Purpose: To evaluate the efficiency of torsional ultrasound (US) under different vacuum levels in eyes with cataract with different degrees of nuclear density.
Setting: Cataract Service, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Methods: In this prospective randomized series, eyes with age-related cataract were divided into 3 groups based on nuclear density. Eyes in each group were randomly assigned to 1 of 3 subgroups and treated with phacoemulsification under vacuum of 250 mm Hg (subgroup 1), 450 mm Hg (subgroup 2), or 600 mm Hg (subgroup 3). Data included preoperative and postoperative corrected distance visual acuity (CDVA), endothelial cell density, and central corneal thickness (CCT) and intraoperative US time and cumulative dissipated energy (CDE).
Results: The study evaluated 998 patients (1073 eyes). In each group, there was a statistically significant decrease in US time, CDE, and postoperative endothelial cell loss with increased vacuum (P<.05). At 1 day and 7 days, the CDVA was statistically significantly better in subgroups 2 and 3 (P<.05) and the CCT was thinner when vacuum was higher. There was no statistically significant difference in CDVA and CCT between subgroups 30 days postoperatively (P>.05).
Conclusions: Torsional US with a high vacuum level was safe for cataract extraction. With less US energy and endothelial cell loss, torsional US was more efficient than with higher vacuum levels with lower levels.