PreserFlo MicroShunt vs. trabeculectomy in patients with uncontrolled glaucoma
verfasst von:
Lukas Höflechner, Thomas Falb, Lena Haiden, Andreas Guttmann, Wolfgang List, Astrid Heidinger, Lukas Keintzel, Fabian Wallisch, Manuel Großpoetzl, Regina Riedl, Ewald Lindner
Glaucoma is one of the leading causes of irreversible blindness, posing a growing global challenge. Trabeculectomy (TE) remains the gold standard in glaucoma surgery, while alternative procedures such as the PreserFlo MicroShunt (PF; Santen Inc., Osaka, Japan) have a lower risk profile and offer comparable intraocular pressure (IOP) reduction.
Methods
This retrospective study analyzed 204 eyes of patients undergoing either trabeculectomy or PreserFlo implantation. The primary endpoint was the change in IOP, while secondary endpoints included postoperative complications, needling rates, and revision procedures. Data were collected over 1 year for statistical analysis.
Results
Both procedures resulted in significant IOP reduction and stabilization of the peripapillary retinal nerve fiber layer (RNFL). Postoperative hypotony was more common after trabeculectomy at 1 week (TE: 22.2% vs. PF: 16.3%), while needling interventions were more frequent with PreserFlo (PF: 52.5% vs. TE: 35.9%). No significant difference in long-term IOP control was observed.
Conclusion
Both trabeculectomy and the PreserFlo MicroShunt are effective for IOP control. PreserFlo has a lower risk of postoperative complications but requires more frequent additional interventions. These findings highlight the importance of individualized treatment decisions based on patient-specific factors.
Hinweise
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Introduction
Glaucoma is one of the most common causes of irreversible blindness worldwide and represents a significant medical and socioeconomic challenge. Its global prevalence is steadily increasing, affecting approximately 76 million people in 2020, of whom, 3.6 million were blind [1, 2]. Currently, the only proven therapy for glaucoma is to lower intraocular pressure (IOP), which can be achieved using medications, laser-based procedures, or surgical interventions such as filtering glaucoma surgery [3]. Filtering glaucoma surgery is a fundamental treatment option, especially for advanced and progressive glaucoma. In addition to trabeculectomy—considered the gold standard—alternative procedures have been developed in recent years, including the PreserFlo MicroShunt (Santen Inc., Osaka, Japan). Recent studies have shown that the PreserFlo MicroShunt offers a comparable IOP reduction, with a lower risk profile and simpler surgical technique [3‐8].
The PreserFlo MicroShunt is a small, flexible tube designed to create a controlled drainage pathway from the anterior chamber to the subconjunctival space. Made of a biocompatible polymer, it is implanted via an ab externo approach and forms a filtering bleb that allows for continuous aqueous humor outflow. Current study data indicate a significantly lower risk of hypotony with the PreserFlo MicroShunt compared to trabeculectomy [5‐8].
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In this retrospective study, we compared postoperative outcomes after PreserFlo implantation and trabeculectomy during the first postoperative year and discuss the current literature.
Methods
This retrospective analysis was based on patient data from the medical records of the University Eye Clinic in Graz from January 1, 2018, to December 31, 2021. Patients ≥ 18 years of age who underwent either trabeculectomy or PreserFlo MicroShunt implantation for IOP reduction were included. Patients with fewer than 6 months of follow-up data were excluded to ensure a valid long-term assessment of therapeutic outcomes.
Preoperative preparation
The IOP-lowering therapy was continued preoperatively. Additionally, patients received MONODEX eye drops (Thea Pharma GmbH, Berlin, Germany) five times daily to optimize conjunctival conditions and reduce inflammatory reactions.
For PreserFlo MicroShunt implantation, an intraconjunctival injection of 0.02 mL mitomycin C (MMC; 0.2 mg/mL) was administered to reduce fibroblastic activity, carefully sparing the limbus. A fornix-based conjunctival and Tenon flap was then prepared in the superonasal quadrant, and the sclera was marked 3 mm from the limbus. After cauterization for hemostasis, a small scleral incision was made with a lancet. A pre-bent 25-gauge needle was used to create a tunnel into the anterior chamber. Intracameral cefuroxime was injected for infection prophylaxis. The PreserFlo MicroShunt was then carefully inserted through the tunnel into the anterior chamber, with the fin anchored securely in the scleral pocket to ensure correct positioning and optimal aqueous outflow. The sufficiency of outflow at the distal end of the shunt was checked by applying gentle pressure with a cotton swab. The Tenon capsule and conjunctiva were closed with polyglycolic acid (PGA) sutures. Finally, the eye was irrigated, and an eye ointment dressing was applied to promote postoperative protection and wound healing.
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For trabeculectomy, an intraconjunctival injection of 0.02 mL MMC (0.2 mg/mL) was also administered before preparing the fornix-based conjunctival/Tenon flap at the 12-o’clock position. After cauterization, a mid-depth scleral flap was created. The trabeculectomy was performed using a scalpel. The anterior chamber was stabilized with viscoelastic fluid, and a peripheral iridotomy was performed with iris forceps and scissors. The scleral flap was closed with two to three single sutures. Tenon’s capsule and conjunctiva were then sutured with two PGA stitches.
Postoperative care
Patients received preservative-free topical steroids (MONODEX eye drops, Thea Pharma) five times daily for 4 weeks, followed by gradual tapering. Additionally, preservative-free topical antibiotics (Ofloxavision, Omnivision GmbH, Vienna, Austria) were given five times daily for 1 week.
Needling and suture lysis
In cases of postoperative pressure increase with signs of bleb fibrosis, needling was performed at the slit lamp with a 27-gauge needle and 0.1 mL (50 mg/mL) 5‑fluorouracil (5-FU). Suture lysis was performed using an argon laser and a Hoskins lens.
To reduce potential bias and improve comparability, patients were matched by age and sex. The primary endpoint was IOP, measured at predefined intervals: preoperatively and postoperatively at 1 week, 1 month, 3 months, 6 months, and 1 year. The IOP was measured using Goldmann applanation tonometry. Secondary endpoints included best-corrected visual acuity (BCVA), the number of IOP-lowering eye drops needed to achieve target pressure, the incidence of postoperative hypotony, as well as the frequency of needling procedures and re-operations required to maintain filtration. The peripapillary retinal nerve fiber layer (RNFL) was measured using an optical coherence tomography (OCT) system (SPECTRALIS Heidelberg Engineering, Heidelberg, Germany), and the visual field was assessed with the Octopus perimeter (Haag-Streit) using the Dynamic program. Hypotony was defined as an IOP below 8 mm Hg.
Statistical analysis
Continuous variables are presented as mean and standard deviation, and categorical variables as frequencies and percentages. Baseline characteristics between groups (PreserFlo, trabeculectomy) were compared using generalized estimating equations (GEE) for repeated measures (both eyes included), with a logit link and a working-independence correlation structure.
Continuous endpoints over time (e.g., IOP, number of medications) were compared between groups using linear mixed models. A banded main diagonal covariance structure (UN [1]) was employed for repeated measurements over time, and a random intercept for each patient was included.
A value of p < 0.05 was considered statistically significant. Statistical analyses were performed with SAS 9.4 (SAS Institute, Cary, NC, USA).
The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the local ethics committee (EK No. 34-269ex 21/22).
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Results
A total of 204 eyes (103 in the trabeculectomy cohort and 101 in the PreserFlo cohort) from 176 patients were included. Baseline data for both groups are shown in Table 1. The average age was 74.8 years (± 12.0) in the trabeculectomy cohort and 74.4 years (± 11.2) in the PreserFlo cohort (p = 0.796). The gender distribution was comparable, with 53 (51.5%) male patients in the trabeculectomy cohort and 49 (48.5%) in the PreserFlo cohort (p = 0.686).
The mean preoperative IOP in the trabeculectomy group was 29.5 mm Hg (± 8.8) with 2.6 (± 1.1) IOP-lowering medications. In the PreserFlo cohort, the preoperative IOP was 25.4 mm Hg (± 8.4) with 2.1 (± 1.2) medications (both p < 0.05).
Patients had moderate to advanced glaucoma with an average MD and sLV of 13.3 (± 7.1) and 5.9 (± 2.2) in the trabeculectomy cohort and 10.7 (± 6.2) and 5.9 (± 2.3) before PreserFlo implantation. A total of 30 (29.4%) patients in the trabeculectomy cohort and 29 (28.7%) in the PreserFlo cohort had pseudophakia prior to filtering surgery (p = 0.802). Laser trabeculoplasty had been performed in 16 (15.5%) before trabeculectomy and 18 (17.8%) before PreserFlo implantation(p = 0.680). In total, 35 (34%) patients in the trabeculectomy cohort and 17 (16.8%) patients in the PreserFlo had undergone a previous glaucoma surgery (p = <0.05).
No significant differences were found regarding other previous treatments: Anti-VEGF therapy was used in six (5.8%) trabeculectomy patients and eight (7.9%) PreserFlo patients (p = 0.560), and vitrectomies had been performed on five (4.9%) trabeculectomy patients and six (5.9%) PreserFlo patients (p = 0.914). Overall, 59 (57.3%) patients in the trabeculectomy cohort and 56 (55.4%) in the PreserFlo cohort had primary open-angle glaucoma. The second most common diagnosis was pseudoexfoliation glaucoma, with 31 (30.1%) in the trabeculectomy cohort and 28 (27.7%) in the PreserFlo cohort.
Table 1
Baseline characteristics
Characteristic
Trabeculectomy
PreserFlo
p
Intraocular pressure (mm Hg, mean ± SD)
29.0 ± 8.8
24.0 ± 8.4
< 0.05
Glaucoma medications, n (mean ± SD)
2.6 ± 1.1
2.1 ± 1.2
< 0.05
Primary open-angle glaucoma (n, %)
59 (57.3%)
56 (55.4%)
–
Pseudoexfoliation glaucoma (n, %)
31 (30.1%)
28 (27.7%)
–
Primary angle-closure glaucoma (n, %)
8 (7.8%)
3 (3.0%)
–
Ocular hypertension (n, %)
2 (1.9%)
6 (5.9%)
–
Inflammatory and neovascular secondary glaucoma
1 (1.0%)
5 (5.0%)
–
Normal-tension glaucoma (n, %)
1 (1.0%)
1 (1.0%)
–
Pigmentary glaucoma (n, %)
1 (1.0%)
2 (2.0%)
–
Mean deviation (mean ± SD)
13.3 ± 7.1
10.7 ± 6.2
–
Standard loss of variation (mean ± SD)
5.9 ± 2.2
5.9 ± 2.3
–
OCT RNFL global (mean ± SD)
59.8 ± 19.8
68.8 ± 20.5
–
Visual acuity logMAR (mean ± SD)
0.3 ± 0.3
0.3 ± 0.3
–
Prior glaucoma surgery (n, %)
35 (34.0%)
17 (16.8%)
< 0.05
Age (years, mean ± SD)
74.8 ± 12.0
74.4 ± 11.2
0.796
Male (n, %)
53 (51.5%)
49 (48.5%)
0.686
Pseudophakic status (n, %)
30 (29.4%)
29 (28.7%)
0.802
Anti-VEGF therapy (n, %)
6 (5.8%)
8 (7.9%)
0.560
Laser trabeculoplasty (n, %)
16 (15.5%)
18 (17.8%)
0.680
Vitrectomy (n, %)
5 (4.9%)
6 (5.9%)
0.914
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Figure 1 shows the IOP course from baseline to 12 months postoperatively. After 12 months, the IOP decreased in both groups: from 29.5 mm Hg (± 8.8) to 15.1 mm Hg (± 5.4) after trabeculectomy and from 25.4 mm Hg (± 8.4) to 16.0 mm Hg (± 6.8) after PreserFlo MicroShunt implantation. The average number of necessary IOP-lowering eye drops to reach target pressure decreased from 2.6 (± 1.1) to 1.0 (± 1.5) after trabeculectomy and from 2.1 (± 1.2) to 0.7 (± 1.2) after PreserFlo implantation. There was no statistically significant difference between groups in pressure reduction or number of IOP-lowering drops at 12 months (p = 0.372; p = 0.249).
Fig. 1
Intraocular pressure (IOP) from baseline to 12 months postoperatively. PF PreserFlo, TE trabeculectomy
Within the first postoperative year, surgical revisions were required in eight (7.8%) cases after trabeculectomy and in ten (9.9%) cases after PreserFlo implantation. As part of the revision procedure, cataract surgery was also performed on three patients in the PreserFlo cohort (2.9%) and one patient in the trabeculectomy cohort (0.9%). Postoperative hypotony occurred in the first week in 20 (22.6%) patients after trabeculectomy and in 13 (16.3%) patients after PreserFlo implantation. After 1 month, hypotony persisted in seven (8.4%) cases in the trabeculectomy cohort and in five (5.1%) in the PreserFlo group.
In the trabeculectomy group, a temporary reduction in mean BCVA (logMAR) from 0.3 (± 0.3) to 0.5 (± 0.3) was observed within the first week and 0.4 (± 0.3) within the first month postoperatively. After 1 year, a BCVA of 0.4 (± 0.4) logMAR was noted. In the PreserFlo group, BCVA remained stable at logMAR 0.3 (± 0.3) after 1 week and 1 month; after 12 months, a BCVA of 0.2 (± 0.3) was observed.
The incidence of needling/suture lysis procedures was 37 (35.9%) after trabeculectomy and 53 (52.5%) after PreserFlo MicroShunt. The BCVA, peripapillary RNFL, as well as MD and sLV remained stable in both groups during the first year.
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Discussion
Filtering glaucoma surgery is an essential component of treating advanced and progressive glaucoma. The ongoing development of new implants offers opportunities for individualized and risk-adapted therapy. Comparative studies between the gold standard (trabeculectomy) and newer bleb-based glaucoma operations are crucial for guiding patient-centered treatment strategies in clinical practice.
In this study, both cohorts achieved a reduction in IOP and a decrease in the number of IOP-lowering medications. However, particularly after 1 week and after 1 month, a higher rate of hypotony was observed following trabeculectomy, suggesting a higher risk profile. Marked differences also emerged in the number of patients who required at least one additional intervention, such as needling or suture lysis. Such additional procedures were more frequently necessary with the PreserFlo MicroShunt, although this did not lead to an increased incidence of surgical revisions within the first year in this study.
In the trabeculectomy cohort, a decrease in visual acuity was observed, especially in the early postoperative phase. Over the course of the first year, there was partial recovery, but average vision remained below preoperative levels. In the PreserFlo cohort, vision remained stable in the first month. The measured visual improvement during the first year is primarily attributable to additional cataract surgeries performed in this cohort during revisions. Neither surgical intervention led to measurable glaucoma progression over the observation period, as assessed by peripapillary RNFL thickness and MD and sLV on perimetry. These findings suggest that both methods provide comparable long-term stabilization of glaucoma.
The results align with observations by Gubser et al. [6], who also reported an initial decline in vision in the trabeculectomy group followed by moderate recovery during the first year. Jamke et al. [7] demonstrated that visual stability was better maintained in the PreserFlo group, supporting our study’s findings. The meta-analysis “PRESERFLO™ MicroShunt versus Trabeculectomy: An Updated Meta-Analysis and Systematic Review” [9] confirms these trends, highlighting that the PreserFlo cohort generally experiences less postoperative visual deterioration than the trabeculectomy group, particularly in the initial months after surgery.
In a study by Pilunat et al. that analyzed IOP reduction and reintervention rates in 26 eyes after trabeculectomy and 26 eyes after PreserFlo MicroShunt implantation, no significant difference in IOP reduction could be demonstrated between trabeculectomy and PreserFlo after 6 months. The reintervention rate was low in both groups but, contrary to the present study’s results, was significantly higher after trabeculectomy than after PreserFlo [8].
A prospective study by Gubser et al. compared the efficiency and safety of PreserFlo MicroShunt versus trabeculectomy. With comparable baseline IOP values, both groups showed significant IOP reduction after 2 years: trabeculectomy from 24.09 ± 1.15 mm Hg to 11.37 ± 1.13 mm Hg and PreserFlo from 21.67 ± 0.77 mm Hg to 15.50 ± 1.54 mm Hg (based on the average of six measurements). Postoperative complications such as hypotony, need for revisions, and bleb leaks occurred less frequently after PreserFlo implantation [6].
In the study by Beckers et al., the safety and effectiveness of the MicroShunt in patients with primary open-angle glaucoma (POAG) were investigated in 81 patients. Results showed that the mean IOP and the reduction in the number of eye drops required were statistically significant and maintained throughout the entire follow-up period. The mean IOP decreased from 21.7 mm Hg preoperatively (on an average of 2.1 medications) to 14.1 mm Hg using an average of 0.5 medications after 2 years [5].
The prospective study by Jamke et al. found IOP reductions from 16.2 (Q1, Q3; 13.8–21.5) to 10.5 (8.9–13.5) in the PreserFlo group and from 17.6 (15.6–24.0) to 11.1 (9.5–12.3) in the trabeculectomy group, each without additional topical therapy.
One possible factor influencing postoperative outcomes is the use of MMC. In the cited studies [6‐8], MMC (0.2–0.4 mg/mL for 2–3 min) was applied using corneal sponges. Reinterventions, such as needling for inadequate wound healing, were observed much less frequently than in our study. These findings suggest that controlled and targeted MMC application via a sponge may offer better dosing and distribution control, thereby increasing efficacy and minimizing potential side effects.
Another factor that could influence postoperative outcomes is previous interventions. In the study by Jamie et al., patients with previous surgeries—other than cataract surgeries—were excluded, whereas Gubser et al. included patients who had undergone previous operations.
Limitations
Several limitations of this study’s design must be acknowledged. As a retrospective study, it is susceptible to selection and information bias. In the trabeculectomy-treated group, the proportion of previously treated patients was higher than in the comparison group, possibly confounding the results due to preexisting conjunctival scarring. Sensitivity analyses adjusted for pretreatment (Yes/No) yielded similar results. Another limiting factor concerns IOP measurement, which was performed once per patient at routine follow-ups due to the retrospective design. To account for diurnal variations, multiple measurements over 24 h would be preferable.
Additionally, MMC was administered intraconjunctivally in both cohorts. Sponge application might allow for more controlled MMC delivery. The follow-up period of 1 year may be too short to draw conclusions about long-term results. Longer follow-up would be desirable to assess the sustainability of these surgical procedures. A larger sample size could also improve the robustness of the results.
Conclusion
This study shows that both trabeculectomy and the PreserFlo MicroShunt are effective methods for lowering intraocular pressure in patients with uncontrolled open-angle glaucoma. While trabeculectomy more frequently causes postoperative hypotony, the PreserFlo required more additional interventions such as needling in our study. Both procedures, however, led to stabilization of the glaucoma without further progression during the first year. These findings highlight the importance of individualized therapy decisions that consider patient-specific risks and preferences.
Conflict of interest
L. Höflechner, T. Falb, L. Haiden, A. Guttmann, W. List, A. Heidinger, L. Keintzel, F. Wallisch, M. Großpoetzl, R. Riedl and E. Lindner declare that they have no competing interests.
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PreserFlo MicroShunt vs. trabeculectomy in patients with uncontrolled glaucoma
verfasst von
Lukas Höflechner Thomas Falb Lena Haiden Andreas Guttmann Wolfgang List Astrid Heidinger Lukas Keintzel Fabian Wallisch Manuel Großpoetzl Regina Riedl Ewald Lindner