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A.S. Mitias, R. Iezzi, G.W. Abrams; Ultrasound Biomicroscopy of Trans–Scleral Entry Sites After Pars Plana Intravitreal Injections . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5662.
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To investigate the incidence of vitreous incarceration into the pars plana following intravitreal injections (IVI), using ultrasound biomicroscopic examination (UBM).
A prospective, observational study was performed on 6 eyes that required an IVI of pegaptanib sodium or triamcinolone acetonide for choroidal neovascularization and macular edema, respectively. Prior to the IVI, the vitreoretinal interface was characterized via biomicroscopic and indirect ophthalmoscopic examination. Injections were performed after a full prep, using topical betadine 10% with 5% betadine irrigation and painting of the eyelashes. A cotton–tipped applicator impregnated with 10% betadine was held at the injection site as the needle was withdrawn. Ultrasound biomicroscopy was performed within 7 days post–operatively to evaluate any vitreous tracking to the injection site. The main outcome measured was the presence of vitreous incarceration. Vitreous incarceration was seen on UBM as echogenic strands converging towards an echolucent scleral defect. A classification of no vitreous incarceration was given to cases in which no vitreous strands were detected at the entry site. A classification of vitreous incarceration was given to any entry site that had vitreous strands adherent to it.
Of the 6 studied eyes prior to IVI, 4 of the eyes had a complete posterior vitreous detachment, 1 with a partially detached posterior vitreous, and 1 with a completely attached vitreous. Three patients had an intravitreal injection of 0.1 cc triamcinolone acetonide with a 30 gauge needle and 3 patients had a 90 µl intravitreal injection of pegaptanib sodium with a 27 gauge needle. Vitreous incarceration was ultrasonically identified at the scleral defect of the entry site in 4 of the 6 eyes. There was no association of vitreous incarceration with the pre–injection vitreous configuration or needle gauge. None of the patients had a complication related to the injection.
Ultrasound biomicroscopy is a useful tool for detecting vitreous incarceration at pars plana entry sites following an IVI. Careful post injection monitoring is imperative because injection–related complications, though uncommon, may lead to permanent vision loss.
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