Background: Translocation of an autologous RPE/Bruch’s membrane/choroid sheet under the macula is currently under investigation as a potential treatment option for exudative AMD. Excimer laser-assisted autologous RPE sheet translocation (EST) employs intraocular excimer laser ablation of excess graft choroidal tissue as a measure to enhance RPE sheet functionality. Herein we sought to assess potential adverse effects of excimer laser treatment on RPE cells in vitro.
Methods: We treated human RPE cells with a 308nm XeCl excimer laser device using a fibre optic probe designed for intraocular laser application. Laser treatment was applied either directly to the cells or to a sheet of explanted human choroid/Bruch’s membrane tissue overlaying the cells. Induced cell death was visualised with trypan blue and quantified by LDH release assay. Apoptosis was detected by ELISA-based analysis of cellular nucleosome release.
Results: Direct laser application with dosages of up to 0.25J/cm2 was below the ablation threshold and did not result in an immediate effect on RPE cells. However, during the following 48 hours treated cells exhibited progressive signs of cytotoxicity. Induced cell death was found to be mediated by apoptosis. Time-course and dose-response relationship were similar to UV-irradiated control cells. Absorption of laser irradiation by a sheet of choroid/Bruch’s membrane tissue covering the RPE cells reduced the cytotoxic effect by 87-95%.
Conclusion: Cultured human RPE cells are susceptible to apoptotic cell death induced by 308nm excimer laser irradiation. Laser absorption by choroid/Bruch’s membrane tissue can largely prevent the cytotoxic effect. In clinical application the residual adverse effect of laser ablation on graft RPE cell viability needs to be outweighed by potential advantageous effects on graft survival and functionality to allow for a sensible application of excimer ablation in RPE translocation surgery.
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