Is the Laminar Flow From the Vitrectomy Infusion Cannula Potentially Harmful?

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Fluid Dynamics

Background:

• Vitrectomy surgery utilizes infusion cannulas to maintain intraocular pressure.
• The fluid dynamics of infusion cannulas, particularly the jet flow, are not fully understood.
• Potential retinal damage from infusion jet impact warrants investigation.

Purpose of the Study:

• To model the jet flow from a 25G vitrectomy infusion cannula.
• To calculate retinal pressure and shear stress from the infusion jet.
• To evaluate the biological response of ex vivo pig retina to this localized pressure.

Main Methods:

• Computational fluid dynamics (CFD) was used to model fluidics, pressure, and shear stress.
• Ex vivo pig eyes were subjected to a 10 mL/min flow via a 25G cannula for 1 or 3 minutes.
• RNA transcripts of proteins related to inflammation, oxidative stress, and apoptosis were measured.

Main Results:

• Infusion flow at 10 mL/min generated jet velocities of 1.33 m/s and pressure increases over 2 mm Hg in a 1 mm wide region.
• Significant increases in RNA transcripts for p65, NF-κB, casp3, p53, iNOS, Keap1, Nrf2, GFAP, IL-1β, and NOX4 were observed.
• These molecular changes occurred within 1 to 3 minutes of flow initiation.

Conclusions:

• 25G vitrectomy infusion cannulas produce high-velocity jets with significant impact pressure on the retina.
• The infusion jet can compromise surgical view and create bubbles.
• Retinal tissue shows a rapid biological response, with increased inflammation, oxidative stress, and apoptosis markers shortly after flow exposure.