Surgical crossroads: what to do after tube-shunt failure

Glaucoma implants may fail for a number of reasons, said Felix Gil Carrasco, MD, at the World Congress of Ophthalmology on Wednesday. However, inappropriate patient selection and improper placement of the shunt are probably the most common reasons.

Tube implants should be only for certain types of patients, like those with neovascular or inflammatory glaucoma, and those who require a careful assessment to discard a thin or softened sclera or a fibrotic conjunctiva. Implants should be avoided when the anterior chamber is non-existent or too narrow, or if there is a closed angle and in nanophthalmos.

"The mental state is also of particular importance, as the implantation will require changes in lifestyle and special care," added Dr. Gil of the Federal University of Sao Paulo and president of the Pan-American Society of Glaucoma. "Future complications are likely if these conditions are ignored - for example in a patient who, against the ophthalmologist's indication, scratches his eye continually due to itching. An expected result might be corneal edema."

Other causes for shunt failure include contact with the endothelium, placement over the iris, and displacements. A narrow chamber, a long tube, or both must be corrected. The tube may also become occluded by fibrin or silicon. This may be rectified using a N:YAG laser, or with mechanical correction. Extrusion is another possible complication. If only partial, Dr. Gil recommended observation, lubrication, and use of antibiotics. In severe cases, removal and reimplantation may be necessary.