An increasing number of microinvasive glaucoma surgery (MIGS) procedures and devices have been developed over the past several years. The rapid expansion of this field has provided numerous options to glaucoma surgeons who are looking to provide safe and effective treatments for their patients that do not carry the same burdens of prolonged recovery and risk of vision-threatening complications that are more typical of traditional filtering surgeries. One of the newest and most innovative devices to enter this space is the Streamline Surgical System from New World Medical.

The Streamline Surgical System is a single-use device designed to create titratable goniotomies and localized canaloplasty in one unified step. It was approved for use by the US Food and Drug Administration in October 2021 to treat ocular hypertension or glaucoma patients with open angles. The device affords surgeons a great deal of versatility because it can be used in either phakic or pseudophakic patients, and in combination with cataract surgery or as an independent treatment. The Streamline System’s handpiece contains a stainless-steel cannula, housed within a polymer outer sleeve, both of which are downstream of an ophthalmic viscosurgical device (OVD) reservoir (Figure 1). The upper aspect of the handpiece contains an actuator button which, when depressed, retracts the outer sleeve. This exposes the inner cannula while simultaneously delivering a bidirectional injection of OVD through its 2 side ports (Figure 2).¹

Intraoperatively, the device is used under direct visualization with the assistance of a gonioscopic lens. The outer sleeve is applanated against the trabecular meshwork (TM), and the actuator button depressed, allowing the cutting cannula to create a 150 µm goniotomy while delivering approximately 7 µL of OVD bidirectionally into Schlemm’s canal. The actuator button is then released and the handpiece retracted, so that the device can be moved to an adjacent untreated area of TM, where the procedure can be repeated. The device contains enough OVD to perform 8 applications, delivering a total of 56 µL of OVD into Schlemm’s canal over several clock hours of the angle. To titrate the size of the goniotomy formed by the initial puncture into the TM, the actuator button is held down to keep the outer sleeve retracted, and the cannula is advanced to either side in a cutting capacity along the TM, with a goal of achieving more than 90° or 3 clock hours of goniotomy.

Pearls for Use

As with any MIGS device, there are several surgical nuances to be aware of when beginning to use the Streamline Surgical System. This first pearl applies before ever stepping foot in the operating room: proper patient selection. Ideal candidates include patients with ocular hypertension or mild to moderate open-angle glaucoma, although any disease severity may be considered. Streamline should be considered in patients who have uncontrolled intraocular pressures (IOP) despite medical therapy or those who are controlled on medical therapy but desire decreased medication dependence due to issues with side effects, allergy, adherence, and/or cost. Gonioscopy should be performed in the clinic to ensure open angles free of any significant anterior synechiae or neovascularization. Patients with coexisting cataracts can be excellent candidates for the procedure to be performed in conjunction with cataract surgery, although the device can be used in patients with a clear lens or who are already pseudophakic.

The second pearl applies to patient and microscope positioning. As with all angle-based surgeries, the microscope should be rotated toward the surgeon as the patient’s head is rotated away, to allow for an en face view of the angle. Due to the configuration of the Streamline handpiece and, in particular, the actuator button located on the upper aspect of the device, visibility can be optimized by slightly under-rotating the patient’s head (approximately 30° to 35°) and slightly over-rotating the microscope (45° to 50°) compared to the typical rotation of 40° to 45° for each. This still allows for the same en face view of the angle but keeps the handpiece lower in the field of view, minimizing any obstruction from the surgeon’s finger as the button is depressed, and maximizing visibility of the angle.

Prior to insertion into the eye, the Streamline device should be primed just outside the corneal incision with a depression of the actuator button to deliver OVD through the cannula and clear the sleeve of any retained air bubbles. Alternatively, this can be done inside the eye just inside the wound to either side of the view. The surgeon should also ensure a comfortable but steady grip on the handpiece, with the index or third finger maneuverable, to allow for depression of the actuator button. The surface area of the button on the Streamline is slightly larger than that on most other MIGS devices and thus, the force required to depress the button may be slightly greater than the surgeon expects. A firm grip on the device is imperative to ensure that no slippage or downward movement of the handpiece occurs when the actuator button is depressed. If a hands-free gonioprism is used, the extra hand can be used to help support the dominant hand holding the device as the button is pushed. Hands-on practice with the device in the wet lab is vital to ensure a secure but comfortable hand grip on the device before heading to the operating room.

There are also a few distinctions to the treatment delivery itself with Streamline. First, the outer blue sleeve can serve as a guide to proper height positioning in the angle. The lateral flares of the sleeve can be aligned with the TM and the sleeve gently applanated against the meshwork before activation of the button. Too much outward pressure may cause corneal striae or collapse the TM into the canal, whereas not enough outward pressure will prevent appropriate entry of the cannula into the canal. When depressing the actuator button, the handpiece should be held in place for 2 seconds before moving on, to allow time for delivery of the OVD down both sides of Schlemm’s canal.

Finally, the surgeon should be aware that the goniotomy and OVD injection performed by the Streamline system may have few if any visual cues during the procedure. This is largely due to the minimal tissue disruption the procedure causes with microgoniotomies that are often too small to visualize directly. However, there are several visual cues that can confirm correct device positioning and treatment. These cues include blood reflux through goniotomy incisions when IOP drops below episcleral venous pressure, blanching or displacement of blood residing in Schlemm’s canal, OVD egress through neighboring goniotomies, and episcleral vessel blanching downstream to the treated clock hours. The surgeon should monitor for these cues to ensure correct device placement and treatment, but also realize they may not be readily evident in every patient despite correct use of the device.

Clinical Outcomes

Given its relatively recent development, there are limited data from studies reporting the outcomes of the Streamline Surgical System in glaucoma patients thus far. One of the first studies to be performed was a prospective, single-arm case series looking at IOP reduction and medication use at 6 months in patients who underwent cataract surgery with Streamline. The study population consisted of 20 eyes with mild to severe primary open-angle glaucoma (POAG). At 6 months follow-up, 89.5% of patients achieved 20% or greater mean IOP reductions, 42.1% were medication free, and no adverse events were reported.²

Another group performed a retrospective case series of eyes with mild to severe open angle glaucoma that underwent cataract surgery with Streamline. At 6 months follow-up, the surgical success rate, defined as IOP reduction of 20% or greater and/or reduction of 1 topical glaucoma medication, was 66.7%. There was 1 reported complication of an IOP spike after surgery, which was treated medically.³

Conclusion

The Streamline Surgical System is a relatively new MIGS device that creates goniotomies and performs canaloplasty without leaving behind an implant. Early clinical data have demonstrated good efficacy with excellent safety for the procedure, but larger studies with longer follow-up are necessary to better understand the utility of the device. As with any new surgical device, surgeons should be aware that the Streamline Surgical System has a short learning curve. Awareness and application of these surgical pearls can help to ensure a smooth adoption of the procedure and may optimize postoperative outcomes. GP

Galia Deitz, MD, is a glaucoma fellow at the University of Colorado School of Medicine in Aurora, Colorado. She reports no disclosures.

Leonard K. Seibold, MD, is a professor of ophthalmology and director of the glaucoma fellowship at the University of Colorado School of Medicine. He reports consultancy to New World Medical. Reach Dr. Seibold at leonard.seibold@cuanschutz.edu.

References

1. New World Medical. New World Medical announces launch details for the Streamline Surgical System. News release. March 1, 2022. Accessed June 20, 2023. https://www.newworldmedical.com/new-world-medical-announces-launch-details-for-the-streamline-surgical-system/
2. Lazcano-Gomez G, Garg SJ, Yeu E, Kahook MY. Interim analysis of Streamline surgical system clinical outcomes in eyes with glaucoma. Clin Ophthalmol. 2022;16:1313-1320. doi:10.2147/OPTH.S358871
3. Temple H, Grove N, Patnaik J, Kahook M, Seibold L. Clinical outcomes with the Streamline Surgical System in mild to severe open angle glaucoma. Presented at: the American Glaucoma Society Meeting; Austin, TX; March 2023.