Outcomes With Glaucoma Drainage Devices

Effect of Lens Status on the Outcomes of Glaucoma Drainage Device Implantation

Stallworth JY, Hekmatjah N, Yu Y, Oatts JT, Ying GS, Han Y¹
Industry support for this study: None

ABSTRACT SUMMARY

This retrospective review evaluated the impact of the crystalline lens’ status on the efficacy of glaucoma drainage devices (GDDs) over a 3-year postoperative period. The study included 243 eyes of 216 patients with various types of glaucomatous optic neuropathy, predominantly primary open-angle glaucoma (56%–63%), as well as secondary glaucoma. Patients who had a history of combined GDD implantation surgery, such as those who underwent a vitrectomy or penetrating keratoplasty at the time of surgery, were excluded from the study.

Study participants were divided into three categories: those with phakic eyes (group A), phakic eyes that underwent cataract extraction within 3 years of receiving a GDD (group B), and pseudophakic eyes (group C). A standard surgical technique for GDD implantation was used. Of note, subconjunctival mitomycin C was administered intraoperatively during most of the GDD procedures (83%–90%), and all the implants were valved devices. Postoperative follow-up occurred at months 1, 3, 6, 12, 24, and 36.

A majority of the patients (90%–94%) received an Ahmed Glaucoma Valve (models S2 and FP7, New World Medical). Tube placement was mostly in the anterior chamber (93%–97%), and a native scleral flap was used to cover the device in 82% to 87% of cases. In group B, the average time from glaucoma surgery to cataract surgery was 1.3 years. The primary outcome measured was the IOP after GDD implantation. Secondary outcomes included changes in patients’ visual acuity and number of topical IOP-lowering drops and the rate of failure. Failure was defined as a loss of light perception vision, the need for additional glaucoma surgery, an IOP that was less than or equal to 5 mm Hg or greater than 21 mm Hg, or an IOP reduction of less than 20% from baseline.

No statistically significant differences in mean postoperative IOP (group A: 15.7 mm Hg, group B: 13.8 mm Hg, and group C: 13.0 mm Hg; P = .56) or the mean number of IOP-lowering drops used (group A: 1.5, group B: 1.3, group C: 1.5; P = .61) were found among groups at the 3-year follow-up visit. There was no discernible difference in patients’ visual acuity among the three groups at 3 years. The failure rate was similar among groups 2 years after GDD implantation (group A: 29.5%, group B: 33.8%, and group C: 28.8%; log-rank P = .68). Group B had the highest rate of complications at 1 month (21%, P = .02) and 3 years (25%, P < .001), largely due to hypotony and shallowing of the anterior chamber.

The study authors concluded that there was an absence of statistical significance in the IOP reduction, change in patients’ use of IOP-lowering medication, and failure rate with respect to lens status and subsequent cataract extraction 3 years following GDD implantation.

DISCUSSION

What are the concerns about pursuing cataract surgery after GDD implantation?

Judgments with respect to the success of glaucoma filtration surgery according to lens status stems from previously more commonly practiced superior conjunctiva–based cataract extraction in the setting of prior trabeculectomy surgery. The concern was that an increase in the number of fibroblasts or a disruption in the blood-aqueous barrier following cataract surgery would cause bleb failure.^2,3 Conjunctival incisional approaches to cataract surgery are still employed under certain circumstances, but the advent of GDD implantation and cataract surgery using a clear corneal incision have shifted the paradigm. Given that this retrospective review found that lens status had no effect on the success of GDD implantation, it can be hypothesized that the failure of glaucoma filtration surgery may be secondary to conjunctiva-based procedures as opposed to lens status.¹

Stallworth and colleagues found that hypotony occurred more frequently as a short- and long-term complication in group B. Hypotony was likely a risk intrinsic to this group of initially phakic eyes as opposed to a direct complication of cataract surgery.¹ The rate of additional glaucoma surgery was nevertheless comparable among all three groups by 3 years postoperatively.

What implications does the study have for real-world practice?

Ophthalmologists may have to decide the order in which to perform cataract surgery and GDD implantation or to plan cataract surgery following successful GDD implantation. The findings reported by Stallworth and colleagues indicate that modern cataract surgery techniques are not associated with a statistically significant risk of compromising the success of prior GDD implantation.

Comparing Outcomes of Tube Versus Trabeculectomy Among Patients With Angle-Closure Glaucoma

El Helwe H, Samuel S, Falah H, Trzcinski J, Solá-Del Valle DA⁴
Industry support for this study: None

ABSTRACT SUMMARY

This retrospective nonrandomized study compared the surgical outcomes of GDD surgery and trabeculectomy with mitomycin C in patients with angle-closure glaucoma (ACG).

The study included 80 eyes with a minimum of 6 months of follow-up that underwent surgery (GDD, n = 50 eyes; trabeculectomy, n = 30 eyes) at Massachusetts Eye and Ear between January 2015 and January 2022. Patients who lacked an ACG diagnosis, who were younger than 18 years of age, or who underwent another IOP-lowering procedure at the time of filtration surgery were excluded. Data were collected at 2, 6, 12, and 24 months following surgical intervention.

Primary outcomes included IOP reduction, glaucoma medication use, patients’ BCVA, complication rates, and surgical success according to the Kaplan-Meier method. A qualified success was defined as maintaining an IOP between 5 and 21 mm Hg and at least a 20% reduction from baseline with or without medication. A complete success was defined as meeting the same IOP criteria without the use of medication.

Both groups had a similar IOP and number of medications used at baseline, but the rates of pseudophakia and prior ocular surgery were significantly higher in the GDD patients. Both filtration procedures achieved a significant IOP reduction at 2 years. The use of IOP-lowering medication was lower in the trabeculectomy group at 1 year but was comparable between groups at 2 years.

A higher rate of complete success was achieved by the trabeculectomy group compared to the GDD group at 1 and 2 years (59% and 41% vs 13% and 11%, respectively; P < .001). The qualified success rates were similar between groups at all time points. Visual acuity outcomes and complication rates were also comparable between groups, with no significant differences in adverse events such as anterior chamber inflammation, hypotony, corneal edema, or cystoid macular edema.

DISCUSSION

Does trabeculectomy or tube shunt surgery achieve superior outcomes in patients with ACG?

El Helwe and colleagues found that both filtration procedures were effective at lowering IOP and reducing the medication burden and that complication rates and patients’ visual acuity outcomes were similar. The reduction in medication burden was initially greater in the trabeculectomy arm but equalized over time, as was observed in the Primary Tube Versus Trabeculectomy (PTVT) study.⁵

Does phakic status influence the effectiveness of trabeculectomy or GDD surgery?

Cataract extraction alone can significantly reduce IOP in patients with ACG.^6,7 Undergoing cataract extraction at the time of filtration surgery did not appear to affect the survivability of trabeculectomy and GDD surgery in the study by El Helwe and colleagues,⁴ but further research is required to determine if there is a relationship to long-term surgical success.