Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
Exp Eye Res. 2011 Oct;93(4):475-81. doi: 10.1016/j.exer.2011.06.009. Epub 2011 Jul 23.
Indentation and histological analysis of the porcine iris were done to assess the relative stiffness of the anterior (stroma) and posterior (dilator and sphincter) layers. The dimensions of the constituent structures were documented histologically by staining with a monoclonal anti-human α-smooth muscle actin antibody to determine the location of the stroma, sphincter, and dilator. Intact porcine irides (4-8 h post-mortem) were bisected into two equal C-shaped halves to indent both surfaces. Indentation experiments were performed using a 1 mm cylindrical indenter tip. The load-displacement curve for each experiment was used to estimate effective instantaneous and equilibrium moduli for the anterior and posterior surfaces of the tissue. A total of 18 irides (9 pairs) with 3-5 indentations per iris surface was performed. The average thickness of the samples was 550 μm; the indentation depth was limited to 60-100 μm depending on the thickness of the sample at each point. Posterior surface indentation gave larger forces than anterior, with the resulting instantaneous modulus of 6.0 ± 0.6 kPa versus 4.0 ± 0.5 kPa (mean ± 95% CI, n = 45, p < 0.001) and equilibrium modulus of 4.4 ± 0.9 versus 2.3 ± 0.3 (p = 0.007). The stress-relaxation analysis revealed that the anterior surface had a shorter relaxation time (121.31 ± 6.84 s) than the posterior surface (210.61 ± 9.41 s, p = 0.03), perhaps due to the permeability of the stroma. Recognizing that our effective modulus calculations in this study did not account for heterogeneity, viscoelasticity, or poroelasticity, we conclude that the posterior components of the iris - dilator, pigment epithelium, and sphincter - are on average stiffer than the stroma and anterior border layer.
对猪虹膜进行缩进和组织学分析，以评估前部（基质）和后部（扩约肌和括约肌）层的相对硬度。通过用单克隆抗人α-平滑肌肌动蛋白抗体染色对组成结构的尺寸进行组织学记录，以确定基质、括约肌和扩约肌的位置。完整的猪虹膜（死后 4-8 小时）被切成两个相等的 C 形半部分，以缩进两个表面。缩进实验使用 1 毫米圆柱形压头进行。每个实验的加载-位移曲线用于估计组织前表面和后表面的有效瞬时和平衡模量。总共进行了 18 只虹膜（9 对），每只虹膜表面进行 3-5 次缩进。样本的平均厚度为 550 μm；根据每个点的样本厚度，缩进深度限制在 60-100 μm。后表面缩进产生的力大于前表面，瞬时模量分别为 6.0±0.6 kPa 和 4.0±0.5 kPa（平均值±95%置信区间，n=45，p<0.001），平衡模量分别为 4.4±0.9 kPa 和 2.3±0.3 kPa（p=0.007）。应力松弛分析表明，前表面的松弛时间（121.31±6.84 s）比后表面（210.61±9.41 s，p=0.03）短，这可能是由于基质的渗透性。由于我们在本研究中的有效模量计算没有考虑到各向异性、粘弹性或多孔弹性，我们得出结论，虹膜的后向组件——扩约肌、色素上皮和括约肌——的平均硬度大于基质和前边界层。
