Abstract
Purpose :
Trabeculectomy ab externo (Trab) remains one of the most commonly performed surgeries targeted at lowering intraocular pressure (IOP). Post-operative episcleral fibrosis over the scleral flap is a common cause of failure. Modulation of wound healing with mitomycin C remains the current gold standard for inhibiting post-operative scarring, and has been shown to extend bleb survival to 30 days post-operatively in rabbits. We hypothesize that the use of a purified collagenase Xiaflex® (Endo Pharmaceutical, {Dublin, Ireland}) given perioperatively may extend the life of glaucoma filtering surgery and re-establish filtration post-operatively in a rabbit model of glaucoma filtering surgery.
Methods :
13 eyes of New Zealand White rabbits underwent limbal-based Trab without the use of antifibrotic agents by the same surgeon (RH). Purified collagenase was delivered peri-operatively and post-operatively by subconjunctival injections of 12.5 µl volumes at varying concentrations. Post-operative filtration was assessed using Moorfield grading of the bleb on examination and photographs, IOP measurements via TonoPen®, fluorescein transmission through the bleb, and ultrasound biomicroscopy (UBM). Clinical bleb failure was defined as increase in IOP to baseline or failure of fluorescein transmission. Eyes undergoing surgery without the administration of collagenase were used as controls.
Results :
Four eyes underwent both peri-operative and post-operative injections of Xiaflex, with improved survival time by IOP and fluorescein transmission compared to controls. Three of the four eyes demonstrated clinical bleb survival beyond 30 days post-operatively. Two of five eyes that underwent only post-operative injections demonstrated an improved survival time compared to controls. Four eyes in the control group demonstrated clinical bleb failure between 11 and 14 days. Adverse events included subconjunctival hemorrhage, eyelid ecchymosis, corneal ectasia and pannus, and conjunctival breakdown. Moorfield grading and UBM was found to be of limited value.
Conclusions :
This pilot study preliminarily demonstrates that Xiaflex can extend the life of glaucoma filtering surgeries. Best results were obtained with peri-operative and post-operative injections of the medication. Further work must be done to optimize dosage and develop a delivery protocol prior to a formal efficacy study.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.