How Does the PreserFlo MicroShunt Stack Up Against Trabeculectomy and Other Drainage Devices?

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Introduction For people with open-angle glaucoma, surgical options aim to lower intraocular pressure (IOP) by creating a new drainage pathway for eye fluid (aqueous humor). The traditional gold-standard surgery is trabeculectomy, a technique that creates a small hole under a scleral flap, forming a filtering bleb under the conjunctiva. In recent years, newer implants have emerged. These include tube shunts (Ahmed, Baerveldt, Molteno implants) that channel fluid from the front of the eye to a plate under the conjunctiva, and minimally-invasive glaucoma surgeries (MIGS) such as the XEN Gel Stent and PreserFlo MicroShunt. The PreserFlo MicroShunt (formerly InnFocus MicroShunt) is a small, ab-externally implanted glaucoma device made of a soft polymer (poly(styrene-block-isobutylene-block-styrene), or SIBS). It drains fluid from the anterior chamber into a posterior subconjunctival bleb. This device is meant to be less invasive than trabeculectomy yet more effective than purely bleb-less MIGS. In this review, we compare PreserFlo to trabeculectomy and other drainage devices (Ahmed valve, Baerveldt and Molteno implants, XEN stent) in terms of how they work, clinical effectiveness, safety, practical use, and current access/cost issues. We use evidence from published trials and registries. When we report results, we note sample sizes and study years. If data are limited or mixed, we say so. Key findings are summarized in the concluding table. Background and Mechanism PreserFlo MicroShunt: The PreserFlo device is an 8.5 mm long tube with a 350 µm outer diameter and a very narrow 70 µm inner lumen (). It is made of SIBS, a biocompatible polymer that resists biodegradation (). The surgeon opens a small conjunctival/Tenon’s flap (much like for trabeculectomy) and uses mitomycin-C (an antifibrotic) under the flap. The MicroShunt is inserted ab externo: a tiny pocket is made in the sclera to accept the device fins, and a tunnel is made into the anterior chamber. The proximal tip sits inside the eye (just anterior to the iris) and the distal end drains fluid beneath the conjunctiva (see image below). Because the lumen is very small, it provides some flow resistance to help prevent severe postoperative hypotony (very low pressure). () Figure: The PreserFlo MicroShunt (red arrow) shunts aqueous humor from the anterior chamber (right) to a bleb under the conjunctiva (left) (). Trabeculectomy: In trabeculectomy, the surgeon creates a scleral flap and manually makes an opening under it (sometimes removing a small piece of iris) to connect the anterior chamber to the subconjunctival space. This creates a bleb. Mitomycin-C is often applied. Trabeculectomy is highly effective at lowering IOP, but it is invasive: it requires extensive dissection, sutures, and careful postoperative management. Tube Shunts (Ahmed, Baerveldt, Molteno): These are aqueous drainage implants. A silicone tube is inserted through the sclera into the anterior chamber. The tube drains fluid to a plate placed under the conjunctiva. The Ahmed Glaucoma Valve (AGV) includes a one-way valve designed to prevent early hypotony. The Baerveldt implant (typically 350 mm² plate) and Molteno implant (typically 275–350 mm²) are non-valved; surgeons ligate or occlude the tube temporarily to prevent immediate overdrainage. In general, valved shunts (Ahmed) cause less early hypotony but may end up at slightly higher pressures, while large non-valved shunts (Baerveldt, Molteno) can achieve lower long-term IOP but risk early overdrainage if not carefully tied off. XEN Gel Stent: The XEN 45 is a soft, gelatin-based 6 mm tube with a 45 µm lumen. It is implanted ab interno (from inside the eye) through a small corneal incision. It also drains to a subconjunctival bleb. No scleral dissection or removable flap is needed – only a gentle subconjunctival elevation of conjunctiva is done and mitomycin-C is often injected under the conjunctiva. Because the XEN lumen is slightly larger than the aqueous outflow resistance of normal trabecular pathways, it provides a controlled flow (and 45 µm lumen is internally limiting flow to avoid hypotony). However, like PreserFlo, it relies on bleb formation and often requires postoperative management (needling) of the bleb. MIGS vs Traditional Spectrum: Surgical options range from classic filtration surgery (trabeculectomy/tubes) at one end to ab interno MIGS at the other. MIGS are generally defined as procedures with an ab interno approach, minimal tissue trauma, faster recovery, and a good safety profile (). Examples of ab interno MIGS that do not form a bleb include stents in Schlemm’s canal (iStent, Hydrus) or suprachoroidal devices. PreserFlo, XEN, and older shunts are unique because they do create a bleb. These “bleb-forming MIGS” are sometimes considered intermediate: they are less invasive than trabeculectomy (especially XEN, which is minimally dissected) but not as simple as trabecular bypass stents. In practice, PreserFlo and XEN are often lumped into the MIGS group (despite ab externo steps in PreserFlo’s case) because they aim to reduce invasiveness and management burden. Efficacy Outcomes IOP Reduction and Success Rates: Clinical studies show that PreserFlo consistently reduces IOP into the mid-teens. In Baker et al. (2021), a large randomized trial of 527 eyes (395 PreserFlo, 132 trab) reported one-year IOP falls from 21.1±4.9 to 14.3±4.3 mmHg (–29% from baseline) after MicroShunt, versus 21.1±5.0 to 11.1±4.3 mmHg (–45%) after trabeculectomy (). Corresponding mean glaucoma medications dropped from 3.1 to 0.6 in the PreserFlo group and 3.0 to 0.3 in the trab group (). By Baker’s success criteria (≥20% IOP reduction without more meds), 53.9% of PreserFlo eyes and 72.7% of trabeculectomy eyes “succeeded” at 1 year (P<0.01) (). This shows that trabeculectomy gave a somewhat larger pressure drop and higher success per this definition. A single-center prospective study by Fili et al. (2022) also compared PreserFlo (150 eyes) vs trabeculectomy (150 eyes) in moderate-to-advanced glaucoma. At 12 months, 81.3% of MicroShunt eyes and 94.0% of trabeculectomy eyes achieved >20% IOP reduction without medications (). Mean IOP at 1 year was 12.9±3.4 mmHg (PreserFlo) and 11.4±4.5 mmHg (trab) (). Medications fell from ~2.5 to 0.4 in the PreserFlo group and to 0 in the trab group (). These results again favor trabeculectomy for lower final IOP, though both groups reached low teens pressures. Other PreserFlo series report similar IOP control. For example, Beckers et al. (2022) studied 81 eyes with PreserFlo at 2 years. Mean IOP fell from 21.7±3.4 mmHg at baseline to 14.5±4.6 mmHg at 1 year and 14.1±3.2 mmHg at 2 years (P<0.0001) (). Overall success (with or without meds) was 74.1% at 1 year (). Medications dropped from 2.1 to 0.5 (mean) by 2 years, with 73.8% of patients medication-free (). In their study, higher mitomycin-C (0.4 mg/ml) trended toward better pressure and med reduction than 0.2 mg/ml (). PreserFlo vs XEN: Available data suggest similar efficacy between these two bleb-based MIGS. In a 2-year comparative series, Scheres et al. (2022) found that mean IOP dropped from 20.1 to 12.1 mmHg (PreserFlo) and from 19.2 to 13.8 mmHg (XEN) at 2 years (p=0.19) (). The probability of “qualified success” (achieving target IOP with or without meds) was 79% for PreserFlo vs 73% for XEN at 24 months (). Both groups had substantial medication reduction. Thus, in this series the two devices gave nearly equivalent pressure outcomes. PreserFlo vs Tube Shunts (Ahmed/Baerveldt): There are no head-to-head trials of PreserFlo versus tube implants. For context, device trials provide a ballpark: The Ahmed vs Baerveldt ABC Study showed at 1 year mean IOP ~15.4 mmHg with Ahmed vs 13.2 mmHg with Baerveldt when starting from 31 mmHg (). Both used adjunctive medications. These results imply that large plate tube shunts can achieve very low pressures (down to ~13 mmHg) often slightly lower than PreserFlo’s typical outcome (low teens). On the other hand, tubes carry more serious surgery for difficult cases. In practice, PreserFlo tends to be used in mild-to-moderate glaucoma; Ahmed/Baerveldt in refractory or severe cases. Longer-Term Durability: Prestigious controlled data (like Baker et al.) reported only 1-year results so far. Longer follow-up is still needed. In the Beckers 2-year series, PreserFlo pressure control was sustained at ~14 mmHg through 2 years (). Fili’s study was only 1 year. The Scheres XEN vs PreserFlo study also had 2-year data (). Notably, Baker’s trial is designed for 2 years (NCT01881425), and longer-term data should clarify durability of the MicroShunt vs trabecular outcomes. Safety and Complications Hypotony (Low IOP): Shunt surgeries often have early postoperative hypotony. In Baker et al., transient IOP ≤5 mmHg occurred in 28.9% of PreserFlo eyes versus 49.6% of trabeculectomy eyes (P<0.01) (). Thus, while PreserFlo had less frequent shallow pressure than trab, more than a quarter of eyes did have an IOP hump to ≤5 mmHg after MicroShunt. Serious hypotony-related complications (maculopathy or required reformation) we

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Introduction. For people with open-angle glaucoma, surgical options aim to lower intraocular pressure IOP by creating a new drainage pathway for eye fluid, aqueous humor. The traditional gold standard surgery is trabeculectomy, a technique that creates a small hole under a scleral flap, forming a filtering bleb under the conjunctiva. In recent years, newer implants have emerged. These include tube shunts, AMED, Barevelt, Molteno implants, that channel fluid from the front of the eye to a plate under the conjunctiva, and minimally invasive glaucoma surgeries, MIGs, such as the Zen gel stent and PreserFlow Microshunt. The Preserflow Microshunt, formerly In-Focus Microshunt, is a small ab externally implanted glaucoma device made of a soft polymer, polystyrene block isobutylene block styrene, or SIBS. It drains fluid from the anterior chamber into a posterior subconjuncal bleb. This device is meant to be less invasive than trabeculectomy, yet more effective than purely blebless MIGs. In this review, we compare PresserFlow to trabeculectomy and other drainage devices, Ahmed valve, barevelt, and Molteno implants, Zen Stent, in terms of how they work, clinical effectiveness, safety, practical use, and current access cost issues. We use evidence from published trials and registries. When we report results, we note sample sizes and study years. If data are limited or mixed, we say so. Key findings are summarized in the concluding table. Background and mechanism Preserflow Microshunt. The Preserflow device is an 8.5mm long tube with a 350mm outer diameter and a very narrow 70 micometers inner lumen. It is made of SIBs, a biocompatible polymer that resists biodegradation. The surgeon opens a small conjunctival tenon's flap, much like for trabeculectomy, and uses mitomasin C, an antifibrotic, under the flap. The micro shunt is inserted ab externo, a tiny pocket is made in the sclera to accept the device fins, and a tunnel is made into the anterior chamber. The proximal tip sits inside the eye, just anterior to the iris, and the distal end drains fluid beneath the conjunctiva, see image below. Because the lumen is very small, it provides some flow resistance to help prevent severe postoperative hypotony, very low pressure. Figure. The preser flow micro shunt, red arrow, shunts aqueous humor from the anterior chamber, right, to a bleb under the conjunctiva, left. Trabeculectomy. In trabeculectomy, the surgeon creates a scleral flap and manually makes an opening under it, sometimes removing a small piece of iris to connect the anterior chamber to the subconjunctival space. This creates a bleb. Mitomycin C is often applied. Trabeculectomy is highly effective at lowering IOP, but it is invasive. It requires extensive dissection, sutures, and careful postoperative management. Tube shunts, Ahmed, barevelt, molteno, these are aqueous drainage implants. A silicone tube is inserted through the sclera into the anterior chamber. The tube drains fluid to a plate placed under the conjunctiva. The Ahmed glaucoma valve, AGV, includes a one-way valve designed to prevent early hypotony. The bare velt implant, typically 350 mm plate, and molteno implant, typically 275 to 350 mm, are non-valved. Surgeons ligate or occlude the tube temporarily to prevent immediate overdrainage. In general, valved shunts AMID cause less early hypotony but may end up at slightly higher pressures, while large nonvalved shunts, barevelt maltino, can achieve lower long-term IOP but risk early overdrainage if not carefully tied off. Zen gel stent. The Zen 45 is a soft, gelatin-based 6mm tube with a 45 mm lumen. It is implanted ab interno from inside the eye through a small corneal incision. It also drains to a subconjunctival bleb. No scleral dissection or removable flap is needed, only a gentle subconjunctival elevation of conjunctiva is done, and mitomycin C is often injected under the conjunctiva. Because the Xen lumen is slightly larger than the aqueous outflow resistance of normal trabecular pathways, it provides a controlled flow and 45 micrometers lumen is internally limiting flow to avoid hypotony. However, like preser flow, it relies on bleb formation and often requires postoperative management, needling of the bleb. MIGs versus traditional spectrum. Surgical options range from classic filtration surgery, trabeculectomy, tubes, at one end to abinterno MIGs at the other. MIGs are generally defined as procedures with an abinterno approach, minimal tissue trauma, faster recovery, and a good safety profile. Examples of abinterno MIGs that do not form a bleb include stents in Schlem's canal, eye stent, hydris, or suprachoroidal devices. Presorflow, Xen, and older shunts are unique because they do create a bleb. These bleb-forming MIGs are sometimes considered intermediate. They are less invasive than trabeculectomy, especially xen, which is minimally dissected, but not as simple as trabecular bypass stents. In practice, preserflow and xen are often lumped into the MIGs group, despite AB externo steps in PrezzerFlow's case, because they aim to reduce invasiveness and management burden. Efficacy outcomes, IOP reduction and success rates. Clinical studies show that PreserFlow consistently reduces IOP into the mid-teens. In Baker et al., 2021, a large randomized trial of 527 eyes, 395 PRIZERFLO, 132 TRAB, reported one-year IOP falls from 21.1-4.9 to 14.34.3 mmLHDRENGES, 29% from baseline after microshunt versus 21.1-5.0 to 11.1-4.3 millimeters gramp and 45% after trabeculectomy. Corresponding mean glaucoma medications dropped from 3.1 to 0.6 in the Preserflow group and 3.0 to 0.3 in the TRAB group. By Baker's success criteria, 20% IOP reduction without more meds, 53.9% of Preserflow eyes, and 72.7% of trabeculectomy eyes succeeded at one year P10.01. This shows that trabeculectomy gave a somewhat larger pressure drop and higher success per this definition. A single center perspective study by Feely et al., 2022 also compared Preserflow 150 eyes versus trabeculectomy 150 eyes in moderate to advanced glaucoma. At 12 months, 81.3% of microshunt eyes and 94. Mean IOP at one year was 12.93.4 mmHggrams presorflow and 11.4.5 millimetergram TRAB. Medications fell from 22.5 to 0.4 in the Preserflow group and to 0 in the TRAB group. These results again favor trabeculectomy for lower final IOP, though both groups reached low teens pressures. Other preserflow series report similar IOP control. For example, Becker's et al. studied 81 eyes with Presorflow at two years. Mean IOP fell from 21.73.4 millimes at baseline to 14.5 to 4.6 millimetes at one year and 4.1 to 3.2 millimeters grow 0.1. Overall success, with or without meds, was 74.1% at one year. Medications dropped from 2.1 to 0.5 mean by two years, with 73.8% of patients medication free. In their study, higher mitomycin C 0.4 mg per mil trended toward better pressure and med reduction than 0.2 mg per milliliter. Presorflow versus Xen, available data suggests similar efficacy between these two bleb-based MIGs. In a two-year comparative series, Shares et al. 2022 found that mean IOP dropped from 20.1 to 12.1 mL presorflow and from 19.2 to 13.8 millimeters drain at two years, P.19. The probability of qualified success achieving target IOP with or without meds was 79% for Preserflow versus 73% for Xen at 24 months. Both groups had substantial medication reduction. Thus in this series the two devices gave nearly equivalent pressure outcomes. Presorflow versus tube shunts, Beerveld. There are no head-to-head trials of PreserFlow versus tube implants. For context, device trials provide a ballpark. The Ahmed vs Bearveld ABC study showed at one year mean IOP by 15.4 mmHz with Ahmed vs. 13.2 mmHg with barevelt when starting from 31 mmhergrams. Both used adjunctive medications. These results imply that large plate tube shunts can achieve very low pressures down to 13 mmHg, often slightly lower than PresorFlow's typical outcome, low teens. On the other hand, tubes carry more serious surgery for difficult cases. In practice, PreserFlow tends to be used in mild to moderate glaucoma, Ahmed Beerveld in refractory or severe cases. Longer term durability prestigious control data like Baker et al. reported only one year results so far. Longer follow-up is still needed. In the Becker's two-year series, PreserFlow pressure control was sustained at 14 mm through two years. Feely's study was only one year. The Shear Zen vs PreserFlow study also had two-year data. Notably Baker's trial is designed for two years, NCT018845 and longer-term data should clarify durability of the microshunt versus trabecular outcomes. Safety and complications hypoteny, low IOP, shunt surgeries often have early postoperative hypoteny. In Baker et al, transient IOP 5 mm occurred in 28.9% of Presorflow eyes versus 49.6% of trabeculectomy eyes, P.01. Thus, while Presorflow had less frequent shallow pressure than TRAB, more than a quarter of eyes did have an IOP hump to 5 mmherg after microshunt. Serious hypoteny related complications, maculopathy or required reformation, were uncommon in both arms. In other series, rates of transient hypoteny after presorflow range up to 30 to 40%, usually mild and resolving. In contrast, classic trabeculectomy studies report chronic hypotany in a significant minority at 3 to 5 years, 23 to 31% in tube versus trabeculectomy study. AMED valves, valved shunts, generally have lower hypoteny rates than nonvalve tubes, but can still have periods of low IOP in the early hypertensive phase. Choroidal effusion detachment fluid can collect under the retina when pressures are low. PRESOR flow series report choroidal detachment in a few percent to over 10% of eyes. Baker's trial showed choroidal detachments occurred more with TRAB, data not explicitly given but implied by higher hypotony, and preserflow had 6.1% versus 13.7% hypotony, not choroid. By contrast, AMD and barevelt implants often have low IOP but choroid changes are usually less dramatic. The encapsulated bleb tends to stabilize pressure before major effusion. Bleb-related issues, leak infection. Any surgery that makes a conjunctival bleb risks leaks or infection. In Baker et al. no sytal positive bleb leaks were seen in the preservation, whereas six cases occurred after trabeculectomy p equals or 0.024. In general, preserflow's more posterior bleb and small tube may reduce leak risk. Late bleb infections, blebitis or endothalmitis are rare but serious. In the published literature endothalmitis has been reported after XEN in up to 3% of eyes. By contrast only a few cases of preserflow exposure and no confirmed infections have been reported. Ahmed bearvelt shunts also have risk of conjunctival erosion over the plate or tube reports range 2 to 7% exposure, which can lead to endothalmitis if not managed. Trabeculectomy blebs can likewise become infected up to 5-7% blebitis in long term. Overall, PF and ZEN share the same spectrum of bleb-related risks as trabeculectomy, while tubes carry plate erosion risks specific to their design. Hyphema bleeding in eye, mild blood reflux often occurs after any glaucoma surgery. In Baker's RCT, Frank hypema was noted in 6.1% of preserflow eyes versus 2.3% of TRAB, difference not statistically significant. Most small hypemas self-resolve without issue tube shunts can also cause hyphema, especially if placed in an anterior chamber with rubbing iris or neovascular membranes. Xen and other MIGs typically have low rates of significant hyphema. Need for reoperations or interventions, postoperative interventions, suture lysis, bleb needling, etc, were common, Baker found 40 8% of microshunt eyes required laser suture lysis or similar procedures, versus 67.4% of trabeculectomy eyes. Similarly, Filiet al observed fewer reoperations in the Presorflow group. Needling of the bleb to revive scarring occurred in roughly 5 to 19% of presor flow cases in published series, compared to much higher rates with SEN, 22-43%. Ahmed bearveld implants sometimes require bleb revision or valve adjustment, especially if the encapsulated plate underdrains. Roughly 15 to 50% of tube eyes may need eye drops or surgical revision over time. Overall preserflow tends to need fewer needle bleb revisions than ab internostents and modestly lower rates of suture loss procedures than trabeculectomy. Corneal endothelial cell loss. Devices placed in the anterior chamber can rub on or injure the cornea over time. The presor flow's tube lies parallel to the iris, usually away from cornea. No large studies have reported marked endothelial cell loss ECD with PF to date. By contrast, AMED and barevelt tubes in the AC can cause progressive ECD loss. For example, one study found a 9.4% drop in central ECD at one year after AMED valves versus only 3% loss after trabeculectomy. Another report showed no significant difference in two-year ECD loss between AMED and Molteno implants, both 12%. In short, bleb-forming MIGs like preserfloxen likely have minimal direct endothelial impact, while tube shunts in the AC can accelerate corneal cell loss, particularly if the tube is too close to the endothelium. Surgical and practical considerations, technique and operative time. Traditional trabeculectomy requires conjunctival peritomy, large scleral flap dissection, iridectomy, suturing, and MMC exposure. It is technically demanding with a steep learning curve. Preserflow implantation is absterno but involves a smaller dissection. The surgeon only needs 90 to 100 degrees of conjunctival tenon's flap, a deep scleral pocket 1 mm3 mm to hold the device fins and a needle track into the anterior chamber. No iridectomy is needed. After placing the microshunt in the pocket, the flap is closed watertight. The procedure is generally faster and simpler than trabeculectomy, though it still requires careful MMC use, typically 0.2 to 0.4 mg per milliliter for two to three minutes. Surgeons report a moderate learning curve, easier than mastering trabeculectomy but needing precision. In comparison, the sense stent is even less invasive. It is inserted via a small corneal incision, abinterno, with minimal conjunctival handling making it very quick and preserving tissue. Tube shunts, Ahmed, bearveld, malteno, require more extensive dissection similar to a trabeculectomy, plus placement of the large plate under tendons, so operative time is usually longer than for presorflow. In short, presorflow lies between very minimal MIGs, like Zen, and full trabeculectomy or tube surgery. Use of antifibrotics. All bleb-forming surgeries use anti-scarring drugs. Trabeculectomy often uses MMC, e.g. 0.1 to 0.5 mg per milliliter. In presorflow implantation, MMC is routinely applied, often 0.2 or 0.4 mg per milliliter for 2-3 min to boost success. The faucet is fully open, without it failure rates are high. Xenon tubes also use antimetabolites, MR5U. One practical note higher MMC, 0.44.2 m in presorflow has been linked to more medication-free eyes, but also potentially more initial IOP dips. Surgeons balance potency and safety case by case. Postoperative management. After trabeculectomy, frequent clinic visits and suture adjustments are typical. PreserFlow patients also need close follow-up in the early months, but perhaps slightly fewer interventions. Needling of the bleb is done in a minority if the pressure creeps up. Overall, studies show that preserflow patients undergo significantly fewer postoperative manipulations than trabeculectomy patients. Nonetheless, the postoperative course is not trivial. A counting plate needs monitoring for flat chambers or leaks and steroid taper can take a while, often longer than non-bleb MIGs. Patient selection ideal candidates for preserflow are patients with primary open angle glaucoma who require more IOP lowering than medication can provide but who still have some healthy conjunctiva. It has been used in primary open angle and pseudoexfoliation glaucoma. It tends to be offered for moderate glaucoma for which MIGs like eye stent might not suffice, but full trabeculectomy might be deferred. Eyes with previous conjunctival scarring failed TRAB, chronic inflammation simbliferon, are less ideal for any bleb surgery. Also, very advanced or low-target glaucoma may still favor traditional TAB or tube because preserflow often does not reach the single digit IOP that such eyes sometimes need. By contrast trabeculectomy is classically reserved for those needing the absolute lowest IOP or who have failed other measures. Tube shunts Ahmed Behrveld are often chosen when trabeculectomy is likely to fail, previous surgery, uveetic neovascular glaucoma or in younger patients at high risk of Tab failure. Zen stent is typically a choice for mild to moderate glaucoma, especially when combining with cataract surgery or when less invasive surgery is desired. In summary, PreserFlow fills a middle niche, more aggressive than Schlem's Canal MIGs, but somewhat gentler than trabeculectomy. Cost, access, and regulatory status approval. Status The PreserFlow Microshunt has CEMARC approval in Europe and is licensed in Canada and other regions, but as of late 2023 it is not yet FDA approved in the United States. It is available in the U.S. only through clinical trials. By contrast, AMID valves and barevelt molteno tubes have long been FDA approved for refractory glaucoma in the U.S. The Zen 45 stent was FDA approved in 2016 for use in open angle glaucoma with or without cataract in the U.S. Reimbursement and cost. Costs vary widely by healthcare system. An analysis from the UK, where healthcare is publicly funded found that PrezorFlow surgery saved around 245 pounds and 566 cents per eye compared to trabeculectomy, mainly because of fewer follow-up visits and interventions. In that study, PreserFlow had a slightly higher device cost but overall lower post-op care costs. By contrast, an older U.S. Medicare based analysis of early trial data estimated the PRESRFLO procedure would cost about $2,058 more per patient than trabeculectomy, largely due to the expensive implant and currently low reimbursement. Xen stents and tube implants also involve significant device costs, but long-term cost effectiveness depends on surgical success and need for additional interventions. As of now, formal cost effectiveness studies are limited, but one can say that if PreserFlow largely replaces trabeculectomy, payers will want evidence of overall savings or at least similar outcomes for the higher price of the device. Expert perspectives and controversies PreserFlow has sparked debate in the glaucoma community. Proponents argue that it offers a predictable and easier alternative to trabeculectomy for many patients. It avoids some of trabeculectomy's nuances, iridectomy multiple scleral sutures, and seems to have a good intermediate safety profile. Critics note that the IOP reduction achieved is generally less than trabeculectomy and some caution that the term minimally invasive may overstate the ease of the surgery. In other words, PreserFlow still requires a filtering bleb and postoperative care, so it is not just another MIG stent. There are concerns that cobbling onto the MIGs trend might mislead both doctors and patients about the surgery. Some surgeons hoped PreserFlow would rival trabeculectomy's effectiveness more closely. For example, Baker et al. showed a notable gap in mean IOP and success rate between the microshunt and trabi. This has led to debate should Presorflow be used in advanced glaucoma when such gaps matter or is it better reserved for moderate cases? Also, because early data are mostly one-year and from industry supported studies, experts call for caution and independent long-term data. As Rosen et al. In summary, the role of PreserFlow is still being defined. It clearly has a place between Traditional trabeculectomy and the gentler MIGs. Surgeons may disagree on the exact indications. Some predict it will become a first-line surgical option for early progressive glaucoma, avoiding TRAB in many cases. Others worry it may compromise outcomes in those who really need the pressure drop that only a TRAB can give. Usage patterns will likely evolve as more data emerge and as U.S. approval status is resolved. Comparative summary, procedure, device, approach, and category, typical IOP outcome, medication reduction, key safety concerns. Presor flow microshunt, preserflow microshunt, bleb forming, ab externo MIGs, soft SIBS tube, low teens in Mahergrai, e.g. 14 mursing at 1 to 2 years, large drop, mean meds, 0.5 in 2 years, transient hypotony, 20-30% early, bleb needling, 5-20%, bleb leaks rare, minimal ECD loss, trabeculectomy, gold standard filtration, scleral flat plus bleb, very low IOP, often mid-teens or below, e.g. 11 mm herdrangs at 1 year, often eliminated meds, e.g. mean 3 or 0.3, more frequent hypotenuse to 50% early, bleb leaks infections, strict monitoring, more reoperatives. AMED glaucoma valve, valved aqueous shunt, tube to plate, low mid-teens, 15-16 mm hergrims at one year, moderate, e.g. 2 meds to 1.8, hypertensive phase, early IOP spike, encapsulation, tube plate exposure, 2-7%, endothelial cell loss 9%. Barevelt glaucoma implant, non-valved shunt, 350 mm plate, tube ligated initially, even lower IOP tar 13 millimerms or below at one year. Moderate similar to AMED. Early ligation required to avoid hypotenuse. More initial post-op complications, risk of flat AC if occlusion dissolves, exposure risk, ECD loss similar to AMED. Moltenoglaucoma implant, non-valved shunt, typically 205 to 350, very low IOP like barevelt, mid-teens or lower, moderate, few meds, similar issues to barevelt, hypoten, exposure, often older technique, generally less used than barevelt in some regions. Anxen 45 gel stent, a b internal bleb-forming MIGs, 45mm lumen, low mid-teens, 13-14 mm at 1 to 2 years, large drop, e.g. 2.5-0.9 meds, blebs leak knot, bleb needling common 243%, hypotony in a minority, device exposure 223%, minimal direct ECD effect. Conclusion. The Preserflow Microshunt is an intermediate glaucoma surgery, more effective at lowering IOP than many non-bleb MIGs, but less invasive and somewhat safer than traditional trabeculectomy. In trials and series, it reliably lowers IOP into the low teens and dramatically cuts medication use. Compared to trabeculectomy, it generally causes less early hypotony and requires fewer postoperative interventions. But TRAB often achieves a slightly lower final pressure. Compared to tube shunts, Presorflow is simpler to implant and avoids an anterior chamber tube, though large tubes may achieve even lower pressures in refractory cases. Compared to the Zen stent, Presorflow appears similarly effective in IOP control, though perhaps slightly less needling is needed with the micro shunt. Safety-wise, Presorflow shares the bleb-related risks of TRAB and Zen, bleb leak, infection, detachment, but in practice, these complications have been infrequent to date. Notably, no significant transplanted vision-threatening events have emerged in studies, and chronic hypotany is uncommon. Importantly, because it avoids an AC tube, Presorflow likely spares the corneal endothelium that can be damaged by Ahmed barevelt tubes. Surgeons consider preserflow for eyes needing more pressure lowering than simple MIGs can give, but who might not yet need full trabeculectomy. It requires good conjunctiva and patient willingness for bleb follow-up. Costs and approval are still hurdles in some regions, e.g., awaiting FDA approval in the U.S. In conclusion, based on current evidence, PreserFlow lives up to its billing as a minimally invasive bleb surgery. It offers an attractive balance of efficacy and safety, but it is not a drop-in replacement for trabeculectomy, nor a mere variant of tube shunts. Its precise place will continue to be refined by ongoing studies and surgeon experience. All links to sources are available in the text version of this article. You can find the full article at VisualFieldTest.com. Thanks for listening. To check your visual field, click the link at the bottom of this article or visit visualfieldtest.com.