Surgery was traditionally used only when treatment had failed to halt the progress of glaucoma, but there is some evidence that earlier surgical intervention is beneficial for selected patients.
Iridectomy
Peripheral iridectomy is performed in cases of angle closure glaucoma, both in the affected eye and prophylactically in the other eye. Most of these cases can be treated with the Nd-YAG laser. Surgery is reserved for difficult or refractory cases.
Drainage surgery
When it is not possible to achieve the target IOP with medical (or laser) therapy in glaucoma, then the next line of management is surgical. The most effective glaucoma filtration procedure is trabeculectomy. In this procedure a guarded channel is created, which allows aqueous to flow from the anterior chamber inside the eye into the sub-Tenon's and subconjunctival space (bypassing the blocked trabecular meshwork). A drainage "bleb" (aqueous under the conjunctiva and Tenon's capsule) can often be seen under the upper lid. Conjunctivitis in a patient with a drainage bleb should always be treated promptly, as there is an increased risk of the infection entering the eye (endophthalmitis).
Possible complications
The main cause of surgical failure is postoperative scarring of the drainage channel and drainage bleb. Scarring can be reduced by using adjuvant antiscarring therapy. Various antiscarring agents are used, including drugs used in anticancer therapy. These are delivered by short applications during surgery to the drainage bed on a sponge or by postoperative injections. The most commonly used drugs are 5-fluorouracil and mitomycin-c.
Glaucoma filtration procedures do carry some risk and the patient should be advised of the risk of postoperative cataract and hypotony (low pressure) and the possibility of a reduction in postoperative best corrected visual acuity.
Although trabeculectomy remains the gold standard glaucoma filtration procedure, several alternative filtration operations also exist. Non-penetrating deep sclerectomy and viscocanalostomy have good safety profiles but have tended to produce less dramatic reductions in IOP in all published trials.
For certain patients with refractory glaucoma, a tube drainage device may be considered. A drainage tube is inserted, connecting the anterior chamber of the eye with a reservoir in the posterior orbit. This has a good chance of controlling IOP, but also has moderately high risk of serious complications.
