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Anterior segment optical coherence tomography scanning protocols and corneal thickness repeatability.
Contact Lens & Anterior Eye ( IF 3.2 ) Pub Date : 2019-12-18 , DOI: 10.1016/j.clae.2019.12.008
Damien Fisher 1 , Michael J Collins 1 , Stephen J Vincent 1
Affiliation  

Purpose

To examine the influence of anterior segment optical coherence tomography imaging protocols on the intraobserver and intrasession repeatability of epithelial, stromal, and total corneal thickness measurements.

Methods

Repeated anterior segment optical coherence tomography (AS-OCT) images (Spectralis, Heidelberg) were obtained from 15 adults using single 8.3 mm wide horizontal line scans with an average of 2, 10, 20, 30, 50 and 100 B-scans. Volumetric scans consisting of nine 8.3 mm horizontal line scans encompassing a 1.3 mm vertical region were also captured (with 20 B-scans per line scan). Single point thickness measures (at the normal to the tangent of the anterior corneal surface) were compared with thickness measures averaged over the central 6 mm. The impact of B-scan averaging and intraobserver variability were examined for single line scans. For volumetric scans, the impact of the number of line scans upon intraobserver and intrasession variability were calculated.

Results

Intraobserver repeatability did not vary significantly as a function of the number of averaged B-scans per line scan, but was lowest for 20–30 averaged B scans. For volumetric scans, increasing the number of line scans did increase scan duration (p < 0.001), with minimal impact upon the average scan quality index (p = 0.06). Averaging more than 3 line scans did not significantly improve intraobserver or intrasession repeatability for either single point or average thickness measurements.

Conclusion

AS-OCT volumetric scans with 3 lines each consisting of 20 B-scans with measurements averaged over a central 6 mm of the cornea provide highly repeatable measures of epithelial, stromal and total corneal thickness (95 % LoA ≤ ±3.2 μm for intraobserver repeatability and ≤ ±3.7 μm for intrasession repeatability). This scanning protocol can provide reliable information when monitoring subtle changes in corneal thickness.



中文翻译:

前段光学相干断层扫描协议和角膜厚度可重复性。

目的

检查眼前节光学相干断层扫描成像协议对上皮、基质和总角膜厚度测量的观察者内和会话内可重复性的影响。

方法

使用平均 2、10、20、30、50 和 100 次 B 扫描的单次 8.3 毫米宽水平线扫描从 15 名成人获得重复的眼前节光学相干断层扫描 (AS-OCT) 图像(Spectralis,海德堡)。还捕获了由九个 8.3 毫米水平线扫描组成的体积扫描,包括 1.3 毫米垂直区域(每行扫描 20 次 B 扫描)。将单点厚度测量值(在角膜前表面切线的法线处)与中央 6 mm 上的平均厚度测量值进行比较。单线扫描检查了 B 扫描平均和观察者内变异性的影响。对于体积扫描,计算了线扫描次数对观察者内和会话内可变性的影响。

结果

观察者内可重复性作为每行扫描的平均 B 扫描次数的函数没有显着变化,但在 20-30 次平均 B 扫描时最低。对于体积扫描,增加线扫描次数确实会增加扫描持续时间 (p < 0.001),对平均扫描质量指数的影响最小 (p = 0.06)。对于单点或平均厚度测量,平均超过 3 次线扫描并没有显着提高观察者内或会话内的可重复性。

结论

AS-OCT 体积扫描有 3 条线,每条线由 20 次 B 扫描组成,测量值在角膜中央 6 mm 上进行平均测量,提供高度可重复的上皮、基质和总角膜厚度测量值(95 % LoA ≤ ±3.2 μm,用于观察者内可重复性和≤ ±3.7 μm 用于会话内可重复性)。在监测角膜厚度的细微变化时,该扫描协议可以提供可靠的信息。

更新日期:2019-12-18
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