For glaucoma patients who have undergone penetrating keratoplasty (PK), a glaucoma drainage device (GDD) may be more successful than trabeculectomy in controlling intraocular pressure (IOP), a recent study found. However, practitioners should be careful with these patients, as the study also found that they seem to have lower corneal graft survival rates.

Researchers from Turkey evaluated 84 eyes of former PK patients who underwent a trabeculectomy—with 42 of those eyes given antimetabolites (AMs) and 12 not given AMs—and compared results with 30 eyes from former PK patients who underwent GDD implantation. Among the most significant measures they looked at were IOP control, corneal graft survival and postoperative ocular complications.

At the final visit, IOP success numbers covered a notable range, with an 86.7% success rate in GDD patients compared with 58.3% for trabeculectomy patients without AMs and 64.3% for trabeculectomy patients with AMs. Additionally, the cumulative probability of IOP success at one and three years post-op was 66.7% and 57.1%, respectively, for trabeculectomy patients without AMs; 80.6% and 64.8%, respectively, for trabeculectomy patients with AMs; and 92.3% and 84.6%, respectively, for GDD patients.

However, the probability of corneal graft survival at one and three years postoperatively wasn’t quite as high for GDD patients, with survival rates of 65.8% and 52.6%, respectively, for these patients compared with 70.0% and 60.0% for trabeculectomy patients without AMs and 76.7% and 67.7% for trabeculectomy patients with AMs.

While the study concluded that trabeculectomy without AMs has limited success both in IOP control and in graft survival and can be considered “in a limited number of patients with a low risk of bleb failure,” overall study conclusions weren’t easy to formulate. “Our results demonstrated that GDDs were more successful in controlling IOP than trabeculectomy with AMs but less successful in graft survival; however, the difference did not reach statistical significance,” the study concluded. “Therefore, the decision for the surgical procedure should be individualized for each patient.”

Yakin M, Eksioglu U, Yalniz-Akkaya Z, et al. Outcomes of trabeculectomy and glaucoma drainage devices for elevated intraocular pressure after penetrating keratoplasty. Cornea. 2018;37(6):705-11.