Comparison of semicircular and bent tips regarding regional differences in oscillation amplitude under various torsional power settings

Abstract

Purpose: To analyze the difference between the behavior of semicircular (balanced) and bent (mini) tips at 20 incremental torsional power settings. Setting: Tsukazaki Hospital, Himeji, Japan. Design: Experimental study. Methods: Using an ultra-high-speed video camera HPV-X2, the 2 tips during torsional oscillation were recorded, comparing tip behavior at power settings from 5% to 100% by tracking points 1 to 5 (tip end and at 1325, 2650, 3975, and 5035 μm from the tip end). Results: Both tips increased their amplitude widths, drawing an S-curve at all points as the torsional power setting was increased, reaching their upper limits from 70% to 90% torsional power. At all 20 power settings, both tips showed significantly different amplitudes (all P < .01), and the difference of the amplitude increased as the power setting increased. Although, at points 1 and 3, the balanced tip amplitude was nearly 1.5 times larger than the mini tip amplitude, the amplitude difference was 10 μm or less at points 2 and 4. At point 5, the mini tip amplitude was at least 3 times more than the balanced tip amplitude. Conclusions: The amplitude does not increase proportionally and varies markedly with the tip shape on reaching the upper limit, suggesting that a higher power setting might not contribute greatly to nuclear fragmentation. The balanced tip might cause greater damage to surrounding tissues if it is inserted at approximately 3 mm from the wound site. To obtain maximum shaft stability using the balanced tip, it is important to insert at least 5 mm.

Torsional Power and Tip Shape Greatly Change Irrigation Flow Feeding Rate

“…The end of the phaco tip reached maximum amplitude at 80% TP in an S-shaped curve. Above 80% TP, the increase in amplitude becomes negligible and may not contribute to nuclear fragmentation [8]. We speculated that the tip motion induced by torsional ultrasound may be the source of resistance to irrigation fluid ejection and is assumed to decrease consistently with the tip amplitude.…”

“…Furthermore, there are multiple types of ultrasound tips. We previously reported that the torsional phacoemulsification amplitude greatly varies with tip shape [7,8].…”