Comparison between MIGS with trabeculectomy in the management of open‑angle glaucoma with cataract: A systematic review

Author: Zaifar A, Pratomo TG, Suryono AN.

Geographical coverage: Not reported

Sector: Glaucoma and cataracts

Sub-sector: Treatment comparison

Equity focus: Not reported

Study population: Adults (>18 years old) with open-angle glaucoma (OAG) and concomitant cataract

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background:

Glaucoma refers to a group of disorders characterised by progressive optic neuropathy that leads to neuronal tissue loss, excavation of the optic disc, and thinning of the nerve fibre layer. Elevated intraocular pressure (IOP) is the primary risk factor, and treatment focuses on reducing IOP through medication or surgery. Primary open-angle glaucoma (POAG) is the most common subtype, and its prevalence increases with age. Cataracts are the leading cause of blindness worldwide, and they often coexist with glaucoma in older adults. Cataract surgery can improve aqueous drainage, but patients may still require postoperative medication. For patients with OAG, combined phacoemulsification and trabeculectomy (phaco-trabeculectomy) is a common approach, although trabeculectomy entails a prolonged recovery and potential complications. Microinvasive Glaucoma Surgery (MIGS) offers a novel approach for mild-to-moderate glaucoma, aiming to lower IOP with minimal trauma and fewer complications. MIGS procedures can enhance trabecular outflow, reduce aqueous production, increase aqueous outflow through alternate pathways, or use subconjunctival filtration. Compared to trabeculectomy, phacoemulsification combined with MIGS provides similar benefits but with fewer complications in appropriately selected patients.

Objective:
To evaluate the current knowledge on combination surgery for patients with cataract and OAG in order to provide comprehensive guidance for clinical practice.

Main findings:
Overall, the authors found that, for patients with OAG and cataracts, phacoemulsification combined with MIGS offers outcomes comparable to phaco-trabeculectomy but with fewer complications.

Four studies were included in this systematic review, comprising one randomised controlled trial (RCT) and three observational studies (one retrospective cohort, one case-control, and one case series). All studies were conducted in various locations and focused on the effectiveness of phacoemulsification with MIGS compared to phacoemulsification with trabeculectomy in patients with OAG and cataracts. Together, these studies included a total of 306 eyes from 276 patients with OAG, of which 140 eyes underwent Phaco-Trab and 119 eyes underwent Phaco-MIGS. All studies were published between 2017 and 2019, and follow-up periods ranged from 1 day to 4 years post-procedure. The observational studies received quality scores ranging from moderate to excellent. The RCT by Ting et al. demonstrated good reliability despite some potential bias due to the lack of blinding of therapists and assessors.

Success criteria for intraocular pressure (IOP) reduction varied among the studies. Ting et al. and Töteberg-Harms et al. defined success as an IOP ≤21 mmHg or a drop of at least 20% from baseline. Lau et al. defined success as an IOP ≤15 mmHg or a reduction of ≥30% from baseline, while Parra et al. defined success as an IOP ≤16 mmHg without medication. Baseline IOP was generally lower in the MIGS group than in the trabeculectomy group. Ting et al. reported no significant differences in mean IOP between the Phaco-AIT and Phaco-Trab groups at 6 and 12 months. Töteberg-Harms et al. observed that although the Phaco-Trab group had a higher baseline IOP, it had a lower median IOP at the 1-year follow-up, with differences between the groups diminishing by 4 years.

Four studies reported on IOP changes over time. Lau et al. and Ting et al. found no significant differences between the two groups. In contrast, Parra et al. and Töteberg-Harms et al. reported significant between-group differences in mean IOP reduction at early follow-up visits, but not after 6 months.

Qualified success and complete success rates varied across studies. Overall, the Phaco-Trab group tended to achieve higher success rates than the Phaco-MIGS group. Töteberg-Harms et al. reported significantly higher success rates for Phaco-Trab at 1-year and 4-year follow-ups. Lau et al. found comparable qualified success rates but a higher complete success rate with Phaco-Trab. Parra et al. also reported a higher complete success rate for Phaco-Trab.

Early postoperative complications included IOP spikes and hypotony. IOP spikes were more common in the Phaco-MIGS group, whereas hypotony was more common in the Phaco-Trab group. Severe complications such as choroidal effusion and hypotony maculopathy were observed only in the Phaco-Trab group. Overall, the incidence of complications did not differ significantly between the two groups.

The authors note that future research should focus on conducting more RCTs to validate these findings, particularly by evaluating different types of MIGS. They also recommend including more diverse populations, especially Asian patients, to understand the influence of race on outcomes. Additionally, criteria for target IOP and definitions of OAG at baseline should be standardised to improve the reliability of the results.

Methodology:
Adults (>18 years old) with OAG and concomitant cataract in either eye who underwent phacoemulsification with trabeculectomy or with a MIGS procedure were included in the review. Eligible study designs included cohort studies, case series, case-control studies, and randomised controlled trials (RCTs). All included studies were in English, with no restrictions on publication year. Two reviewers independently screened the titles and abstracts of all identified articles against the eligibility criteria. Full-text reviews were then performed, and relevant data were extracted. The Newcastle–Ottawa scale was employed for case series, case‑control, and cohort studies, whereas the PEDro scale was used to determine the risk of bias in RCT studies.

Applicability/external validity:
The review acknowledges the limited number of studies on this topic, with data from only 259 OAG eyes across four studies. This small sample size, along with the varying definitions of target IOP used as success criteria among the studies, might influence the interpretation of the overall success rates. Additionally, the review notes a risk of bias due to the homogeneous racial profile of participants (most were Caucasian, with few Asian participants). This racial homogeneity might affect the generalisability of the results to other populations.

Geographic focus:
The review did not report the geographic location of the included studies.

Summary of quality assessment:
There is low confidence in the review’s conclusions due to language bias (only English-language studies were included). Additionally, the review lacked methodological details on data extraction and did not address how the findings might have been affected by the risk of bias in the included studies.