Institute of Applied Physics, Friedrich-Alexander-University of Erlangen-Nürnberg, Erlangen, Germany.
Invest Ophthalmol Vis Sci. 2012 May 17;53(6):2960-7. doi: 10.1167/iovs.11-8409.
Pseudoexfoliation (PEX) syndrome is a systemic disorder of the elastic fiber system that can lead to PEX glaucoma. Elastotic alterations in the lamina cribrosa (LC) of PEX eyes suggested biomechanical implications predisposing to pressure-induced optic nerve damage. In this pilot study, the stiffness of LC and peripapillary sclera (ppSC) in eyes with and without PEX syndrome were analyzed by atomic force microscopy (AFM) nanoindentation.
Unfixed cryosections (5-μm thick) were prepared from the optic nerve heads (ONH) of three donor eyes with PEX syndrome and three age-matched control eyes. AFM force mapping was performed in selected regions of the central, midperipheral, and peripheral LC and the ppSC using a spherical cantilever tip. To determine the local Young's modulus of elasticity (YME) as a measure of tissue stiffness, force curves were acquired and analyzed using the spherical Hertz model.
For the LC, the median YME values calculated from single stiffness maps averaged 17.2 (±2.7) kPa in normal eyes and 10.1 (±1.4) kPa in PEX eyes, indicating a significant PEX-related decrease in stiffness by over 40% (P < 0.01). The corresponding YME values for the ppSC, which revealed a 9-fold higher tissue stiffness than in the LC, averaged 158.3 (±59.8) kPa for control and 85.8 (±16.9) kPa for PEX samples.
AFM was proven suitable for determining the stiffness of ONH tissues, encouraging further large-scale analyses. The marked decrease in stiffness, implying an increased deformability of the ONH in PEX eyes, may reflect an inherent tissue weakness rendering these eyes more vulnerable to glaucomatous damage.
假性剥脱（PEX）综合征是一种弹性纤维系统的全身性疾病，可导致 PEX 青光眼。PEX 眼中的筛板（LC）弹性改变表明存在生物力学影响，容易导致压力引起的视神经损伤。在这项初步研究中，通过原子力显微镜（AFM）纳米压痕分析了 PEX 综合征眼和非 PEX 综合征眼中 LC 和视盘周围巩膜（ppSC）的刚度。
从 3 只 PEX 综合征供体眼和 3 只年龄匹配的对照眼的视神经头部制备 5μm 厚的冷冻切片。使用球形悬臂尖端在 LC 的中央、中周和周边以及 ppSC 的选定区域上进行 AFM 力映射。为了确定作为组织刚度测量的局部杨氏模量（YME），通过球形赫兹模型获得并分析力曲线。
对于 LC，从单个刚度图计算得出的中位数 YME 值在正常眼中平均为 17.2（±2.7）kPa，在 PEX 眼中为 10.1（±1.4）kPa，表明刚度显著降低超过 40%（P<0.01）。ppSC 的对应 YME 值，其组织刚度比 LC 高 9 倍，在对照样本中平均为 158.3（±59.8）kPa，在 PEX 样本中为 85.8（±16.9）kPa。
AFM 被证明适合于确定 ONH 组织的刚度，鼓励进一步的大规模分析。LC 刚度的明显降低，意味着 PEX 眼中的 ONH 柔韧性增加，这可能反映了组织固有弱点，使这些眼睛更容易受到青光眼损伤。
