Ortillés Ángel, Rodríguez-Matas José F, Ariza-Gracia Miguel Á, Pascual Gemma, Calvo Begoña
J Refract Surg. 2017 Mar 1;33(3):184-192. doi: 10.3928/1081597X-20161206-02.
To assess the feasibility of characterizing and following up the mechanical behavior of the corneal tissue after corneal cross-linking (CXL) by using a combined mechanical (in vivo indentation and in vitro uniaxial tensile tests) and morphological (immunohisto-chemistry) experimental protocol.
CXL (3 mW/cm; 370 nm) for 20 minutes (total dose 3.6 J/cm) was performed on 12 New Zealand rabbits. The mechanical behavior of the cornea was characterized in small and large strain regimens using an in vivo indentation test with a laboratory device and an in vitro uniaxial tensile test, respectively. These tests and corneal immunohistochemistry were performed before (PreCXL) and on the 7th (PostCXL-7d) and 56th days (PostCXL-56d) after CXL. The intraocular pressure and corneal thickness were measured before each test.
For the indentation tests, significant differences were found between PreCXL and PostCXL-7d and between PostCXL-7d and PostCXL-56d, but not between PreCXL and PostCXL-56d. On average, for the small strain regimen, PostCXL-7d corneas showed the most compliant behavior, with progressive recovery of the corneal stiffness over time. For the large strain regimen, significant differences in the maximum tangent modulus between PreCXL and PostCXL-7d and between PreCXL and PostCXL-56d were observed for the uniaxial tensile tests, with no significant differences between PostCXL-7d and PostCXL-56d. Immunohistochemistry showed a lack of cells in the anterior stroma at PostCXL-7d, but at PostCXL-56d the cell density and morphology were comparable to PreCXL.
Indentation tests cannot characterize the changes in the corneal collagen scaffold caused by the CXL, but the uniaxial test can. However, indentation tests can assess the recovery of keratocyte density after CXL. [J Refract Surg. 2017;33(3):184-192.].
通过联合机械（体内压痕试验和体外单轴拉伸试验）和形态学（免疫组织化学）实验方案，评估表征和随访角膜交联（CXL）后角膜组织力学行为的可行性。
对12只新西兰兔进行CXL（3 mW/cm；370 nm），持续20分钟（总剂量3.6 J/cm）。分别使用实验室设备进行体内压痕试验和体外单轴拉伸试验，在小应变和大应变条件下表征角膜的力学行为。这些试验以及角膜免疫组织化学在CXL前（PreCXL）、CXL后第7天（PostCXL-7d）和第56天（PostCXL-56d）进行。每次试验前测量眼压和角膜厚度。
对于压痕试验，PreCXL与PostCXL-7d之间以及PostCXL-7d与PostCXL-56d之间存在显著差异，但PreCXL与PostCXL-56d之间无显著差异。平均而言，对于小应变条件，PostCXL-7d角膜表现出最柔顺的行为，角膜硬度随时间逐渐恢复。对于大应变条件，单轴拉伸试验中观察到PreCXL与PostCXL-7d之间以及PreCXL与PostCXL-56d之间最大切线模量存在显著差异，PostCXL-7d与PostCXL-56d之间无显著差异。免疫组织化学显示PostCXL-7d时前基质中细胞缺失，但PostCXL-56d时细胞密度和形态与PreCXL相当。
压痕试验无法表征CXL引起的角膜胶原支架变化，但单轴试验可以。然而，压痕试验可以评估CXL后角膜细胞密度的恢复情况。[《屈光手术杂志》。2017；33(3)：184 - 192。]
