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A. Ivarsen, J. Thøgersen, S.R. Keiding, T. Moller-Pedersen; Plastic Particles at the LASIK Interface . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2587.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate the origin, composition, and persistency of the interface particles that frequently are observed after LASIK. Methods: Four patients received LASIK using a Schwind Supratome and a MEL 70 excimer laser and were examined during one year using slit-lamp and in vivo confocal microscopy. Four rabbits received a monocular microkeratome incision and were examined immediately after surgery without lifting the flap. After monthly evaluation for four months, two corneas were processed for histology and serially sectioned. To measure the iron content, atomic absorption spectrometry was performed on two operated and two unoperated rabbit corneas. The chemical composition of the microkeratome blade metal and plastic parts was identified using energy dispersive X-ray fluorescence, infrared and Raman spectroscopy. Before and after oscillation in air, the microkeratome blade and motor-head were examined using light and fluorescence microscopy. In serial sections interface particles were identified and coherent anti-stokes Raman scattering microscopy was used to examine their molecular resonance at 1780 and 3100 cm-1 (Chosen from the Raman spectra of cornea, microkeratome metal and plastic parts). Results: In LASIK patients, thousands of brightly reflecting particles (< 30 µm) were observed at the interface. The highest particle density was detected where the microkeratome blade had first entered. The morphology, distribution, and density of particles remained unaltered throughout the study. Immediately after the microkeratome incision in rabbit corneas, similar particles were observed at the interface where they persisted. Operated and unoperated rabbit corneas had comparable iron contents, demonstrating that particles were not fragments of the steel blade. Few particles were observed on the unused microkeratome motor-head and blade, whereas numerous fluorescent particles were present after oscillation in air; the amount of particles increasing with oscillation time. Interestingly, the only fluorescent part of the microkeratome was the plastic segment of the blade. This plastic (polyetherimide) emitted fluorescence identical to that of the particles generated during oscillation. In serial sections, interface particles showed equivalent fluorescence properties and exhibited molecular resonances (at 1780 and 3100 cm-1) matching the Raman spectrum of polyetherimide. Conclusions: Numerous plastic particles are generated during microkeratome oscillation and deposited at the interface during LASIK. The particles persist unaltered for at least one year.
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