Burk R O, Vihanninjoki K, Bartke T, Tuulonen A, Airaksinen P J, Völcker H E, König J M
Department of Ophthalmology, University of Heidelberg, Germany.
Graefes Arch Clin Exp Ophthalmol. 2000 May;238(5):375-84. doi: 10.1007/s004170050368.
Topometry of the optic disc is the quantitative assessment of the structure of the optic nerve head by means of three-dimensional parameters. The parameter values depend on definitions of intraocular reference planes.
To describe the development of intraocular reference planes in laser scanning tomography for the Heidelberg Retina Tomograph (HRT) using image intrinsic data with a fixed offset reference plane (320 microm) and to present a contour-line-based "flexible" standard reference plane ("SRP") for calculation of intrapapillary stereometric parameters taking the interindividual variability of optic disc topography into account.
Ten-degree triple images were obtained by laser scanning tomography from 99 glaucoma eyes and 180 normal eyes. The images were evaluated to assess the variability of height measurements of an optic disc border contour-line segment (6 degrees width) corresponding to the site of the papillo-macular bundle as indicated by the average optic disc surface inclination angle.
The average optic disc surface inclination angle was -7 degrees +/- 3 degrees below the horizontal meridian (0 degrees). The 6 degrees wide contour-line segment for the SRP was chosen according to the average surface inclination angle (-10 degrees to -4 degrees). The reproducibility of the SRP-segment height measurements was 16.0+/-10.8 microm for normal eyes and 23.4+/-18.0 microm for glaucoma eyes. To ensure that the automatic reference level determination for intrapapillary parameters remained below the disc border height, we defined the SRP level at a 50 microm offset (>2 SD of average segment height reproducibility in glaucoma) added to the individual height position of the 6 degrees contour line segment.
The flexible standard reference plane allows for automatic determination of intrapapillary variables once a disc border contour line is interactively defined. In contrast to a fixed offset reference plane (e.g. 320 microm below the mean retina height), the interindividual variability of optic disc topography (oblique insertion, glaucomatous surface flattening) is respected at the cost of the need for an accurate optic disc border outline.
视盘地形图是通过三维参数对视神经乳头结构进行的定量评估。参数值取决于眼内参考平面的定义。
描述使用具有固定偏移参考平面（320微米）的图像固有数据在海德堡视网膜断层扫描仪（HRT）的激光扫描断层成像中眼内参考平面的发展，并提出一种基于轮廓线的“灵活”标准参考平面（“SRP”），用于计算考虑视盘地形个体间变异性的视盘内立体测量参数。
通过激光扫描断层成像从99只青光眼眼和180只正常眼中获取10度三重图像。对图像进行评估，以评估视盘边界轮廓线段（6度宽）高度测量的变异性，该线段对应于由平均视盘表面倾斜角指示的视乳头黄斑束的位置。
平均视盘表面倾斜角在水平子午线（0度）以下为-7度±3度。根据平均表面倾斜角（-10度至-4度）选择SRP的6度宽轮廓线段。正常眼SRP段高度测量的重复性为16.0±10.8微米，青光眼眼为23.4±18.0微米。为确保视盘内参数的自动参考水平确定保持在视盘边界高度以下,我们将SRP水平定义为在6度轮廓线段的个体高度位置上增加50微米的偏移量（>青光眼平均段高度重复性的2个标准差）。
一旦交互式定义了视盘边界轮廓线，灵活的标准参考平面允许自动确定视盘内变量。与固定偏移参考平面（例如平均视网膜高度以下320微米）相比，视盘地形的个体间变异性（倾斜插入、青光眼性表面变平）得到了考虑，但代价是需要精确的视盘边界轮廓。
