Evaluating the efficacy of Nd:YAG fourth harmonic (266 nm) in comparison with ArF excimer (193 nm) in laser corneal reshaping: ex vivo pilot study

Abstract

Abstract Purpose 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. Methods 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. Results 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. Conclusion Solid-state laser at 266 nm could be a good alternative to the common 193-nm excimer laser for corneal reshaping procedures.