Caveats to obtaining retinal topography with optical coherence tomography.
Caveats to obtaining retinal topography with optical coherence tomography.
复制标题
使用光学相干断层扫描获得视网膜地形图的注意事项。
DOI：
10.1167/iovs.14-15212
复制
发表时间：
2014
影响因子：
4.4
通讯作者：
Izatt,JosephA
中科院分区：
文献类型：
--
作者：
Kuo,AnthonyN;Carrasco-Zevallos,Oscar;Toth,CynthiaA;Izatt,JosephA
我们怀着极大的兴趣阅读了Oh等人1关于使用光谱域光学相干断层扫描（SD-OCT）评估近视眼视网膜地形图的文章。在他们的文章中，研究人员描述了视网膜地形图的不同特征，以指示近视眼的眼球形状变化（例如视网膜向鼻侧倾斜与向颞侧倾斜）。与之前使用磁共振成像（MRI）测量近视眼后眼形状的类似研究一样，我们同意这项视网膜地形图的工作为近视眼的分类和风险分层提供了重要的见解。然而，我们想强调一个关于使用后段SD-OCT图像进行绝对视网膜地形图测量的误解。在讨论部分中，指出“地形（RPE）层图像中的彩虹伪色表示距离眼睛冠状面的高度，蓝色表示低高度，红色表示高高度。在OCT中，参考平面不是冠状平面或眼睛内的任何平面。相反，参考平面是OCT装置本身中的参考延迟路径长度。2 OCT图像内的轴向距离（高度）表示相对于光程长度中的参考延迟的样本距离。因此，因为参考在OCT装置中而不是在眼睛本身中，所以眼睛相对于OCT装置的定位方式影响眼睛在OCT图像中的外观。例如，文章中描述的所有三种不同的视网膜倾斜亚型（鼻、中和颞）可以通过简单地相对于瞳孔中心稍微移动瞳孔中的OCT扫描光束位置从同一只眼睛产生（见图）。相反，如果受试者的眼睛相对于OCT设备移动，也会发生相同的效果。此外，后眼的OCT图像会因扫描几何形状和光学伪影而失真，正如我们小组和其他人之前所描述的那样。3-5累积效应是后眼的OCT图像不是眼睛本身的精确空间复制品或数字“模型”。因此，当使用OCT测量后眼的绝对地形时，必须考虑这些成像效应，以将其与这些近视眼中存在的实际地形差异分开。
We read with great interest the article by Oh et al. 1 on the assessment of retinal topography in myopic eyes using spectral domain optical coherence tomography (SD-OCT). In their article, the investigators described different characteristics of retinal topography to indicate variations in ocular shape in myopia (such as a retina sloped nasally versus temporally). Like similar prior studies using magnetic resonance imaging (MRI) to measure posterior eye shape in myopia, we agree this work in retinal topography provides important insight into classifying and risk stratifying myopic eyes. However, we would like to highlight a misconception regarding the use of posterior segment SD-OCT images for absolute retinal topography measurements. In the Discussion section, it is stated that ‘‘The rainbow pseudo-colors in the topographic (RPE) layer image represent height from the coronal plane of the eye, with blue indicating low height and red indicating high height.’’In OCT, the reference plane is not the coronal plane or any plane within the eye. Instead, the reference plane is a reference delay path length in the OCT device itself. 2 Axial distance (height) within an OCT image represents sample distances relative to that reference delay in optical path length. Therefore, because the reference is in the OCT device and not in the eye itself, how the eye is positioned relative to the OCT device affects the eye’s appearance in the OCT image. For example, all three distinct subtypes of retinal sloping described in the article (nasal, middle, and temporal) can be produced from the same eye simply by moving the OCT scan beam position in the pupil slightly relative to the pupil center (see Figure). The same effect also would occur if, conversely, the subject’s eye moved relative to the OCT device.Further, OCT images of the posterior eye are distorted by scan geometry and optical artifacts as our group and others have described previously. 3–5 The cumulative effect is that an OCT image of the posterior eye is not an exact spatial replica or digital ‘‘cast’’of the eye itself. Hence, when using OCT to measure the absolute topography of the posterior eye, these imaging effects must be considered to separate them from actual topographic differences present in these myopic eyes.