Corneal Transplant Center, Pellegrini Hospital, Naples, Italy.
Department of Medicine and Health Science "V. Tiberio" University of Molise, 86100, Campobasso, Italy.
Exp Eye Res. 2021 Apr;205:108484. doi: 10.1016/j.exer.2021.108484. Epub 2021 Feb 3.
The purpose of the study was to determine the decrease in pachymetry of very thin corneas with advanced keratoconus due to corneal compaction from the ultraviolet-A (UV-A) irradiation phase of transepithelial (epi-on) cross-linking. Twenty removed corneal buttons were obtained from patients who underwent penetrating keratoplasty for advanced keratoconus. Removed corneal buttons selected from among the post-surgical specimens for this study had intact epithelium, no scarring or surgical cautery, endothelial cell density >2500 cells/mm, and average pachymetry over the measured points of below 400 μm. Corneas were mounted in a Franz chamber. Each epithelial surface was soaked in isotonic riboflavin and D-alpha-tocopheryl polyethylene glycol 1000 succinate (Ribocross® IROMED Group, Italy) for 15 min. Pachymetry was measured at three points over both the shielded and unshielded corneal halves for each corneal button. Surfaces were then washed in saline to remove the Ribocross®. Shields from UV-A irradiation over half of each cornea were then fixed to stand 5 mm above the test corneas. UV-A irradiation using the custom fast cross-linking (CF-CXL) protocol was then performed for the typical 10 ± 1.5 min, for a total energy of 1.08 ± 0.6 J/cm after which pachymetry was re-measured. The average percent change in pachymetry was -0.43% ± 0.38% (maximum -1.06%) in the shielded half. Pachymetry change was -6.2% ± 2.2% (maximum 12%) in the cross-linked halves. In conclusion, we estimate that the change in corneal thickness from corneal compaction due to the cross-linking reaction itself was -5.8% ± 2.2%. Scanning electron microscopy of cross-linked corneal segments showed stromal fiber contraction.
本研究旨在确定由于经上皮（epi-on）交联的紫外线-A（UV-A）照射相引起的角膜压缩，极薄的圆锥角膜的角膜厚度会减少。从接受穿透性角膜移植术治疗晚期圆锥角膜的患者中获得了 20 个切除的角膜瓣。为这项研究从术后标本中选择的切除角膜瓣具有完整的上皮，没有疤痕或手术烧灼，内皮细胞密度> 2500 个细胞/mm，并且在测量点以下的平均角膜厚度超过 400 μm。角膜被安装在 Franz 室中。每个上皮表面都在等渗核黄素和 D-α-生育酚聚乙二醇 1000 琥珀酸（Ribocross® IROMED Group，意大利）中浸泡 15 分钟。对于每个角膜瓣，在被屏蔽和未屏蔽的角膜半部分的三个点上测量角膜厚度。然后用盐水冲洗表面以除去 Ribocross®。然后将来自每个角膜的一半的 UV-A 照射的屏蔽固定在距离测试角膜 5 毫米的位置。然后使用定制的快速交联（CF-CXL）方案进行 UV-A 照射，通常为 10±1.5 分钟，总能量为 1.08±0.6 J/cm，之后再次测量角膜厚度。在屏蔽的一半中，角膜厚度的平均百分比变化为-0.43%±0.38%（最大值为-1.06%）。交联的一半中角膜厚度的变化为-6.2%±2.2%（最大值为 12%）。总之，我们估计由于交联反应本身引起的角膜压缩导致的角膜厚度变化为-5.8%±2.2%。交联角膜段的扫描电子显微镜显示基质纤维收缩。
