Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, CA 90095-7002, USA.
Department of Physics, Virginia Commonwealth University, Richmond, VA, USA.
J Biomech. 2014 Jun 3;47(8):1899-903. doi: 10.1016/j.jbiomech.2014.02.011. Epub 2014 Feb 14.
Extra-ocular tendons (EOTs) transmit the oculorotary force of the muscles to the eyeball to generate dynamic eye movements and align the eyes, yet the mechanical properties of the EOTs remain undefined. The EOTs are known to be composed of parallel bundles of small fibers whose mechanical properties must be determined in order to characterize the overall behavior of EOTs. The current study aimed to investigate the transverse Young׳s modulus of EOT fiber bundles using atomic force microscopy (AFM). Fresh bovine EOT fiber bundle specimens were maintained under temperature and humidity control, and indented 100nm by the inverted pyramid tip of an AFM (Veeco Digital Instruments, NY). Ten indentations were conducted for each of 3 different locations of 10 different specimens from each of 6 EOTs, comprising a total of 1800 indentations. Young׳s modulus for each EOT was determined using a Hertzian contact model. Young׳s moduli for fiber bundles from all six EOTs were determined. Mean Young׳s moduli for fiber bundles were similar for the six anatomical EOTs: lateral rectus 60.12±2.69 (±SD)MPa, inferior rectus 59.69±5.34MPa, medial rectus 56.92±1.91MPa, superior rectus 59.66±2.64MPa, inferior oblique 57.7±1.36MPa, and superior oblique 59.15±2.03. Variation in Young׳s moduli among the six EOTs was not significant (P>0.25). The Young׳s modulus of bovine EOT fibers is highly uniform among the six extraocular muscles, suggesting that each EOT is assembled from fiber bundles representing the same biomechanical elements. This uniformity will simplify overall modeling.
眼外肌（EOT）将肌肉的眼外旋转力传递到眼球，以产生动态眼球运动并使眼睛对齐，但 EOT 的力学性质仍未定义。已知 EOT 由小纤维的平行束组成，为了表征 EOT 的整体行为，必须确定其力学性质。本研究旨在使用原子力显微镜（AFM）研究 EOT 纤维束的横向杨氏模量。新鲜牛 EOT 纤维束标本在温度和湿度控制下保存，并通过 AFM（Veeco Digital Instruments，NY）的倒金字塔尖端压入 100nm。每个 EOT 的 6 个标本的 10 个不同位置中的每个位置进行 10 次压痕，总共进行 1800 次压痕。使用赫兹接触模型确定每个 EOT 的杨氏模量。确定了来自所有 6 个 EOT 的纤维束的杨氏模量。六个解剖 EOT 的纤维束杨氏模量平均值相似：外直肌 60.12±2.69（±SD）MPa，下直肌 59.69±5.34MPa，内直肌 56.92±1.91MPa，上直肌 59.66±2.64MPa，下斜肌 57.7±1.36MPa，和上斜肌 59.15±2.03MPa。六个 EOT 之间杨氏模量的变化不显著（P>0.25）。牛 EOT 纤维的杨氏模量在六个眼外肌之间高度均匀，表明每个 EOT 由代表相同生物力学元素的纤维束组装而成。这种均匀性将简化整体建模。
