Medications or surgery for the treatment of open angle glaucoma (OAG)

Open angle glaucoma is the most common form of glaucoma and an important cause of blindness. Having a high intraocular pressure (IOP) is an important risk factor. Treatment for OAG aims to lower the IOP and thus reduce the risk of progressive loss of vision. Intraocular pressure can be lowered by medications (eye drops), laser therapy or surgery. There are many different types of eye drops available and these are compared in a recent Cochrane review (Vass 2007). Surgery for glaucoma has evolved in the last 40 years. The most common type is trabeculectomy, another type of operation involves inserting a tube, both types of surgery facilitate fluid drainage out of the eye. All these operations potentially lower the IOP, however, they may have complications during and after the operation and may fail in the long term due to scarring. Drainage surgery forms a 'bleb' i.e. small blister like elevation on the surface of the eye which can sometimes be uncomfortable. It is not clear whether medication or surgery is the better treatment for OAG. The purpose of this review was to review and assess evidence from randomised studies to compare treatment with medications with surgery in terms of how well they work, their relative safety and cost-effectiveness. Four relevant trials were identified, treating 888 people. Three studies were in the UK and one in the US. These trials had been initiated over many years from 1968 up to the most recent trial in 1993. The earlier trials used medications, and in one trial surgical techniques, that are now rarely used. Findings of these studies suggest that, in mild OAG, worsening of the condition was not different whether first treatment was medication or surgery, but surgery was associated with more eye discomfort, an increased risk of cataract and a slight reduction in distance vision at five years. In more severe glaucoma, surgery lowered IOP significantly more than medications (not widely used anymore) and reduced the risk of progressive loss of visual field. In three trials the risk of developing cataract was higher with surgery (trabeculectomy). There was insufficient evidence to determine how well more recently available medications work compared with surgery in more severe OAG, and which was the more cost-effective treatment option. More research is required.