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目的 探讨Orbscan角膜地形图系统 (Orbscan系统 )的测量误差及其影响因素 ,为临床使用提供依据。方法 使用Orbscan系统和A超仪 ,测量 2 0 0例 ( 40 0只眼 )行准分子激光原位角膜磨镶术 (laserinsitukeratomileusis,LASIK)患者和 5 0例 ( 10 0只眼 )行准分子激光屈光性角膜切削术(photorefractivekeratectomy,PRK)患者手术前、后的角膜厚度和中央前房深度 ;分别于PRK和LASIK手术前、后使用Orbscan系统测量患者的角膜后表面屈光力 ,并对测量值进行分析比较。结果 Orbscan系统测量的角膜厚度值LASIK和PRK术前低于A超仪的测量值 ,差值为 18 83～ 2 4 2 9μm ;LASIK和PRK术后与A超仪测量值的差值为 5 6 32～ 139 5 2 μm ,明显高于术前。LASIK和PRK手术前、后Orbscan系统测量的中央前房深度值与A超仪测量值的差值为 0 16～ 0 2 5mm ,无临床意义。LASIK手术前、后Orbscan系统测量的角膜后表面屈光力差值约为 - 0 6 0D ;PRK手术前、后Orbscan系统测量的角膜后表面屈光力差值低度组为 - 0 5 1D ,中度组为 - 1 12D。结论 Orbscan系统测量值的精确性尚待进一步提高 ;LASIK和PRK术后角膜雾状混浊和角膜前表面屈光力的改变是导致Orbscan系统测量误差增大的主要原因 ;Orbscan系统的测量误差是临床工作不可忽
Objective To investigate the measurement error and its influencing factors of Orbscan corneal topography system (Orbscan system), and provide the basis for clinical use. Methods 250 patients (40 eyes) underwent laser in situ keratomileusis (LASIK) and 50 patients (100 eyes) underwent excimer laser Corneal thickness and central anterior chamber depth before and after PRK were measured before and after PRK and LASIK respectively. The Orbscan system was used to measure the corneal posterior refractive power of the patients. The measurement values analyse and compare. Results The values of corneal thickness measured by Orbscan system were lower than those measured by A-scan before LASIK and PRK, with a difference of 18 83 ~ 2 4 2 9 μm. The difference between LASIK and PRK measured by A-scan was 56 32 ~ 139 5 2 μm, significantly higher than preoperative. The difference between the central anterior chamber depth measured by the Orbscan system before and after LASIK and PRK surgery and the A-super-instrument measurement was 0 16 ~ 0 2 5 mm, which is not clinically significant. The difference of corneal posterior surface refractive power measured by Orbscan system before and after LASIK surgery was about -060D. The difference of corneal posterior surface refractive power measured by Orbscan system before and after PRK surgery was -0.51D, - 1 12D. Conclusion The accuracy of Orbscan system measurement needs to be further improved. The changes of corneal opacity and corneal anterior refractive power after LASIK and PRK are the main causes of Orbscan system measurement error. The measurement error of Orbscan system is not clinical work suddenly