Engineering Applications of Laser Department, The National Institute of Laser Enhanced Sciences, Cairo University, Giza, 12613, Egypt.
Department of Cytology and Histology, Faculty of Veterinary Medicine, Cairo University, Giza, 12211, Egypt.
Int Ophthalmol. 2023 Sep;43(9):3087-3096. doi: 10.1007/s10792-023-02708-z. Epub 2023 Apr 21.
Laser corneal reshaping is a common eye surgery utilized to overcome many vision disorders. Different UV laser wavelengths can be effective in the treatment. However, the ArF excimer laser (193 nm) is the most commonly used due to its high absorption in the cornea. In the current study, we investigate the efficacy of applying a solid-state laser (Nd:YAG fourth harmonic at 266 nm) for the corneal reshaping procedure.
The utilized laser is generated using an optical setup based on a BBO nonlinear crystal which converts the Q-switched laser (532 nm) to its fourth harmonic (266 nm). Different pulse energies were applied with the same number of the shoots on ex vivo rabbit corneas, and the histological effect is studied. Moreover, the possible thermal damage on the treated corneal tissues was inspected via electron microscope. Additionally, the DNA damage on the corneal cells due to the application of the proposed laser was examined and compared with the existing technology (ArF Excimer laser at 193 nm) using the comet assay.
The histological examination revealed an appropriate ablation result with the minimum thermal effect at 1.5 mJ and 2.0 mJ. The overall results show that applying 50-shoots of the 1.5-mJ pulse energy using the proposed 266-nm solid-state laser produces the optimum ablation effect with the minimum thermal damage, and almost the same DNA damage occurred using the commercial 193-nm ArF excimer laser.
Solid-state laser at 266 nm could be a good alternative to the common 193-nm excimer laser for corneal reshaping procedures.
激光角膜重塑是一种常见的眼科手术，用于治疗多种视力障碍。不同的紫外激光波长在治疗中可能有效。然而，由于在角膜中具有高吸收率，ArF 准分子激光（193nm）是最常用的激光。在目前的研究中，我们研究了应用固态激光（Nd：YAG 四倍频在 266nm）进行角膜重塑程序的效果。
所使用的激光是使用基于 BBO 非线性晶体的光学装置产生的，该晶体将调 Q 激光（532nm）转换为其四倍频（266nm）。在离体兔角膜上应用不同的脉冲能量，并以相同数量的射击次数进行实验，研究其组织学效果。此外，通过电子显微镜检查处理后的角膜组织上可能存在的热损伤。此外，还通过彗星试验检查了由于应用所提出的激光而导致的角膜细胞的 DNA 损伤，并与现有的技术（193nm 的 ArF 准分子激光）进行了比较。
组织学检查显示，在 1.5mJ 和 2.0mJ 时，具有最小热效应的适当消融结果。总体结果表明，应用 50 次 1.5mJ 脉冲能量的 266nm 固态激光可产生最小热损伤的最佳消融效果，并且使用商业 193nm ArF 准分子激光时，几乎发生相同的 DNA 损伤。
266nm 的固态激光可能是用于角膜重塑手术的常见 193nm 准分子激光的良好替代品。
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