Biomechanical evidence of the distribution of cross-links in corneas treated with riboflavin and ultraviolet A light
Biomechanical evidence of the distribution of cross-links in corneas treated with riboflavin and ultraviolet A light
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DOI：
10.1016/j.jcrs.2005.12.092
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发表时间：
2006-02-01
影响因子：
2.8
通讯作者：
Pillunat, LE
中科院分区：
文献类型：
--
作者：
Kohlhaas, M;Spoerl, E;Pillunat, LE
目的：探讨在角膜的哪个深度有生物力学可检测到的硬化效应。单位：德国德累斯顿大学眼科。方法：选取40只去核猪眼，20只眼用光敏剂核黄素（0.1%）和紫外线A （UVA）光（370 nm, 3 mW/cm(2)， 30分钟）处理；另外20只眼睛作为对照。每只眼取2个200亩厚的皮瓣，用微角刀切下，制成宽5毫米、长7毫米的条带。用材料测试仪测量了应力-应变行为，以表征加筋效果。用同样的方法测试了五对人类捐赠者的眼睛。结果：在猪角膜中，前处理皮瓣的硬化效果强于后处理皮瓣和对照皮瓣（P = 0.001）。前处理皮瓣的应力为261.7 +/- 133.2 × 10(3) N/m(2)，前控制皮瓣的应力为104.1 +/- 52.7 × 10(3) N/m(2)，应变为5%。后处理皮瓣(105.0 +/- 55.8 × 10（3) N/m(2)）与后对照皮瓣(103.7 +/- 61.8 × 10（3) N/m(2)）差异无统计学意义（P = 0.95）。在人眼中也观察到类似的硬化效应，但与猪角膜相反，在人类角膜中，前对照皮瓣比后对照皮瓣更硬（P = 0.027）。结论：核黄素和UVA治疗角膜仅在前200 pm显著硬化角膜。这种深度依赖的硬化效应可以用核黄素处理的角膜对UVA的吸收行为来解释。65 - 70%的UVA辐射在前200 μ m内被吸收，而在后200 μ m内仅吸收20%。因此，深层结构甚至内皮不受影响。
PURPOSE: To examine to which depth of the cornea the stiffening effect is biomechanically detectable.SETTING: Department of Ophthalmology, University of Dresden, Dresden, Germany.METHODS: Of 40 enucleated porcine eyes, 20 eyes were treated with the photosensitizer riboflavin (0.1%) and ultraviolet A (UVA) light (370 nm, 3 mW/cm(2), 30 minutes); the other 20 eyes served as control. From each eye, 2 flaps of 200 mu m thickness were cut with a microkeratome, and strips of 5 mm width and 7 mm length were prepared. Stress-strain behavior was measured with a material tester to characterize the stiffening effect. Five pairs of human donor eyes were tested in the same way.RESULTS: In porcine corneas, the stiffening effect was stronger in the anterior-treated flaps than in the posterior-treated flaps and the control flaps (P = .001). A 5% strain was achieved at a stress of 261.7 +/- 133.2 x 10(3) N/m(2) in the anterior-treated flaps and 104.1 +/- 52.7 x 10(3) N/m(2) in the anterior control flaps. The posterior-treated flaps (105.0 +/- 55.8 x 10(3) N/m(2)) and the posterior control flaps (103.7 +/- 61.8 x 10(3) N/m(2)) showed no difference (P = .95). A similar stiffening effect was observed in human eyes, but contrary to findings in porcine corneas, in human corneas the anterior control flaps were stiffer than the posterior control flaps (P = .027).CONCLUSIONS: Treatment of the cornea with riboflavin and UVA significantly stiffened the cornea only in the anterior 200 pm. This depth-dependent stiffening effect may be explained by the absorption behavior for UVA in the riboflavin-treated cornea. Sixty-five percent to 70% of UVA irradiation was absorbed within the anterior 200 mu m and only 20% in the next 200 mu m. Therefore, deeper structures and even the endothelium are not affected.