Purpose:
To study the impact of different parameters such as duty cycle, vacuum, and cut rate on vitreous flow behaviour during vitrectomy by using a computational fluid dynamics model.
Methods:
A two dimensional model focusing on the tip of the vitrector and the surrounding vitreous was developed to investigate vitreous flow behavior during vitrectomy. The vitreous is considered to be a Newtonian fluid. Major vitrectomy parameters, such as vitreous probe size (port and inner tube diameter), cut rate, duration of each guillotine phase (opening, opened, closing, and closed), as well as the duty cycle, were studied to assess their impact on vitreous flow behavior (flow rate and vitreous velocity around the probe). Flow performances and vorticity along the vitrector were also studied at different cut rates.
Results:
Linear changes in flow rate were observed with vacuum and cut rate variations. Different time-varying flow rates were found at different cut rates and vacuum. The flow rate increased during the opening phase and dropped dramatically when the gate suddenly closed. The flow rate during the fully opened phase was dependent on vacuum, cut rate, and guillotine opening speed. The vorticity of the vitreous along the guillotine, which depended on cut rate, demonstrated a dramatic impact on the flow rate performances.
Conclusions:
Evaluation of computational fluid dynamics demonstrates the impact of vitrectomy parameters on flow rate behavior.FigureChanges in flow rate over time for different vacuum settings throughout vitrector cut cycle (vitreous cutter at 2000 CPM).
Keywords: computational modeling • vitreoretinal surgery • vitreous