Abstract
Abstract: :
Purpose: To prevent fibrosis of the filtering bleb, after trabeculectomy 5-FU may be injected at the bleb site. 5-FU is extremely caustic and topical administration can cause corrosive damage. This study ascertained whether repeated injection of 5-FU into the bleb has toxic effects on intraocular structures. Methods: After unilateral trabeculectomy in anesthetized New Zealand rabbits, 5-FU (5.0 mg) was injected at the trabeculectomy site weekly for 3 wk. Slit lamp and confocal microscopy, for in vivo evaluation, and IOP were performed weekly. After sacrifice, aqueous humor (AH) was drawn and eyes excised for examination of the anterior chamber structures by scanning electron microscopy (SEM) and light microscopy. Results: 5-FU injection had no effect on IOP beyond that of trabeculectomy. Bleb height remained constant, thickness increased and vascularity decreased without necrosis or inflammation of surrounding tissue. Protein in AH increased to 19.784.45 ug/ml after trabeculectomy but only to 0.890.62 ug/ml after 5-FU injection. In vivo confocal microscopy revealed consistent epithelial and endothelial cell number and size similar to control eyes. Similarly, analysis by SEM of corneal endothelium showed a minor shift toward smaller cells, based on area in the treatment group compared to controls. SEM of corneal epithelium revealed a similar shift toward smaller cells but a wider range of cell size. By light microscopy, no inflammation was observed in the bleb or surrounding tissues. There were no differences in cornea, Schlemm«s canal, ciliary body, iris pigmented epithelium and stroma, secretory epithelium or lens between the treated and control eyes. Conclusions: Injection of 5-FU into the bleb did not provoke an intraocular inflammatory response and was not toxic to extraocular structures. Repeated administration did not cause cumulative toxic effects to intraocular structures including no significant changes to corneal epithelium and endothelium. In vivo measurements of corneal epithelium and endothelium by confocal microscopy were confirmed by SEM. Therefore, multiple injections of 5-FU into the filtering bleb pose minimal risk to intraocular structures.
Keywords: 390 drug toxicity/drug effects • 471 microscopy: confocal/tunneling • 317 anterior chamber