Tabibian David, Kling Sabine, Hammer Arthur, Richoz Olivier, Hafezi Farhad
J Refract Surg. 2017 Jan 1;33(1):56-60. doi: 10.3928/1081597X-20161006-02.
To study whether repeated collagen cross-linking (CXL) performed in vivo in mice shows an additive effect on mechanical corneal stiffness.
In this experimental study, epithelium-off CXL was performed in a total of 18 eyes from male C57BL/6 mice, with 0.27%-riboflavin solution applied for 20 minutes, followed by ultraviolet-A (UVA) irradiation (365 nm, 9mW/cm) for 2:50 minutes (fluence 1.53 J/cm). CXL was performed as either a single (1×CXL) or a repeated (2×CXL) treatment. Un-irradiated corneas served as controls. In the 2×CXL group, the procedure was performed on day 1 and day 4 to ensure complete reepithelialization between sessions. Biomechanical analysis was performed on day 7. Corneas were harvested with a small scleral ring and mounted on a customized two-dimensional flap holder. The biomechanical measurement consisted of three parts: (1) pre-conditioned during three cycles from 0.04 to 0.4 N, (2) stress relaxation during 120 seconds following 0.4 N force application, and (3) stress-strain curve until break.
After the relaxation period of 120 seconds, highly significant differences (P < .001) were found between the controls and both 1×CXL corneas and 2×CXL corneas. No significant difference (P = .70) was detected between the 1×CXL and 2×CXL groups. The stress remaining after relaxation was 355 ± 25.2 kPa in the control group, 457 ± 34.1 kPa in the 1×CXL group, and 463 ± 22.2 kPa in the 2×CXL group. No significant differences in the stress-strain curves were found between the conditions.
Repeated CXL 3 days after the first procedure does not further increase corneal stiffness in mice in vivo. [J Refract Surg. 2017;33(1):56-60.].
研究在小鼠体内重复进行胶原交联（CXL）是否对角膜机械硬度有累加效应。
在这项实验研究中，对雄性C57BL/6小鼠的18只眼睛进行上皮剥脱性CXL，用0.27%的核黄素溶液滴眼20分钟，随后用紫外线A（UVA）照射（365nm，9mW/cm）2分50秒（能量密度1.53J/cm）。CXL作为单次（1×CXL）或重复（2×CXL）治疗。未照射的角膜作为对照。在2×CXL组中，该操作在第1天和第4天进行，以确保两次治疗之间角膜完全重新上皮化。在第7天进行生物力学分析。用一个小的巩膜环取下角膜，并安装在定制的二维瓣片固定器上。生物力学测量包括三个部分：（1）在0.04至0.4N的三个循环中进行预调节，（2）在施加0.4N力后120秒内进行应力松弛，（3）直至破裂的应力-应变曲线。
在120秒的松弛期后，对照组与1×CXL组角膜和2×CXL组角膜之间均存在高度显著差异（P <.001）。1×CXL组和2×CXL组之间未检测到显著差异（P = 0.70）。对照组松弛后剩余应力为355±25.2kPa，1×CXL组为457±34.1kPa，2×CXL组为463±22.2kPa。不同条件下应力-应变曲线未发现显著差异。
首次操作3天后重复进行CXL不会进一步增加小鼠体内角膜的硬度。[《屈光手术杂志》。2017；33(1):56 - 60。]
