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H. F. Mietz, A. Wan, G. Welsandt; A Torsional Phacoemulsification Technique Significantly Increases the Energy Delivered to the Anterior Chamber During Cataract Surgery. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1077.
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Torsional phaco is a new development in cataract surgery which was introduced to the market this year. In torsional phaco, the phaco tip does not move forward and backward like in the standard ultrasound technique. Instead, the tip oscillates about 32.000 times per second from side to side. This advancement is meant to be more efficient for removing especially dense and hard lens nuclei. The technique can be used for all cataract cases, and the time needed to remove the nucleus is proposed to be less. The phaco machine notes the ultrasound time as measured in seconds and the total energy used for the surgery in a relative value. Both data combined and additional factors accumulate in a specific value called cumulative dissipated energy (CDE). These values can be compared and are low in soft lenses and higher for hard cataracts. In this first evaluation, we wanted to determine whether there is a difference between standard phaco and torsional phaco with regard to the cumulative dissipated energy.
This is a retrospective evaluation of CDE values that were recorded in the years 2005 and 2006 by a single surgeon (HM). Each 100 consecutive cases of standard phacoemulsification and torsional phaco were randomly selected. The investigation was started after completion of all surgeries. All data evaluated was on file in the operating room documentation of all surgical procedures performed at our institution. In all cases, the same phaco machine and equipment were used, and the CDE values were calculated by the algorithm that was part of the software supplied by the manufacturer. The surgeon had been initially introduced by a technician from the company how to use the torsional phaco technique and had gained sufficient experience.
For both different techniques, the CDE values of 100 cases were evaluated. For standard ultrasound, the CDE value was 2.35+/-1.53 (mean+/-standard deviation), for torsional phaco it was 7.20+/-5.11. This represents an increase of 206%; the difference was significant with a p-value smaller 0.0001 (Mann-Whitney, unpaired samples). The range of CDE values was 0.07 to 7.99 for standard phaco and 0.00 to 23.19 for torsional phaco.
The results of this first evaluation suggest, that the torsional phaco technique uses more energy to remove the lens nucleus. It remains to be seen and will be subject of a prospective study to determine whether this difference has a clinical relevance.
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