Discrepancies in CDE and Measured Phaco Tip Energy: Comparison of Energy Produced in Longitudinal and Torsional Ultrasound Using Calorimetry.

Abstract

Purpose: This study aims to investigate the differences between the heat energy produced during cataract surgery and Cumulative dissipated energy (CDE). CDE is often used as a medium for understanding the energy delivered to the eye during cataract surgery. However, the actual energy produced at the tip level of the tip is not well understood. We propose that a discrepancy may exist between the CDE reported by the surgical machine and the actual energy delivered to the eye.

Methods: About 50 mL of distilled water were degassed and placed in an isobaric calorimeter. Using the Alcon Centurion and Ozil handpiece fitted with the balanced tip, an investigator immersed the phaco tip into the water and pressed the foot pedal to position 3. The device was set to 100% continuous power, vacuum to 0 mmHg, with aspiration 12 mL/min aspiration. To prevent system changes in the system within the calorimeter, the aspiration tubing was occluded. Temperature change recorded by another investigator was observed from 0 to 60 seconds. After 60 seconds the first researcher immediately released the pedal and removed the phaco tip from the water. Trials were performed 10 times using solely torsional or longitudinal settings and averaged. CDE also was recorded and averaged.

Results: No significant difference was seen in the temperature change or energy calculated in Joules between ultrasound modalities, with torsional producing a magnitude of 163 J and longitudinal producing 172 J (P = 0.2). However, the CDE generated in the 60 seconds period was significantly different, with a magnitude of 61 for longitudinal compared to 24 for torsional (P < 0.001).

Conclusion: Significantly more energy was generated using torsional ultrasound than longitudinal at the tip level of the tip. CDE did not appear to accurately reflect these differences. This suggests that other factors should be considered when evaluating CDE and surgical outcomes.