With a failure rate between 30% and 50% within five years, glaucoma drainage device implantation (GDI) can leave some clinicians scratching their heads about the best course of action after some patients experience failure. A recent meta-analysis sheds some much-needed light on the problem: try again. Although no randomized control trials or prospective cohort studies on this topic exist, researchers found nine retrospective studies to compare the pre- and post-op IOP and number of glaucoma medications after a second GDI in 254 eyes.

Results show that a second implant led to a much lower post-op IOP, by as much as 10.3mm Hg. In addition, patients required 1.1 fewer post-op medications. Depending on the definition of success, upwards of 80% of the secondary GDIs were successful in the first to third years post-op, the study authors note in their paper.

The studies included Baerveldt (AMO/Johnson & Johnson Vision; 41.5% of primary implants, 51.8% of secondary), Ahmed (New World Medical; 36.1% primary, 30.7% secondary) and Molteno (Katena; 22.4% primary, 17.5% secondary) implants.

However, approximately 80% of the patients included in these studies still required medication to maintain IOP control at one year. The researchers also found the second GDI tended to fail sooner than the first implant when comparing their results with the Tube vs. Trabeculectomy study. Because the most often cited reason for failure of the primary implantation is fibrosis around the implant, the researchers speculate that “patients who failed the first GDI may be more prone to excessive fibrosis around the second GDI and consequently experience early failure of the second GDI.” 

Yoon D, Vajaranant T. A meta-analysis on the outcome of sequential glaucoma drainage implantation. J Glaucoma. December 23, 2019. [Epub ahead of print].