Vihanninjoki Kyösti, Burk Reinhard O W, Teesalu Pait, Tuulonen Anja, Airaksinen P Juhani
Department of Ophthalmology, University of Oulu, Oulu, Finland.
Acta Ophthalmol Scand. 2002 Feb;80(1):47-53. doi: 10.1034/j.1600-0420.2002.800110.x.
The Heidelberg Retina Tomograph (HRT) is a confocal scanning laser tomograph that produces high resolution optical section images of the optic disc and central retina. Measurement accuracy and reproducibility is good. Several of the stereometric variables depend on the definition of a reference plane level. The purpose of the present study was to evaluate the four different reference levels in terms of their advantages and disadvantages in clinical work.
Sixty-seven randomly chosen eyes belonging to 67 subjects were included in this study. Forty of the eyes were healthy and 27 had glaucoma. The HRT with software versions 1.09 and 1.11 was used to acquire and evaluate topographic measurements of the optic disc. Image analysis was performed at four different reference levels: 320 microm fixed offset reference level (REFd) (version 1.09), an individually determined reference level (REFi), a papillo-macular reference level (REFm) and a flexible reference level (REFf) (version 1.11). ANOVA was used to determine differences in the topographic parameters between the reference levels.
In terms of the healthy eyes, all the variables using different reference levels give rather similar results. However, with advanced glaucoma the measurement values provided with REFd are clearly different to those of the other reference levels. The measurement values using REFm and REFf provide fairly similar results in all clinical groups. REFf indicates the lowest point in the segment between 350 degrees and 356 degrees along the contour line and thus provides the most stable and clinically useful reference level at present.
At present, the flexible reference level REFf gives the most reliable and adequate HRT measurement values, both in normal and in glaucomatous eyes.
海德堡视网膜断层扫描仪（HRT）是一种共焦扫描激光断层扫描仪，可生成视盘和视网膜中央的高分辨率光学断层图像。测量准确性和可重复性良好。几个立体测量变量取决于参考平面水平的定义。本研究的目的是评估四种不同参考水平在临床工作中的优缺点。
本研究纳入了67名受试者的67只随机选择的眼睛。其中40只眼睛健康，27只患有青光眼。使用软件版本1.09和1.11的HRT获取并评估视盘的地形图测量值。在四个不同的参考水平上进行图像分析：320微米固定偏移参考水平（REFd）（版本1.09）、个体确定的参考水平（REFi）、视乳头黄斑参考水平（REFm）和灵活参考水平（REFf）（版本1.11）。采用方差分析确定参考水平之间地形图参数的差异。
就健康眼睛而言，使用不同参考水平的所有变量给出的结果相当相似。然而，在晚期青光眼患者中，REFd提供的测量值与其他参考水平的测量值明显不同。在所有临床组中，使用REFm和REFf的测量值提供了相当相似的结果。REFf指示了沿轮廓线在350度至356度之间的节段中的最低点，因此目前提供了最稳定且临床上有用的参考水平。
目前，无论是在正常眼睛还是青光眼眼中，灵活参考水平REFf都能给出最可靠和合适的HRT测量值。
