Abstract
Purpose: :
The management of post-operative scarring after trabeculectomy remains clinically challenging. Current treatment of failing blebs is with subconjunctival 5-Fluorouracil (5FU) injections. Bleb vascularity is one of the clinical predictors of poor bleb function. TGF beta stimulates VEGF production in human conjunctival fibroblasts. We postulate that VEGF is actively involved in the post-op scarring response and bleb failure. The aim of the study was to determine the effect of Bevacizumab on bleb survival following trabeculectomy in the rabbit and compare its effect alone with that combined with 5FU.
Methods: :
Twenty-two New Zealand White rabbits underwent modified filtering surgery. The animals were randomized to one of three treatment groups ie. placebo (phosphate buffered saline) (n=7), Bevacizumab (n=8) or Bevacizumab + 5FU (n=7). Subconjunctival injections of the agent(s) were administered immediately after surgery and then weekly. The primary outcomes were bleb survival and bleb vascularity. These parameters were graded by two masked observers. The animals are sacrificed and the eyes immunohistologically analysed for signs of scarring, and levels of VEGF, TGF beta and collagen I expression at the bleb site quantified by RT-PCR.
Results: :
At day 21, all the blebs (n=7, 100%) in the Bevacizumab /5FU treated group remained functioning compared to 4 (50%) blebs with Bevacizumab treatment alone, and 1 (14%) in Placebo group. Near normal conjunctival vascularity was observed in Bevacizumab treated eyes, compared to Bevacizumab /5FU eyes, where more avascularity was noted.
Conclusions: :
Bevacizumab/5FU treatment resulted in greater bleb survival than Bevacizumab treatment alone in the rabbit, although the conjunctival vascularity was more normal with Bevacizumab only.
Keywords: wound healing • drug toxicity/drug effects