Nagel E, Vilser W, Fink A, Riemer T
Augenarztpraxis, Rudolstadt.
Klin Monbl Augenheilkd. 2007 May;224(5):411-6. doi: 10.1055/s-2007-963093.
Static vessel analysis is a method to determine the diameter of retinal vessels in images of the ocular fundus. The suitability of non-mydriatic and mydriatic images for that method and the influence of mydriasis on the results were examined.
In the prospective study, 30 eyes of 15 patients (10 women, mean age 51.6 +/- 13.2 years) were examined. At first, 3 images were taken of each eye with the retinal camera Topcon NW 200 (magnification 1). After pupil dilation with tropicamid eye drops, 3 more images were taken using the Topcon and 3 others using the system Visualis (IMEDOS, Jena/Germany, FF450plus, 535-561 nm, 30 degrees image, 1840 x 1360 pixel). The vessel diameters were measured with the software Vesselmap2 (IMEDOS). The investigator assigned vessels to arteries or veins and their diameters were calculated automatically by the software. There is the possibility to define the vessel edge manually in cases of a poor image quality. The calculation of the central retinal arterial and venous equivalent (CRAE, CRVE) as well as the arterio-venous ratio (AVR) were made according to the formula of Parr-Hubbard. Furthermore, the nasal retinal vessels > 60 microm were examined to estimate the influence of tropicamid on the vessel diameter.
Because of insufficient illumination and poor contrast in 21 % of the non-mydriatic images not all vessels could be detected automatically. Additionally, fewer vessels could be detected in 7 % of the non-mydriatic images compared to the mydriatic images. The average coefficient of variation of CRAE and AVR of each triplet of images was higher in non-mydriatic images (2.6 % and 3.2 %, respectively) than in mydriatic images of the Topcon (1.8 %; 2.3 %) and the FF 450 (1.7 %; 1.8 % ANOVA p < 0.05). No significant differences were found between the various examination methods for both the coefficient of variation of CRVE (1.9 %; 1.8 %; 1.7 %) and the average values of CRAE, CRVE and AVR. With regard to their diameters, the nasal retinal arteries and veins > 60 microm, were depicted sufficiently in all images, and only differed insignificantly between the three methods.
The quality of non-mydriatic images is often lower than that of mydriatic images. This fact can account for the high variance of measured parameters in the non-mydriatic images. The depiction of all relevant vessel segments is a precondition for the image-based analysis. An influence of the mydriasis caused by tropicamid on the retinal vessel diameters > 60 microm was not found.
静态血管分析是一种用于确定眼底图像中视网膜血管直径的方法。本研究检测了散瞳和不散瞳图像对该方法的适用性以及散瞳对结果的影响。
在这项前瞻性研究中，对15例患者（10名女性，平均年龄51.6±13.2岁）的30只眼睛进行了检查。首先，使用拓普康NW 200视网膜相机（放大倍数1倍）为每只眼睛拍摄3张图像。在用托吡卡胺滴眼液散瞳后，使用拓普康相机再拍摄3张图像，并用Visualis系统（德国耶拿IMEDOS公司，FF450plus，535 - 561nm，30度图像，1840×1360像素）拍摄另外3张图像。使用Vesselmap2软件（IMEDOS公司）测量血管直径。研究人员将血管分为动脉或静脉，软件自动计算其直径。在图像质量较差的情况下，可以手动定义血管边缘。根据帕尔 - 哈伯德公式计算视网膜中央动脉和静脉等效值（CRAE、CRVE）以及动静脉比（AVR）。此外，对直径大于60微米的鼻侧视网膜血管进行检查，以评估托吡卡胺对血管直径的影响。
由于21%的不散瞳图像光照不足且对比度差，并非所有血管都能自动检测到。此外，与散瞳图像相比，7%的不散瞳图像中检测到的血管较少。不散瞳图像中每组三张图像的CRAE和AVR平均变异系数（分别为2.6%和3.2%）高于拓普康散瞳图像（1.8%；2.3%）和FF 450散瞳图像（1.7%；1.8%，方差分析p<0.05）。对于CRVE的变异系数（1.9%；1.8%；1.7%）以及CRAE、CRVE和AVR的平均值，不同检查方法之间未发现显著差异。就直径而言，直径大于60微米的鼻侧视网膜动脉和静脉在所有图像中均能充分显示，三种方法之间仅存在微小差异。
不散瞳图像的质量通常低于散瞳图像。这一事实可以解释不散瞳图像中测量参数的高变异性。描绘所有相关血管段是基于图像分析的前提条件。未发现托吡卡胺引起的散瞳对直径大于60微米的视网膜血管有影响。
