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M. Topaz, E.I. Assia, D. Meyerstein, N. Meyerstein, A. Gedanken; Reduction of Acoustic Cavitation Effects Under Simulated Phacoemulsification Conditions In Vitro . Invest. Ophthalmol. Vis. Sci. 2003;44(13):183.
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Purpose: A common, and sometimes vision-threatening, complication of phacoemulsification is damage to the unilayer corneal endothelium, which has been attributed mainly to mechanical injury. The generation of acoustic cavitation (AC) in aqueous medium transforms acoustic energy into chemical, mechanical, electromagnetic and thermal energies. Our objective was to investigate the chemical reactions induced by AC under conditions simulating phacoemulsification, and to qualitatively and quantitatively assess free radicals (FR) generated by this phenomenon. Various gases and antioxidants were evaluated for their effectiveness in reducing cavitation and free radicals generated by AC. Methods: The experimental setup consisted of a high-intensity ultrasound energy (HIUE) processor (phacoemulsifier, Master 10,000, ALCON) operating in an aqueous medium (BSS) within parameters matching the application of phacoemulsification in clinical cataract surgery. Measurement of sonoluminescence was a direct indication of AC and was detected by a sensitive photomultiplier tube. FRs and the effects of various antioxidants on their concentrations were analyzed by electron paramagnetic resonance (EPR) spectroscopy. Results: AC was suppressed and practically eliminated by saturation of irrigating solution with CO2. Analyses of AC revealed generation of hydroxyl radicals and singlet dioxygen. The effective concentrations of antioxidants that substantially reduced the concentration of radicals in the sonicated medium were determined. Conclusions: Phacoemulsification may generate AC and induce endothelial damage by means of chemical and mechanical mechanisms. The saturation of irrigating solution with multiatomic gases suppresses and practically eliminates AC. The introduction of biocompatible water-soluble antioxidants to the sonicated medium reduces the concentration of radicals. Suppression of AC effects may lead to reduced corneal endothelium damage in clinical application. We introduce the Cavitation Safety Index (CSI) for standardizing phacoemulsification instrumentation and improved biosafety.
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