Day 7 IOP May Predict Long-Term MicroShunt Outcomes for Glaucoma

Juan Batlle, MD

MicroShunt implantation effectively reduced intraocular pressure (IOP) for patients with glaucoma that was inadequately controlled on maximum tolerated medical therapy or for those with glaucoma progression that warranted surgery. Findings presented in a pooled analysis of 3 studies presented at the 2019 American Academy of Ophthalmology (AAO) Annual Meeting showed that IOP at day 7 post MicroShunt implantation may be useful for predicting outcomes 1-year following the procedure.

"This pooled analysis of 3 single-arm studies showed a greater reduction in IOP from baseline to year 1 in patients with a low IOP (≤9 mmHg) compared with a high IOP (≥9 mmHg) on day 7 post-surgery," Juan Batlle, MD, from the Centro Laser, Santo Domingo, and other studies authors, wrote in their poster at the meeting. "Low resistance outflow from the bleb may be important in achieving low IOP following MicroShunt implantation."

The MicroShunt used across the studies was an 8.5 mm long device made from SIBS, which is a biocompatible and bioinert material. The device was inserted ab externo to provide drainage and to lower IOP.

The analysis looked at those with low initial IOP at day 7 (≤9 mmHg) and those with high IOP at day 7 following the procedure (>9 mmHg). Those in the low group had a mean age of 63.6 years and those in the high group had a mean age of 64.5 years. Across both groups, most had phakic lens status (~70%). Mean baseline IOP was similar between groups at 22.0 in the low group and 23.2 mmHg in the high group. The mean number of prior glaucoma treatments was around 2 (2.1 to 2.3). More patients were medication-free at baseline in the high group compared with the low group (17% vs 7%, respectively).

There was a mean reduction from baseline to year 1 of 9.5 mmHg in those with low IOP at day 7 compared with a decline of 9.0 mmHg in the high group. This was equivalent to a 21.6% drop in the low arm and a 24.2% decline in the high group. A significant between-group difference in IOP was observed at all postoperative visits (P <.05): from day 1 to the end of 1-year IOP remained lower in those with lower day 7 IOP.

The overall success rates in the low- and high-IOP groups were 81.7% and 84.9%, respectively. Moreover, 81.3% of patients in the low-IOP group were medication-free at 1 year compared with 68.6% in the IOP-high arm. This was reverse from the baseline of the trial, when more patients were medication-free in the high group versus low.

Adverse events (AEs) were similar between the groups, with 62% of patients having an AE in the low group versus 66% in the high group. Serious AEs were reported for 5.6% versus 3.8%, in the low and high groups, respectively. Reoperations were need for 3 patients in the low IOP group, and 4 patients in the low group required bleb revisions. Only one patient in the high group required a bleb revision.

"There was no significant between-group difference in mean visual acuity over time," Batlle et al wrote. "There were no long-term sight-threatening AEs reported and no cases of blebitis or implant extrusion. One eye in the low IOP group experienced implant migration."

MicroShunts have grown in popularity as a treatment for glaucoma in recent years, with sessions reaching the AAO “hot topics” session. In August 2019, Santen announced that its DE-128 MicroShunt had demonstrated promising findings for patients with mild, moderate, and severe primary open-angle glaucoma. The company plans to pursue FDA approval in the United States.

In the study, the DE-128 MicroShunt was implanted intraoperatively with 0.2 mg/ml of mitomycin C (MMC). This group was compared with trabeculectomy and MMC. At 12 months, IOP dropped from 21.1 to 14.2 mmHg in the MicroShunt group compared with a drop from 21.1 to 11.2 mmHg in the trabeculectomy arm. There was a reduction in medication use with DE-128. In the MicroShunt arm, 71.6% of patients were medication-free at 12 months compared with 84.8% in the trabeculectomy arm.

“Although, the IOP-lowering effect of trabeculectomy (11 mmHg) was statistically superior than that of the MicroShunt, the trabeculectomy arm had a greater incidence of hypotony, bleb leaks, and lens opacity, complications typically associated with trabeculectomy," Paul Palmberg, MD, PhD, of the Bascom Palmer Eye Institute, Miami, said in a statement. "If approved by regulators, the MicroShunt would be an effective and safe option for patients with mild, moderate or severe glaucoma requiring surgery. This will allow the glaucoma surgeon to identify the subset of patients for whom the risk benefit profile of the MicroShunt offers benefit."

Batlle JF, Beckers HJ, Riss I, et al. Pooled One-Year Outcomes in Patients With Low IOP Following MicroShunt Implantation. Presented at: 2019 AAO Annual Meeting, San Francisco, CA, October 12-15, 2019.