Gold Micro Shunt demonstrates low complication rate, but limited success

This study published in the British Journal of Ophthalmology in November investigated the efficacy after two years of Gold Micro Shunt (GMS) (SOLX, Boston) implantation in the supraciliary space in refractory glaucoma patients. Two-thirds of patients achieved qualified success but only 5.5 percent achieved complete success. The authors conclude that while other surgical techniques may achieve higher rates of successful outcomes, the GMS surgical approach is relatively simple and has a low rate of complications.

This is the first prospective study to look at the outcomes of a GMS in the setting of refractory glaucoma, although it was an uncontrolled study. Fifty-five patients (55 eyes) were included. They were required to have failed at least one previous glaucoma surgical procedure (average 1.9) and have IOP greater than 21 on maximum medical therapy. Their mean baseline IOP at the beginning of this study was 30.8.

The authors defined complete surgical success as lowering of IOP to below 21 mmHg combined with a reduction in baseline IOP of 33 percent without topical medications, and a qualified success as lowering of IOP to below 21 mmHg together with a reduction in baseline IOP by 33 percent with or without topical medications. Treatment failure was prospectively defined as IOP greater than 21 mmHg or less than a 33 percent reduction below baseline IOP on two consecutive follow-up visits after three months, IOP less than 5 mm Hg on two consecutive follow-up visits after three months, reoperation for glaucoma or loss of light perception.

In successful patients, mean IOP decreased from 27.6 at baseline to 13.7 mmHg after two years of follow-up. The mean number of medications used postoperatively was 1.4 compared with 2.5 prior to GMS implantation. Mild side effects occurred in 21 patients, with mild or moderate postoperative hyphema the most frequent. Development of a thin membrane obstructing the anterior holes was the most important factor affecting the device's efficacy, occurring in 12 patients who failed the treatment (66.7 percent of failures).

It is noteworthy that three eyes were excluded because the surgeon was "compelled" to remove the GMS, and the success rate was lower than that for traditional tube shunt implantation for refractory glaucoma. However, the potential for success was low given the refractory nature of these glaucoma cases. Perhaps it is reasonable to consider a GMS in these cases as the device is associated with a low rate of complications, minimizes conjunctival involvement and limits subconjunctival fibrosis. Nevertheless, additional studies are needed in order to further define the role of GMS in the surgical management of glaucoma.