Corneal pachymetry mapping with high-speed optical coherence tomography
Corneal pachymetry mapping with high-speed optical coherence tomography
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DOI：
10.1016/j.ophtha.2006.01.048
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发表时间：
2006-05-01
期刊：
影响因子：
13.7
通讯作者：
Huang, D
中科院分区：
文献类型：
--
作者：
Li, Y;Shekhar, R;Huang, D
目的：应用光学相干断层扫描仪(OCT)测量准分子激光原位角膜磨镶术(LASIK)前后角膜厚度。设计：横断面观察性研究。受试者：21例(42只眼)正常人，行准分子激光原位角膜磨镶术。方法：采用高速(2000次/秒)1.3微米波长的角膜及眼前段OCT样机进行角膜扫描。扫描图案为以顶点反射为中心的8条经络上10 mm的放射线。在0.5秒内获得了1024次A扫描的整个扫描模式。我们开发了用于三维角膜重建和测量的自动计算机处理。角膜厚度垂直于前表面测量，并以彩色角膜厚度图和分区统计的形式显示。地图分为中心区(2 Mm)和3个环状区域(中心周围2~5 mm；过渡区5~7 mm；周边7~10 mm)，并进一步划分为象限区域。计算直径为7 mm的区域的平均、最小和最大角膜厚度。分别于术前、术后3个月进行3次光学相干断层扫描和超声角膜厚度测量。结果：准分子激光原位角膜磨镶术前角膜中央厚度(CCT)为546.9+/-29.4µm(平均+/-SD)，超声为553.3+/-33.0µm。准分子激光原位角膜磨镶术后，OCT为513.7±44.5mm2，B超为498±46.6mm2。光学相干断层扫描与超声CCT高度相关(准分子激光原位角膜磨镶术前皮尔逊相关系数r=0.97，术后相关系数r=0.98)。术前光学相干断层扫描CCT略小于超声CCT(平均差-6.4微米；95%符合限-23.2~10.4微米)，而术后略大于超声CCT(15.7微米；-1.6~33微米)。这些差异有统计学意义，但不超过超声测厚仪之间的CCT测量差异。OCT带状测厚仪的平均重复性约为2微米。结论：高速OCT可在大面积角膜上提供非接触式、快速、可重复性的测厚仪。它相当于超声测量LASIK术前、术后的CCT，对角膜屈光性手术方案的制定和角膜疾病的诊断有一定的参考价值。
Objective: To map corneal thickness before and after LASIK with optical coherence tomography (OCT). Design: Cross-sectional observational study.Participants: Forty-two eyes of 21 normal subjects undergoing LASIK.Methods: A high-speed (2000 axial scans/second) 1.3-mu m-wavelength corneal and anterior segment OCT prototype was used for corneal scanning. The scan pattern consisted of 10-mm radial lines on 8 meridians centered on the vertex reflection. The entire scan pattern of 1024 a-scans was acquired in 0.5 seconds. We developed automated computer processing for 3-dimensional corneal reconstruction and measurement. Corneal thickness was measured normal to the anterior surface and presented as color pachymetry maps and zonal statistics. The maps were divided into a central zone (< 2 mm) and 3 annular areas (pericentral, 2-5 mm; transitional, 5-7 mm; peripheral, 7-10 mm), which were further divided into quadrantal zones. The average, minimum, and maximum corneal thicknesses were computed for zones within the 7-mm diameter. Optical coherence tomography and ultrasound pachymetry were measured 3 times at the preoperative and 3-month postoperative visits. Reproducibility was assessed by the pooled standard deviations (SDs) of the repeated measurements.Main Outcome Measures: Optical coherence tomography pachymetric map and zonal statistic, and ultrasound pachymetry.Results: Before LASIK, central corneal thicknesses (CCTs) were 546.9 +/- 29.4 mu m (mean +/- SD) for OCT and 553.3 +/- 33.0 mu m for ultrasound. After LASIK, CCTs were 513.7 +/- 44.5 mu m for OCT and 498 +/- 46.6 mu m for ultrasound. Optical coherence tomography and ultrasound CCT were highly correlated (Pearson correlation r = 0.97 before LASIK and 0.98 afterwards). Optical coherence tomography CCT was slightly less than ultrasound CCT before surgery (mean difference, -6.4 mu m; 95% limits of agreement, -23.2 to 10.4 mu m) but slightly greater after LASIK (15.7 mu m; -1.6 to 33 mu m). These differences were statistically significant, but no more than the CCT measurement differences between ultrasound pachymeters. The reproducibility of the OCT zonal pachymetry averages was roughly 2 Am.Conclusions: High-speed OCT provided noncontact, rapid, reproducible pachymetric mapping over a wide area of the cornea. It is equivalent to ultrasound for CCT measurement before and after LASIK This technology could be valuable for planning keratorefractiveprocedures and diagnosis of corneal diseases.