Torsional ultrasound modality for hard nucleus phacoemulsification cataract extraction

Aim: To evaluate the efficacy and safety of phacoemulsification using torsional modality with different parameter settings for hard nucleus cataract extraction. Design: A prospective, randomised clinical study. Methods: A clinical practice study conducted at the Cataract Service, Zhongshan Ophthalmic Center, Sun-Yat-Sen University, and Guangzhou. One eye each from 198 consecutive patients with cataract density grade IV according to the Emery-Little system classification system, requiring phacoemulsification and intraocular lens implantation, was included. Eyes were randomly assigned to the Linear Torsional combined with Ultrasound power group (Linear Tor+US group, n = 66), 100% Fixed Torsional group (Fixed Tor group, n = 65) and conventional Ultrasound burst group (US group, n = 67). All surgeries were performed by a single experienced surgeon and outcomes evaluated by another surgeon masked to treatment. Intraoperative parameters were Ultrasound Time (UST), Cumulative Dissipated Energy (CDE) and surgical complications. Patients were examined on post-op days 1, 7 and 30. Postoperative outcomes were final best corrected visual acuity (BCVA), average central and incisional corneal thickness and central endothelial cell counts. Results: The mean UST was lower in the Fixed Tor group than in the US group and in the Lin US+Tor group (p <= 0.0001). The mean CDE was lower in the Lin Tor+US group and in the Fixed Tor group than in the US group (p <= 0.0001). Comparing with the two Tor group, the US group had a lower average BCVA on post-op 1, 7 (p <= 0.0001) and 30 (p>0.01), greater average central corneal and incisional thickness on days 1, 7 (p <= 0.0001) and 30 (p>0.01), and higher average corneal endothelial cell losses on day 7 and 30 days (p <= 0.0001). Conclusions: Torsional combined with ultrasound power or high fixed torsional amplitude can yield more effective hard nucleus phacoemulsification than conventional ultrasound modality.