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M. Takayama, T. Senoo, H. Matsushima, K. Mukai, H. Iwamoto, Y. Katsuki; Influence of Free Radicals in Corneal Endothelial Cell Dysfunction After Laser Iridotomy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2846. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
We experimentally validate whether irradiation with an argon laser (Ar) and YAG laser (YAG), both of which are used in laser iridotomy (LI), generates free radicals.
10% 5,5-dimethyl-pyrroline-N-oxide (DMPO) were injected into a clear quartz cell. Brown paper serving as an iris substitute was then placed in the cell, which was then irradiated with each type of laser. After irradiation, the DMPO-free radical adducts generated in the cell was measured by electron spin resonance (ESR) spectroscopy. Intensity of free radical was quantified by expressing as percentage relative to the waveform for a standard preparation of manganese. Laser irradiation intensity was set to 2 mJ for YAG and 200 mW for Ar, with an irradiation time of 0.05 seconds and a spot size of 100 µm. Irradiation was performed under the following four conditions:Condition 1: YAG, 5 shots Condition 2: YAG, 50 shotsCondition 3: Ar, 10 shots Condition 4: Ar, 100 shots
Generation of hydroxyl radicals was detected under all conditions of laser irradiation. The relative intensities of hydroxyl radicals under conditions 1, 2, 3, and 4 were 0.855, 1.347, 2.098, and 2.560, respectively; larger amounts of free radicals were generated with Ar than with YAG, and the amount increased as the number of laser shots increased.
Ar causes more intense oxidative stress in the eye immediately after laser irradiation than YAG. Given that there have been more clinical reports of bullous keratopathy (BK) following LI with Ar than with YAG, Ar-induced generation of free radicals may contribute to the development of BK.
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