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M. J. Pollhammer, C. Wuellner, R. Tornow, P. Pogorelov, C. Donitzky, F. E. Kruse; Refractive Surgery With a New UV-Femtosecond Laser: Safety Profile and Basic Considerations. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3359.
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Refractive surgery with UV-femtosecond lasers (345nm) requires ten times less energy than infrared-femtosecond lasers currently used for clinical treatment. Moreover, during the process of flap creation with infrared-femtosecond lasers a large part of the initially applied energy penetrates the eye and reaches the retina. This potentially harmful transmission could be reduced with the use of UV-femtosecond lasers. The present study investigated the spectrum, the transmittance and the energy of the emerging primary and secondary radiation during this procedure on different locations in rabbit eyes.
Corneal flaps with a diameter of 6 mm were cut with a prototype UV-femtosecond laser (100 kHz, 345nm, based on Ytterbium technology) on freshly enucleated eyes of New Zealand White rabbits. During this process the power transmission and the spectrum of light was measured on three locations: behind the cornea, behind the lens and on the surface of the retina. After preparation, an integrating sphere (ø 100 mm) was placed below the eye segments. Spectral and power measurements were performed with a dedicated fibre optic spectrometer and optometer.
More than 99% of the energy was absorbed by the cornea, the lens and the vitreous body. Only less than 1% of the initially applied energy reached the retina. The secondary radiation showed a spectrum from 200nm to 800 nm including a band at 440nm, which is of importance for the so called Blue Light Hazard.
Compared to infrared-femtosecond lasers, most of the applied energy during flap creation with a UV-femtosecond laser was absorbed by the cornea, the lens and the vitreous body and only less than 1% reached the retina. Even if the transmittance of light centered on 440nm is little, it has to be investigated, because it corresponds to the Blue Light Hazard which is known to threaten ocular structures, such as lens and retina.
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