The Right Patients for iStent inject

In my practice, and across the ophthalmology industry, microinvasive glaucoma surgery (MIGS) has become a preferred surgical treatment plan for patients with mild to moderate glaucoma who are taking multiple medications to control IOP. The milder glaucoma patients with coexisting cataracts is an important subgroup and make up a majority of the patients we see in clinic today. Treating both ocular diseases in these patients is paramount and can be accomplished at the same time using the same small, self-sealing incision. Aside from lowering IOP and reducing the amount of postoperative medications, there are other pathologies to consider that can also benefit from MIGS.

Ocular Surface Disease and Glaucoma

Two of my practice specialties are cataract surgery, specifically with refractive cataract surgery, and ocular surface disease management. When I receive referrals from my medical community, they often refer with these two components in mind. Ocular surface disease and glaucoma are more common in older patients, and the standard first line of therapy for both is topical medications.¹ Ocular surface disease, in its various forms and presentation, frequently coexists with glaucoma and may be initiated or exacerbated by topical glaucoma medications. For this reason, it is important to devise a surgical plan that offers the patient the best possible outcome for overall eye health.

Treating glaucoma with topical medications may cause chronic inflammation or aggravate a concomitant ocular surface disease. Studies demonstrate that more than 90% of prostaglandin analogue users have clinically significant meibomian gland dysfunction, which is a blockage or other abnormality of the meibomian glands, so they do not secrete enough oil into the tears.² This demonstrates an extremely high correlation between the use of topical medications and ocular surface disease. The toxicities of the medication compounds and preservatives of the vehicle can lead to various ocular surface complications including hypersensitivity keratoconjunctivitis and/or corneal staining. The proinflammatory nature of prostaglandin analogues (PGAs) and chronic follicular conjunctivitis of brimonidine are just a few examples of the problematic nature of the active ingredients in glaucoma medications. It is well known that preservatives, particularly benzalkonium chloride, can further irritate the ocular surface with chronic use.³

Patients on these medications oftentimes develop intolerances to the medication, which leads to patient compliance issues and overall ineffectiveness of the intended outcome. Patient compliance in itself is an issue whether it is derived from the cost of the medication, missing the eye with the drops, or simply forgetting to use required medications. Patients with relatively stable IOPs and with minimal to no field loss that demonstrate early, preperimetric glaucoma characteristics such as changes in the optic disc and increased vulnerability to damage in the retinal nerve fiber layer are the perfect target candidates to consider a MIGS procedure such as the iStent inject (Glaukos).

The iStent inject is designed to help lower IOP by improving the aqueous outflow through the trabecular meshwork (TM) and spares destruction of the actual angle structures in the event that more significant glaucoma surgeries are needed in the future. Additionally, the iStent inject procedure, when conducted at the time of cataract surgery, has proven discontinuance of at least one of multiple postoperative glaucoma medications.⁴ This helps on multiple levels including allowing physicians to achieve a higher level of patient satisfaction and to combat poor patient compliance for patients who have been long-term users of multiple medications including the PGAs.

Expanding Options for Cataract Surgery

Consider a patient who has maintained a stable IOP on a prostaglandin with early to moderate glaucoma, without progression on their visual field, and who has early to moderate ocular surface disease. I would not offer them a presbyopia-correcting IOL implant knowing they are prone to ocular surface disease such as corneal staining. But if I know a patient responds well to preoperative optimization of the ocular surface, and they are not recalcitrant dry eye disease patients, but respond well to therapy, these are the patients that, if we stop a PGA, they could potentially see an improvement and turnover in their ocular surface. This allows them the option of greater spectacle freedom, whether that is for distance or greater range of vision. For these cases, this is when MIGS—particularly iStent inject—would be my first choice of treatment strategy. Being in a position to offer this to my patients is a great benefit and expands options for cataract surgery.

First Line of Defense—iStent inject

We are fortunate today to have multiple MIGS procedures—and even MIGS itself—to consider when thinking about a patient’s glaucoma treatment plan. We want to achieve the most impactful and safest outcome for our patients. We want a treatment plan designed to significantly lower IOP and reduce the amount of required medications. For patients with mild to moderate glaucoma the iStent inject is my first line of choice. When building a treatment plan, I prefer to opt for a device that spares the TM including space in Schlemm’s Canal. It needs to have low side effects, low complications, a high safety profile, and proven efficacy. This is where the iStent inject truly shines.

Since January 2019, I have been using the iStent inject regularly for cataract patients with mild to moderate glaucoma needing clinical intervention. In the beginning, there was some trepidation over what the efficacy profile might look like because the iStent inject is the smallest device available in a time when other devices are actually becoming larger and more invasive to qualify as MIGS. Professionally, I was curious if this device had the same power as the traditional iStent with mini goniotomy. I was extremely pleased to see a significant IOP-lowering effect while doing minimal to no destruction in the nasal region of where I was placing the iStent inject. In each patient where the iStent inject was used we’ve been able to discontinue at least one of their medications.

Efficacy and Targeted Outcomes

One of the key factors of the iStent inject is its efficacy profile. After 6 months of choosing this surgical plan, I found the efficacy of the iStent inject to be a key benefit. What makes the iStent inject a great surgical option is that it is not a destructive procedure of the TM. The incidence of hyphema or other postoperative IOP complications from other available procedures is truly minimal with the iStent inject.⁵ For MIGS in general, it is a good rule of practice to learn multiple procedures that reduce IOP in different ways. For surgeons considering the iStent inject for the first time, the learning curve is quite short. I found it to be straightforward to use once I got the idea of mastering intraoperative gonioscopy. Practicing the use of a gonioscope with your nondominant hand to get the angle positioning and aim at a comfortable level is key.

Conclusion

The results of my 6-month experience using the iStent inject for patients with mild to moderate glaucoma mirrors that of recent studies.⁶ In my practice, we’ve achieved the targeted outcomes of significantly lowering IOP and reducing required glaucoma management medications in patients with simultaneous cataract surgery. Compared to the first generation iStent, the second generation iStent inject demonstrated greater efficacy and fewer, nearly nonexistent, adverse events.

INDICATION FOR USE. The iStent inject ® Trabecular Micro-Bypass System Model G2-M-IS is indicated for use in conjunction with cataract surgery for the reduction of intraocular pressure (IOP) in adult patients with mild to moderate primary open-angle glaucoma. CONTRAINDICATIONS. The iStent inject is contraindicated in eyes with angle-closure glaucoma, traumatic, malignant, uveitic, or neovascular glaucoma, discernible congenital anomalies of the anterior chamber (AC) angle, retrobulbar tumor, thyroid eye disease, or Sturge-Weber Syndrome or any other type of condition that may cause elevated episcleral venous pressure. WARNINGS. Gonioscopy should be performed prior to surgery to exclude congenital anomalies of the angle, PAS, rubeosis, or conditions that would prohibit adequate visualization of the angle that could lead to improper placement of the stent and pose a hazard. MRI INFORMATION. The iStent inject is MR-Conditional, i.e., the device is safe for use in a specified MR environment under specified conditions; please see Directions for Use (DFU) label for details. PRECAUTIONS. The surgeon should monitor the patient postoperatively for proper maintenance of IOP. The safety and effectiveness of the iStent inject have not been established as an alternative to the primary treatment of glaucoma with medications, in children, in eyes with significant prior trauma, abnormal anterior segment, chronic inflammation, prior glaucoma surgery (except SLT performed > 90 days preoperative), glaucoma associated with vascular disorders, pseudoexfoliative, pigmentary or other secondary open-angle glaucomas, pseudophakic eyes, phakic eyes without concomitant cataract surgery or with complicated cataract surgery, eyes with medicated IOP > 24 mmHg or unmedicated IOP < 21 mmHg or > 36 mmHg, or for implantation of more or less than two stents. ADVERSE EVENTS. Common postoperative adverse events reported in the randomized pivotal trial included stent obstruction (6.2%), intraocular inflammation (5.7% for iStent inject vs. 4.2% for cataract surgery only), secondary surgical intervention (5.4% vs. 5.0%) and BCVA loss ≥ 2 lines ≥ 3 months (2.6% vs. 4.2%). CAUTION: Federal law restricts this device to sale by, or on the order of, a physician. Please see DFU for a complete list of contraindications, warnings, precautions, and adverse events.

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