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J. S. Brown, R. Iezzi; Wound Architecture, Intraocular Pressure and Wound Leakage in Small Gauge Sclerotomy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2964.
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© ARVO (1962-2015); The Authors (2016-present)
We developed a model to asses wound closure in small gauge sutureless vitrectomy (SGSV) that allows for assessment of both the dynamic IOP changes that occur during sclerotomy closure and the resistance characteristics of sclerotomes in relation to IOP.
127 porcine scleral discs were mounted on an artificial anterior chamber. Sclerotomies were created using small-gauge trochars with various techniques. Wounds were tested during pressure cycling procedures using a syringe infusion pump. Parameters assessed included: gauge (23 vs. 25), blade design (beveled vs. MVR-style), angle of entry (90°, 45°, 15°), scleral thickness, uniplanar vs. biplanar insertion, and intraocular tamponade (fluid vs. air). The IOP was modulated and the resistance to wound leakage was compared between the various techniques. Scleral thickness, wound angle, and incision length were measured. Ultrasound biomicroscopy (UBM) was used to observe the dynamic changes in wound architecture as IOP was cycled.
Blade design, scleral thickness and trochar gage did not show a significant difference in wound closure rates. Smaller angles of insertion, air tamponade and uniplanar insertions showed statistically increased rates of closure. There was a decrease in closure rate with steeper angles (15°-incision had a 75% closure, 45° a 20% closure (p<0.05), and 90° a 0% closure rate (p<0.05)). With a beveled-style blade a uniplanar incision had increased rates of wound closure (uniplanar incision had a 79% closure, bevel-up biplanar incision had a 0% closure (p<0.05), and bevel-down biplanar incision had a 40% closure (p<0.05)). Air tamponade of uniplanar 15° incisions resulted in a Seidel negative rate of 100% compared to 76% in fluid filled eyes (p=0.09). Air tamponade of uniplanar 45° incisions resulted in 100% Seidel negative compared to 20% of fluid filled eyes (P<0.05). UBM demonstrated that wound leakage was associated with disruption of the internal aspect of the sclerotomy. Pressure cycling maneuvers showed that sclerotomies acted as pressure-sensitive valves that were more likely to close at high pressure. Raising IOP and/or pushing on the sclerotomy increased resistance and in many cases closed the sclerotomy.
More tangential incisions, air tamponade, and uniplanar incisions increase wound closure rates. Sclerotomy resistance can be increased through IOP modulation (increasing IOP) after the trochar is removed and often facilitates sclerotomy closure. Porcine scleral discs mounted in a pressure-monitored chamber serve as a useful model for assessing wound leakage in SGSV.
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