不同方法测量近视眼准分子激光原位角膜磨镶术前后角膜厚度的变化

Comparison of corneal pachymetry before and after LASIK using different methods

目的对用Visante眼前节光学相干断层扫描仪(anterior segment optical coherence tomography,AS-OCT)、Orbscan-Ⅱ眼前节分析仪以及超声角膜测厚仪测量近视眼准分子激光原位角膜磨镶术(laser in situ keretomileusis,LASIK)前、后的角膜厚度结果准确性进行分析,为临床应用提供参考。方法49例(98眼)近视眼患者于LASIK手术前及手术后第1个月,分别用Visante眼前节光学相干断层扫描仪、Orbscan-Ⅱ眼前节分析仪以及超声角膜测厚仪进行角膜中央厚度测量,对不同测量方法间的比较进行配对t检验,相关性采用Pearson相关性分析。结果Visante眼前节光学相干断层扫描仪、Orbscan-Ⅱ眼前节分析仪(校正系数分别为0.92和0.95)以及超声角膜测厚仪在LASIK手术前测量角膜中央厚度依次为(528.40±30.73)μm、(531.56±33.09)μm、(548.90±34.17)μm和(549.92±31.35)μm,三种检查仪测量结果有高度相关性。AS-OCT测量所得的角膜中央厚度较超声法测量结果薄(21.52±14.17)μm,差异有统计学意义(t=10.52,P=0.000);Orbscan-Ⅱ法采用0.92校正系数时其测量结果较超声法薄(18.35±11.14)μm,差异有统计学意义(t=11.41,P=0.000),而采用0.95的校正系数时,测量结果较超声法薄(1.02±11.53)μm,差异无统计学意义(t=0.613,P=0.543)。LASIK手术后第1个月,上述仪器测量结果依次为(448.85±35.53)μm、(434.37±42.07)μm、(448.39±43.26)μm和(445.71±34.84)μm。AS-OCT测量角膜中央厚度较超声法测量结果厚(2.52±9.61)μm,差异无统计学意义(t=-1.82,P=0.076);Orbscan-Ⅱ法采用0.92校正系数时其测量结果较超声法薄(11.47±15.08)μm,差异有统计学意义(t=5.27,P=0.000),采用0.95的校正系数时,测量结果较超声法厚(2.68±15.95)μm,差异无统计学意义(t=-1.165,P=0.250)。结论LASIK手术前,Visante眼前节光学相干断层扫描仪角膜中央厚度测量值较小,手术后测量结果与超声测量结果一致;Orbscan-Ⅱ眼前节分析仪采用厂家默认校正系数时手术前后测量结果均较薄,采用合理校正系数时测量结果可信。

Objective To analyze the accuracy of central corneal thickness （CCT） measured by Visante anterior segment optical coherence tomography （AS-OCT）, Orbscan-Ⅱ and A-scan ultrasound pachymetry （USP） before and after laser in situ keretomileusis （LASIK） in myopic patients. Methods Forty-nine myopic patients （98 eyes） underwent Visante AS-OCT, Orbscan-Ⅱ （acoustic equivalent correction factors of 0.92 and 0.95 were used） and USP examination pre- and 1-month post-LASIK. The differences between the instruments were evaluated by t tests. The correlation between the measurements was evaluated using Pearson correlation coefficients. Results Before LASIK, the mean measurements of average CCTs with the Visante AS-OCT, Orbscan-Ⅱ （acoustic equivalent correction factors of 0.92 and 0.95） and USP were （528.40±30.73）μm, （531.56±33.09）μm, （548.90±34.17）μm and （549.92±31.35）μm, respectively. There was a high correlation among the instruments. The mean CCT measurement with the AS-OCT was （21.52±14.17）μm was less than that with USP and the difference was significant（t=10.52, P=0.000）. The mean CCT measurement with the Orbscan-Ⅱ （0.92） was （18.35±11.14）μm less than that with USP, and the difference was significant （t=11.41, P=0.000）. However, with the 0.95, the difference was （1.02±11.53）μm, which was not significant（t=0.613, P=0.543）. After LASIK, the mean measurements of average CCTs with the Visante AS-OCT, Orbscan-Ⅱ （acoustic equivalent correction factors of 0.92 and 0.95） and USP were （448.85±35.53）μm, （434.37±42.07）μm, （448.39±43.26）μm, and （445.71±34.84）μm, respectively. The mean CCT measurement with the AS-OCT was （2.52±9.61）μm, which was thicker than that with USP but the difference was not significant （t=-1.82, P=0.076）. The mean CCT measurement with Orbscan-Ⅱ with the default acoustic equivalent correction factor 0.92 was （11.47±15.08）μm, which was lower than that with USP, and the difference was significant （t=5.27, P=0.000）; however, with the acoustic equivalent correction factor of 0.95, the difference was （2.68±15.95）μm, which was not significant （t=-1.165, P=0.250）. Conclusion The AS-OCT underestimates CCT when it is compared to that measured with USP pre-LASIK but is in agreement with USP post-LASIK. Orbscan-Ⅱ underestimates CCT with the default acoustic equivalent correction factor both before and after LASIK, but with the acoustic equivalent correction factor of 0.95, it is in agreement with USP.