Karim Shaheen, Clark Robert A, Poukens Vadims, Demer Joseph L
Department of Ophthalmology, David Geffen Medical School at the University of California, Los Angeles, California, USA.
Invest Ophthalmol Vis Sci. 2004 Apr;45(4):1047-51. doi: 10.1167/iovs.03-1246.
To use magnetic resonance imaging (MRI) to measure the diameter along the course of the intraorbital optic nerve in living subjects and cadaveric specimens, and to validate measurements histologically in the same specimens.
Measurements of the intraorbital optic nerve were made in 23 living human subjects and in three formalin-fixed orbits using high-resolution, surface coil MRI in the coronal plane. Fixed orbits were then serially sectioned in the same plane, and stained by Masson's trichrome for digital morphometry of nerve diameter and densitometry of connective tissue constituents.
In cadaveric specimens, MRI and histologic measurements of optic nerve dimensions were in close quantitative agreement, showing significant decrease in the average optic nerve diameter along its retrobulbar course. This finding was confirmed by MRI in living subjects, with average optic nerve diameter declining from 3.99 +/- 0.04 mm (SEM) just posterior to the globe, to 3.50 +/- 0.04 mm at 10 mm further to the posterior (P < 0.0001). Color densitometry demonstrated a consistent cross-sectional area of nervous tissue, but decreasing amounts of collagen posteriorly.
There is a significant decrease in normal optic nerve diameter along its length in normal subjects, reflecting reduction in connective tissue. High-resolution MRI is a valid and sensitive method of detecting subtle changes in retrobulbar optic nerve size and can be useful in the investigation of structural optic nerve lesions. Optic nerve diameters must be measured, however, at similar distances posterior to the globe to allow meaningful comparisons.
利用磁共振成像（MRI）测量活体和尸体标本眶内视神经全程的直径，并在同一标本上进行组织学测量验证。
对23名活体人类受试者和3个福尔马林固定的眼眶进行眶内视神经测量，采用高分辨率表面线圈MRI在冠状面成像。然后将固定的眼眶在同一平面进行连续切片，用马松三色染色法进行神经直径的数字形态测量和结缔组织成分的密度测定。
在尸体标本中，MRI和组织学测量的视神经尺寸在数量上密切相关，显示出视神经平均直径在球后段全程显著减小。这一发现也在活体受试者的MRI检查中得到证实，视神经平均直径从眼球后方刚过处的3.99±0.04mm（标准误），到向后10mm处的3.50±0.04mm（P<0.0001）。颜色密度测定显示神经组织的横截面积一致，但向后胶原蛋白含量减少。
正常受试者正常视神经直径沿其长度显著减小，反映了结缔组织的减少。高分辨率MRI是检测球后段视神经细微变化的有效且敏感的方法，可用于视神经结构病变的研究。然而必须在眼球后方相似距离处测量视神经直径，以便进行有意义的比较。
