Glaucoma is usually a chronic condition associated with raised intraocular pressure. It leads to progressive damage to the optic nerve. Early stages are usually asymptomatic. But, as the condition progresses, it causes visual field impairment and, if untreated, blindness. There are several types of glaucoma but the most common type of glaucoma in the UK is primary (or chronic) open-angle glaucoma.
NICE's guideline on glaucoma describes its diagnosis and management. Treatment usually involves eye drops containing different drugs that either reduce aqueous humour production or increase its drainage. Surgical procedures such as trabeculectomy, drainage tubes, deep sclerectomy, viscocanalostomy, laser trabeculoplasty and cyclodiode laser treatment may also be used.
Trabeculectomy with an adjunctive biodegradable collagen matrix aims to modify wound healing and improve the drainage of aqueous humour to lower intraocular pressure. It reduces or avoids the use of antimetabolites and antifibrotic agents (mitomycin C, 5‑fluorouracil).
In this procedure, with the person under local (intracameral) anaesthesia, the conjunctiva is lifted (or an opening is created) to access the sclera, and then a partial-thickness scleral flap is dissected. Within the scleral bed, a full-thickness opening (or a perforating scleral entrance) is created into the anterior chamber, to allow drainage of aqueous humour. Sometimes trabecular meshwork and adjacent structures are also removed. The scleral flap is then sutured loosely with 1 or 2 loops, to allow the aqueous fluid to drain into the subconjunctival space through the scleral hole. Cohesive viscoelastic is injected under the scleral flap. Then a subconjunctival biodegradable collagen matrix implant is placed directly on top of the scleral flap, and the conjunctiva is sutured (using continuous sutures) and closed around it.