Abstract
PURPOSE: To assess whether the use of a patented, novel feedback device intended to accurately control phacoemulsification tip elongation is effective under varying machine settings and material resistance. METHODS: Sculpt mode phaco (550-mm Hg Venturi pump; elongations, 35 and 70 µm) and quadrant settings (550-mm Hg Venturi pump; elongations, 15, 30, and 60 µm) were used in agar gel of incremental density (1%, 2%, 3%, and 6% in demineralized water). Dispersed lens fragments were also simulated with 6% agar gel spherules (2-5 mm in diameter; 550-mm Hg vacuum, and 60-µm elongation). Actual phaco tip elongation was measured on voltage readings from the piezoelectric crystals and compared to nominal elongation with feedback control off and on. RESULTS: Mismatch between nominal and actual elongation when feedback control was off in sculpt mode varied between -13.51 µm and -23.07 µm of nominal elongation; in quadrant mode, mismatch varied between -2.79 µm and -20.41 µm. When the feedback control system was switched on, mismatch varied between -0.02 µm and +0.43 µm (P < 0.001 for all matchings). When the feedback system was off, the elongation mismatch among the 1%, 3%, and 6% agar was also statistically significant (P < 0.001). Elongation was 44.72 ± 4.16 µm with feedback control off and 60.02 ± 1.63 µm with it on (nominal elongation 60 µm; P < 0.001) when emulsifying agar 6% gel fragments. Dispersion of elongation data was also significantly wider when feedback control was turned off. CONCLUSIONS: A novel feedback control system effectively controls elongation accuracy regardless of the resistance offered by incremental agar gel concentrations. TRANSLATIONAL RELEVANCE: Implementing feedback control in phaco handpieces dramatically improves surgical accuracy. The translational value of this research relies on its immediate applicability to routine cataract surgery, resulting in a more appropriate use of ultrasound energy.