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October 2004

Rinsing of the Cannula Prior to Intravitreal Injection

Arch Ophthalmol. 2004;122(10):1571-1572. doi:10.1001/archopht.122.10.1571-b

With great interest we read the article by Gillies et al1 ontheir 1-year results after intravitreal injection of 4 mg of triamcinoloneacetonide for treatment of exudative age-related macular degeneration. Wecongratulate the authors on their excellent study. We would like to ask theauthors whether the 27-gauge needle they used for intravitreal injection wasrinsed with the triamcinolone acetonide suspension prior to the injection.The 27-gauge cannula has an inner volume of about 40 µL. Rinsing thecannula may be important for removing air, which, when injected into the vitreouscavity, may lead to peripheral retinal tears in the inferior hemisphere ofthe fundus. If the needle was not emptied of air and was not filled with thetriamcinolone acetonide suspension prior to the injection, or if the cannulawas rinsed with solutions other than the triamcinolone acetonide suspension,a volume of up to 40 µL or 40% of the whole injection volume of 0.1mL would have been left over in the cannula at the end of the injection. Asthe authors discussed, a weakness of the study may be a possible underdosingof triamcinolone acetonide; thus, the issue of preinjection filling of thecannula with the triamcinolone acetonide suspension may be relevant.