Department of Ophthalmology, Antwerp University Hospital (UZA), Edegem, Belgium.
Department of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.
Ophthalmic Physiol Opt. 2021 Jul;41(4):748-756. doi: 10.1111/opo.12821. Epub 2021 Apr 16.
To present a descriptive system for the elliptic demarcation area seen in keratoconus densitometry maps (obtained with a Scheimpflug tomographer) and to evaluate its suitability for clinical practice.
The subjects were 30 keratoconus patients at different stages and 20 healthy subjects. The averaged densitometry maps ('two-layers' scan, with fixed layers 120 µm and endothelium) were analysed using a system of four categories (termed 'Brightness', 'Contrast', 'Decentration' and 'Octants surrounded by a dark line') that we created to characterise the demarcation area. Four examiners (three corneal specialists and one junior resident) used the system to classify the maps. The inter-rater agreement was calculated for two subgroups: (1) clinical keratoconus patients and (2) both healthy patients and forme fruste keratoconus patients. Intra-rater agreement was also determined.
Inter-rater agreement on classification was higher when analysing clinical keratoconus, reaching levels of substantial agreement. Despite this, only low levels of agreement were found in 'Decentration', penalized due to the skewness in the distribution of this descriptor. Almost perfect intra-rater agreement was obtained for all descriptors in the first subgroup of clinical keratoconus, whereas the agreement was generally moderate within the second subgroup of normal and forme fruste eyes. Agreement was slightly lower with the less experienced observer. At least three observers agreed on four forme fruste keratoconus eyes presenting abnormalities in the images. The observers reported that the 'Brightness' descriptor was subjective and redundant with 'Contrast'.
The description of the area was repeatable and reproducible, and may be a valuable supplement when documenting clinical keratoconus stage and progression in daily practice. However, a minor learning curve was noticed and agreement was higher among the more experienced observers. Since the descriptor 'Brightness' was found to be subjective and redundant, it was excluded from the final proposed classification.
提出一种描述性系统，用于角膜地形图（使用 Scheimpflug 断层扫描仪获得）中所见的圆锥角膜密度图的椭圆形边界区域，并评估其在临床实践中的适用性。
研究对象为 30 名处于不同阶段的圆锥角膜患者和 20 名健康受试者。使用我们创建的四个类别系统（称为“亮度”、“对比度”、“偏心”和“被暗线包围的八角形”）分析平均密度图（“两层”扫描，固定层 120μm 和内皮），以描述边界区域。四位检查者（三位角膜专家和一位初级住院医师）使用该系统对地图进行分类。计算了两个亚组（1）临床圆锥角膜患者和（2）健康患者和非典型圆锥角膜患者的组内评分者间一致性。还确定了组内评分者的一致性。
分析临床圆锥角膜时，分类的组间评分者间一致性更高，达到了显著一致的水平。尽管如此，在“偏心”方面仅发现了低水平的一致性，这是由于该描述符分布的偏态所致。在临床圆锥角膜的第一个亚组中，所有描述符的组内评分者间一致性几乎为完美，而在正常和非典型圆锥角膜的第二个亚组中，一致性通常为中度。经验较少的观察者的一致性略低。至少有三位观察者同意，在四个表现出图像异常的非典型圆锥角膜眼中，有四个观察者同意。观察者报告说，“亮度”描述符是主观的，与“对比度”冗余。
该区域的描述是可重复和可再现的，在日常实践中记录临床圆锥角膜阶段和进展时可能是有价值的补充。然而，注意到一个较小的学习曲线，并且经验丰富的观察者之间的一致性更高。由于发现描述符“亮度”是主观的和冗余的，因此将其从最终提出的分类中排除。
