Effects of Ultrasound Modality, Viscosurgical Devices, and Automated Energy Modulation on Intraocular Thermal Exposure During Phacoemulsification

PURPOSE: To characterize determinants of intraocular thermal exposure during phacoemulsification-ultrasound modality, ophthalmic viscosurgical device (OVD) use, and delivered ultrasound energy-and to evaluate whether automated energy modulation (Thermal Sentry) reduces anterior chamber and corneal incision temperature. SETTING: Masked for review. DESIGN: Controlled ex vivo laboratory investigation using a porcine eye model. METHODS: Continuous phacoemulsification was performed for 90 seconds using the UNITY Vitreoretinal Cataract System (UNITY VCS; Alcon Vision LLC, Fort Worth, TX, USA) in 80 enucleated porcine eyes under standardized settings (intraocular pressure 37 mmHg, vacuum limit 50 mmHg, aspiration flow rate 18 cc/min, ultrasound power 100%). Anterior chamber and incision temperatures were compared across three modalities (4D, torsional, longitudinal) with Thermal Sentry ON or OFF (n = 10/group), and under OVD-assisted 4D-mode conditions with Thermal Sentry ON or OFF (n = 10/group). Delivered energy (Joules) and cumulative dissipated energy (CDE) were recorded. RESULTS: Thermal exposure differed significantly among modalities (Thermal Sentry OFF), with longitudinal ultrasound producing the greatest elevation and 4D mode the smallest (all P < 0.001). OVD use increased thermal exposure during 4D-mode phacoemulsification. Temperature elevation correlated strongly with Joules (r = 0.857) and CDE (r = 0.860, both P < 0.001). Thermal Sentry reduced anterior chamber temperature elevation across all modalities and OVD conditions, and reduced incision temperature during torsional and longitudinal ultrasound, through reductions in delivered energy. CONCLUSIONS: Intraocular thermal exposure during phacoemulsification is influenced by ultrasound modality and OVD use and is closely associated with cumulative delivered energy. Automated ultrasound energy modulation is an effective strategy for limiting thermal exposure across the conditions tested.