To compare vitreous concentrations of triamcinolone acetonide (TA) achieved by prior therapeutic intravitreal and subtenon injections. Interventional case series. Vitreous samples were collected from patients who required vitreous surgery, six having received a subtenon injection of TA and another six, an intravitreal injection. Vitreous concentrations of TA were measured by high-performance liquid chromatography. Vitreous concentrations of TA after intravitreal injection were 1.22 ± 0.24 μg/ml, significantly higher than those after subtenon injection (<0.001 μg/ml, P =. 003). Vitreous concentrations of TA after subtenon injection and TA-assisted vitrectomy performed in a few patients to visualize the transparent vitreous gel were 0.20 ± 0.11 μg/ml, an intermediate amount between these two groups. Much higher vitreous concentrations of TA after intravitreal injection than subtenon injection may accelerate therapeutic effect when intravitreal injections are given to reduce macular edema. Subtenon injections of TA may act via the sclera as opposed to the vitreous.
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