser in situ keratomileusis （ LASIK ） group （ 27 patients, 53 eyes ） and advanced surface ablation （ASA） group （25 cases, 50 eyes）. In both groups, the patients were subgrouped by ablation depth/corneal thickness ratio （AD/CT） ： subgroup 1 （ AD/CT GO. 15 ） and subgroup 2 （ AD/CT 〉 0. 15）. Routine ophthalmological examinations and corneal topography were performed before operation and 1 week, 1 month, and 3 months after operation. The main outcome measures included surface asymmetry index （SAI）, surface regularity index （SRI）, Asimulated keratoscopy reading （ASimK）, and simulated keratoscopy reading （SimK）. Results In subgroups L2 and A2, all the three postoperative SAI values improved significantly compared with preoperative values （ P = O. 000）, but not in subgroups L1 and A1 （ P 〉 0. 05 ）. In subgroup L2, the SRI value improved significantly 1 week after surgery （P = 0. 010）, but not after 1 month and 3 months （P 〉 0. 05 ）. In subgroup A2, the SRI values improved significantly 1 week and 1 month after surgery （P = O. 000, P = 0. 005 ）, but not after 3 months （P 〉 O. 05 ）. The SRI showed no significant difference among different time points in both subgroup L1 and A1 （ P 〉 0. 05 ）. In all patients, both ASimK and SimK equivalent value decreased significantly after the operation （P = O. 000）. The changes of SAI and ASimK were influenced by both surgery type and the ablation ratio （ P 〈 0. 05 ）, while the changes of SRI and SimK equivalent only by ablation ratio （P 〈 0. 05）. Conclusions The postoperative corneal topographic parameters change after excimer laser refractive surgery. The changes after LASIK are larger than those after advanced surface ablation, and the changes increase with the ablation ratio.