Device-modified trabeculectomy for glaucoma.

BACKGROUND

Glaucoma is an optic neuropathy that leads to visual field defects and vision loss. It is the second leading cause of irreversible blindness in the world. Treatment for glaucoma aims to reduce intraocular pressure (IOP) to slow or prevent further vision loss. IOP can be lowered with medications, laser, or incisional surgery. Trabeculectomy is a surgical approach which lowers IOP by shunting aqueous humor to a subconjunctival bleb. Device-modified trabeculectomy techniques are intended to improve the durability and safety of this bleb-forming surgery. Trabeculectomy-modifying devices include the Ex-PRESS, the XEN Gel Stent, the PreserFlo MicroShunt, as well as antifibrotic materials such as Ologen, amniotic membrane, expanded polytetrafluoroethylene (ePTFE) membrane, Gelfilm and others. However, the comparative effectiveness and safety of these devices are uncertain.

OBJECTIVES

To evaluate the benefits and harms of different devices as adjuncts to trabeculectomy on IOP control in eyes with glaucoma compared to standard trabeculectomy.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search was August 2021.

SELECTION CRITERIA

We included randomized controlled trials in participants with glaucoma comparing device-modified trabeculectomy techniques with standard trabeculectomy. We included studies that used antimetabolites in either or both treatment groups.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were 1. change in IOP and 2. mean postoperative IOP at one year. Our secondary outcomes were 3. mean change in IOP from baseline, 4. mean postoperative IOP at any time point, 5. mean best-corrected visual acuity (BCVA), 6. visual field change, 7. quality of life, 8. proportion of participants who are drop-free at one year, 9. mean number of IOP lowering medications at one year, and 10. proportion of participants with complications.

MAIN RESULTS

Eight studies met our inclusion criteria, of which seven were full-length journal articles and one was a conference abstract. The eight studies included 961 participants with glaucoma, and compared two types of devices implanted during trabeculectomy versus standard trabeculectomy. Seven studies (462 eyes, 434 participants) used the Ex-PRESS, and one study (527 eyes, 527 participants) used the PreserFlo MicroShunt. No studies using the XEN Gel Stent implantation met our criteria. The studies were conducted in North America, Europe, and Africa. Planned follow-up periods ranged from six months to five years. The studies were reported poorly, which limited our ability to judge risk of bias for many domains. None of the studies explicitly masked outcome assessment. We rated seven studies at high risk of detection bias. Low-certainty of evidence from five studies showed that using the Ex-PRESS plus trabeculectomy compared with standard trabeculectomy may be associated with a slightly lower IOP at one year (mean difference (MD) -1.76 mmHg, 95% confidence interval (CI) -2.81 to -0.70; 213 eyes). Moderate-certainty of evidence from one study showed that using the PreserFlo MicroShunt may be associated with a slightly higher IOP than standard trabeculectomy at one year (MD 3.20 mmHg, 95% CI 2.29 to 4.11). Participants who received standard trabeculectomy may have a higher risk of hypotony compared with those who received device-modified trabeculectomy, but the evidence is uncertain (RR 0.73, 95% CI 0.46 to 1.17; I² = 38%; P = 0.14). In the subgroup of participants who received the PreserFlo MicroShunt, there was a lower risk of developing hypotony or shallow anterior chamber compared with those receiving standard trabeculectomy (RR 0.44, 95% CI 0.25 to 0.79; 526 eyes). Device-modified trabeculectomy may lead to less subsequent cataract surgery within one year (RR 0.46, 95% CI 0.27 to 0.80; I² = 0%).

AUTHORS' CONCLUSIONS: Use of an Ex-PRESS plus trabeculectomy may produce greater IOP reduction at one-year follow-up than standard trabeculectomy; however, due to potential biases and imprecision in effect estimates, the certainty of evidence is low. PreserFlo MicroShunt may be inferior to standard trabeculectomy in lowering IOP. However, PreserFlo MicroShunt may prevent postoperative hypotony and bleb leakage. Overall, device-modified trabeculectomy appears associated with a lower risk of cataract surgery within five years compared with standard trabeculectomy. Due to various limitations in the design and conduct of the included studies, the applicability of this evidence synthesis to other populations or settings is uncertain. Further research is needed to determine the effectiveness and safety of other devices in subgroup populations, such as people with different types of glaucoma, of various races and ethnicity, and with different lens types (e.g. phakic, pseudophakic).