Abdelkawi Ahmed Salwa, Mohi Eldin Taher Ibrahim, Fouad Ghoneim Dina, Ahmed Elnaggar Mohammed, Hassan Aziza Ahmed
Department of Vision Science, Biophysics and Laser Science Unit, Research Institute of Ophthalmology, Giza, Egypt.
Ophthalmic Unit, National Institute of Laser Enhanced Science, Cairo University, Egypt.
J Ophthalmic Vis Res. 2023 Feb 21;18(1):24-33. doi: 10.18502/jovr.v18i1.12722. eCollection 2023 Jan-Mar.
To study the alterations on the lenticules extracted after femtosecond (Femto) small incision lenticule extraction (SMILE) versus the corneal free cap removed using a microkeratome.
The visuMax (500 kHz; laser energy: 180 nJ) was used for small-incision lenticule extraction. Free caps from human cadaveric corneas were excised by microkeratome. The collected lenticules were examined with the light and transmission electron microscope (TEM) for histological analysis, DNA fragmentation was assessed by agarose gel electrophoresis, DNA damage was evaluated using comet assay, and corneal proteins secondary structure was assessed by Fourier transform infrared spectroscopy (FTIR).
Light microscopic examination showed the presence of more edematous stroma under Femto SMILE than under free cap with a percentage change of 101.6%. In the Femto SMILE group, TEM examination showed pyknotic keratocytes, disruption, and cavitation of the collagen arrays stromal area under Femto SMILE. The DNA fragmentation for the Femto SMILE group revealed one undefined band with a size of 1.1 Kbp. The comet assay analysis indicated the presence of 3% and 8.0% tailed cells for the free cap and Femto SMILE groups, respectively. The tail lengths were 1.33 0.16 and 1.67 0.13 µm ( 0.01), the percentage of tail DNA was 1.41 0.18% ( 0.01) and 1.72 0.15%, and the tail moments were 1.88 0.12 AU and 2.87 0.14 AU ( 0.001) for the free cap and Femto SMILE groups, respectively. FTIR spectroscopy of the Femto smile group revealed disorders in the secondary and tertiary structure of the proteins.
Femto SMILE technique induced more structural changes, DNA fragmentation, DNA damage, and corneal proteins secondary structure alteration than those induced by a microkeratome cutting. These changes may be attributed to the deep penetration of high energy levels to the corneal layer. These findings may highlight the potential impact of the Femto SMILE on the cornea and the necessity for managing the laser parameters used.
研究飞秒（Femto）小切口透镜切除术（SMILE）后取出的透镜与使用微型角膜刀切除的角膜游离帽相比的变化情况。
使用visuMax（500 kHz；激光能量：180 nJ）进行小切口透镜切除术。用微型角膜刀切除人尸体角膜的游离帽。对收集的透镜进行光镜和透射电子显微镜（TEM）检查以进行组织学分析，通过琼脂糖凝胶电泳评估DNA片段化，使用彗星试验评估DNA损伤，并通过傅里叶变换红外光谱（FTIR）评估角膜蛋白二级结构。
光镜检查显示，飞秒SMILE术后水肿基质比游离帽组更多，百分比变化为101.6%。在飞秒SMILE组中，TEM检查显示飞秒SMILE术后角膜细胞固缩、胶原纤维束基质区域破坏和空泡形成。飞秒SMILE组的DNA片段化显示有一条大小为1.1 Kbp的未明确条带。彗星试验分析表明，游离帽组和飞秒SMILE组的拖尾细胞分别为3%和8.0%。游离帽组和飞秒SMILE组的尾长分别为1.33±0.16和1.67±0.13 µm（P<0.01），尾DNA百分比分别为1.41±0.18%（P<0.01）和1.72±0.15%，尾矩分别为1.88±0.12任意单位和2.87±0.14任意单位（P<0.001）。飞秒SMILE组的FTIR光谱显示蛋白质二级和三级结构紊乱。
与微型角膜刀切割相比，飞秒SMILE技术引起更多的结构变化、DNA片段化、DNA损伤和角膜蛋白二级结构改变。这些变化可能归因于高能水平对角膜层的深度穿透。这些发现可能突出了飞秒SMILE对角膜的潜在影响以及控制所用激光参数的必要性。
