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

## TL;DR

This study investigates whether the fluid jet from a vitrectomy cannula could harm the retina by measuring pressure, stress, and biological responses in pig eyes.

## Contribution

The study introduces a novel ex vivo model to evaluate the biological impact of vitrectomy infusion jet flow on retinal tissue.

## Key findings

- Infusion flow reached 1.33 m/s velocity and increased pressure by over 2 mm Hg at the retina.
- RNA transcripts linked to inflammation, oxidative stress, and apoptosis significantly increased after 1-3 minutes of flow.
- Jet flow may create harmful bubbles and compromise surgical visibility.

## Abstract

To model the jet flow of a 25G vitrectomy infusion cannula onto the opposite retina in a balanced salt solution–filled eye, calculate pressure and shear stress at the retina, and evaluate the biologic response to the localized increase of pressure on an ex vivo pig retina model.

Fluidics, pressure, and shear stress were calculated using computational fluid dynamics. Ten pig eyes within 4 hours of slaughter were prepared to receive a 10 mL/min flow for 1 or 3 minutes after removing the vitreous and inserting a 25G infusion cannula in the usual fashion. RNA transcripts of selected proteins involved in inflammation, oxidative stress, and apoptosis were amplified and measured.

At a 10 mL/min infusion flow rate, the average fluid velocity at outlet reached 1.33 m/s and pressure at impact site increased more than 2 mm Hg in a region approximately 1 mm wide. RNA transcripts of p65, nuclear factor κB, casp3, p53, inducible nitric oxide synthase, Keap1, Nrf2, and glial fibrillary acidic protein reached statistical significance on analysis of variance at the 0.01 level and interleukin-1b and NOX4 exceeded 2log2 units fold-change.

The jet flow generated by 25G vitrectomy infusion cannulas not only may compromise the surgeons’ view blowing on dyes and create potentially harmful perfluorocarbon liquid bubbles, it also reaches significant velocity and remarkable pressure at the impact site. RNA transcripts of proteins involved in inflammation, oxidative stress, and apoptosis significantly increase as soon as 1 and 3 minutes after flow starts.

Evaluation of the infusion jet consequences on the retina lays the foundations for finding solutions that reduce pressure increase and tissue response.