Comparison of 4D and Torsional Ultrasound Phacoemulsification for Dense Cataracts

Overview

This ex vivo bench study compared the Alcon UNITY Cataract System using 4D ultrasound with the Alcon CENTURION Vision System using torsional ultrasound in emulsifying dense nuclear cataracts. The UNITY system demonstrated shorter emulsification times and lower energy indices, suggesting improved efficiency in this ultra-dense cataract model.

Background

Cataracta nigra represents an extremely dense nuclear cataract that often requires prolonged ultrasound during phacoemulsification, increasing risks of corneal endothelial damage and thermal injury at the incision site. Traditional phacoemulsification modalities include longitudinal and torsional ultrasound, with torsional motion generally reducing chatter and improving fragment followability. The Alcon UNITY system introduces 4D ultrasound, combining axial and lateral motions with dynamic stroke modulation to potentially enhance emulsification efficiency. Bench models allow controlled comparison of energy delivery and emulsification performance between these technologies.

Data Highlights

Key Findings

• UNITY 4D ultrasound achieved emulsification in significantly less time (12.0 s) compared to CENTURION torsional ultrasound (43.5 s).
• Console-reported effective phaco time (EPT) was lower with UNITY (4.2 s) versus CENTURION (15.2 s), indicating reduced ultrasound exposure.
• Cumulative dissipated energy (CDE) was markedly lower with UNITY (1.12 percent-seconds) compared to CENTURION (15.01 percent-seconds), suggesting less energy delivery.
• Video assessment showed UNITY had more continuous fragment engagement with minimal chatter, whereas CENTURION exhibited initial fragment repulsion and turbulence.
• Both systems were tested under identical user-selected settings (35% power, IOP 36 mmHg, vacuum 450 mmHg, aspiration flow 30 mL/min) to ensure comparability.
• Findings are preliminary from a single-specimen ex vivo model and console-derived energy indices reflect relative rather than absolute physical energy delivery.

Clinical Implications

The 4D ultrasound mode of the UNITY system may offer improved emulsification efficiency and reduced ultrasound energy exposure in managing ultra-dense nuclear cataracts, potentially lowering risks of endothelial and thermal injury. These bench findings support further clinical evaluation to determine if such advantages translate into improved surgical outcomes and safety profiles in patients with dense cataracts.

Conclusion

This pilot ex vivo study suggests that 4D ultrasound technology may enhance phacoemulsification efficiency compared to torsional ultrasound in dense nuclear cataracts. Further research with additional specimens and clinical cohorts is warranted to confirm these benefits.

References

1. Alcon UNITY Cataract System and CENTURION Vision System Study 2024 -- Comparison of 4D Ultrasound and Torsional Ultrasound Phacoemulsification Techniques