Across of all medicine, no matter the disease, the later we wait to treat, the more difficult and complex the treatment becomes and the more likely it is to fail. When our surgical choices for glaucoma patients consisted of trabs and tubes, the high-risk nature of the procedures meant we would delay intervening as long as possible.¹ Even for patients who are well controlled, drop therapy has barriers and drawbacks that limit its utility in the long run. These include noncompliance, ocular surface disease and other side effects, financial considerations or physical inability to self-administer eyedrops.²

The introduction of micro-invasive glaucoma surgery (MIGS) has created an opportunity for surgeons to intervene sooner in the disease progression and further capitalize on the pressure-lowering benefit of cataract surgery by performing combined procedures.³

THE CASE FOR MIGS + CATARACT SURGERY

MIGS in conjunction with cataract surgery has demonstrated significantly greater reduction in medication use and IOP compared to cataract surgery alone, with similar safety.^4-7 Treatment with MIGS has also been shown to reduce visual field (VF) loss.

A secondary analysis of almost 3,000 VFs in the 5-year HORIZON study of the Hydrus Microstent (Alcon) found that cataract surgery with the Hydrus had a significant effect on VF preservation in glaucoma patients vs cataract surgery alone.⁸ The mean rate of progression was -0.26 dB/y for cataract surgery plus the Hydrus and -0.49 dB/y for cataract surgery alone (P = .0138).

The authors wrote that the difference in IOP only explained 17% of the effect (P < .0001). Five-year survival analysis showed an increased probability of VFs worsening by 5.5 dB (P = .0170), indicating a greater proportion of fast progressors in the cataract surgery arm.

MIGS procedures — many of which can be incorporated into traditional phacoemulsification surgery with a minimal learning curve — are surgical interventions that have a high safety profile, offer minimal disruption of normal anatomy, can be done through an ab interno approach, are effective for IOP lowering and are patient and physician friendly.⁹

WHERE TO START?

IOP lowering can be achieved by enhancing outflow across the trabecular meshwork and through Schlemm’s canal by selective laser trabeculoplasty, placing a trabecular meshwork bypass stent, surgical incision and/or excision of this tissue, and dilation/expansion of Schlemm’s canal. Other MIGS target the uveoscleral outflow pathway with microstent placement in the suprachoroidal space. A third approach involves decreasing aqueous production by ablation of the ciliary body using endocyclophotocoagulation (ECP).

Of the 3.7 million cataract surgeries yearly in the United States, anywhere from 15% to 20% of the patients also have glaucoma.^10,11 The “low-hanging fruit” in terms of cataract surgery plus MIGS are glaucoma patients who are stable and not progressing on one or two classes of medication and are motivated to lessen their reliance on drops. Even if they are well controlled, angle surgery using a stent or a goniotomy along with cataract surgery will increase the likelihood they can reduce or come off drops. This opportunity should absolutely be discussed with patients during the informed consent process prior to cataract surgery.

If one is just beginning to incorporate MIGS procedures, excisional goniotomy is a good place to start, as there is no hardware left behind. After becoming proficient at gonioscopy, ophthalmologists might jump into the stent market. The hierarchy is usually a couple of clock hours goniotomy procedures followed by stents. Generally, the larger the stent, the more surgical expertise is involved in making sure that it’s properly placed. Larger incisional goniotomies would be the next level — only because there’s a slightly higher risk of blood reflux and hyphema that must be managed.

Here is a review of several MIGS procedures that can be performed along with cataract surgery/phacoemulsification.

TARGET: TRABECULAR MESHWORK

Stents

iStent and iStent inject (Glaukos). The iStent is a heparin-coated, non-ferromagnetic titanium stent, 0.3 mm in height and 1 mm in length, preloaded into a single-use sterile injector.

The pivotal trial found that, at 12 months, 72% of iStent-plus-phaco eyes had reached the primary endpoint of IOP ≤21 mm Hg without medications vs 50% of phaco-only eyes. About two-thirds of iStent eyes had achieved an IOP reduction ≥20% compared to 48% of phaco-only eyes; there was no difference in adverse events.¹²

The iStent inject measures 360 µm by 230 µm. Its pivotal trial found that at 24 months, 75.8% of patients who received iStent inject plus phaco had at least a 20% reduction in IOP vs 61.9% for phaco alone. The combination group also had a mean IOP reduction of 7.0 ± 4.0 mm Hg compared to 5.4 ± 3.7 mm Hg in the phaco alone group, and 84% of combination eyes were medication free at 23 months compared to 67% of phaco-only eyes.⁴

Hydrus Microstent (Alcon). The nitinol microstent is 8 mm in length and 290 µm in diameter and spans 90 degrees of the trabecular meshwork. The pivotal HORIZON study found that at 24 months, 77.3% of eyes in the combination group experienced at least a 20% reduction in IOP compared to 57.8% of eyes in the phaco-only group. The mean change in unmedicated IOP at 24 months was -7.6 ± 4.1 mm Hg in the combination group compared to -5.3 ± 3.9 mm Hg in the phaco-only group.

The patients in the combination group went from 1.7 ± 0.9 drops to 0.3 ±0.8 drops at 24 months vs 1.7 ± 0.9 drops to 0.7 ± 0.9 drops at 24 months in the phaco-only group.⁴

Tissue excision

Kahook Dual Blade (KDB; Alcon). KDB is a specialized single-use, disposable goniotomy blade. One-year outcomes of KDB with phaco showed that mean IOP at 6 months decreased from 17.4 ± 5.2 mm Hg to 12.8 ± 2.6 mm Hg, and 58.3% of patients had an IOP reduction of ≥20% from baseline. The number of medications decreased from 1.6 ± 1.3 to 0.9 ± 1.0.¹³

Another study revealed that eyes that underwent phaco with KDB goniotomy experienced a significant reduction in mean IOP at 1 year from 16.8 ± 0.6 mm Hg at baseline to 12.4 + 0.3 mm Hg. In addition, 57.7% of eyes experienced a 20% reduction in IOP, and the number of medications decreased from 1.6 ± 0.2 to 0.8 ± 0.1 eyedrops.¹⁴

An additional study evaluated 12-month outcomes of phaco-KDB vs KDB alone with success defined as ≥20% IOP reduction and/or reduction of at least one glaucoma medication. Phaco-KDB had a success rate of 71.8% compared to 68.8% with KDB alone.¹⁵

Trabectome (MicroSurgical Technology). The system performs an ab interno trabeculotomy via a single-use, disposable handpiece that performs electrocautery, irrigation and aspiration. In patients with combined phaco and Trabectome, mean IOP decreased from 20.0 ± 6.3 mm Hg to 15.5 ± 2.9 mm Hg at 1-year postoperative, and the average number of topical medications was reduced from 2.65 ± 1.13 to 1.44 ± 1.29 drops.¹⁶

Gonioscopy-assisted transluminal trabeculotomy (GATT). GATT surgical technique circumferentially bypasses the trabecular meshwork via a suture or catheter. A study of 24-month follow-up on GATT combined with phaco found that IOP was reduced from 26.40 ± 6.37 mm Hg on 3.12 ± 0.80 medications preoperatively to 14.61 ± 2.28 mm Hg on 0.27 ± 0.71 medications at 12 months and 16.08 ± 2.38 mm Hg on 0.45 ± 0.96 medications at 24 months after combined surgery.¹⁷

TARGET: SCHLEMM’S CANAL

OMNI Surgical System (Sight Sciences). This implant-free approach allows for performing canaloplasty followed by trabeculotomy with a single instrument.

Patients receiving the procedure plus phaco had a 5.6 ± 4.5 mm Hg (P < .001) IOP drop. More than two-thirds of patients had a >20% reduction in IOP.¹⁸

Ab Interno Canaloplasty (ABiC) with iTrack canaloplasty microcatheter system (Nova Eye Medical). The iTrack is a 250-µm microcatheter that is advanced through a nasal goniotomy into Schlemm’s canal and withdrawn while performing viscodilation of the canal and the distal outflow system. One 12-month efficacy study found no significant difference between IOP reduction in eyes that underwent standalone ABiC vs eyes that underwent combined ABiC/phaco.

The average IOP reduction at 12 months post-op was a little more than 30% in both groups; 84.9% of eyes experienced an IOP reduction of greater than 20% from baseline. The average number of IOP-lowering drops decreased from 2.8 ± 0.9 drops to 1.1 ±1.1 drops, a 60% average reduction. At 1 year follow-up, 40% of eyes were off all IOP-lowering drops.¹⁹

STREAMLINE Surgical System (New World Medical). This is a single-use, disposable device that pierces the trabecular meshwork to create a goniotomy while delivering viscoelastic for dilation. Data so far show that at 6 months, patients with phaco plus STREAMLINE had significantly lower IOP with a ≥20% reduction achieved in 89.5% of eyes and mean medication use went from 2.0 ± 0.8 to 1.1 ± 1.1.²⁰

TARGET: SUBCONJUNCTIVAL SPACE

The XEN Gel Stent (Allergan). XEN, a 6-mm long, 45-µm lumen diameter stent made of tissue-conforming gelatin, is the only FDA-approved device to use this approach. Results from a meta-analysis that included eight studies comparing XEN plus phaco with XEN alone found a significant difference in lowering IOP (1,034 eyes, standard mean differences [SMD] 0.22, 95% CI, 0.05 to 0.40, I²=38%) and reducing the number of medications (729 eyes, SMD 0.20, 95% CI, –0.06 to 0.46, I²=62%).²¹

TARGET: CILIARY BODY ABLATION

Endocyclophotocoagulation (ECP). ECP uses a laser endoscopic probe inserted through a clear corneal incision to directly visualize and ablate the ciliary body.

A study of eyes that underwent phaco vs phaco with ECP showed that at 2 years post-op follow-up IOP in the combined group decreased to 16.0 ± 3.3 mm Hg compared to 17.3 ± 3.2 mm Hg in the phaco-only group (statistically significant). The mean number of glaucoma medications decreased from 1.5 ± 0.8 to 0.4 ± 0.7 drops at 2 years in the study group and from 2.4 ± 1.0 to 2.2 ± 1.1 in the control group.²²

CONCLUSION

Modern interventional glaucoma encompasses not only treatment but an early and confident diagnosis of the risk of progression to determine the best, safest intervention to maximize pressure reduction, keep patients disease free with low complications, lessen the medication burden — and ultimately improve their quality of life. OM

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Arsham Sheybani, MD, is an associate professor of ophthalmology and visual sciences; Residency Program Director Fellowship Director Advanced Anterior Segment and Glaucoma Surgery in the John F. Hardesty, MD, Department of Ophthalmology & Visual Sciences at Washington University School of Medicine. Disclosures: Alcon, Allergan, Ivantis and Santen.