A framework for comparing structural and functional measures of glaucomatous damage
A framework for comparing structural and functional measures of glaucomatous damage
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DOI：
10.1016/j.preteyeres.2007.08.001
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发表时间：
2007-11-01
影响因子：
17.8
通讯作者：
Kardon, Randy H.
中科院分区：
文献类型：
--
作者：
Hood, Donald C.;Kardon, Randy H.
虽然人们常说青光眼的结构性损害先于功能性损害，但这种说法的含义并不总是很清楚。这次审查有两个目的：第一，表明一个简单的线性关系描述了一个特定的功能测试（标准自动视野检查（SAP）），一个特定的结构测试（光学相干断层扫描（OCT））相关的数据;和，第二，提出一个一般框架，结构和功能的损害，并评估如果一个先于另一个。第2节描述了所采用的具体功能和结构试验。为了比较SAP敏感性损失与视网膜神经纤维层（RNFL）损失，需要将局部视野区域与视盘局部区域相关联的标测图，如第3节所述。当将椎间盘的上级和下级弓形部分中的RNFL厚度相对于视野的相应弓形区域中的SAP灵敏度损失（dB单位）作图时，对于大于约10 dB的灵敏度损失，RNFL厚度变得渐近。这些数据通过第4节中给出的简单线性模型得到了很好的描述。该模型假设用OCT测量的RNFL厚度具有两个分量。一个组成部分是视网膜神经节细胞的轴突，另一个，残余物，是其他一切（例如神经胶质细胞，血管）。假设轴突部分以线性方式减少，SAP敏感性损失（以线性单位计）;假设剩余部分保持恒定。基于前部缺血性视神经病变（AION）中严重的SAP损失，弓形区域中的残余RNFL厚度平均为该区域发病前（正常）厚度的约三分之一。该模型还预测，第一近似，SAP的敏感性在对照组不依赖于RNFL厚度。数据（第6节）通常与该预测一致，表明RNFL厚度与SAP敏感性之间的相关性非常弱。在第7节中，该模型用于估计在24-2 SAP现场测试中显示异常之前，OCT RNFL测试中显示统计学异常（劣于第5百分位数）的患者比例。忽略测量误差，当健康时，具有相对厚的RNFL的患者将更有可能在统计学上显著的OCT RNFL损失之前显示出显著的SAP敏感性损失，而对于那些健康时开始具有平均或相对薄的RNFL的患者，情况正好相反。因此，了解对照受试者中RNFL厚度的广泛变化的影响非常重要。第8节描述了导致这种变化的两个因素，血管位置的变化和场区域到盘扇区的映射的变化。最后，在第7节和第9节中，研究结果与文献中关于结构性和功能性青光眼损伤之间关系的一般性辩论有关，并提出了一个框架，以理解“青光眼中结构性损伤先于功能性损伤吗？“重点是需要区分这个问题的“统计”和“关系”含义。(C)2007爱思唯尔有限公司保留所有权利。
While it is often said that structural damage due to glaucoma precedes functional damage, it is not always clear what this statement means. This review has two purposes: first, to show that a simple linear relationship describes the data relating a particular functional test (standard automated perimetry (SAP)) to a particular structural test (optical coherence tomography (OCT)); and, second, to propose a general framework for relating structural and functional damage, and for evaluating if one precedes the other. The specific functional and structural tests employed are described in Section 2. To compare SAP sensitivity loss to loss of the retinal nerve fiber layer (RNFL) requires a map that relates local field regions to local regions of the optic disc as described in Section 3. When RNFL thickness in the superior and inferior arcuate sectors of the disc are plotted against SAP sensitivity loss (dB units) in the corresponding arcuate regions of the visual field, RNFL thickness becomes asymptotic for sensitivity losses greater than about 10 dB. These data are well described by a simple linear model presented in Section 4. The model assumes that the RNFL thickness measured with OCT has two components. One component is the axons of the retinal ganglion cells and the other, the residual, is everything else (e.g. glial cells, blood vessels). The axon portion is assumed to decrease in a linear fashion with losses in SAP sensitivity (in linear units); the residual portion is assumed to remain constant. Based upon severe SAP losses in anterior ischemic optic neuropathy (AION), the residual RNFL thickness in the arcuate regions is, on average, about one-third of the premorbid (normal) thickness of that region. The model also predicts that, to a first approximation, SAP sensitivity in control subjects does not depend upon RNFL thickness. The data (Section 6) are, in general, consistent with this prediction showing a very weak correlation between RNFL thickness and SAP sensitivity. In Section 7, the model is used to estimate the proportion of patients showing statistical abnormalities (worse than the 5th percentile) on the OCT RNFL test before they show abnormalities on the 24-2 SAP field test. Ignoring measurement error, the patients with a relatively thick RNFL, when healthy, will be more likely to show significant SAP sensitivity loss before statistically significant OCT RNFL loss, while the reverse will be true for those who start with an average or a relatively thin RNFL when healthy. Thus, it is important to understand the implications of the wide variation in RNFL thickness among control subjects. Section 8 describes two of the factors contributing to this variation, variations in the position of blood vessels and variations in the mapping of field regions to disc sectors. Finally, in Sections 7 and 9, the findings are related to the general debate in the literature about the relationship between structural and functional glaucomatous damage and a framework is proposed for understanding what is meant by the question, 'Does structural damage precede functional damage in glaucoma?' An emphasis is placed upon the need to distinguish between "statistical" and "relational" meanings of this question. (C) 2007 Elsevier Ltd. All rights reserved.