Purpose

To investigate the repeatability and reproducibility of choroidal thickness measurements using Lenstar images in young myopic children before and after one-month orthokeratology (ortho-k) treatment.

Method

Ocular biometry of 39 subjects were performed using the Lenstar 900. The first five measurements with maximum differences of 0.02 mm in axial length in the right eyes were saved and used for measurement of choroidal thickness. Subfoveal choroidal thickness were manually measured by identifying the signals from the retinal pigmented epithelium layer and chorioscleral interface. Repeatability was determined by comparing measurements of the same images made by the same observer on two separate occasions (four weeks apart), while reproducibility was calculated by comparing measurements of the same images made by two independent observers. Data was analysed using intra-class correlation coefficients (ICC) and non-parametric Bland and Altman plots.

Results

The choroidal peaks could not be identified in all five measurements in all subjects. On average, only 71% subjects had at least four definable images. Compared with the use of fewer than four images, reliability using an average of four definable images improved statistically, but remained clinically unacceptable (>10 µm), although pre- and post-ortho-k ICC values were good to excellent for repeatability (0.867 and 0.975, respectively) and excellent and good for reproducibility (0.959 and 0.868, respectively). Non-parametric pre- and post-ortho-k limits of agreement (2.5% and 97.5% percentiles) obtained were −45.8 to 79.3 µm and −30.3 to 9.5 µm, respectively for repeatability, and −29.0 to 33.5 µm and −21.8 to 70.0 µm, respectively for reproducibility.

Conclusion

Choroidal thickness measurements using the Lenstar did not show good reliability, despite the high ICC values, non-parametric Bland and Altman plots demonstrated a wide variability of measurement errors. Any changes in subfoveal choroidal thickness, measured by Lenstar, of <80 µm may not represent real changes.

中文翻译：

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在角膜塑形术治疗前后使用 Lenstar 图像手动测量儿童脉络膜厚度的可重复性和可重复性

目的

研究在 1 个月的角膜塑形术 (ortho-k) 治疗前后使用 Lenstar 图像对年轻近视儿童进行脉络膜厚度测量的可重复性和可重复性。

方法

使用 Lenstar 900 对 39 名受试者进行眼部生物测量。保存右眼轴向长度最大差异为 0.02 mm 的前五次测量值，并用于测量脉络膜厚度。通过识别来自视网膜色素上皮层和脉络膜巩膜界面的信号手动测量中心凹下脉络膜厚度。可重复性是通过比较同一观察者在两个不同场合（相隔 4 周）拍摄的相同图像的测量结果来确定的，而可重复性是通过比较两个独立观察者拍摄的相同图像的测量结果来计算的。使用类内相关系数 (ICC) 和非参数 Bland 和 Altman 图分析数据。

结果

在所有受试者的所有五次测量中都无法识别出脉络膜峰。平均而言，只有 71% 的受试者至少有四个可定义的图像。与使用少于四张图像相比，使用平均四张可定义图像的可靠性在统计学上有所提高，但在临床上仍然不可接受（>10 µm），尽管角膜塑形术前后的 ICC 值在可重复性方面非常好（0.867）和 0.975，分别）和良好的再现性（分别为 0.959 和 0.868）。对于可重复性，获得的非参数正交 k 前后一致性限值（2.5% 和 97.5% 百分位数）分别为 -45.8 至 79.3 µm 和 -30.3 至 9.5 µm，以及 -29.0 至 33.5 µm 和 -21.8 至70.0 µm，分别用于重现性。

结论

尽管 ICC 值很高，但使用 Lenstar 进行的脉络膜厚度测量并未显示出良好的可靠性，非参数 Bland 和 Altman 图显示了测量误差的广泛可变性。Lenstar 测量的中心凹下脉络膜厚度的任何变化小于 80 µm 可能并不代表真正的变化。