University of California, San Francisco, Department of Ophthalmology, 10 Koret Way, K301, San Francisco, CA 94143-0730, USA.
Exp Eye Res. 2012 Oct;103:17-21. doi: 10.1016/j.exer.2012.06.010. Epub 2012 Aug 1.
Exogenous collagen cross-linking has been investigated as method of reinforcing scleral biomechanics, with the goal of counteracting scleral weakening that occurs at the onset of myopia. This study uses whole globe inflation testing to investigate the biomechanical effect of treating posterior sclera with the collagen cross-linking agents methylglyoxal and genipin. Pairs of porcine eyes were treated in four ways. Three groups involved 1% methylglyoxal: two-hour (Group I) or thirty-minute (Group II) incubation of the whole globe, and thirty-minute incubation of only the posterior sclera of the intact eye (Group III). Group IV consisted of a thirty-minute incubation of the posterior sclera in 1% genipin. Following treatment, each eye was subjected to inflation testing under physiological pressure levels (0-150 mmHg); four strain markers on the posterior pole were tracked, providing displacement measurements in two directions. Results were used to derive load versus deformation behavior and to calculate stiffness at 0.25% strain (toe stiffness) and at peak strain (peak stiffness). Toe stiffness of Group I was 4.8 and 1.3 times greater than controls (sagittal and transverse directions, respectively: 5.23 ± 0.39 vs. 0.90 ± 0.08 mHg, P < 0.001; and 3.41 ± 0.19 vs. 1.51 ± 0.22 mHg, P < 0.01; values in mean ± SE). Group II was 7.4 and 4.3 times stiffer than controls (sagittal and transverse directions, respectively: 5.26 ± 0.49 vs. 0.63 ± 0.10 mHg, P < 0.02; and 3.44 ± 0.44 vs. 0.65 ± 0.07 mHg, P < 0.003). Group III was 3.6 and 3.4 times stiffer than controls (sagittal and transverse directions, respectively: 5.21 ± 0.39 vs. 1.13 ± 0.31 mHg, P < 0.01; and 4.94 ± 1.48 vs. 1.13 ± 0.25, P < 0.01), while Group IV was 8.2 and 2.8 times stiffer than controls (sagittal and transverse: 12.36 ± 1.96 vs. 1.35 ± 0.14 mHg, P < 0.01; and 12.45 ± 1.34 vs. 3.27 ± 0.50 mHg, P < 0.05). In all groups, there was no significant difference in peak stiffness after scleral cross-linking (SXL). At low strain, the posterior sclera was stiffer in both measured directions following methylglyoxal and genipin treatments, however at peak strain the treated sclera was not stiffer. Additionally, the saturation level of scleral stiffening by methylglyoxal can be reached within thirty minutes of treatment.
外源性胶原蛋白交联已被研究作为增强巩膜生物力学的方法，目的是对抗近视发生时巩膜的弱化。本研究使用全眼球膨胀测试来研究用交联剂甲基乙二醛和京尼平处理后巩膜的生物力学效应。用四种方法处理了成对的猪眼。三组涉及 1%甲基乙二醛：全眼球两小时（I 组）或三十分钟（II 组）孵育，以及完整眼后部巩膜三十分钟孵育（III 组）。IV 组由 1%京尼平处理的后巩膜三十分钟孵育组成。治疗后，每只眼睛都在生理压力水平（0-150mmHg）下进行膨胀测试；在后极的四个应变标记物被跟踪，提供两个方向的位移测量。结果用于推导出负载与变形行为，并计算 0.25%应变（起始刚度）和峰值应变（峰值刚度）下的刚度。I 组的起始刚度比对照组大 4.8 和 1.3 倍（矢状和横向方向分别为 5.23±0.39 和 0.90±0.08mmHg，P<0.001；和 3.41±0.19 和 1.51±0.22mmHg，P<0.01；平均值±SE）。II 组比对照组分别大 7.4 和 4.3 倍（矢状和横向方向分别为 5.26±0.49 和 0.63±0.10mmHg，P<0.02；和 3.44±0.44 和 0.65±0.07mmHg，P<0.003）。III 组比对照组分别大 3.6 和 3.4 倍（矢状和横向方向分别为 5.21±0.39 和 1.13±0.31mmHg，P<0.01；和 4.94±1.48 和 1.13±0.25，P<0.01），而 IV 组比对照组分别大 8.2 和 2.8 倍（矢状和横向：12.36±1.96 和 1.35±0.14mmHg，P<0.01；和 12.45±1.34 和 3.27±0.50mmHg，P<0.05）。在所有组中，交联后（SXL）后巩膜的峰值刚度没有显著差异。在低应变下，甲基乙二醛和京尼平处理后巩膜在两个测量方向都更硬，但在峰值应变时处理后的巩膜并没有更硬。此外，甲基乙二醛对巩膜硬度的饱和水平可以在 30 分钟的治疗时间内达到。
