Trabeculectomy is still the gold standard in the surgical treatment of glaucoma patients. Development of a bleb is the primary goal of this procedure and the conjunctival status is therefore decisive. Only a good functioning bleb renders good intraocular pressure (IOP) control. Scar tissue formation leads to bleb failure which is quite common despite the use of antiproliferative agents, such as mitomycin C and 5 fluoruracil. Wound healing is important and is influenced and impaired by the chronic use of topical antiglaucoma drugs. Therefore, complete abstinence is recommended from 4-6 weeks prior to a planned trabeculectomy; however, it seems mandatory to completely abolish preservatives such as drops containing benzalkonium chloride to enhance trabeculectomy success rates.