Davies D C, McCoubrie P, McDonald B, Jobst K A
Department of Anatomy, St George's Hospital Medical School, London.
Br J Ophthalmol. 1995 Jun;79(6):596-600. doi: 10.1136/bjo.79.6.596.
AIMS/BACKGROUND: Visual symptoms are a common but not invariable feature of Alzheimer's disease (AD) and such symptoms appear to become more pronounced as the severity of the dementia increases. Pathology in both the pregeniculate and cortical parts of the visual system has been suggested to underlie the visual deficits in AD. In order to investigate the former possibility, the effect of AD on the optic nerve was investigated.
Intraorbital segments of optic nerve were taken at autopsy from nine patients with AD and seven patients with no history of psychiatric or neurological disease and no abnormal neuropathology. All patients had functional vision before death and appeared free of retinal, optic nerve, or microvascular disease. The optic nerves were processed into resin, semi-thin sections cut perpendicular to the long axis of each optic nerve, and stained with paraphenylenediamine. The sections were then investigated using an image analysis system and standard morphometric techniques.
There was no significant difference in the mean cross sectional neural area of AD compared with control optic nerves. Neither were there any significant differences between myelinated axon surface density, total axon number, or mean cross sectional axon area in AD compared with control optic nerves.
These results indicate that optic nerve degeneration is not a feature of AD and suggest that the visual deficits in the disease result from cortical dysfunction. This view is supported by the fact that visuospatial dysfunction appears to be the most common visual problem in AD.
目的/背景：视觉症状是阿尔茨海默病（AD）常见但并非一成不变的特征，且随着痴呆严重程度的增加，这些症状似乎会变得更加明显。视觉系统膝状体前和皮质部分的病理改变被认为是AD视觉缺陷的基础。为了研究前一种可能性，我们研究了AD对视神经的影响。
在尸检时从9例AD患者和7例无精神或神经疾病史且无异常神经病理学的患者身上获取眶内段视神经。所有患者生前均有功能性视力，且无视网膜、视神经或微血管疾病。将视神经制成树脂块，垂直于每条视神经长轴切取半薄切片，并用对苯二胺染色。然后使用图像分析系统和标准形态计量技术对切片进行研究。
与对照视神经相比，AD患者视神经的平均横截面积神经区域无显著差异。与对照视神经相比，AD患者的有髓轴突表面密度、轴突总数或平均横截面积轴突也无显著差异。
这些结果表明视神经变性不是AD的特征，并提示该疾病的视觉缺陷是由皮质功能障碍引起的。这一观点得到了以下事实的支持，即视觉空间功能障碍似乎是AD中最常见的视觉问题。
