Tube-shunt surgery

Tube-shunt surgery does the same thing as trabeculectomy: it lets aqueous humor out of the eye. It was designed to work when the normal area where fluid would drain out in a trabeculectomy has been scarred by prior surgery. The device that is implanted is a tiny tube of flexible plastic that goes into the front chamber of the eye and leads back to a flat area of plastic that is sewn to the sclera of the eye far back behind (Figure 25). Fluid drains out of the eye, into the tube (Figure 26) and is sopped up in a large cavity that forms around the flat plastic plate back behind the eye. Some brands of tube-shunts have a valve inside the tube that is intended to keep the pressure from going too low soon after surgery, while with others the surgeon blocks the tube off with a temporary stitch that dissolves about four to six weeks after surgery.

Tube-shunt Diagram
Figure 25: Tube-shunt Diagram. Drawings of tube—shunt operation seen from the front (left) and from a cutaway view (right). A tube is placed into the front chamber of the eye, leading back behind the eye where a reservoir is created to drain off fluid and lower eye pressure.

Tube-shunt Photograph
Figure 26: Tube-shunt Photograph. Photograph of a tube shunt (arrow) as seen inside the eye in front of the brown iris.

Materials that are sewn onto the eye tend to work their way out, that is, they can erode free to the surface, so the tube portion is covered by material from donated eye bank eyes that has been sterilized. The conjunctiva covers over the procedure and most often no sutures need removal.

Most of the pre- and post-operative experiences for trabeculectomy and tube-shunt surgery are similar. A recent study randomly compared tube-shunt surgery to trabeculectomy in eyes that had undergone prior surgery of some kind. In those eyes, the tube cases did as well or better than trabeculectomy in a number of areas, though each kept the pressure at or below target at about the same rate. The tube cases had fewer eyes that went too low in pressure, while the trabeculectomies needed fewer glaucoma eye drops in the short to medium term. Infections would be expected more often with trabeculectomy, but tube operations still can have the tube erode to the surface and may need recovering or removal. As many as one in ten eyes with tube—shunts have double vision for a time. This is because the materials sewn onto the eye prevent it from moving fully for a while.

Presently, studies are ongoing to see if tube-shunt operations might be good for eyes that have not had prior surgery. In some eyes, trabeculectomy might be a poor first choice—for example, people who must wear contact lenses, eyes with bad inflammation, eyes with secondary glaucoma that have new blood vessels growing, and some eyes of children with glaucoma (see section Secondary glaucoma and see section Children and glaucoma).

If you would like to support the cost of providing and maintaining this book with a charitable donation of any size, please click here.