iStent inject allows early glaucoma intervention
A surgeon says implantation of the device is an elegant, straightforward procedure.
Glaucoma is a disease with no cure; left untreated, it can result in partial or complete loss of vision over time. It is not only the leading cause of blindness among African Americans and Hispanics in the United States, but it is also a leading cause of irreversible blindness globally. In the U.S., more than 3 million Americans are affected by glaucoma, with the majority having open-angle glaucoma.
Because older patients have a higher incidence of cataracts and the majority of this population segment in the United States has open-angle glaucoma, this permits the use of microinvasive technology during cataract surgery. Surgeons who utilize this combined surgical approach for patients with cataracts and glaucoma greatly augment the chance of improving vision, lowering IOP and possibly decreasing the overall number of glaucoma medications.
In this column, Dr. Nguyen describes the use of the iStent inject in his patients with cataract and glaucoma.
Thomas “TJ” John, MD
OSN Surgical Maneuvers Editor
With the number of glaucoma patients on the rise, the need for earlier glaucoma intervention has never been more relevant. Microinvasive glaucoma surgeries have changed the algorithm for treating glaucoma and offer an opportunity to intervene earlier in the disease spectrum to delay or even avoid the need for conjunctival incisional glaucoma surgery. Earlier intervention allows for better IOP control and the possibility of medication burden reduction, which lead to preservation of vision and quality of life.
While modern cataract surgery is well established to effectively lower IOP, there are still questions of consistency and the duration of time the IOP will remain lowered. With MIGS procedures such as the recently approved iStent inject (Glaukos), the IOP-lowering effect of phacoemulsification not only can be enhanced but extended, in addition to reducing glaucoma medications.
The iStent inject is indicated for patients with mild to moderate glaucoma in conjunction with cataract surgery and has been demonstrated to be effective in IOP lowering. I have found implanting the iStent inject to be an elegant, straightforward procedure with a reasonable learning curve.
In my practice, I prefer to implant the iStent inject after successful cataract surgery. My surgical routine for phacoemulsification is unchanged when adding iStent inject. While familiarity with intraoperative gonioscopy and comfort in maneuvering both the patient’s head position and the microscope are important, the key is visualization of the angle and maintaining clear visualization throughout the implantation. With that in mind, I prefer to use miotics such as Miostat (carbachol intraocular solution, Alcon) to constrict the pupil and also aid in maintaining stiffness of the iris. The use of cohesive viscoelastic such as Healon GV (sodium hyaluronate, Johnson & Johnson Vision) is my preferred choice to provide superior visualization and maintain a stable anterior chamber during the procedure.
I routinely coach the patient in the preoperative area regarding the head maneuvering that is expected so the patient is not surprised during the surgery. I also find that speaking to the anesthesiologist before the case is helpful in setting the level of the patient’s alertness parameter for a MIGS procedure. After uncomplicated phacoemulsification, I will go through the routine steps for angle surgery, which includes proper microscope tilting and asking the patient to rotate the head to the proper angle. Before implantation, I will view the angle one last time with my Swan-Jacob goniolens for final confirmation of angle anatomy and my location of implantation. At this time, I remind the patient to hold still as best as possible and tell the patient that he or she may experience a pressure sensation during implantation. The delivery system of the iStent inject enters through the previously fashioned temporal clear corneal incision and advances toward the nasal quadrant. The first iStent inject is deployed superior or inferior in the nasal quadrant, and the second iStent inject is implanted 2 to 3 clock hours away from the first one.
Once the two stents are well placed, I then thoroughly remove the viscoelastic via the irrigation and aspiration probe. For canal-based MIGS such as iStent inject, I prefer to maintain a stable anterior chamber by leaving the IOP at the end of the case in the mid to high teens, which also serves to minimize any blood reflux that may occur.
In the postoperative period, my patients follow the same steroid and antibiotic regimen as with any typical phacoemulsification procedure. In my practice, glaucoma medications are usually not withdrawn immediately until I observe a stable and downward IOP trend once inflammation, if any, has resolved. Once I am certain IOP is stable in the postoperative period (up to 4 weeks), patients who are on monotherapy will discontinue their medication and be asked to return in 6 weeks for an IOP check and to re-establish a new baseline IOP. For patients who are on multiple glaucoma medications, I typically withdraw the adjunctive medications first and observe IOP trends. Then, if IOP continues to show a downward trend, I will discontinue all glaucoma medication.
In summary, when adding a MIGS procedure such as iStent inject to an elegant and well-established procedure such as phacoemulsification, it is imperative that the visual acuity outcome is comparable to cataract surgery alone because patients expect great visual results. The iStent inject fulfills a treatment gap in glaucoma management as a procedure that is effective at lowering IOP and reducing medication burden while maintaining the excellent safety profile of modern cataract surgery.
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- Samuelson TW. Prospective, randomized, multicenter clinical investigation of the Glaukos iStent inject. Presented at: American Society of Cataract and Refractive Surgery annual meeting; April 13-17, 2018; Washington.
- Tham YC, et al. Ophthalmology. 2014;doi:10.1016/j.ophtha.2014.05.013.
- Voskanyan L, et al. Adv Ther. 2014;doi:10.1007/s12325-014-0095-y.
- For more information:
- Quang H. Nguyen, MD, associate head of the Division of Ophthalmology and director of Glaucoma Service at Scripps Clinic Medical Group, can be reached at Scripps Clinic Torrey Pines, 10666 N Torrey Pines Road, La Jolla, CA 92037; email: firstname.lastname@example.org.
- Edited by Thomas “TJ” John, MD, a clinical associate professor at Loyola University at Chicago and in private practice in Oak Brook, Tinley Park and Oak Lawn, Ill. He can be reached at email: email@example.com.
Disclosures: Nguyen and John report no relevant financial disclosures.