Force comparison of air currents produced by a standard and modified infusion cannula

Abstract

Objective: To develop and characterize an infusion cannula that reduces the intraocular jet forces created during fluid-air exchange.

Methods: A new infusion cannula was manufactured by adding a baffle 1.0 mm perpendicular to the distal opening of a 20-gauge infusion. The forces generated by the modified and standard cannulas were measured at a constant air infusion pressure of 50 mmHg by using a force sensor coupled to a schematic eye with eight radial positions from 0 degrees to 180 degrees along the circumference. Five different orientations relative to the baffle support of the modified cannula were evaluated at each position to assess the turbulent flow.

Results: The standard cannula produced a maximum force of 0.14 mmHg at 180 degrees from the sensor. The modified cannula generated a maximum pressure of 0.017 mmHg at 67.5 degrees from the sensor. Overall, the force from the modified cannula was an order of magnitude less than the standard infusion cannula (P < 0.01).

Conclusions: The modifications of the new infusion cannula are passive with respect to its surgical performance. However, the additional baffle transforms laminar air currents into turbulent ones and allows dispersion of the jet forces, which should reduce barotrauma and desiccation of the retina during fluid-air exchange.