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U. Vossmerbaeumer, J.B. Jonas; Energy Absorption Characteristics of Femtosecond Laser Procedures in Corneal Tissue . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2919.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Femtosecond lasers appear suggestive as novel tools in corneal surgery. Scientific data is still largely deficient on absorption characteristics for optimized results. Our study aims at defining optimum corridors of procedure parameters for the use of a near–infrared femtosecond laser device. This includes energy thresholds as well as spot–spacing patterns for surgical use in curative and refractive corneal procedures. Methods:We performed fs laser procedures in 25 freshly enucleated porcine eyes and in 20 human corneal donor specimen not suitable for patient use. Pulse patterns were programmed for customized trephination, endothelial die preparation and superficial flaps. Specimen were evaluated for tissue disruption quality according to the histological FLIRS (Femtosecond Laser Integrated Result Score) scheme. Correlation was subsequently established between energy and tissue separation patterns. Results:Energy levels of fs laser pulses leading to tissue separation ranged from 2,2 µJ to 15µJ with pulse duration under 500 fs. Intrastromal bubbles were > 10µm with a sealing effect of supposed cellular debris in the outer lineage with narrow variation corridor. Z spacing of focus points allowed variation between 4 and 7 µm (spot 5µm). Linear contingency in vertical orientation required spacing of 4–8 µm. FLIRS scores of 8 (out of 12) could be realized at lowest energy levels without significant increase in higher energy procedures. Conclusions:Our work provides novel technical insight into the applicative potential of femtosecond lasers in corneal microsurgery. Narrow variation corridors could be due to the differential elasticities in corneal layers. The FLIRS scheme is used to evaluate effects for proposed surgical procedures, thus providing a framework for result control in keratoplasty and refractive procedures by fs lasers.
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