Aqueous shunts for glaucoma

Full citation:
 Tseng VL, Coleman AL, Chang MY, Caprioli J. Aqueous shunts for glaucoma. Cochrane Database of Systematic Reviews 2017, Issue 7. Art. No.: CD004918. DOI: 10.1002/14651858.CD004918.pub3

What was the aim of this review
We aimed to learn:
1. how successful and safe aqueous shunts are for lowering eye pressure when compared with standard surgery (trabeculectomy);
2. how successful and safe various types of aqueous shunts are when compared with each other; and
3. how successful and safe aqueous shunts are when the procedure is modified.
Our search for relevant studies identified 27 trials.

Key messages
It is uncertain if aqueous shunts are more effective or are safer than standard surgery (trabeculectomy) for glaucoma (very low-certainty evidence). The Baerveldt and Molteno aqueous shunts may reduce eye pressure more than the Ahmed shunt (moderate- and low-certainty evidence).

What did we study in this review
Glaucoma is a condition caused by the build-up of fluid in the front part of the eye. This build-up of fluid raises the eye pressure, which can lead to damage of the optic nerve and vision loss. Some people with glaucoma need surgery to reduce eye pressure. Standard surgery is called trabeculectomy. In trabeculectomy, a small hole is made to the tissue in the front of the eye to create a drain for the fluid. Alternatively, a small implant called an aqueous shunt can be inserted into the eye to create a pathway for fluid to drain.

What were the main results of this review
We found 27 studies. Four studies compared an aqueous shunt (either Ahmed or Baerveldt) with standard surgery (trabeculectomy). Five trials compared two different types of shunt (Ahmed versus Baerveldt, Ahmed versus Molteno, Molteno versus Schocket). Eighteen studies compared modifications to aqueous shunts.
The results of the review were as follows.
1. The evidence comparing aqueous shunts with trabeculectomy was of very low-certainty.
2. There were some differences between different implants: the Baerveldt and Molteno implants may work better than the Ahmed implant; eye pressure was reduced more and fewer antiglaucoma medications were needed (moderate- and low-certainty evidence). The Molteno implant may work better than the Schocket implant (low-certainty evidence on eye pressure only).
3. Although 18 trials looked at modifications to aqueous shunts, many different modifications were studied, and the evidence was inconclusive.

How up-to-date is this review? 
We searched for studies that had been published up to 15 August 2016.