Four-dimensional ultrasound versus torsional ultrasound phacoemulsification in cataracta nigra: a single-nucleus

Cataracta nigra, an extremely dense nuclear cataract, often requires prolonged ultrasound use during phacoemulsification, increasing the risk of corneal endothelial injury and incision-site thermal damage. We compared the Alcon UNITY Cataract System using 4-dimensional (4D) ultrasound with the Alcon CENTURION Vision System with torsional ultrasound in an ex vivo cataracta nigra bench model. A single human cataracta nigra nucleus was divided into four fragments; two fragments were emulsified with UNITY and two with CENTURION under identical user-selected console settings (35% power; IOP 36 mmHg; vacuum 450 mmHg; aspiration flow 30 mL/min). Endpoints included emulsification time, effective phaco time (EPT), cumulative dissipated energy (CDE), and qualitative video assessment of fragments behavior. In this single-specimen model, compared with CENTURION, UNITY showed shorter emulsification time (mean 12.0 s vs 43.5 s) and lower console-reported energy indices (mean EPT 4.2 s vs 15.2 s; mean CDE 1.12 percent-seconds vs 15.01 percent-seconds). Video review suggested more continuous fragment engagement with minimal chatter using UNITY, whereas CENTURION more often showed initial fragment repulsion and turbulence. Because EPT and CDE are console-derived, these findings should be interpreted as relative performance under matched user-selected settings rather than equivalent physical energy delivery. These preliminary findings suggest that the 4D ultrasound mode might be associated with improved emulsification efficiency compared to torsional mode in ultra-dense nuclear material. Further studies using additional specimens and clinical cohorts are needed to determine whether these bench findings translate into meaningful surgical benefit.