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.