Garway-Heath D F, Poinoosawmy D, Wollstein G, Viswanathan A, Kamal D, Fontana L, Hitchings R A
Glaucoma Unit, Moorfields Eye Hospital, City Road, London EC1V 2PD.
Br J Ophthalmol. 1999 Jun;83(6):664-9. doi: 10.1136/bjo.83.6.664.
The development of imaging and measurement techniques has brought the prospect of greater objectivity in the measurement of optic disc features, and therefore better agreement between observers. The purpose of this study was to quantify and compare the variation between observers using two measurement devices.
Optic disc photographs and images from the Heidelberg retina tomograph (HRT) of 30 eyes of 30 subjects were presented to six observers for analysis, and to one observer on five separate occasions. Agreement between observers was studied by comparing the analysis of each observer with the median result of the other five, and expressed as the mean difference and standard deviation of differences between the observer and the median. Inter- and intraobserver variation was calculated as a coefficient of variation (mean SD/mean x 100).
For planimetry, agreement between observers was dependent on observer experience, for the HRT it was independent. Agreement between observers (SD of differences as a percentage of the median) for optic disc area was 4.0% to 7.2% (planimetry) and 3.3% to 6.0% (HRT), for neuroretinal rim area it was 10.8% to 21.0% (planimetry) and 5.2% to 9.6% (HRT). The mean interobserver coefficient of variation for optic disc area was 8.1% (planimetry) and 4.4% (HRT), for neuroretinal rim area it was 16.3% (planimetry) and 8.1% (HRT), and (HRT only) for rim volume was 16.3%, and reference height 9.1%. HRT variability was greater for the software version 1.11 reference plane than for version 1.10. The intraobserver coefficient of variation for optic disc area was 1.5% (planimetry) and 2.4% (HRT), for neuroretinal rim area it was 4.0% (planimetry) and 4.5% (HRT).
Variation between observers is greatly reduced by the HRT when compared with planimetry. However, levels of variation, which may be clinically significant, remain for variables that depend on the subjective drawing of the disc margin.
成像和测量技术的发展为视盘特征测量带来了更高客观性的前景，从而使观察者之间的一致性更好。本研究的目的是使用两种测量设备量化并比较观察者之间的差异。
将30名受试者的30只眼睛的视盘照片和海德堡视网膜断层扫描仪（HRT）图像提供给6名观察者进行分析，并在5个不同场合提供给1名观察者。通过将每个观察者的分析结果与其他5名观察者的中位数结果进行比较来研究观察者之间的一致性，并表示为观察者与中位数之间差异的平均差和标准差。观察者间和观察者内变异以变异系数（平均标准差/平均值×100）计算。
对于平面测量法，观察者之间的一致性取决于观察者的经验，对于HRT则与之无关。视盘面积观察者之间的一致性（差异标准差占中位数的百分比）为4.0%至7.2%（平面测量法）和3.3%至6.0%（HRT），神经视网膜边缘面积为10.8%至21.0%（平面测量法）和5.2%至9.6%（HRT）。视盘面积的平均观察者间变异系数为8.1%（平面测量法）和4.4%（HRT），神经视网膜边缘面积为16.3%（平面测量法）和8.1%（HRT），（仅HRT）边缘体积为16.3%，参考高度为9.1%。软件版本1.11的参考平面的HRT变异性大于版本1.10。视盘面积的观察者内变异系数为1.5%（平面测量法）和2.4%（HRT），神经视网膜边缘面积为4.0%（平面测量法）和4.5%（HRT）。
与平面测量法相比，HRT大大降低了观察者之间的变异。然而，对于依赖于视盘边缘主观绘制的变量，仍存在可能具有临床意义的变异水平。
