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S. Garg, L. F. Hagemann, L. C. Zacharias, B. D. Kuppermann; Comparison of Leakage Pressures in Bevel Down versus Bevel Up Sclerotomy Incisions Using a 23 Gauge Vitrectomy Trochar System. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2230.
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© ARVO (1962-2015); The Authors (2016-present)
Compare leakage pressure between bevel down versus bevel up sclerotomy incisions in 23 gauge vitrectomy surgery.
Twenty freshly enucleated New Zealand white rabbit eyes underwent 23 gauge vitrectomy (Alcon Surgical, Ft. Worth,TX). An infusion was placed 2 mm from the limbus at the 6 o’clock position. A second cannula was inserted with a trochar using a tunnel style sclerotomy incision at 10 o’clock by passing the trochar obliquely at a 15 degree angle with the bevel down. Vitrectomy was performed until free flow of fluid was observed through the sclerotomy. The cannula was then removed with the intraocular pressure set to zero. Pressure was then increased progressively until leakage was noticed from the incision site, or the eye reached maximum machine pressure of 120 mmHg. Balanced salt solution stained with Indocyanine Green (200mg/l) was infused into the eye to facilitate leak visualization. In another 10 eyes, the same procedure was performed with the trochar being inserted in a bevel up fashion rather than bevel down.
Ten incisions were performed in the bevel down group and 10 in the bevel up group. In 3 incisions of the bevel down group, leakage at low pressure was observed (2-7 mmHg), at which time massage of the incision site with a cotton swab was performed and the infusion pressure was raised to 35 mmHg to facilitate wound closure. These eyes achieved a maximum machine pressure of 120 mmHg after massage. The maximum machine pressure of 120 mmHg was achieved for all other 7 incisions in the bevel down group without massage. In the bevel up group, only one eye required massage for a leak observed at 5 mmHg. All 9 other eyes achieved a maximum machine pressure of 120 mmHg without massage. Mean leak IOP for the bevel down group without massage was 85.1 mmHg (range 2-120 mmHg, SD=56.2) and for the bevel up group without massage was 108.5 mmHg (range 5-120 mmHg, SD=36.4). The was no difference between the two groups (p=0.444)
There is no difference in integrity to elevated intraocular pressures when comparing 23 gauge tunnel incisions with respect to whether the trochar is inserted with the bevel down or up.
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