Glaucoma is a complex disease that can lead to progressive and irreversible vision loss if left untreated. Its cardinal risk factor is elevated IOP due to increased outflow resistance in the conventional outflow pathway. Aqueous angiography studies have shown that, in addition to the trabecular meshwork (TM) and Schlemm canal, outflow resistance also occurs through the distal collector channels.1 Procedures that target all three areas of resistance provide patients with the best chance of controlling IOP and combatting glaucoma progression, but some are more invasive—and therefore riskier—than others.
Combined ab interno trabeculotomy and viscodilation of the Schlemm canal is a novel surgical approach that targets both proximal and distal points of resistance in the conventional outflow pathway in a single, implant-free, minimally invasive procedure. The OMNI Surgical System (Sight Sciences) can be used either in a standalone surgical procedure or in combination with cataract surgery to significantly reduce IOP from baseline levels. This article highlights its usefulness as a highly efficacious MIGS procedure.
When performing any glaucoma procedure, identifying where resistance occurs in the conventional outflow pathway can be challenging. Addressing the TM alone, or isolating a single point, may not be enough to achieve the desired IOP-lowering effect. The possibility of resistance occurring at any point suggests that a surgical option that addresses all three points of possible resistance (TM, the Schlemm canal, and the distal collector channels) may offer the best chance of surgical success.
Today, a novel MIGS approach that targets all three points of resistance is available. The OMNI Surgical System allows surgeons to combine ab interno trabeculotomy with viscodilation in an easy-to-perform, safe, and efficacious procedure that consistently and predictably lowers IOP in patients with open-angle glaucoma. OMNI can be performed in combination with phacoemulsification or as a standalone procedure, and it is titratable based on patient needs and surgeon preferences. It can be used in patients with mild, moderate, and severe primary and secondary open-angle glaucoma.
A STEPWISE APPROACH
I use a stepwise approach for management of open-angle glaucoma. The OMNI procedure closes the gap between conservative glaucoma therapy with eye drops and invasive stenting procedures that are typical in Schlemm canal surgery. I have been using the OMNI Surgical System for 4 years and find that it represents a psychological stepladder for my glaucoma patients who decide not to have conventional surgery because it is too invasive and risky.
I typically use the OMNI in patients with mild to moderate glaucoma (IOPs between 15 and 20 mm Hg), which is most of the glaucoma patients I treat. In patients with early-stage glaucoma, I perform the viscodilation portion of the procedure only to address the Schlemm canal and to enhance the natural outflow by reducing the resistance in the collector channels. The channel is widened with a viscoelastic alone, not by introducing a stent or other foreign body.
In patients with more severe open-angle glaucoma, I perform both the viscodilation and trabeculotomy portions of the OMNI procedure to simultaneously lower the resistance in the TM, the Schlemm canal, and the collector channels.
There are several advantages of the OMNI procedure.
Advantage No. 1: It provides the opportunity for more consistent IOP-lowering outcomes. The OMNI procedure addresses all three points of potential resistance in the conventional outflow pathway: the TM, Schlemm canal, and collector channels. This provides the opportunity to produce more consistent results, especially in combined cataract and MIGS cases.
Advantage No. 2: It creates the potential to use the procedure in a standalone fashion in a certain population of patients. This includes patients who are not willing or able to use eye drops, pseudophakic patients with glaucoma, younger patients without cataract, and patients with a history of failed glaucoma surgery such as trabeculectomy.
Advantage No. 3: It is an implant-free system. I like that the OMNI procedure ensures that the natural pathway for the outflow of aqueous humor is open without introducing a foreign body into the eye. I leave nothing permanently in the eye—only a viscoelastic is introduced into the eye, which disappears relatively quickly. No other technology is available today, besides a stent, that can widen the collector channels and create the potential opportunity to lower the IOP by restoring outflow.
Advantage No. 4: The OMNI Surgical System spares the conjunctiva and sclera. Therefore, it becomes possible to perform other glaucoma surgeries in the future as needed.
Advantage No. 5: It produces consistent results in both combination surgery and in standalone procedures. In our experience, the OMNI Surgical System produces similar results to stenting procedures, and this is true whether the surgery is combined with cataract surgery or performed in a standalone procedure. The benefit of a combined procedure, of course, is that we can enhance patients’ quality of life twofold, by lowering their IOP and by providing better quality of vision, in a single procedure.
Interestingly, cataract surgery can indeed lower IOP on its own; however, its effect is minimal, at best only 1 or 2 mm Hg. In most glaucoma patients, this decrease is not significant enough to alter their need for glaucoma drops or therapy. Most of the lowering potential of a combined procedure originates from introduction of the stent2 or from the OMNI procedure. Once the TM is opened and the Schlemm canal is functioning properly, the IOP will begin to decrease more significantly.
Advantage No. 6: It simplifies the surgical intervention. For surgeons with familiarity of the anatomical structures of the chamber angle, the learning curve with the OMNI is short. It is a sophisticated procedure, but most surgeons should become comfortable performing the procedure within about the first five cases. This is not like learning trabeculectomy, which can take years.
Viscodilation and trabeculectomy are highly efficacious. Due to the complexity of the surgeries, however, many doctors are not comfortable offering these procedures to their patients.
The availability of an equally efficacious procedure that is easier to perform and that targets all three points of resistance in the conventional outflow pathway has changed the way in which we can provide care to our glaucoma patients.
The OMNI Surgical System offers the efficacy of viscodilation and trabeculotomy but in a MIGS platform. It is a powerful tool for glaucoma and cataract surgeons to use in combined and standalone surgeries.
1. Huang AS, Peneteado RC, Saha SK, et al. Fluorescein aqueous angiography in live normal human eyes. J Glaucoma. 2018;27:957-964.
2. Hengerer FH, Auffarth GU, Riffel C, Conrad-Hengerer I. Second-generation trabecular micro-bypass stents as standalone treatment for glaucoma; a 36-month prospective study. Adv Ther. 2019;36(&):106-1617.