The effect of longitudinal and torsional ultrasound on corneal endothelium cells: An experimental study in rabbit eyes.

Purpose To compare corneal endothelial damage from longitudinal and torsional ultrasound during phacoemulsification. Setting John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. Design Experimental Study. Methods Nine New Zealand white rabbits underwent bilateral surgery. After incision, the Intrepid Balanced tip of the Centurion (Alcon) Ozil handpiece was inserted into the anterior chamber and the following settings were used: 50 mL/minute flow, 70 mmHg intraocular pressure, 600 mmHg vacuum, and 60% longitudinal (one eye) or torsional (contralateral eye) ultrasound for 30 seconds. Cumulative dissipated energy (CDE) was noted. After euthanasia and enucleation, the corneas were removed, stained with trypan blue/alizarin red, and photographed (X400 photographs from 5 specific areas, and 1 overview photograph from each corneal button). The ImageJ program was used to evaluate cell damage and loss in the photographs obtained from each cornea. Results Cavitation bubbles around the phaco tip was generally observed in the longitudinal group. CDE was 17.4 +/- 0.58 and 6.93 +/- 0.15 in the longitudinal and torsional groups, respectively (P = 0.003). The percentage of intact cells was statistically higher in the torsional group, and the percentage of lost cells was statistically higher in the longitudinal group (P = 0.003). This was observed in the analysis of the X400 photographs, as well as the overview photographs. Conclusion This study suggests that torsional ultrasound was associated with significantly less corneal endothelial cell damage than classical longitudinal tip motion, providing further insight on mechanisms of corneal endothelial damage during phacoemulsification.