Preserflo MicroShunt Implantation: A Narrative Review of Its Standalone Benefits vs. Combined Use with Phacoemulsification in Managing Open-Angle Glaucoma

Abstract

Glaucoma and cataract often coexist. Patients with both conditions who qualify for surgical treatment may undergo either a combined surgical procedure or sequential treatments such as cataract surgery followed by an antiglaucoma procedure. A combined procedure with phacoemulsification is related to an increased risk of fibrosis of the filtering bleb; however, it is a rational approach for patients with high intraocular pressure and clinically significant lens opacification. Trabeculectomy has been a traditional filtration procedure for decades, effectively lowering intraocular pressure. It is highly effective; however, it may cause sight-threatening complications. The Preserflo MicroShunt, introduced less than a decade ago in the field of glaucoma surgery, has shown similar hypotensive efficacy to trabeculectomy, and is a less invasive procedure with a better safety profile. Despite their shared mechanism of action to reduce intraocular pressure, the two procedures differ in the extent of scleral incision and filtration bleb morphology, which may influence the extent of the post-surgery inflammation process. This review evaluated and compared reports on the efficacy and safety of Preserflo MicroShunt implantation as a standalone procedure versus combined with cataract removal in surgical treatment for patients with open-angle glaucoma and concomitant cataract.

Key Summary Points

The effectiveness of Preserflo Microshunt (PMS) for treating patients with open-angle glaucoma and concomitant cataracts, both when used as a standalone procedure and in combination with phacoemulsification, was reviewed.

Comparing different studies was complicated due to variations in how they defined surgical success, types of glaucoma included, and other patient populations involved.

Most studies indicated no significant difference between using PMS standalone or combined with phacoemulsification.

This review underscores the need for additional research to determine optimal treatment strategies for patients with glaucoma and coexisting cataract and identify associated risks for surgical failure.

Introduction

Glaucoma remains the second leading cause of irreversible blindness worldwide, with approximately 118 million people worldwide expected to be affected by this disease by 2040 [1]. Lowering intraocular pressure (IOP) is the only confirmed method that may halt the progression of glaucomatous neuropathy and prevent vision loss. Therefore, glaucoma treatment focuses on IOP reduction using pharmacological, laser, and surgical techniques. Numerous studies confirm that surgical procedures are the most effective in lowering IOP [2, 3]. Trabeculectomy remains the gold standard in glaucoma treatment [3]; however, for over a decade, research has focused on the development of less invasive surgical methods that offer a higher safety profile with similar efficacy.

Glaucoma and cataract often occur concurrently. Patients with both conditions, who are eligible for surgical treatment, may undergo either combined procedures or a two-stage approach (a phacoemulsification with subsequent trabeculectomy or vice versa). Both approaches have their strengths and weaknesses. The two-stage approach, starting with cataract removal, is currently the preferred method for treating angle-closure glaucoma (ACG). For open-angle glaucoma (OAG), the influence of phacoemulsification on lowering IOP is moderate and decreases over time [4–6] moreover postoperative IOP spikes are common. This makes the approach debatable for patients with significant lens opacity and advanced optic neuropathy.

A drawback of beginning with trabeculectomy in phakic eyes in the two-staged approach is that the surgery itself may cause cataract formation, particularly in the case of excessive inflammation and hypotony during the postoperative period [7, 8]. Additionally, cataract surgery performed after glaucoma surgery may deteriorate filtering bleb, leading to surgical failure [9, 10]. Performing the combined procedure is an appealing option because it is time-saving, cost-effective, and reduces patient stress. However, it may increase the risk of postoperative complications and decrease the effectiveness of the glaucoma surgery due to inflammation generated by cataract surgery, which may accelerate the fibrosis of filtering bleb [11]. Reducing the risk of IOP spike caused by phacoemulsification is an advantage of combined phaco-trabeculectomy [12].

Studies on that issue have shown conflicting results; some demonstrated a comparable effectiveness between combined and solo procedures [13–19], whereas others show a higher failure rate in patients undergoing combined surgery [21–24]. Research by Ciociola et al. [23], which used the IRIS registry, analyzed the results of 95,924 trabeculectomies and phaco-trabeculectomies. The authors found that solo procedures led to a more pronounced IOP reduction in comparison to combined procedures (35.3% vs. 23.1%, respectively, p < 0.05). However, the reoperation rate within 3 years was lower after combined procedures than after solo procedures (7.3% vs. 11.5%, respectively, p < 0.05).

Despite the high effectiveness of trabeculectomy and drainage devices in lowering IOP, they may lead to vision-threatening adverse events [24]. This prompted the search for surgical techniques that cause less trauma to ocular tissues, have minimal impact on eye anatomy and physiological structures, and offer a favorable safety profile without the complications typical of traditional filtering procedures. One such option is the Preserflo MicroShunt (PMS) (Santen Inc., Miami, FL, USA) designed for implantation with an ab externo subconjunctival approach in patients with early and moderate OAG. It is categorized as a minimally penetrating glaucoma surgery or minimally invasive bleb surgery, which includes bleb-forming devices that create a new aqueous humor outflow pathway underneath Tenon’s capsule. Recent evidence has shown that the PMS is similarly effective to traditional filtration surgery while significantly improving safety [25, 26]. The PMS is a tube made from a combination of polystyrene, isobutylene, and styrene (SIBS) and is associated with less inflammation and reduced fibrosis compared to other implants (especially those of silicone rubber). The current model is 8.5 mm long with an outer diameter of 350 µm and an inner diameter of 70 µm. Those dimensions position the filtration bleb further from the corneal limbus (8.5 mm), potentially leading to less postoperative fibrosis compared to the bleb formed after trabeculectomy, which is placed 6 mm from the limbus and stem cells [26, 27], (Fig. 1). According to recent studies the total surgical success rate for patients operated with PMS combined with phacoemulsification is higher than for those treated with phaco-trabeculectomy (80% vs. 56%, respectively, after 12 months) [26, 27].

Fig. 1.

Step-by-step technique of Preserflo MicroShunt implantation.

Copyright by Santen S.A.; Genève, Switzerland; reproduced with permission. MMC mitomycin C

Concurrent phacoemulsification is considered to affect the outcomes of traditional filtration surgeries, although the effectiveness of combined procedures with the PMS and cataract removal versus the PMS alone remains unclear. This study reviewed the literature regarding the efficacy and safety of PMS implantation as a standalone procedure versus combined with phacoemulsification in patients with OAG. We hope to contribute to the discussion on whether combined or standalone PMS procedures are preferable. To our knowledge, such a review is not yet available in the current literature.

Methods

Search Strategy

The following databases were searched: PubMed, Ovid MEDLINE, EMBASE, ClinicalTrials.gov. Two authors (MC and JK) independently searched databases from the inception to May 29, 2024. The following keywords were used as search terms: “glaucoma,” “open-angle glaucoma,” “primary open-angle glaucoma,” “Preserflo MicroShunt,” “combined procedures,” “penetrating surgery,” and “filtering bleb.” We analyzed the abstracts for relevance to the patient groups consistent with the focus of our review. Publications available only as abstracts or conference posters were excluded. After reviewing the abstracts, full-text articles related to the topic were selected. We analyzed publications only in English without restrictions based on the publication date. The references of the included studies were checked to identify additional relevant research on the topic. To find citations of publications that referenced the studies included in our review, we used the Science Citation Index. Additionally, we contacted the authors of relevant studies to identify any additional research.

The inclusion criteria for articles in this literature review were: randomized and non-randomized controlled trials involving patients with OAG, pseudoexfoliative glaucoma (PEXG), or pigmentary glaucoma (PG), age-related cataract, and who underwent implantation of the PMS combined with phacoemulsification or as a standalone procedure; studies that analyzed variables such as IOP and the amount of antiglaucoma eye drops used before and after surgery, postoperative complications, and surgical success; and studies with a follow-up period of at least 6 months.

The exclusion criteria for articles in this literature review were: studies that were case reports or review articles; studies describing partial results; and studies that did not account for all the analyzed factors. The exact number of records at each stage of the literature search is shown in Fig. 2.

Fig. 2.

PRISMA flowchart of study selection process

Ethics approval was not required for this study since it was not conducted with human participants or animals and is based on previous studies performed by other authors.

Results

We found only two articles directly comparing standalone and combined procedures using the PMS [28, 29]. The two-center retrospective study by Martinez-de-la-Casa et al. [29] focused on a Spanish population over a 12-month follow-up period. The authors included 58 patients with uncontrolled primary open-angle glaucoma (POAG), who received a PMS implant as standalone procedure (group 1: PMS, n = 35) or combined with phacoemulsification in case of concomitant cataract (group 2: PMS + Phaco, n = 23). Total surgical success was defined as an IOP of ≤ 18 mmHg at 12 months and a IOP reduction of ≥ 20% from baseline, without the use of IOP-lowering medications. Qualified surgical success was defined using the same criteria although allowed for the use of antiglaucoma medications. Failure was considered for patients with an IOP of < 6 mmHg, those requiring additional glaucoma surgery, or the need of another surgery due to complications. Mitomycin C (MMC) was applied subconjunctivally for 2 min in a concentration of 0.2 mg/ml. The average IOP dropped from 21.3 ± 3.2 to 14.4 ± 3.4 mmHg in the PMS group and from 21.7 ± 3.5 mmHg to 14.9 ± 3.6 mmHg in the PMS + Phaco group. Except for the first day, when the IOP was significantly lower in the PMS group, no differences in the IOP at any of the follow-up visits between the PMS and PMS + Phaco groups were found. The average number of IOP-lowering drops decreased from 2.4 ± 0.9 at the beginning of the study to 0.3 ± 0.8 medications at the end of the follow-up, indicating no statistically significant differences between the groups. At 12 months, the complete surgical success rate was 68.6% (24/35 eyes) in the PMS group and 52.2% (12/23 eyes) in the PMS + Phaco group (p = 0.19). Surgical failure occurred in five (14.3%) eyes in group 1 and five (21.7%) eyes in group 2. Considering the safety, the most frequent adverse events in the PMS and PMS + Phaco groups were contact of the implant with the endothelium (8.6% vs. 8.7%), fibrosis of the filtration bleb (8.6% vs. 8.7%), and bleb leakage (2.8% vs. 8.7%); (with no differences between the groups).

In a multicenter study conducted by Rabiolo et al. [30] involving an American population, the outcomes of 220 surgeries with PMS implantation were analyzed. The study included 146 standalone procedures and 73 combined with phacoemulsification, with a follow-up of 8.4 months; individuals with OAG, PEXG, PG, juvenile glaucoma, and ACG were included. Four different criteria for surgical success were established: (1) IOP ≤ 21 mmHg with a drop of ≥ 20% as compared to pre-surgery values; (2) IOP ≤ 18 mmHg with a decline of ≥ 20%; (3) IOP ≤ 15 mmHg with a drop of ≥ 25%; and (4) IOP ≤ 12 mmHg with a reduction of ≥ 30%. Qualified success was classified when these criteria were fulfilled with or without IOP-lowering eye drops, while total success was defined as fulfilling these criteria without any IOP-lowering eye drops. Surgical failure was classified as: IOP not meeting the abovementioned criteria during two consecutive follow-up visits, need for an further glaucoma surgery, removal or revision of the PMS, loss of vision, need for oral acetazolamide, or the occurrence of serious complications such as endophthalmitis or malignant glaucoma. MMC application protocols differ between the centers and it ranged from 0.2 mg/ml to 0.4 mg/ml with an application time of 2 or 3 min. The mean IOP before surgery in the entire study group was 23 mmHg (range 20–28 mmHg), which decreased to 12 mmHg (range 9.8–16 mmHg) by the end of follow-up. Medication burden decreased from 3 to 0 by the end of follow-up. The study found no differences in postoperative success rates for PMS + Phaco and standalone PMS (p ≥ 0.9). The authors identified the following risk factors for surgical failure: PEXG, ACG, inflammatory glaucoma, lower concentration of mitomycin C (MMC) during the procedure, and a higher amount of IOP-lowering eye drops used before surgery.

In a prospective study conducted by Fili et al. [28] with a 12-month observation period, the outcomes of PMS + Phaco (15 eyes, group A) were compared to those of PMS alone (15 eyes, group B). Topical MMC was applied for 2 min in a concentration of 0.2 mg/ml. The average IOP decreased from 23.47 ± 8.99 mmHg before the procedure to 11.62 ± 1.6 mmHg at the end of the follow-up period in group A and from 26.9 ± 8.68 mmHg to 13.8 ± 3.6 mmHg in group B (no statistical significance). The amount of IOP-lowering eye drops decreased to 0 at the end of the follow-up period in group A and 0.6 ± 0.8 in group B in comparison to 3.13 ± 1.02 in group A (p < 0.001) and 2.4 ± 1.45 in group B (p = 0.004) before the procedure. An additional procedure with transscleral cyclophotocoagulation and the MicroPulse laser was required in one eye in group A, and one bleb revision was also required in group B at 4 weeks after the procedure. A higher success rate was achieved in PMS + Phaco as compared to the PMS alone (group A: 80% vs. group B: 60%, p = 0.022).

A single-center, retrospective study conducted with a Spanish population by Barbera et al. [31] for a 9-month follow-up period examined 64 eyes. In the PMS alone group (51 eyes), the IOP dropped from 22.5 ± 0.9 mmHg before the procedure to 12.8 ± 0.4 mmHg at the end of the follow-up period, whereas in the PMS + Phaco group (n = 13), the IOP declined from 20.1 ± 1.3 mmHg to 12.5 ± 0.6 mmHg (no statistical significance between the groups). The MMC application protocol was 0.2 mg/ml MMC for 2 min. Across the entire study population, the average IOP significantly decreased from 22.03 ± 0.7 mmHg to 12.7 ± 0.4 mmHg at the end of follow-up, p < 0.0001 (on average: 11 ± 1.4 months). The number of antiglaucoma medications dropped from 2.7 ± 0.7 to 0.2 ± 0.5 (p < 0.0001) without statistical differences between the groups (PMS alone, 0.2 ± 0.08; PMS + Phaco, 0.1 ± 0.1; p = 0.2). Complete surgical success was achieved in 70.3% of the patients, whereas 12.5% had qualified success at the end of follow-up. The most common complications were hypotony (7.8%) and anterior chamber shallowing (1.6%). Regarding additional procedures, 1.6% of eyes required needling and 15.6% filtering bleb revision.

A single-center, prospective, non-randomized study by Batlle et al. [32] followed 14 Dominican patients during a 3-year follow-up period, and assessed 23 eyes that received PMS alone and nine eyes that received PMS implantation combined with cataract extraction. The qualified success rates (IOP ≤ 14 mmHg and IOP reduction ≥ 20%) were achieved in 100% of patients at 1 year (n = 23), 91% at 2 years (n = 22), and 95% at the end of follow-up (n = 22). MMC application protocol was 0.4 mg/ml MMC for 3 min. The mean IOP declined from 23.8 ± 5.3 mmHg to 10.7 ± 2.8 mmHg after 1 year, 11.9 ± 3.7 mmHg after 2 years, and 10.7 ± 3.5 mmHg after 3 years, and the average amount of antiglaucoma eye drops was reduced from 2.4 ± 0.9 to 0.3 ± 0.8 after 1 year, 0.4 ± 1.0 after 2 years, and 0.7 ± 1.1 after 3 years of observation. In the PMS + Phaco group, the IOP was 10.2 mmHg at the end of the observation period as compared to 11.2 mmHg in the PMS solo group (no statistical significance). The most frequent adverse events were hypotony (13%, 3/23) and choroidal detachment (8.7%, 2/23), all of which resolved spontaneously without surgical intervention. Remarkably, there were no instances of wound leakage, infections, corneal complications, persistent corneal edema, or other long-term complications.

A single-center, retrospective study by Schlenker et al. [33] that focused on an American population involved 436 eyes that underwent antiglaucoma surgery. Among these, 86 (20%) underwent PMS + Phaco, 127 (29%) had a history of refractory glaucoma with previously failed surgical interventions, and 234 (51%) underwent PMS alone without prior surgical interventions. The average pre-surgery IOP was 20 mmHg (range 17–21 mmHg) in the PMS alone group, 23 mmHg (range 20–29 mmHg) in the PMS + Phaco group, and 21 mmHg (range 18–28 mmHg) in the refractory glaucoma group. The application time of MMC was 2 min with different concentrations: 0.2 , 0.4 , and 0.5 mg/ml. After 1 year of observation, the IOP was 10, 14, and 14 mmHg, respectively, in the PMS solo, PMS + Phaco, and refractory glaucoma groups. Remarkably, the medication count plummeted from 4 to 0 by the end of follow-up across all groups. Notably, there were no statistical differences in IOP levels or the number of antiglaucoma eye drops between the standalone and the combined procedure at any time during the follow-up. The medication burden was higher in the refractory glaucoma group at 9 and 12 months of observation as compared to the other groups. Total surgical success (defined as achieving an IOP of 6–17 mmHg without medication) was 64.0% for combined procedures, 58.1% for refractory glaucoma, and 74.8% for solo procedures without prior surgical interventions; the qualified success rates (defined as achieving an IOP of 6–17 mmHg with medications) were 90.7, 84.7, and 92.4%, respectively. At the end of the observation period, 67% of patients were not using any IOP-lowering medications. Significant failure risk factors included undergoing PMS + Phaco in the refractory glaucoma group, lower doses of MMC (< 0.4 mg/ml), having treatment-resistant glaucoma, undergoing combined procedures and the cumulative number of antiglaucoma medications. Adverse events (hypotony, hypotony maculopathy, choroidal detachment, shallow anterior chamber), occurred in 31% of eyes, more frequently in those that received the MMC at a dose of ≥ 0.4 mg/ml and in the refractory glaucoma group. Needling was performed in 12% of eyes, more frequently in treatment-resistant eyes (23%) and combined procedures (13%) as compared to solo procedures (7%; P < 0.001). Revisions and reoperations were performed in 4% and 1.4% of eyes, respectively (Tables 1, 2, 3).

Table 1.

Performance metrics of standalone Preserflo MicroShunt surgeries

Author (reference number)	Follow-up duration (months)	Sample size (N)	Preoperative IOP (mmHg)	Postoperative IOP (mmHg)	Complete success rate
Martinez-de-la-Casa et al. [27]	12	35	21.3 ± 3.2	14.4 ± 3.4	68.6%
Rabiolo et al. [28]	8.4	146	23	12	p > 0.9
Fili et al. [26]	12	15	23.47 ± 8.99	11.62 ± 1.6	80%
Ibarz Barberá et al. [29]	9	51	22.5 ± 0.9	12.8 ± 0.4	70.3%
Batlle et al. [30]	36	14	23.8 ± 5.3	11.2	95%
Schlenker et al. [31]		234	20	10	74.8%

IOP intraocular pressure, mean ± standard deviation

Table 2.

Performance metrics of Preserflo MicroShunt surgeries combined with phacoemulsification (Preserflo MicroShunt + phacoemulsification)

Author (reference number)	Follow-up duration	Sample size (N)	Preoperative IOP (mmHg)	Postoperative IOP (mmHg)	Complete success rate
Martinez-de-la-Casa et al. [27]	12 m	23	21.7 ± 3.5	14.9 ± 3.6	52.2%
Rabiolo et al. [28]	8.4 m	73	23	12	p > 0.9
Fili et al. [26]	12 m	15	26.9 ± 8.68	13.8 ± 3.6	60%
Ibarz Barberá et al. [29]	9 m	13	20.1 ± 1.3	12.7 ± 0.4	70.3%
Batlle et al. [30]	36 m	9	23.8 ± 5.3	10.2	95%
Schlenker et al. [31]		86	23	14	64%

IOP intraocular pressure, mean ± standard deviation

Table 3.

Medication burden in the PMS alone and PMS + Phaco groups

Author (reference number)	Cumulative number of medications in the PMS group (preoperative/postoperative)	Cumulative number of medications in the PMS + Phaco group (preoperative/postoperative)
Martinez-de-la-Casa et al. [27]	2.4 ± 0.9/0.3 ± 0.8	2.4 ± 0.9/0.3 ± 0.8
Rabiolo et al. [28]	3/0	3/0
Fili et al.[26]	3.13 ± 1.02/0	2.4 ± 1.45/0.6 ± 0.8
Ibarz Barberá et al. [29]	2.7 ± 0.7/0.2 ± 0.08	2.7 ± 0.7/0.1 ± 0.1
Batlle et al. [30]	2.4 ± 0.9/0.7 ± 1.1	2.4 ± 0.9/0.7 ± 1.1
Schlenker et al. [31]	4/0	4/0

Phaco phacoemulsification, PMS Preserflo MicroShunts

A prospective, single-center study conducted over a 2-year period on a Dutch cohort involved the examination of 72 eyes that had undergone Preserflo implant surgery [34]. Of these, 59 eyes underwent a standalone procedure, while 13 eyes underwent a combined procedure involving cataract extraction. No significant differences were observed in IOP or the number of IOP-lowering medications between the two groups. Overall, there was a significant reduction in mean IOP from 21.72 ± 8.35 mmHg to 15.92 ± 8.54 mmHg in both groups, demonstrating a reduction of 23.6% vs. 38.2% in standalone and combined procedure respectively; p = 0.234. Furthermore, a reduction in medication was observed, from 3.40 to 0.93 (p < 0.001, representing a 72.6% decrease), following a year of follow-up. Additionally, 19.4% of eyes required further surgery, with the majority (71.4%) occurring within the initial 6 months. The most prevalent complication was hypotony, occurring in 2–39% of cases.

The reduction of IOP following cataract surgery in patients with glaucoma and a comparison of this effect with IOP reduction following a combined cataract and trabeculectomy procedure with MMC demonstrate significant differences. The reduction in IOP following phacoemulsification in patients with narrow angles and angle-closure glaucoma was dependent on the baseline IOP, anterior chamber depth and angle width. It accounted to 5.3 mmHg in patients with a baseline IOP above 20 mmHg, and 4.6 mmHg in the group with IOP in the range of 18 to 20 mmHg, 2.5 mmHg in the group with IOP of 15 to 18 mmHg, and 1.4 mmHg in the group with IOP of 15 mmHg or less. The mean follow-up period was 3.0 ± 2.3 years [35].

In a clinical trial conducted by Ferguson et al. it was observed that in patients with OAG, the average IOP prior to surgery was 19.25 ± 6.97 mmHg, and after 12 months, it decreased to 14.38 ± 3.63 mmHg [36].

In another study, it was found that phacoemulsification in cases of OAG results in a limited reduction of pressure. This suggests that additional surgical procedures, such as trabeculectomy, may be necessary for more favorable outcomes [37].

Conversely, the combined approach, comprising cataract extraction in conjunction with trabeculectomy and the administration of MMC, yielded a more substantial and sustained reduction in IOP compared to cataract surgery alone. A review indicated that the use of MMC during trabeculectomy provides an additional reduction in IOP of 2–4 mmHg compared to cataract surgery alone [38].

Cataract surgery alone can lead to a moderate reduction in IOP in patients with glaucoma; however, the combined cataract and trabeculectomy procedure with MMC is more effective in reducing IOP, with a more significant and sustained reduction in IOP.

Discussion

The findings from this literature review indicated that both the PMS alone and PMS combined with phacoemulsification were effective and relatively safe in lowering the IOP and decreasing burden of antiglaucoma medications in patients with OAG over a 12-month follow-up. Although the analyzed data did not confirm significant differences in IOP reduction or the decrease in hypotensive medications between PMS as standalone procedure and PMS in combination with phacoemulsification groups, two studies [23, 30] have recognized combined surgery as a risk factor for higher failure rates compared to the solo surgery. Furthermore, combined procedure has also been associated with a greater need for additional postoperative procedures [33]. The strongest evidence are from prospective randomized studies; however, conducting such research to evaluate combined versus solo procedures poses practical challenges and complicates the control of confounding factors. The question remains: what is the best approach for treating patients with cataract and concomitant glaucoma—performing phacoemulsification followed by PMS implantation, performing PMS first followed by phacoemulsification, or opting for a combined procedure?

The question of the optimal sequence of surgical interventions—remains unresolved in the literature. Each sequence has the potential to offer benefits and raise considerations. The sequence of procedures may be modified to commence with phacoemulsification followed by PMS. This approach may facilitate anterior chamber access and subsequent PMS implantation. Following cataract surgery, some patients experience a reduction in IOP, which may potentially reduce the necessity for more invasive glaucoma surgery. Nevertheless, postponing glaucoma surgery may extend the duration of elevated IOP, which could entail risks for patients with advanced glaucoma. A potential benefit of starting with PMS is that it may help to achieve better IOP control at an earlier stage, thereby stabilizing the eye before performing cataract surgery. This approach may be beneficial for patients with uncontrolled IOP, where rapid pressure reduction is crucial. A potential disadvantage of performing PMS implantation prior to cataract surgery is the possibility of complications during subsequent Phaco procedures due to anatomical alterations in the eye following glaucoma surgery. A combined intervention, comprising both PMS and Phaco, has the advantage of addressing both cataracts and IOP management in a single surgical procedure. This approach may be more convenient for the patient and may also reduce the risks and costs associated with multiple surgeries. A potential disadvantage of this combined approach is that it may entail greater complexity and an elevated risk of surgical complications. Furthermore, careful coordination is required to achieve a balance between the goals of cataract and glaucoma management. Currently, there is no definitive evidence to suggest that one approach is superior across all cases. The choice of approach often depends on individual patient features, such as the glaucoma stage, the degree of IOP elevation, and the presence of cataract affecting vision. Many studies advocate for a personalised approach based on patient-specific conditions.

The reason for the higher failure rates associated with combined procedures may have been due to a persistent low-grade inflammatory response after cataract removal, lasting at least 3–6 months [39]. This response could be related to the effects of ultrasound and subsequent release of lens epithelial cells and proteins circulating in the aqueous humor, which could disrupt the blood–aqueous barrier [40]. Additionally, studies have shown that the levels of proinflammatory cytokines in the aqueous humor samples can remain elevated for up to 17 months after phacoemulsification, particularly those cytokines participating in wound healing processes [41].

The most effective postoperative therapeutic regimens are usually individualized, based on the specific needs of the patient and the surgical context. For uncomplicated cataract surgery, non-steroidal anti-inflammatory drugs (NSAIDs) such as bromfenac have been shown to be an effective treatment option [42], particularly when combined with a short-term corticosteroid regimen. Combined procedures require a more intensive approach, often requiring long-term use of corticosteroids in combination with NSAIDs to adequately control inflammation and decrease the risk of side effects such as cystoid macular edema [43]. The evidence base for the standard use of systemic therapy in the postoperative period after cataract surgery remains limited. Most studies suggest that systemic corticosteroids are limited to patients with postoperative complications or pre-existing inflammatory conditions. Furthermore, if they are administered, they are usually tapered to minimize the risk of adverse effects [44].

Conversely, glaucoma surgery itself triggers a cascade of cytokine production and healing processes that persist for up to 4 weeks. Interestingly, recent studies have demonstrated that levels of interleukin-6 and monocyte chemotactic protein-1 are somewhat lower in the aqueous humor of rabbits undergoing the PMS implantation as compared to those undergoing trabeculectomy [45]. A recent consensus has emerged regarding the optimal application of PMS in glaucoma surgery [46, 47]. Thirteen European experts participated in a Delphi panel to formulate recommendations, discussing various aspects of glaucoma surgery, including combining PMS implantation with phacoemulsification. This expert panel has agreed that in the case of combined procedure, it is possible to achieve comparable results to solo procedures; however, a careful consideration of the surgical approach, depending on individual patient conditions. Although preliminary data suggest the effectiveness and safety of the combined PMS and Phaco procedure, further research with longer follow-up is needed [25].

Postoperative Observations on Other Implants

The XEN® Gel Stent is a well-known implant widely applied in glaucoma surgery. When comparing the outcomes of the PMS literature review with studies on XEN 45, it becomes evident that the IOP lowering effect of PMS is similar to XEN as well as the reduction in antiglaucoma medications burden (16, 48–50). Poelman et al. [51] did not observe any statistical differences between the use of XEN alone or combined with cataract extraction; the reductions in IOP reported were 32.6% and 20.9%, respectively (p = 0.054), and a similar drop of IOP-lowering medications (66.9% and 63.8%, respectively, p = 0.638).

Likewise, a meta-analysis assessing the results of the XEN implant alone versus XEN + Phaco did not reveal any significant differences in IOP reduction between the two strategies during the long-term follow-up (12 and 18 months). However, in the immediate postoperative period (up to 1 month), the XEN alone demonstrated greater effectiveness [51, 54, 55]. Given these findings, it follows the recommendation by Shields et al. [52], and subsequently by Brown et al. [53], that for patients with stable IOP, cataract surgery should be the first-choice surgical procedure, whereas for patients with borderline IOP, combined procedures are suggested. In cases where the IOP is high, sequential procedures are recommended.

Direct comparison of the study results presents challenges due to differences among authors regarding inclusion criteria, types of glaucoma eligible for surgery, patient demographics, varying protocol of MMC application (concentration 0.2 mg/ml to 0.5 mg/ml with duration time 2 or 3 min), and the definitions of surgical success. Despite these limitations, whether used as a standalone or combined procedure, PMS has proven effective in treating patients with OAG. Further studies are needed to explore possible risk factors leading to surgical failure as well as to investigate the optimal concentration and time of application of the MMC on the results of surgery.

Conclusion

In summary, the choice of procedure should be guided by the desired IOP reduction. Clinicians should consider both standalone PMS and PMS combined with phacoemulsification, depending on the patient’s clinical condition. The related literature lacks extensive comparative data on the long-term safety and efficacy of standalone PMS implantation versus combined PMS and cataract surgery. For combined procedures, it may be necessary to tailor the surgical approach, potentially utilizing higher doses of MMC, extending application times, and providing more intensive postoperative care, which includes more frequent follow-up visits, additional procedures (such as needling and anti-metabolite injections), and prolonged use of topical steroids. Even though there is encouraging initial data indicating the efficacy and safety of the combined PMS with phacoemulsification research with longer follow-up are necessary to assess its effectiveness and to recognize aspects that may improve clinical outcomes, such as restraining post-surgery inflammation.

Author Contributions

The authors confirm their contributions to the manuscript as follows: study conception and design: Joanna Konopińska; data collection: Małgorzata Chilmonczyk and Emil Saeed; analysis and interpretation of results: Małgorzata Chilmonczyk and Kinga Gołaszewska; draft manuscript preparation: Małgorzata Chilmonczyk. All authors reviewed the results and approved the final version of the manuscript.

Funding

No funding or sponsorship was received for this study or publication of this article. The Rapid Service Fee was funded by the Medical University of Bialystok.

Data Availability

Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study.

Declarations

Conflict of Interest

The authors, Małgorzata Chilmonczyk, Kinga Gołaszewska, Emil Saeed, and Joanna Konopińska, declare no conflicts of interest.

Ethical Approval

Ethics approval was not required for this study, as it did not involve human participants or animals and was based on previous research conducted by other authors.