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For decades, corticosteroids have been known to reduce inflammation and, depending on their concentration, to suppress proliferation of cells. Applied either locally or systemically, steroids have consequently been used for treatment of various ocular diseases. Often, however, the intraocular concentrations of cortisone were not sufficiently high, or the systemic side effects were too pronounced, to effectively treat the ocular disorder. Taking into account that the eye comprises only 0.01% of the whole body volume, and considering that for achieving high concentrations of a drug at its site of action it is best to apply it directly into the region of requested action, Machemer and other researchers studied the possibility of injecting cortisone directly into the eye.1 Clinical studies have correspondingly revealed that a single intraocular injection of triamcinolone acetonide may be a therapeutic option as adjunctive treatment of exudative age related macular degeneration, diabetic cystoid macular oedema, and proliferative diabetic retinopathy.2–5
It has been unknown so far, how long after a single intravitreal injection, clinically detectable concentrations of triamcinolone acetonide are available in the eye. Ophthalmoscopic findings of patients who received an intravitreal injection of triamcinolone acetonide suggest that triamcinolone acetonide crystals remain visible in the eye up to about 6 months after the injection.5 The aim of this study was, therefore, to assess the concentration of triamcinolone acetonide in silicone oil samples removed from patients who had previously undergone pars plana vitrectomy with silicone oil endotamponade.
The study included three patients (one woman, two men) with a mean age of 57.7 (SD 5.4) years. They had undergone pars plana vitrectomy with silicone oil endotamponade as treatment of proliferative vitreoretinopathy (n=2) or proliferative diabetic vitreoretinopathy (n=1). At the end of surgery, 25 mg of triamcinolone acetonide were injected into the silicone oil bubble. Silicone oil was removed 2, 5, and 8 months, respectively, after the instillation, and the concentrations of triamcinolone acetonide were determined.
The concentration of triamcinolone acetonide was 3 μg/kg silicone oil in the silicone oil sample removed from the eye which had undergone pars plana vitrectomy 4 months before the oil removal, and in which the retina remained attached after the release of silicone oil. Concentration of triamcinolone acetonide was 61 μg/kg silicone oil in the sample removed 7 months after the instillation into the eye in which the retina was attached before the silicone oil removal, in which, however, the retina re-detached within 1 week after release of the oil. In the sample which was removed 8 months after instillation, concentration of triamcinolone acetonide was 11 μg/kg silicone oil. In that eye, the retina was partially detached before the removal of the silicone oil, and the eye underwent a second pars plana vitrectomy.
The results suggest that detectable concentrations of triamcinolone acetonide can be found in intraocular silicone oil samples up to 8 months after its instillation. Future studies may evaluate which factors, besides the time interval after its injection, may be responsible for the varying concentration of triamcinolone acetonide.
Proprietary interest: none.