Abstract
Abstract: :
Purpose: Intravitreal injection of triamcinolone acetonide (TA) has recently been used for a variety of vitreoretinal conditions. However there is little information on the effect of TA on the retina, especially when used in high doses or repeatedly as long–term treatment. In the present study, we evaluated the dose–related effects of intravitreal TA on the retina of rabbits. In addition, the effects of repeated injection were explored. Methods: The 4mg, 8mg, and 20mg doses were prepared and concentrated if necessary into a 0.1ml volume from commercially supplied Kenalog 40 (40mg/1ml, Bristol–Myers Squibb, USA). 0.1ml of these doses were injected into the vitreous cavity; preservative–free saline or vehicle was injected in other eyes as controls. The rabbits were periodically examined and photographed, and sacrificed for light and electron microscopic examination on 14days after injection. For repeated injection, 20mg was injected second time 3 weeks after the first injection. Results: After single injections of 4mg, 8mg, and vehicle, some swollen RPE cells with mildly increased melanin pigment were observed. The 20mg injection produced a remarkable disorganization of RPE and degeneration of outer segments with swelling of inner nuclear cells, with macrophages evident in the subretinal space. After two injections of 20mg, these structural changes of the retina displayed some progression but did not differ substantially from the initial 20mg injection. Conclusion: This study demonstrated minimal changes in the RPE after a single intravitreal Kenalog dose of 4mg, 8mg, or vehicle, without visible damage to the overlying neural retina, and the significance of these changes is unknown. A single or repeated 20 mg dose produced profound RPE and retinal changes. These effects underline the need to explore more subtle drug effects and suggests that studies should be initiated for comparison of relative retinal toxicity of other preparation to provide safer intraocular administration.
Keywords: drug toxicity/drug effects • corticosteroids • retinal pigment epithelium