Public Health Implications of the 1540 nm Laser on the Cornea
Uniformed Services University Of The Health Sciences Bethesda United States
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The mid-infrared spectral region is considered to be eye safe due to the unique absorption properties of the cornea. The wavelengths between 1400 and 2000 nm are absorbed by the corneal tissue before they can be focused and injure the retinal portion of the eye. This unique property of the mid-infrared spectrum has lead to numerous applications of lasers. The expanded use of lasers within this spectrum dictates that further research into the bio-effect of the mid-infrared laser be explored. Of particular interest is the 1540 nm laser as it absorption characteristic extends the full thickness of the cornea. Depending on the radiant energy applied this wavelength may cause permanent stromal scarring and necrosis to the endothelial layer of the cornea. This study explored the effects of the 1540 nm laser on three separate corneal models in-vitro, ex-vivo and in-vivo. The study found the median effective dose to produce aninjury was different for the three models, but that a fixed number could correlate the in-vitro and ex-vivo models to the in-vivo model. The study also found that the in-vitro and ex-vivo models histology was similar to each other and to the in-vivo model except that the in-vivo model showed a proliferative response in the endothelial cells. The mechanism causing the proliferative response in the in-vivo endothelial cells requires further research to determine if there is a way to use the 1540 nm laser to trigger a proliferation response in human endothelial cells. The thermal response of the in-vivo tissue was also characterized and indicates that further research is required to determine if there is successive heating with serial exposures across the eye.