The Use of Bevacizumab as a Modulator of Wound Healing Following Trabeculectomy Surgery

Pharmacological enhancement of trabeculectomy using Mitomycin C (MMC) has significantly improved success rates. Despite this, some patients still mount aggressive scarring responses post-operatively and require additional subconjunctival injections of antifibrotic agents, such as 5-Fluorouracil (5-FU) to reduce scar formation and reduce the likelihood of surgical failure. There is concern that these agents are potentially toxic and may result in side effects such as keratopathy (loss of corneal epithelium) and are also painful for the patient. For those patients that are showing clinical evidence of potential scar formation, a more predictable and less toxic modulator of wound healing is desirable.

Vascular endothelial growth factor (VEGF) has been associated with angiogenesis in numerous pathological situations, including tumor growth, proliferative retinopathy, and rheumatoid arthritis. VEGF is also thought to play a pivotal role in ocular wound healing. It mediates the signal transduction cascade leading to tenon's fibroblast migration and proliferation and collagen gel contraction at the site of surgery, as well as angiogenesis. VEGF also causes persistent vascular permeability and vasodilation at the level of existing microvessels. Vessels with increased permeability are typically tortuous and dilated and this is the clinical appearance within the conjunctiva, suggestive of future excessive wound healing and scar formation following trabeculectomy. Early interventions such as subconjunctival injections of 5-Fluorouracil (5-FU) are therefore often considered when these clinical findings are apparent, in order to modify the course of wound healing.

The investigators propose a pilot study looking at the effect of serial injections of bevacizumab (an anti-VEGF agent) on modifying the wound healing response in patients showing early signs of future failure, compared to 5-Fluorouracil (5-FU). The purpose of the pilot is to also gather outcome data and information relating to safety and recruitment with a view to powering a definitive study addressing this issue.

Inclusion criteria

• Age 18 to 85 years, inclusive
• Patient must have undergone standard trabeculectomy augmented with Mitomycin C, within the past 4-6 weeks.
• Patients who in the clinician's opinion are mounting an aggressive wound healing response and demonstrate objective increase in bleb vascularity (moderate or severe on MBGS). Bleb function still needs to be maintained in the clinicians opinion and flat, scarred blebs are not to be included.

Exclusion criteria

• Unwilling or unable to give consent, unwilling to accept randomization, or unable to return for scheduled protocol visits.
• Pregnant or nursing women.
• A history of cardiovascular or cerebrovascular events in the previous 6 months, such as angina, arrhythmia, Transient Ischaemic Attack, strokes, myocardial infarction.
• Uncontrolled hypertension defined as systolic blood pressure >160millimeters of mercury (mmHg) or diastolic blood pressure >90millimeters of mercury (mmHg)
• Subject hypersensitive to bevacizumab, 5-Fluorouracil (5-FU), and Mitomycin-C (MMC) and its excipients
• Failed trabeculectomy bleb
• Persistent wound leak following trabeculectomy at the time of randomisation

The following exclusions apply to the study eye only (i.e. they may be present for the non study eye

• No light perception.
• Aphakia
• Previous, or planned, ocular surgery: vitreo-retinal, conjunctival surgery, etc considered likely to interfere with trabeculectomy outcome
• Complicated cataract surgery
• Cataract surgery less than 6 months in duration
• Secondary glaucoma, other than Pigment Dispersion Syndrome (PDS) and Pseudoexfoliative (PXF)
• Ocular trauma within the past 3 months
• Active iris neovascularization or active proliferative retinopathy.
• Severe posterior blepharitis.
• Unwilling to discontinue contact lens use after surgery.
• Current or recent (<3months) use of bevacizumab into the study eye.