# Comparing the Efficiency of Valved Trocar Cannulas for Pars Plana Vitrectomy

## TL;DR

This study compares how well different valved cannulas maintain eye pressure during vitrectomy surgery, finding that all meet safety standards despite varying performance.

## Contribution

The study introduces a direct comparison of valved cannulas from multiple manufacturers under simulated surgical conditions.

## Key findings

- 25G cannulas opened at higher pressure than 23G and 27G during BSS infusion.
- 27G cannulas showed significantly higher leakage pressure under air infusion compared to 25G and 23G.
- All tested cannulas maintained a surgically negligible pressure difference under both BSS and air infusion.

## Abstract

Purpose: To compare the efficiency of different manufacturers’ valved cannulas (23G, 25G and 27G) (Alcon, Bausch & Lomb, BVI, DORC, Optikon) in maintaining intraocular pressure during vitrectomy by measuring leak pressure and the difference between set and actual intraocular pressure, under BSS and air infusion. Methods: A BSS-filled reservoir was connected to a model eye allowing placement of leak-proof valved cannulas. A pressure sensor was interposed and the bottle height increased until leakage occurred. Air leakage was measured by connecting an air pump to different manufacturers’ valved cannulas, inserted upside down to blow air against the valve with inside-out direction and immersed in soapy water to detect air bubbling. Results: The average BSS leaking pressure was 7.69 ± 0.77 mmHg for 23G, 9.92 ± 0.57 mmHg for 25G and 7.57 ± 0.80 mmHg for 27G. The 25G valved cannulas opened at higher pressure (p < 0.05). The difference between set and actual pressure in BSS never exceeded 4 mmHg. Leakage pressure under air ranged between 10 and 55 mmHg. The 27G valves opened at an average 47.2 ± 3.9 mmHg vs. 29.4 ± 7.2 for 25G and 24.1 ± 16.5 for 23G (27G vs. other gauges p < 0.05). The difference between set and actual pressure under air infusion never exceeded 2 mmHg. Conclusion: Despite significant differences, all tested valved cannulas satisfy safety criteria by keeping a surgically negligible difference between the set and actual intraocular pressure. The minimal leakage measure may act as a safety pressure damper under critical conditions.