Introduction: Glaucoma is the second leading cause of blindness worldwide. While most patients are managed with topical treatment, some will require surgery.

Non-penetrating glaucoma surgery: Glaucoma surgery can be broadly categorised into penetrating (PGS) – trabeculectomy – and non-penetrating (NPGS) techniques. NPGS avoids entering the anterior chamber, thereby reducing the incidence of hypotony-related complications, bleb-associated problems, as well as serious complications like endophthalmitis. Resistance to aqueous outflow is provided by the trabecular meshwork and Descemet’s membrane, offering better control over aqueous drainage. Two main categories of NPGS include deep sclerectomy (DS) and viscocanalostomy (VC). In the former, aqueous is intended to drain subconjunctivally, while VC aims to be ‘bleb-free’, with aqueous drainage via Schlemm’s canal. In addition to the reduced risk of serious complications, NPGS may induce less postoperative inflammation, requiring less intensive follow-up than PGS. Disadvantages of NPGS are that it may be less effective at lowering intraocular pressure than PGS, and has a steep learning curve.

The use of antifibrotic agents such as Mitomycin C and 5-fluorouracil has been applied to NPGS. Although improvements in success rates have been reported, their use is also associated with increased complications such as late leakage from blebs.

Concomitant cataract and VC surgery has shown favourable success rates in terms of intraocular pressure control. Combined phacoemulsification with DS on the other hand does not appear to offer any clear benefit.

Discussion: Although NPGS offers an effective alternative to PGS with a more favourable risk profile, the higher efficacy in terms of intraocular pressure control of trabeculectomy makes it likely to continue to be an important player in glaucoma management. Newer micro-invasive glaucoma surgery techniques offer low surgical complication rates and are likely to require less surgical training than NPGS techniques, and may also take on an important role in glaucoma surgery.