Histopathology of triamcinolone in the subconjunctiva

Triamcinolone acetonide (TA) was injected subconjunctivally in nine human eyes one week before trabeculectomy. A biopsy specimen of conjunctiva and subconjunctiva was obtained from the site of drug injection, as well as a site 6 mm from the injection at the time of trabeculectomy. The tissue was evaluated by electron microscopy. TA was similarly injected subconjunctivally in ten normal rabbit eyes. For control purposes, six eyes were injected with the vehicle. Five animals were euthanized at one and two weeks post-injection and subconjunctival biopsy specimens from the drug site, at the margin of the drug site, and 180 degrees away from the drug site were subsequently examined by light and electron microscopy. At the drug site in both humans and rabbits, the subconjunctival fibroblasts were necrotic, the collagen fibers were altered in appearance, and there was infiltration of macrophages. The control site was unremarkable. These local morphologic changes may explain, in part, the mechanism(s) of action of injected TA.