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. 2025 Jan 10;122(1):23–29. doi: 10.3238/arztebl.m2024.0240

Minimally Invasive Glaucoma Surgery

Bogomil Voykov 1,2, Verena Prokosch 1,3, Jan Lübke 4,*
PMCID: PMC12416010  PMID: 39670502

Abstract

Background

Approximately 1.4 % of the German population aged 35 to 74 suffers from glaucoma, which is one of the more common causes of blindness. The only evidence-based treatment option at present is lowering the intraocular pressure. Modern minimally invasive surgical procedures hold out the prospect of lowering the intraocular pressure without the risk of serious complications.

Methods

This is a selective review of pertinent publications retrieved by a search in PubMed, including randomized, controlled trials and meta-analyses.

Results

The intraocular pressure can be lowered with eyedrops, laser procedures, and surgery. Trabeculectomy is the reference standard in glaucoma surgery but leads to complications in 3–15% of cases. In minimally invasive glaucoma surgery, very small stents can be implanted to lower the intraocular pressure. These procedures have a better safety profile but are only indicated for mild or moderate glaucoma. The Kahook Dual Blade, iStent inject, and Hydrus Microshunt procedures have been studied in randomized, controlled trials. An additional pressure-lowering effect beyond that of cataract surgery was demonstrated only for the latter two procedures (1.9 mmHg and 1.8 mmHg, respectively). Other procedures have only been investigated in cohort studies to date; a pressure-lowering effect was found for some of them. Moreover, iStent and Hydrus Microshunt have been found to slow the progression of visual field defects.

Conclusion

There are robust data documenting the effect of iStent and Hydrus Microshunt in lowering the intraocular pressure and lessening the need for eyedrops. High-quality controlled trials are still needed to test the efficacy of other procedures.

Information on CME

This article has been certified by the North Rhine Academy for Continuing Medical Education. The questions may be found at the end of this article. The closing date for entries is January 9, 2026.

Participation is possible at: cme.aerzteblatt.de

Glaucoma is a group of chronic, progressive, potentially blinding, and irreversible optic neuropathies, whose common feature is a set of morphological changes in the optic disc and retinal nerve fiber layer. These changes are associated with a progressive loss of retinal ganglion cells and a corresponding progressive loss of the visual fields. Because of compensatory mechanisms of the brain, the affected persons only notice the visual field loss when the disease is at an advanced stage (1).

Learning objectives

This article should enable the reader to:

  • know the current minimally invasive methods of glaucoma surgery,

  • have a realistic idea of the intraocular pressure reduction that can be achieved by these procedures, and

  • know the differences between modern minimally invasive methods and the surgical procedures that have long been in established use.

Prevalence

Glaucoma is the leading cause of irreversible blindness worldwide (2). The global prevalence of glaucoma is approximately 3.5% in among persons aged 40 to 80 (3). The prevalence of glaucoma triples with each decade of life (4). It is estimated that the number of persons with glaucoma around the world was more than 64 million people in 2013 and 76 million people in 2020; it is expected to rise to 111 million people in 2040 (3). In 2020, 3.6 million persons worldwide were blind because of glaucoma (5).

In 2006, it was estimated that about 7 in every 100,000 people in Germany were blind or severely visually impaired due to glaucoma, which was the second most common cause of blindness after macular degeneration (6). The Gutenberg Health Study revealed a prevalence of glaucoma of 1.4% among persons aged 35 to 74 (4). A projection yielded a figure of 923,000 people with glaucoma in Germany in 2017 (7). According to the German Federal Statistical Office, 334,600 people who were certified as severely handicapped in 2021 had blindness or visual impairment as their most severe diagnosis. Among these individuals, 66,245 were blind.

The goal of treatment

The goal of glaucoma treatment is to preserve the patients’ visual function (visual acuity and visual fields) and quality of life. The central visual acuity must be maintained, and the risk of losing visual field must be minimized. From an ophthalmological point of view, the only treatment option that has been shown to preserve visual function in glaucoma is to lower the intraocular pressure (2). The extent to which it needs to be lowered depends on a variety of factors including age, initial pressure level, stage of the disease, life expectancy, and the patient’s individual circumstances. The intraocular pressure need not be elevated for glaucoma to develop (statistically normal range 10–21 mmHg), but lowering it is always beneficial in patients with glaucoma (8). In practice, this means that the target intraocular pressure level should be determined individually and adjusted continually over the course of the disease.

Aside from the relative elevation of intraocular pressure, insufficient perfusion of the optic nerves is also thought to play a role in the pathophysiology of glaucoma. Especially in patients whose intraocular pressure is in the statistically normal range, optimizing cardiovascular function is important (9). The mean arterial blood pressure should not fall more than 20% at night compared to the daytime, and it should lie in the range of 65 to 90 mmHg (9). This can only be achieved through interdisciplinary collaboration with specialists from other fields.

The available options for lowering intraocular pressure include eyedrops, laser treatment, and surgery. As a rule, the treatment begins with eyedrops. If the individually determined target pressure level is not reached with eyedrops alone, if the glaucoma findings progress despite treatment, or if drug intolerance develops, the treatment is escalated to laser and surgical procedures.

Conventional filtering surgery can markedly lower the intraocular pressure and achieve long-term control. In these procedures, aqueous humor is drained from the anterior chamber through artificial fistula leading out of the eye and under the conjunctiva. Conventional operations for glaucoma, such as trabeculectomy and glaucoma drainage implants, have been in use for decades (10, 11). Trabeculectomy with the use of cytostatic drugs (mitomycin C and 5-fluorouracil) is still considered the reference standard of glaucoma surgery (10). These procedures, however, may lower the pressure excessively, leading to permanent visual deterioration. The reported frequency of this complication ranges from 3% to 15% (12, 13). The risk of serious bleeding also rises if the intraocular pressure is too low; this occurs in about 1% of patients (13). In the last 10–15 years, many new procedures have been developed to make glaucoma surgery safer. These procedures are much less invasive than the conventional ones and carry a low risk of complications (14). In 2012, Saheb and Ahmed defined this new type of glaucoma surgery as “micro-invasive glaucoma surgery” (MIGS). Ideally, MIGS procedures should meet five criteria: the surgical approach should be ab interno (i.e. starting from the anterior chamber of the eye), the operation should be minimally traumatic and highly biocompatible (without provoking a foreign-body reaction), it should be at least moderately effective and very safe, and the recovery after surgery should be rapid, with minimal impairment of the quality of life until the patient recovers (15).

The definition of MIGS is not entirely uniform, as the European Glaucoma Society (EGS) and the American Glaucoma Society (AGS) offer slightly different definitions. For example, the EGS does not count filtering microstent procedures as MIGS (2). In recent years, many different types of stents, some of them very small, have emerged onto the market, in an attempt to fulfill the promise of minimally invasive surgery. The target group for MIGS procedures consists of those patients who have mild to moderate open-angle glaucoma that can be controlled with one to two eyedrops. As MIGS can easily be combined with cataract surgery, patients who have both cataracts and glaucoma often undergo MIGS as well (16). Compared to conventional filtering procedures such as trabeculectomy or glaucoma drainage implants, MIGS involves a higher target pressure and, as a rule, do not eliminate the need for glaucoma medication after surgery (16). According to the current EGS guidelines, the severity of the glaucoma and the preoperative intraocular pressure should be given particular consideration in the decision-making process (10).

In this CME article, we will present the most important types of MIGS procedures, along with a discussion of the modern variants of conventional filtration surgery (eSupplement). these have also been designated as “minimally-invasive bleb surgery” (MIBS) and are classified by the AGS as a subtype of MIGS called “bleb-forming MIGS” (17).

eSupplement.

Supplementary discussion: bleb-forming MIGS

Aside from the MIGS procedures that have been designed to improve aqueous humor drainage without any artificial fistula under the conjunctiva, modern variants of the classic trabeculectomy have been developed. In these procedures, microstents are used to establish a communication between the anterior chamber and the subconjunctival space. The EGS does not consider these procedures to be MIGS, while the AGS classifies them as bleb-forming MIGS. They have also been designated minimally-invasive bleb surgery (MIBS).

There are now two microstent-based bleb-forming procedures: the XEN Gel Stent and the Preserflo MicroShunt. Both are based on the same principle as trabeculectomy and thus belong in the category of filtering glaucoma surgery. The microstents are designed in accordance with Poiseuille’s law to provide a certain amount of outflow resistance in order to limit the risk of permanent postoperative intraocular hypotension. The main difference between the two types of microstent is the surgical access route for their implantation. The XEN Gel Stent is implanted ab interno without any conjunctival incision. In contrast, the Preserflo MicroShunt is implanted ab externo after the conjunctiva is opened.

Like trabeculectomy, both of these procedures require the use of antifibrotic agents such as mitomycin C (MMC) and 5-fluorouracil (5-FU) to lessen postoperative fibrosis and improve the probability of success. It must be emphasized, however, that the use of MMC and 5-FU in glaucoma surgery is off-label. This is a major reason why randomized and controlled trials of the XEN Gel Stent and the Preserflo MicroShunt would be extremely expensive and are therefore hardly feasible. Nonetheless, a large number of prospective and retrospective studies yield information on their efficacy and safety.

XEN

The XEN Gel Stent is a microstent made of cross-linked gelatin that has been approved for the treatment of primary open-angle glaucoma. It is 6 mm long and available in two sizes with different lumen width: 45 µm and 63 µm. The theoretical outflow pressure gradient is 6–8 mmHg for the narrower version and 2–3 mmHg for the wider version.

Only one randomized, controlled trial has been published to date comparing the XEN Gel Stent with trabeculectomy in terms of its safety and efficacy. Both procedures were found to lower the intraocular pressure and the use of IOP-lowering medication significantly after one year of follow-up. The primary (combined) endpoint of the trial was the percentage of patients with an IOP reduction of ≥ 20% from baseline, without any increase in topical IOP-lowering medication, clinically significant intraocular hypotension, a decline in visual acuity to finger counting, and/or further surgery such as trabeculectomy or drainage implants, at 12 months. With regard to this primary endpoint, the XEN Gel Stent was found to be non-inferior to trabeculectomy (62.1% versus 68.2%, intergroup difference –6.1%; 95% confidence interval: [–22.9; 10.8]; p = 0.487). The mean IOP was 2.8 mmHg lower in the trabeculectomy group at 12 months, and this difference was statistically significant ([0.4; 5.2]; p = 0.024). Both procedures led to a significantly lower use of local pressure-lowering medication than before the procedure (from 2.8 ± 1.2 to 0.6 ± 1.1 in the XEN Gel Stent group, and from 2.5 ± 1.3 to 0.3 ± 0.6 in the trabeculectomy group; p < 0.001 for each group). In the XEN Gel Stent group, there were fewer interventions after surgery, and fewer complications, and the recovery of visual acuity after surgery was better (40). A systematic review and meta-analysis of 56 studies involving 4,410 eyes, published in 2022, similarly concluded that the XEN Gel Stent is safe and effective in the treatment of both primary open-angle glaucoma and various types of secondary glaucoma. It achieves an IOP reduction of 35% at a pressure level of around 15 mmHg with significantly less use of pressure-lowering eyedrops. The incidence of vision-threatening complications was less than 1% (e1).

Preserflo

The Preserflo MicroShunt is made of a thermoplastic elastomer called poly(styrene-block-isobutylene-block-styrene) (SIBS). The material was originally used to manufacture cardiac stents and was later applied to the pressure-lowering treatment of glaucoma. The microstent has a length of 8.5 mm and a lumen diameter of 70 µm and theoretically provides an outflow pressure gradient of 6 mmHg.

The safety and efficacy of the Preserflo MicroShunt and trabeculectomy were compared in an RCT in 2021. The primary endpoint of the trial was the percentage of patients with an IOP reduction of ≥ 20% from baseline without any increase in topical IOP-lowering medication at one year. The success rate was significantly lower in the Preserflo Micro-Shunt group than in the trabeculectomy group (53.9% vs. 72.7%; intergroup difference, –18.8%; [–27.9; 9.8]; p < 0.01). Notably, the differences between the two procedures were statistically significant only for the groups with an initial IOP < 18 mmHg or in the range of 18–20 mmHg, but not for the group with initial IOP ≥ 21 mmHg. In the Preserflo Micro-Shunt group, the mean IOP was lowered at one year from 21.1 ± 4.9 mmHg to 14.3 ± 4.3 mmHg (p < 0.01); in the trabeculectomy group, it was lowered from 21.1 ± 5.0 mmHg to 11.1 ± 4.3 mmHg (p < 0.01). In a post-hoc analysis of patients who achieved success in relation to the primary endpoint, the mean intraocular pressure was lowered from 21.6 ± 4.7 mmHg to 12.6 ± 3.0 mmHg (p < 0.01) in the Preserflo MicroShunt group and from 21.5 ± 5.1 mmHg to 10.8 ± 3.3 mmHg (p < 0.01) in the trabeculectomy group. Significantly more postoperative interventions, including laser suture lysis, were required in the trabeculectomy group (40.8% vs. 67.4%). Furthermore, transient postoperative intraocular hypotension was significantly more common in the trabeculectomy group (49.6% vs. 28.9%, p<0.01). No difference was found between the two procedures with regard to vision-threatening complications (e2). A recent systematic review and meta-analysis of seven studies involving 1353 eyes yielded a statistically significant lower mean postoperative IOP of 0.78 [0.66; 0.90], p < 0.001 in the trabeculectomy group compared to the Preserflo MicroShunt group. The reduction in postoperative pressure-lowering medication was also greater in the trabeculectomy group (mean difference, MD = -0.32 [-0.58; –0.07], p = 0.014). The safety profiles of the two procedures were similar, and the rate of postoperative interventions was low in both groups (e3).

Types of micro-invasive glaucoma surgery

In what follows, we will present what we consider to be the main types of MIGS and their clinical efficacy. A listing of these techniques is given in Table 1. The anterior chamber of the eye and its various outflow structures are shown schematically in Figure 1.

Table 1. Overview and classification of the main current MIGS techniques.

Trabecular meshwork Canal of Schlemm Suprachoroidal space
• Destructive
– Kahook Dual Blade
– trabeculectomy
– excimer-laser trabeculotomy
• Stent-based
– iStent
– Hydrus Microshunt		 – OMNI microcatheter
– iTrack Advance		 – MINIject
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MIGS, minimally invasive glaucoma surgery

Figure 1.

Figure 1

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The anterior chamber of the eye with the structures relevant to the outflow of aqueous humor.

Procedures involving the trabecular meshwork

The trabecular meshwork in the angle of the anterior chamber is the first relevant site of outflow resistance for the aqueous humor and thus an obvious surgical target. There are a variety of surgical means of lowering this resistance. The aim of the procedures involving the trabecular meshwork is to open it and clear a path to the canal of Schlemm, which is the next structure in the aqueous humor outflow pathway, thus establishing a connection from the anterior chamber to the canal of Schlemm. This can be achieved either by destroying the trabecular meshwork or by inserting stents.

Destroying the trabecular meshwork

The trabecular meshwork can be opened or removed with a variety of surgical instruments. This can be done either manually with a knife (e.g. the Kahook Dual Blade, Figure 2a) or by electroablation (trabectome). An excimer laser can also be used to create small openings in the trabecular meshwork (excimer laser trabeculotomy, Figure 2b), to enable the outflow of fluid from the chamber into the canal of Schlemm.

Figure 2.

Figure 2

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Schematic depiction of

a) Kahook Dual Blade

b) excimer-laser trabeculotomy

c) iStent

d) Hydrus Microshunt

e) Miniject implant

Stent techniques involving the trabecular meshwork

In addition to destructive methods, there are various stents that can be inserted into the trabecular meshwork. These include the iStent inject W (Figure 2c) and the Hydrus Microshunt (Figure 2d). The iStent is a titanium stent with a length and width of 360 µm that bypasses the trabecular meshwork. The Hydrus Microshunt is an 8-mm-long wire scaffold made of nitinol that additionally widens the canal of Schlemm. Both of these devices can inserted with pre-loaded injectors. According to the manufacturers, both are compatible with MRI of fields strengths up to 3 Tesla.

Pressure reduction by methods involving the trabecular meshwork

In principle, all interventions on the trabecular meshwork can be assumed to yield similar reductions in intraocular pressure by lowering the outflow resistance of the trabecular meshwork. From a physiological point of view, it should make no difference to the aqueous humor flow whether the connection between the anterior chamber and Schlemm’s canal is established by stents or by removal of the meshwork. Many studies of the efficacy of these procedures in reducing the intraocular pressure have dealt with the procedures in combination with cataract surgery. There have been no more than a few controlled trials with carefully selected control groups that have compared the effects of these procedures as a single intervention.

A number of studies have documented the pressure-reducing effect of these procedures when performed in combination with cataract surgery, compared to cataract surgery alone. A Hydrus microshunt in addition to cataract surgery lowered the intraocular pressure to a significantly greater extent than cataract surgery alone (8.3 vs. 6.5 mmHg) and also lowered the consumption of eyedrops of five years of subsequent follow-up a (18). 49.5% of the patients who underwent both procedures achieved an intraocular pressure below 18 mmHg, compared to 33.8% of those who had cataract surgery alone. In contrast, a randomized controlled trial (RCT) comparing the Kahook Dual Blade in addition to cataract surgery with cataract surgery alone showed no additional effect over a follow-up period of one year (19). A Cochrane analysis of the additional effect of stent implantation showed a greater reduction in pressure compared to cataract surgery alone, but overall level of evidence for this conclusion was low (20). This additional effect was, however, also demonstrated in a more recent meta-analysis from 2023: stents were shown both to lower the intraocular pressure and to lessen the use of eyedrops. The intraocular pressure was lowered by 4.7 mmHg by iStent implantation combined with cataract surgery, compared to 2.8 mmHg by cataract surgery alone.

The COMPARE trial showed that the lowering of intraocular pressure is similar for the two stent procedures in combination with cataract surgery, and that the amount of pressure-lowering eyedrops needed after the insertion of a Hydrus Microshunt is significantly lower one year after surgery (22). There have not been any randomized, controlled trials to assess the putative additional benefit of either trabectome or excimer laser trabeculotomy in combination with cataract surgery. For trabectome, however, meta-analyses of observational studies do indeed show a lowering of pressure, even when the procedure is performed alone, i.e., without cataract surgery. The pressure is reportedly lowered by 31% over two years, with the achievement of a target pressure of ca. 15 mmHg (23). Only a few studies have shown a lasting pressure-lowering effect of excimer laser trabeculotomy in combination with cataract surgery: values of ca. 15 mmHg have achieved after up to 8 years of follow-up (24). Nonetheless, the evidence for this procedure, especially as a stand-alone intervention, remains limited.

Procedures involving dilatation of the canal of Schlemm

Ab interno canaloplasty is a method for the dilatation of the canal of Schlemm and the trabecular meshwork. In this procedure (unlike ab externo canaloplasty as described by Stegmann), the canal is opened and dilated from within, but through a minimally invasive approach (16). The goal of canaloplasty is to enhance the physiological outflow of fluid from the chamber through the trabecular meshwork and the canal of Schlemm (25, 26).

Two systems are now available to serve as microcatheters for ab interno canaloplasty:

  • the iTrack Advance microcatheter system and

  • the OMNI microcatheter.

The two procedures vary slightly in terms of surgical technique.

The safety and efficacy of ab interno canaloplasty (both in isolation and in combination with cataract surgery) have been demonstrated in several studies. In a prospective study, an average reduction in IOP of 32.8% (from 20.4 ± 4.7 mmHg to 13.3 ± 1.9 mmHg) was reported at 12 months after ab interno canaloplasty. Furthermore, the average number of antihypertensive eyedrops was lowered from 2.8 ± 0.9 to 1.1 ± 1.1, corresponding to an average reduction of 60% (27). Comparable results were reported in further studies (28, 29). All three studies, however, are retrospective case series.

Suprachoroidal techniques

Aside from procedures that bypass the trabecular meshwork or lower its resistance, or widen the canal of Schlemm, another group of minimally invasive procedures create an artificial drainage pathway for the aqueous humor. These include procedures that open up the suprachoroidal space and drain the aqueous humor into it. This space is located between the sclera and the choroid and is anatomically separated from the anterior chamber by the ligament of the ciliary body. Under normal circumstances, this space is closed off from the aqueous humor. The ligament of the ciliary body can, for example, be detached as the result of ocular trauma, thus releasing the suprachoroidal space. As a sharp drop in intraocular pressure can often be observed in such eyes, the idea of using this space for targeted and controlled aqueous drainage has long been entertained. At present, only one implant or procedure is approved in Germany for opening the suprachoroidal space and for aqueous humor drainage there, the so-called MINIject implant. An injector is used to insert the 5-mm-long implant, which is made of sponge-like silicone, into the space to create a connection to the anterior chamber (Figure 2e). A meta-analysis of three prospective, non-randomized studies on the MINIject implant in 66 eyes revealed a lowering of pressure by almost 40% to a mean value of 14.4 mmHg with 1.4 medications applied over two years of follow-up (30). No studies are yet available for a comparison of the MINIject implant with a control group, or concerning its efficacy in combination with cataract surgery.

Studies for the evaluation of the individual procedures are listed in Table 2.

Table 2. Overview of the best available evidence on each of the individual MIGS procedures.

Category Procedure (ref.) Design Content Result (main conclusion) Comments
Destruction of the trabecular meshwork Kahook Dual Blade (19) randomized, controlled trial comparison of cataract surgery and Kahook Dual Blade versus cataract surgery alone no significant difference one-year follow-up
trabectome (23) observational studies (meta-analysis) reduction in pressure with trabeculectomy alone or in combination with cataract surgery 31% pressure reduction at two years, target range approx. 15 mmHg no comparison groups
excimer lasertrabeculotomy (ELT) (24) cohort study follow-up of combined cataract-ELT surgery pressure reduction from 19.3 mmHg to 15.4 mmHg at eight years no comparison groups, study with longest follow-up (eight years), but fewer than half of the patients were evaluated for longer than four years
Trabecular meshwork stent iStent (21) meta-analysis comparison of cataract surgery combined with iStent versus cataract surgery alone IOP reduction: 4.7 mmHg (with iStent), 2.8 mmHg (without iStent) varying follow-up periods in the individual studies
Hydrus Microshunt (18) randomized, controlled trial comparison of cataract surgery combined with Hydrus versus cataract surgery alone IOP reduction: 8.3 mmHg (with Hydrus), 6.5 mmHg (without Hydrus); IOP < 18 mmhg without drops: 49.5% (with hydrus), 33.8% (without hydrus) five-year follow-up
Dilatation of the canal of Schlemm OMNI microcatheter (27) retrospective comparative study comparison of ab interno canaloplasty alone and in combination with cataract surgery significant IOP and drop reduction, both as a single procedure and in combination, at one year short follow-up; comparison group available
iTrack Advance
Suprachoroidal space Miniject (30) meta-analysis of cohort studies follow-up after Miniject implantation IOP reducction by 39%, from 23.8 to 14.4 mm Hg, at two years no comparison group, but only Miniject implants
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If available, randomized controlled trials or meta-analyses are cited here; otherwise, observational studies with the longest possible follow-up.

The procedures for dilatation of the canal of Schlemm are considered together. IOP, intraocular pressure; MIGS, minimally invasive glaucoma surgery;

RCT, randomized and controlled trial.

Criticism of the MIGS techniques

Although various MIGS procedures have been available for more than a decade, the evidence for most of them is still considered to be weak (10). No clear recommendation can be made for one such procedure over another (10), as only a few high-quality comparative studies between the various MIGS procedures have been performed to date (10). Some of these studies are to be viewed critically because of conflicts of interest, as they were funded by MIGS manufacturers. Others lack information on relevant endpoints, such as complications (31, 32).

Furthermore, many of these studies did not focus on the patient-relevant endpoints of visual acuity and visual field preservation, but instead only used the reduction of intraocular pressure as an endpoint. Data are, exceptionally, available on visual field preservation with iStent and Hydrus implants. For example, a meta-analysis concerning the iStent (which, however, was not limited to randomized, controlled trials) showed that, after iStent implantation, the rate of visual field deterioration was very low (0.024 dB per year) (33). In a randomized controlled trial of the Hydrus microshunt, a deterioration rate of 0.26 dB per year was measured in patients who had undergone combined surgery; this was significantly better than in the group that had undergone cataract surgery alone (34).

The findings of some randomized, controlled trials suggest that MIGS procedures combined with phacoemulsification are superior to phacoemulsification alone. However, long-term results from multiple studies are still lacking, as the follow-up periods are often limited to one to two years, and only selected procedures have been studied in RCTs (10, 35).

Data on complications are scarce; many reports merely state that no clinically relevant complications occurred. However, values for endothelial cell loss are available for the iStent, Hydrus Microshunt, and Miniject implant. The reported values can be considered acceptable for all three procedures (18, 21, 30).

Moreover, aspects such as the experience and training of the glaucoma surgeons and the available infrastructure must be considered as well, especially with newer surgical procedures such as MIGS (10). Some MIGS procedures require higher initial costs, but they are generally easier to learn than conventional glaucoma surgery (10). They are nonetheless demanding techniques that have to be learned (36).

The cost-effectiveness of MIGS procedures is also unclear. A systematic review examined the results of multiple randomized, controlled trials and observational studies, as well as non-randomized controlled trials, comparing MIGS with trabectome or other glaucoma surgery (36). Because the available evidence is limited, no conclusion could be drawn regarding cost-effectiveness, i.e., whether the costs of MIGS are offset by savings over time, resulting from reduced medication or a lesser need for further interventions, among other factors (36).

Discussion

Since the early 2000s, MIGS procedures have been gaining ground as a treatment option for patients with mild to moderate glaucoma [37]. MIGS procedures generally achieve a moderate reduction in intraocular pressure, can lessen the need for pressure-lowering eyedrops, have a favorable safety profile, and can be combined with cataract surgery.

At the same time, the wide range of different procedures with comparable reduction of intraocular pressure and comparable risk profiles also creates a challenge in the choice of the best procedure for each patient (16). The individual target pressure should be the main factor in the choice of procedure. Other factors such as lens status, prior surgery, the condition of the conjunctiva, age, rate of progression, and the stage of glaucoma must be considered as well. There is no consensus yet about the most effective or safest MIGS procedure, and hardly any comparisons between the individual procedures are available.

On the basis of the available literature, the EGS considers trabecular stent procedures to be a suitable treatment for patients with non-progressive, mild to moderate glaucoma in combination with cataract surgery and target pressure in the “mid to upper teens” (10). The aim of trabecular MIGS is generally to lessen the inconvenience and side effects of eyedrops (the “drop burden”) (10). Combining trabecular MIGS with planned cataract surgery appears to be a suitable surgical approach. The time and material resources saved by combined surgery compared to two separate procedures are ecologically and economically beneficial. These procedures can also be performed alone in patients with ocular surface disease, poor adherence, or other comorbidities (10).

Although some authors postulate that the suprachoroidal outflow pathway affords a higher potential of lowering both intraocular pressure and the need for medications than the trabecular outflow pathway (16), the current EGS guideline does not contain any recommendation of this type, because the relevant data are sparse (10). One limitation is the currently low evidence level for most MIGS procedures in terms of reducing intraocular pressure and the need for pressure-reducing medications; in particular, long-term data are lacking (10, 16). The suprachoroidal CyPass microstent can serve as a negative example: it initially showed a very promising 20–30% pressure reduction, with a simultaneous reduction in eyedrop consumption, for up to three years after implantation (38). The COMPASS-XT follow-up study, however, revealed a significant loss of corneal endothelial cells five years after implantation (39), with the result that the CyPass microstent was voluntarily taken off the market. This should be kept in mind when new procedures show good results in studies with relatively short follow-up.

In the future, therefore, randomized and controlled trials with long-term follow-up will be needed so that optimized, evidence-based guidelines can be written for patients with glaucoma.

Further Information on CME.

  • The completion time for all newly started CME units is 12 months. The results can be accessed 4 weeks following the start of the CME unit. Please note the respective submission deadline at: cme.aerzteblatt.de

  • CME points can be managed using the “uniform CME number” (einheitliche Fortbildungsnummer, EFN). The EFN must be stated during registration on www.aerzteblatt.de (“Mein DÄ”) or entered in “Meine Daten”, and consent must be given for results to be communicated. The 15-digit EFN can be found on the CME card (8027XXXXXXXXXXX).

Questions on this article.

Participation is possible at cme.aerzteblatt.de. The submission deadline is 9 January 2026.

Only one answer is possible per question. Please select the answer that is most appropriate.

Question 1

What are the main features of glaucoma?

  1. degenerative changes in the macula and the optic nerve

  2. morphological changes in the optic nerve head and the retinal nerve fiber layer

  3. hypertrophic changes in the cornea and the chamber angle

  4. atrophic changes in the iris and the ciliary body

  5. proliferative changes in the retina and the vitreous humor

Question 2

What age group has the highest prevalence of glaucoma?

  1. 20–30 years

  2. 30–40 years

  3. 40–50 years

  4. 40–80 years

  5. over 80 years

Question 3

According to the Gutenberg Health Study, what is the prevalence of glaucoma among persons aged 35–74 in Germany?

  1. 0.6%

  2. 1%

  3. 1.4%

  4. 1.8%

  5. 2.2%

Question 4

What treatment options are available for lowering the intraocular pressure?

  1. eye drops, laser treatment, and surgery

  2. systemic medications and physical therapy

  3. vision training and endurance sports

  4. light therapy and cryoextraction

  5. stricture division of the lacrimal ducts and systemically acting medications

Question 5

Which of the following statements about procedures in the chamber angle is correct?

  1. The trabecular meshwork plays only a minor role in the aqueous humor outflow pathway.

  2. Removal of the trabecular meshwork cannot be expected to lower the intraocular pressure.

  3. The trabecular meshwork can be bypassed with small stents.

  4. The various methods have been compared in many clinical trials.

  5. Laser procedures cannot be used in the chamber angle.

Question 6

Which of the following statements about trabeculectomy is true?

  1. It is a non-invasive method.

  2. It is considered the reference standard for glaucoma surgery.

  3. It is only indicated for young patients.

  4. It is a laser treatment.

  5. It is an alternative surgical procedure to cryoretinopexy.

Question 7

Which patients are suitable for MIGS?

  1. Those who are referred on an emergency basis with a dangerously elevated intraocular pressure.

  2. Those with mild to moderate glaucoma that can be controlled with one or two eyedrops.

  3. Those with acute bacterial eye infections and increased intraocular pressure.

  4. Those who wish to wear contact lenses postoperatively.

  5. Those with severely increased intraocular pressure and blepharitis.

Question 8

What is the role of blood pressure in the treatment of glaucoma?

  1. It should not drop by more than 20% at night compared to day.

  2. It should always remain constant.

  3. It is of no importance in the treatment of glaucoma.

  4. It should be at least 20% lower during the day than at night.

  5. It should only be lowered if a cataract is present.

Question 9

An 82-year-old woman with marked lens opacification and mild glaucoma, under treatment with two eyedrops at a pressure of ca. 18 mmHg, asks about cataract surgery. Which of the following statements is correct?

  1. Combined MIGS and cataract surgery is not advisable if the patient is already using eyedrops to treat glaucoma.

  2. Combined MIGS and cataract surgery may stabilize the intraocular pressure without the need for further eyedrops.

  3. Combined MIGS and cataract surgery is not recommended for persons over age 75.

  4. Combined MIGS and cataract surgery would carry a high risk of complications in this particular case.

  5. Combined MIGS-cataract surgery must be performed, as cataract surgery alone is contraindicated in patients with glaucoma.

Question 10

Which of the following ophthalmological procedures is not considered MIGS?

  1. opening of the suprachoroidal space

  2. dilatation of the canal of Schlemm

  3. destruction of the trabecular meshwork

  4. stent placement in the trabecular meshwork

  5. phacoemulsification

Participation is possible only via the Internet:

cme.aerzteblatt.de

Acknowledgments

Acknowledgement

the authors thank Ms. Irena Stingl for creating the figures.

Translated from the original German by Ethan Taub, M.D.

References (abbreviated)

1. Crabb DP, et al.: Ophthalmol 2013; 120: 1120–6.

2. EGS: European Glaucoma Society Guidelines–5th Edition. 2021.

3. Tham YC, et al.: Ophthalmol 2014; 121: 2081–90.

4. Höhn R, et al.: Graefes Arch Clin Exp Ophthalmol 2018; 256: 1695–702.

5. GBD 2019 Blindness and Vision Impairment Collaborators, Vision Loss Expert Group of the Global Burden of Disease Study: Lancet Glob Health 2021; 9: e144–60.

6. Finger RP, et al.: Br J Ophthalmol 2011; 95: 1061–7.

7. Schuster AK, et al.: Ophthalmologe 2019; 116: 829–37.

8. Krieglstein GK: Der Ophthalmologe 2003; 100: 484–92.

9. Pillunat KR, et al.: Ophthalmologe 2021; 118: 431–8.

10. Abegao Pinto L, et al.: Br J Ophthalmol 2023; 107: 1–114.

11. Kirwan JF, et al.: Ophthalmology 2013; 120: 2532–9.

12. Panarelli JF, et al.: Ophthalmology 2024; 131: 266–76.

13. Gedde SJ, et al.: Am J Ophthalmol 2012; 153: 804–14.e1.

14. Chen DZ, et al.: J Ophthalmol 2017; 2017: 3182935.

15. Saheb H, et al.: Curr Opin Ophthalmol 2012; 23: 96–104.

16. Klabe K, et al.: Ophthalmologie 2023; 120: 358–71.

17. Fellman RL, et al.: Ophthalmol Glaucoma 2020; 3: 1–6.

18. Ahmed IIK, et al.: Ophthalmology 2022; 129: 742–51.

19. Ventura-Abreu N, et al.: Graefes Arch Clin Exp Ophthalmol 2021; 259: 2771–81.

20. Le JT, Bicket AK, et al.: Cochrane Database Syst Rev 2019; 3: CD012743.

21. Kahale F, et al.: Ophthalmic Research 2023; 66: 1020–9.

22. Ahmed IIK, et al.: Ophthalmology 2020; 127: 52–61.

23. Kaplowitz K, et al.: Br J Ophthalmol 2016; 100: 594–600.

24. Riesen M, et al.: Graefes Arch Clin Exp Ophthalmol 2022; 260: 1611–21.

25. Stegmann R, et al.: J Cataract Refract Surg 1999; 25: 316–22.

26. Lewis RA, et al.: J Cataract Refract Surg 2007; 33: 1217–26.

27. Gallardo MJ,et al.: Clin Ophthalmol 2018; 12: 2149–55.

28. Koerber N, et al.: Klin Monbl Augenheilkd 2023; 240: 1394–404.

29. Khaimi MA, et al.: Clin Ophthalmol 2024; 18: 173–83.

30. Dick HB, et al.: Am J Ophthalmol 2024; 260: 172–81.

31. Bonnar J, et al.: Eye 2023; 37: 1774–7.

32. Rosdahl JA, et al.: Clin Ophthalmol 2020: 14: 231–43.

33. Gillmann K, al.: BMJ Open Ophthalmol 2024; 9: e001575.

34. Montesano G, et al.: Am J Ophthalmol 2023; 251: 143–55.

35. Yuan PHS, et al.: Am J Ophthalmol 2024; S0002–9394(24)00333–7.

36. Agrawal P, et al.: Ophthalmol Ther 2018; 7: 49–73.

37. Luebke J, et al.: Clin Epidemiol 2021; 13: 581–92.

38. Sandhu A, et al.: Cochrane Database Syst Rev 2021; 5: CD012802.

39. Reiss G, et al.: Am J Ophthalmol 2019; 208: 219–25.

40. Sheybani A, et al.: Am J Ophthalmol 2023; 252: 306–25.

Footnotes

Conflict of interest statement

JL has served as a paid consultant for Santen Pharma and AbbVie and has received lecture honoraria from Alcon, AbbVie, iStar, Glaukos, and Santen Pharma.

VP has received financial support and honoraria for continuing medical education presentations from Alcon, Glaukos, AbbVie, Santen, and Elios.

BV has received personal financial support and honoraria for continuing medical education presentations from AbbVie and Santen.

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