Minimally Invasive Glaucoma Surgery (MIGS)
Although there are no strict criteria for the definition of MIGS, in general it refers to surgical procedure which aims to increase aqueous humor outflow by directing it to the suprachoroidal or subconjunctival space or by-passing the resistance of outflow in trabecular meshwork. Often endoscopic cyclophotocoagulation is considered as MIGS as well. Frequently MIGS includes an implant or a specific device to open the trabecular meshwork.
There are a diversity of MIGS surgeries and no one conclusion can be made, whether they are useful or not. It is clear that more high quality studies in the field are needed. There is variability in the study outcomes. Often comparisons are made between MIGS+phaco and phaco alone. There are very few studies comparing different MIGS procedures head-to-head or to traditional glaucoma surgeries (trabeculectomy, deep sclerectomy, shunts).
Systematic Review 1
In the Cochrane-review of King et al (2018) devices draining aqueous humor to the subconjunctival space were reviewed. The reviewers found no randomized controlled trials filling in the inclusion criteria «King AJ, Shah A, Nikita E ym. Subconjunctival drai...»1.
Systematic Review 2
The Cochrane-review (Le et al 2019) compared Istent results to those of medication, trabeculectomy, and to other MIGS, as well as Istent compared with cataract surgery compared to cataract surgery alone. Seven studies (all sponsored by Glaukos) were included. They also identified 13 ongoing studies. Only scarce evidence was found to support that Istent would lead to less postoperative medications or better IOP control. Compared to cataract surgery alone (2 studies), there was larger proportion of medication-free eyes 6-18 month postoperatively, and those on medications required them less «Le JT, Bicket AK, Wang L ym. Ab interno trabecular...»2.
Systematic Review 3
The systematic review by Rosdahl and Gupta (2020) the reviewers found 138 prospective studies about MIGS for open-angle glaucoma written in English. Of them, 87 articles were selected for quality assessment. Only 12 articles were graded as good enough quality and were summarized in the review.
Endoscopic cyclophotocoagulation (ECP) was as effective as the Ahmed-shunt in refractory glaucoma and had less complications (54 patients, 24 months of follow-up)
Phaco+trabeculectomy reduced IOP more than phaco+ECP. Phaco+ECP group had less complications (58 patients, different follow-up periods)
Trabeculectomy was more effecitive than ab-interno trabeculectomy and had more complications (32 patients, 24 months follow-up)
Treatment-naive patients had more often IOP <18 mmHg in the Istent group compared to the Travatan-treated eyes (73 patients, 36 months follow-up)
IOP reduced more in the phaco-Istent group than in the phaco-alone group (33 patients, 1 year of follow-up)
In the phcao-Istent group, the need for medications was less than in the phaco-alone group (33 patients, 15 monts follow-up). After 4 years, no difference in number of medication was detected (24 patients, 4 years follow-up)
The Hydrus-group needed less medication than the SLT-group, but the groups were not randomized (55 patients, 12 months follow-up)
Phaco+Hydrus reduced IOP >20% more often than the phaco-alone group (78 patients, 24 months follow-up)
Phaco+Hydrus had lower IOP without medications compared the phaco-alone group (556 patients with 95 % with 24 months of follow-up)
Cypass+phaco had more often >20% IOP reduction than the phaco-alone group. Cypass has been off market due to loss endothelial cells.
The reviewers concluded that the studies suffered from small sample sizes, narrow spectrum of glaucomatous disease, and conflicts of interest «Rosdahl JA, Gupta D. Prospective Studies of Minima...»3.
Systematic Review 4
Wang et al (Wang et al 2015) included in their Cochrane-review the Express-shunt which some authors consider as a MIGS. Based on three studies (165 eyes, low-quality evidence), the Express was more effective than trabeculectomy alone in reducing IOP (mean difference -1,58, 95%CI -2,74 - -0,42) «Wang X, Khan R, Coleman A. Device-modified trabecu...»4.
Cost analysis
The authors analyzed the relative cost of various glaucoma surgical procedures and selective laser trabeculoplasty surgery per mm Hg IOP reduction. A US perspective was adopted, using Medicare allowable costs at 1 year postoperatively.
Conventional glaucoma surgeries and selective laser trabeculoplasty surgery were the most cost-efficient surgical methods to lower IOP compared with the various minimally invasive glaucoma surgeries options. They may be more appropriate management when cost is an important issue «Elhusseiny AM, Yannuzzi NA, Khodeiry MM ym. Cost-a...»5.