HISTOLOGY OF CONJUNCTIVAL VASCULAR ENDOTHELIUM AFTER FILTERING SURGERY WITH MITOMYCIN-C IN RABBITS

Objective: To examine histologic changes in conjunctival vasculature d uring the first 72 hours following filtering surgery with adjunctive m itomycin C in rabbits. Design: Thirty-six New Zealand white rabbits un derwent unilateral posterior lip sclerectomy. In 18 rabbits mitomycin C (0.5 mg/mL) was applied subconjunctivally for 5 minutes. The remaini ng 18 animals were treated with the phosphate-buffered saline vehicle for 5 minutes. Three rabbits from either group were killed at 0, 4, 12 , 24, 48 and 72 hours postoperatively. Outcome measures: Degree of vas cularity of filtering blebs on gross examination and appearance of con junctival vascular specimens on light and transmission electron micros copy, as assessed by three masked observers, Results: On gross examina tion the filtering blebs in the mitomycin C group were slightly less h yperemic than those in the control group at 12, 24 and 48 hours and we re markedly less hyperemic at 72 hours, Light microscopy showed tightl y packed erythrocytes within the conjunctival vessels of the experimen tal blebs and an almost total absence of endothelium within many of th e vascular channels by 72 hours. Transmission electron microscopy show ed focal loss of vascular endothelial cells and thrombus formation in the experimental blebs, as early as 12 hours postoperatively. Conclusi ons: Our findings suggest that the decreased vascularity of filtering blebs observed after trabeculectomy with adjunctive mitomycin C is at least partially due to a toxic effect of the agent on the endothelial cells of the conjunctival vessels.