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M. E. Steen, T. Smith, R. Raney, A. Gwon, W. Fishkind; Thermal Comparisons of Phacoemulsification Ultrasonic Modalities. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6093.
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A by-product of Phacoemulsification is tissue heating caused by the delivered ultrasonic energy. This thermal effect often results in unwanted tissue damage. The purpose of the study was to compare thermal effects at the incision site caused by the three leading ultrasonic modalities for tissue fragmentation, that of continuous longitudinal, transversal, and torsional.
The surgical evaluation was performed on four mature rabbits, controlled by comparing procedures in the two eyes of each animal. Each of the tests used the same surgical techniques, fluidic settings, phaco power settings, bottle height and fluid temperature, tip sizes, and incision sizes. Temperature data were collected using a thermal camera, and operational parameters were recorded from the phaco machine.
Increased duration of ultrasonic energy in conjunction with reduced aspiration flow by occlusion of lens tissue produced observable collateral thermal effects. Recorded temperatures ranged from 33.0º to 37.1ºC for continuous transversal, 46.0º to 50.1ºC for continuous torsional and 36.3ºC to 41.1ºC for continuous longitudinal. Temperatures were recorded during continuous ultrasonic time periods greater than three seconds and typically five seconds for maximum recorded temperatures. Collateral tissue damage can be observed at temperatures exceeding 45º C.
All Phacoemulsification modalities can create collateral thermal effects related to duration, ultrasonic power and tissue occlusion. Torsional ultrasound created the most notable temperature rise, followed by longitudinal and the least generated by transversal. Given continuous ultrasonic tissue removal times of 5 seconds, torsional exceeded collateral damage thresholds; temperature rise was below that threshold for both longitudinal and transversal.
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