Simulation of vitreous traction force and flow rate of high speed dual-pneumatic 7500 cuts per minute vitrectomy probes

Abstract

Purpose: To develop methods to simulate vitreous flow and traction during vitrectomy and qualify these methods using laboratory measurements. Methods: Medium viscosity and phase treatment were adjusted to represent vitreous (Eulerian two-phase flow) or saline solution (single-phase Navier-Stokes flow). Retinal traction was approximated using a one-way fluid-structure interaction simulating cut vitreous volume coupled to a structural simulation of elastic stretching of a cylinder representing vitreous fibers entrained in the flow. Results: Simulated saline solution flow decreased, but vitreous flow increased with increasing cut rate, consistent with experimental trends observed for the 50/50 duty cycle mode. Traction simulations reproduced all trends in variation of traction force with changes in conditions. Simulations reproduced the majority of traction measurements within experimental error. Conclusions: A scientific basis is provided for understanding how flow and traction vary with operational parameters. This model-based analysis serves as a “virtual lab”to deter-mine optimal system settings to maximize flow efficiency while reducing traction. Translational Relevance: The model provides a better understanding regarding how instrument settings can help control a vitrectomy procedure so that it can be made as efficient as possible (maximizing the rate of vitreous removal) while at the same time being made as safe as possible (minimizing retinal traction).