Despite decades of research, glaucoma has remained incurable, with treatment focused mainly on delaying disease progression by reducing intraocular pressure (IOP).1 The traditional glaucoma armamentarium comprises medications, lasers, and filtration surgeries like trabeculectomy and tube shunts. However, the compliance issues, side effects, and costs associated with antiglaucoma medications2,3 and the risk of sight-threatening complications with invasive filtering surgeries4 have necessitated a continued search for safer and more efficient methods of IOP control.
With minimally invasive glaucoma surgery (MIGS), treatment options for glaucoma patients have broadened, particularly for mild to moderate disease uncontrolled by medications or laser, where the potential risks of invasive surgery may not be justified. While MIGS have good safety profiles and faster postoperative recovery, the IOP-lowering efficacy is modest compared to traditional filtration surgeries, because most MIGS act on the conventional outflow pathway and cannot obtain pressures lower than the episcleral venous pressure.5 However, suprachoroidal and subconjunctival MIGS theoretically are not limited by this floor effect because they shunt aqueous into the suprachoroidal and subconjunctival spaces, respectively. Subconjunctival MIGS employ similar principles as trabeculectomy and tube shunts, and are thought to have the most potential to match the efficacy of these surgeries.5
Minimally invasive microsclerostomy (MIMS; Sanoculis Ltd) is a novel MIGS procedure that involves the ab interno creation of a sclero-corneal tunnel that shunts aqueous from the anterior chamber into the subconjunctival space.6 Theoretically, it combines the minimally invasive nature of MIGS with the efficacy of filtration surgeries, and it leaves no stent in the eye, thus not carrying the risk of stent-related complications as observed with other subconjunctival MIGS.7 The procedure is not yet approved in the United States — FDA clearance is estimated in the second half of 2026 — but the procedure has already received the CE Mark in the European Union and an initial clinical trial has shown encouraging safety and efficacy in early open-angle glaucoma (OAG) cases requiring target IOP in the mid-to-high teens.8 We further investigated the real-world performance of MIMS in a larger cohort of patients.
MIMS Outcomes
Figure 1. The MIMS surgical system includes the activation device with foot pedal, along with a disposable handpiece (pictured). The device is not yet approved by the US Food and Drug Administration. Figure courtesy Sanoculis.
We conducted a prospective, single-center study on 120 patients (120 eyes; mean age 69±10 years) with primary OAG or pseudoexfoliative glaucoma who were uncontrolled (IOP >21 mmHg) despite maximal tolerated medications.9 Thus, these patients were candidates for invasive filtration surgery according to the traditional glaucoma treatment algorithm. Our aim was to evaluate whether MIMS could control IOP and delay invasive surgeries in such patients. MIMS was performed as a standalone surgery in eyes with no or insignificant cataract (n=100), while MIMS was combined with phacoemulsification in eyes with significant cataract (n=20).
The MIMS procedure utilizes a rotating cutting tool to create a 100 µm drainage channel in the sclera (Figures 1 and 2). After subconjunctival injection of 0.1 ml of 0.02% mitomycin C (MMC), we injected ophthalmic viscosurgical device (OVD) subconjunctivally at the superonasal quadrant near the limbus to create space for the protrusion of the cutting tool. The surgical tool was inserted through a temporal paracentesis and advanced to the superonasal angle, above the trabecular meshwork. The rotating microtrephine was then activated by pressing a foot pedal to create the sclerostomy. We found the procedure to be rapid (mean duration 2:01±0:41 min:sec) and simple with a short learning curve. Scleral drainage channels (Figure 3) were successfully created in all cases with no intraoperative complications.
Figure 2. On pressing the foot pedal of the MIMS surgical system, a rotating microtrephine protrudes from its protective sleeve to create a 100-µm scleral tunnel. Figure courtesy Sanoculis.
Figure 3. Anterior-segment optical coherence tomography (OCT) scan at 52 weeks showing patent scleral tunnel (arrowheads) leading from the angle of the anterior chamber (a) to subconjunctival filtering bleb (b). Figure courtesy Lilit Voskanyan, MD, PhD.
With MIMS, both IOP and medications were significantly reduced at 52 weeks postoperatively (n=95). Mean IOP was lowered by 38% (27.9±3.7 to 17.3±5.3 mmHg; P<0.001) and mean number of medications dropped by 85% (1.8±0.8 to 0.3±0.7; P<0.001). Mean IOP and medication reduction was 37.4% and 83.9%, respectively, in standalone MIMS (n=78; P<0.001) and 40.6% and 91.6%, respectively, for MIMS with phacoemulsification (n=17; P<0.001), demonstrating that the efficacy of MIMS was independent of any IOP-lowering effect of phacoemulsification (Figure 4).
MIMS also obtained good success rates, with complete success (IOP ≤21 mmHg or >20% reduction from baseline without medications) achieved in 70.5% patients, while 82.1% patients achieved qualified success (criteria as above with medications equal to or lesser than at baseline). Twenty-three patients (24%) were categorized as failure ( IOP >21 mmHg or increase in medications at 52 weeks), with 2 patients (2.1%) requiring trabeculectomy; however, 16 of those 23 patients (69%) were not on any medications at last visit (compared to 2.1 medications preoperatively), so it is likely that a significant proportion of these patients could have achieved qualified success were they candidates to be administered antiglaucoma medications.
Figure 4. The top graph (A) tracks intraocular pressure (mean±SD) at all study visits in standalone MIMS cases (blue) and MIMS combined with phacoemulsification cases (red). The lower graph (B) shows the number of antiglaucoma medications (mean±SD) reported at all study visits in standalone MIMS cases (blue) and MIMS combined with phacoemulsification cases (red). Figure courtesy Lilit Voskanyan, MD, PhD.
More importantly, efficacy outcomes with MIMS were found to be comparable to other subconjunctival MIGS at similar timepoints.10,11 Compared with trabeculectomy, MIMS achieved comparable medication reduction with similar success rates.12,13 These results were especially encouraging when considered with the high safety profile observed with MIMS, because no serious or sight-threatening complications related to the procedure were observed. The most common complication was iris plugging of the channel’s internal ostium (n=18, 15%), which was successfully managed by topical pilocarpine followed by laser application in all except 3 patients. Early IOP spikes (>30 mmHg) due to retained OVD in the anterior chamber were seen in 15 patients (12.5%) and resolved in all patients without sequelae. These complication rates compare favorably with invasive filtration surgeries4 and other subconjunctival MIGS that can be associated with implant-related complications, such as corneal decompensation, device extrusions, and endophthalmitis.7
For subconjunctival filtration procedures, the limiting factor for surgical success is bleb failure due to fibrosis. With MIMS, most blebs formed were diffuse and mildly vascularized. Only 2 patients (2.1%) required secondary trabeculectomy after treatment failure due to bleb scarring, while 1 patient required needling. Glaucoma reoperation rates were lower than for other subconjunctival MIGS,7 which could be attributed to the minimal conjunctival manipulation in MIMS.
MIMS in the Glaucoma Treatment Algorithm
Our study showed that MIMS safely and effectively controlled IOP in uncontrolled OAG while also significantly reducing medication burden and delaying the need for invasive surgical interventions up to 1 year postoperatively. It must be noted that the final mean IOP achieved was in the high teens, which may not be sufficient in advanced glaucoma.
Our study was limited by the lack of a comparator group and a nonrandomized, open-label design. Further randomized controlled trials and studies with longer follow-ups are needed to refine the clinical indications and establish the long-term efficacy of MIMS. However, the early results for this procedure are certainly promising, particularly when considering that most surgeries were standalone and the IOP and medications lowering effectiveness was not confounded by phacoemulsification, which is known to lower IOP.
The main idea of MIGS, and interventional glaucoma in general, is to bridge filtration surgery and topical therapy with procedures that are less invasive and yet effective in lowering IOP and medications burden, and to be able to tailor the procedure in each glaucoma patient to the greatest degree possible. MIMS is another tool in the glaucoma
surgery armamentarium and is a rapid and simple subconjunctival MIGS with significant safety and effectiveness. GP
References
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6. Sanoculis sponsored content. Leave no thing behind: MIMS — a new surgical procedure for glaucoma — simplifies treatment and keeps patients’ options open. The Ophthalmologist. December 15, 2020. Accessed July 22, 2024. https://theophthalmologist.com/subspecialties/leave-no-thing-behind
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9. Voskanyan L, Ahmed IIK, Gershoni A, et al. Minimally invasive micro sclerostomy (MIMS) procedure in the treatment of open-angle glaucoma. BMC Ophthalmol. 2024;24(1):122. doi:10.1186/s12886-024-03384-y
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