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The unwanted proliferation of intraocular tissue such as vascular retinal cells in eyes with ischaemic retinopathies, subretinal neovascular tissue in eyes with exudative age related macular degeneration, and retinal pigment epithelium cells in the case of proliferative vitreoretinopathy, is one of the important problems still mostly unsolved in clinical ophthalmology. Since the early 1950s, corticosteroids have been used in ophthalmology to suppress intraocular inflammation by reducing inflammatory exudation and inhibiting proliferation of fibroblasts and formation of granulation tissue. They have been applied either topically as eyes drops, locally by subconjunctival, parabulbar or retrobulbar injections, or systemically as oral medications or intravenous or intramuscular injections. Machemer et al, based on clinical observations and pathogenic considerations, suggested the intravitreal application of cortisone to locally suppress intraocular inflammation and proliferation of cells, especially in patients with proliferative vitreoretinopathy.1 Since cortisone is washed out of the eye within approximately 24 hours after a single intravitreal injection,2 Machemer et al suggested the use of the crystalline form of cortisone, which may provide intraocularly available cortisone for a longer period than the single injection of soluble cortisone. 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.3–6
It is 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.6 The purpose of the present study was, therefore, to assess the concentration of triamcinolone acetonide in aqueous humour samples obtained from patients who had previously received an intravitreal injection of triamcinolone acetonide.
The study included three female patients aged 74, 76, and 80 years. They had received an intravitreal injection of 25 mg of triamcinolone acetonide as an attempt to treat exudative age related macular degeneration with subfoveal occult neovascularisation. All patients were fully informed about the experimental character of the treatment and all patients signed an informed consent. The ethics committee of the university had approved the study following the tenets of the Declaration of Helsinki. A sample of aqueous humour was obtained from the anterior chamber through a paracentesis at the start of cataract surgery which had become necessary because of the cataractogenic effect of steroids (n = 2), or which was performed before a intravitreal re-injection of triamcinolone acetonide (n = 1).
The concentration of triamcinolone acetonide was 13 μg/l in the sample removed 3.5 months after the intraocular application of triamcinolone acetonide. The concentration of triamcinolone acetonide was 3 μg/l in the aqueous humour sample obtained from the eye which had undergone the intravitreal triamcinolone injection 6 months before sampling. Triamcinolone acetonide was not detectable in the aqueous humour sample removed 12 months after the intraocular application of triamcinolone acetonide.
The results suggest that detectable concentrations triamcinolone acetonide can be found in the aqueous humour up to 6 months after its intravitreal instillation. Future studies may evaluate whether the concentrations of 13 μg/l or 3 μg/l are sufficient for an antiproliferative effect of triamcinolone acetonide in eyes with exudative age related macular degeneration or other proliferative intraocular diseases; which factors, besides the time interval after its injection, may be responsible for the varying concentrations of triamcinolone acetonide; and which is the therapeutic range of concentrations of intraocular triamcinolone acetonide for an antiproliferative or antiexudative effect.
Proprietary interest: none.