Pressurized Air Infusion Induced Intraocular Jet Flow and Focal Pressure Increase: Mechanisms of Focal Chorioretinal Damage During Fluid-air Exchange

Abstract

 

Purpose

 

The primary aim of this study was to analyze the flow of the infused air and pressure distribution on retina based on fluid dynamics, so that we can understand the mechanisms of retinal damage by pressurized air infusion.

 

Methods

 

A computer simulation was conducted using three-dimensional modeling software. We simulated the fluid dynamics of infused air in an air-filled eye. Air flow in the vitreous cavity was simulated with a conventional mesh-based techniques. Infusion port size and infusion pressure were altered for each simulated iteration. Detailed pressure distribution on retina and vitreous cavity, and flow velocity of infused air were recorded.

 

Results

 

Infused air flowed straightly into vitreous cavity from the infusion port. During air infusion, highest pressure was observed at a point on the part of retina contralateral to the infusion port (vulnerable point). With a 20-gauge system, pressures at optic nerve head and vulnerable point were 11.8 and 13.7 mmHg at infusion pressures of 20 mmHg, and 25.0 and 29.0 mmHg at infusion pressure of 40 mmHg, respectively. Pressure differential between the optic nerve head and vulnerable point were 1.9 mmHg at infusion pressure of 40 mmHg in 23-gauge system, and smaller in 25-gauge system. Dynamic pressure (tractional force) induced by infused air were under 1.0 mmHg at each infusion pressure.

 

Conclusions

 

According to the simulation, tangential element of force (shearing force) induced by infused air particles is insignificant to cause the retinal surface damage. Considering the retinal perfusion pressure and retinal capillary pressure, pressure difference more than 4 mmHg can cause the focal collapse of retinal capillaries. Prolonged focal collapse can induce the ischemic changes of corresponded retinal structures. The findings of our study can provide a better understanding of fluid dynamics during fluid-air exchange.

 

 

Figure 1. Pressure distribution on the retina and vitreous cavity with various gauge port and infusion pressures during continuous air infusion in air-filled eye. Highest pressure is always observed at the part of retina contralateral to the infusion port.

 

 

Figure 2. Schematic drawing of air flow in the vitreous cavity during continuous air infusion in air-filled eye. Each air particle which collides with retina, brings the shearing force on the retina in the tangential direction.

 

Keywords: 568 intraocular pressure • 762 vitreoretinal surgery • 688 retina