Avastin in the prevention of postoperative scarring after glaucoma filtration surgery.

Particpants will be invited into the study if they suit the eligibility criteria. Written informed consent will be obtained from all participants. Participants will be randomised into a treatment group or a control group. Patients are randomised by opening a masked envelope that contains a randomisation group category generated by a computer based sequence table. All Participants will have the standard antiscarring treatment (5 FU) and if the participant is randomised into the treatment group, will then receive the additional study drug (Avastin). A thorough eye examination and photos of the surgical/treatment site will be performed at all follow up visits. Study Drug Dose = a single 1mg dose. Mode of Administration of Study Drug = dose is administered according to the established clinical hospital protocol for antifibrotic agents given via a subconjunctival injection into the filtration bleb. Study Drug Duration = A single injection of the study drug is given with an expected half life of up to 20 days.