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Posters

The impact of valved and non-valved cannula on intraoperative fluid dynamics and vitreous

Poster Details

First Author: D.J.Abulon USA

Co Author(s):    M. Charles                  0   0 0   0 0   0 0   0 0

Abstract Details



Purpose:

During vitrectomy, intraoperative intraocular pressure (IOP) drop, fluid leakage out of the eye, and vitreous incarceration can be associated with instrument removal from trocar cannulas. This study replicates unoccupied trocar cannula conditions and compares intraoperative IOP, flow, and vitreous incarceration associated with the use valved and non-valved trocar cannulas in various eye models.

Setting:

Experimental study.

Methods:

Three surgical conditions were replicated: 1) an air-filled eye, 2) a fluid-filled eye, and 3) an eye with vitreous. In the air-filled eye model, three incisions were created in a rubber globe using all 23-gauge valved or non-valved trocar cannulas. Air was infused through one cannula at 30 mmHg and two cannulas remained unoccupied for the duration of the tests. A pressure sensor attached directly to the model eye captured IOP. The mean IOP and standard deviations were reported (n=6 tests per cannula type). With the fluid-filled eye model, three 23-gauge cannulas were glued into an acrylic globe. Balanced salt solution was infused through an infusion cannula at 30 mmHg. An in-line flow meter connected to the infusion cannula measured flow through the eye. A pressure transducer connected to the globe measured IOP. Mean IOP, mean flow and standard deviations were reported (n=6 tests per cannula type). For vitreous incarceration tests, three 23-gauge incisions were created in each cadaveric rabbit eye for one infusion cannula, one valved cannula, and one non-valved cannula. After triamcinalone was injected into the valved and non-valved cannula, a microscope captured still images of incarcerated vitreous and imaging software calculated the percent of incarceration (n=10 tests).

Results:

In the air-filled eye model, the IOP associated with two unoccupied non-valved cannulas decreased from the set infusion pressure of 30 mmHg to 1.8±1.5 mmHg. Conversely, valved cannulas maintained IOP at 28.4±1.5 mmHg using the same applied infusion setting. In the fluid-filled eye model, IOP associated with non-valved cannulas decreased from a 30 mmHg infusion setting to 5.6±1.9 mmHg. Valved cannulas maintained fluid pressure at 30.3±0.7 mmHg. The pressure drop with non-valved cannulas was statistically significantly higher than the valved cannulas (P<<0.05). Fluid flow through the non-valved eye model (23.13±1.97 cc/min) was statistically significantly higher than the valved cannula model (0.54±0.50 cc/min). Out of ten paired valved and non-valved tests, vitreous was incarcerated into ten non-valved cannula and two valved cannula. In tests where vitreous incarceration was observed, non-valved cannula incarcerated significantly more vitreous than valved cannula (25% vs 2%, respectively; P<<0.05).

Conclusions:

Based on the reported data, valved cannulas appear to be the optimal trocar cannula choice for maintaining intraoperative IOP, minimizing fluid loss, and minimizing vitreous incarceration.

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