Interventional Glaucoma and the OD’s Role

Optometrists play a critical role in the preservation of vision in the battle against glaucoma. We are often the first to diagnose, educate, and make treatment decisions for patients with glaucoma. A range of modern therapies, including topical glaucoma medications, laser procedures, and minimally invasive glaucoma surgeries (MIGS), allows optometrists to be more proactive in glaucoma management.

We understand the consequences of long-term preservative use on the ocular surface, including epithelial cell loss, meibomian gland dropout, loss of tear film homeostasis, and reduced corneal sensitivity.¹ These effects can lead to decreased quality of life, decreased treatment adherence, and, ultimately, disease progression. A 2019 survey of 204 patients found that more than 30% reported not using their topical therapy consistently.² We frequently encounter patients with advanced ocular surface disease (OSD) who have been using multiple glaucoma drops for years and are dissatisfied with their general comfort and visual quality. Short-term steroid use or additional drops such as immunomodulators feel like a temporary band-aid in the uphill battle against glaucoma. In these situations, we need to think outside the box and beyond drops.

THE VALUE OF DROPS

Topical therapy still has its place in glaucoma management. Topical agents can effectively reduce IOP and preserve visual fields for our patients. In situations where patients are surgery-resistant, have OSD, or require treatment after selective laser trabeculoplasty (SLT) or MIGS, several preservative-free formulations are available. Preservative-free latanoprost (Iyuzeh, Thea Pharma) showed similar IOP-lowering results and fewer reported side effects compared with latanoprost (Xalatan, Mylan) in a study of more than 330 patients.³ Tafluprost (Zioptan, Thea Pharma) is another preservative-free prostaglandin analog. Compounded preservative-free options exist that combine a variety of different medications. These are useful options for advancing glaucoma that requires multiple combinations of topical therapy, but clinical studies are limited.

A PLACE FOR LASER

The LIGHT study, which advocates for the use of SLT early in the disease process, demonstrated that SLT is slightly better at obtaining target IOP than topical therapy as a first-line treatment for ocular hypertension or mild to moderate open-angle glaucoma.⁴ At the 6-year mark, there was less visual field progression and fewer invasive surgeries needed in the laser group compared with the topical therapy group.⁴ This, along with a large proportion of SLT-first patients remaining medication-free, highlights the value of presenting SLT as a first-line option alongside topicals.⁴ This procedure is repeatable, and the literature suggests a second SLT is likely to have a similar IOP-lowering effect if the original response lasted longer than 12 months.⁵

Direct SLT helps alleviate the challenge of SLT lens intolerance by using a translimbal approach without an SLT lens to deliver energy to the trabecular meshwork (Figure 1). Early studies show a similar rate of IOP reduction compared with standard SLT.⁶ The full therapeutic effect of SLT treatment is typically 6 to 8 weeks, and ODs should follow patients to re-evaluate the response and treatment plan. The side effect profile is safe, and the incidence of effects such as elevated IOP, anterior chamber inflammation, and corneal edema is less than 1%.⁴

SURGICAL OPTIONS

MIGS are popular adjunct therapies for mild to moderate glaucoma that aim to reduce IOP. These procedures use an ab-interno approach, can be standalone or in combination with phacoemulsification, and have a better safety profile than traditional glaucoma filtering procedures. MIGS function by lowering IOP via the conventional aqueous outflow pathway.

Current trabecular meshwork bypass stents, such as the 2-stent (iStent Inject, Glaukos) and 3-stent (iStent Infinite, Glaukos), can enhance outflow in up to 240° of Schlemm canal (Figure 2). The 2-stent system is indicated for patients with mild to moderate glaucoma with a visually significant cataract. The 3-stent system is typically reserved for more advanced glaucoma patients who have failed with other therapies. A 12-month study showed that 74% of patients achieved > 20% reduction in IOP and 47% achieved > 30% reduction after a standalone procedure after failing medications.⁷

The Schlemm canal microstent (Hydrus, Alcon), approved for patients with mild to moderate glaucoma with a visually significant cataract, lowers IOP through trabecular bypass and dilation of Schlemm canal. The Horizon study showed that the microstent was more effective than phacoemulsification alone, with 73% of patients receiving the microstent free of additional medications at the 3-year mark compared with 48% in the phacoemulsification-only group.⁸

Goniotomy is another widely used MIGS procedure that involves trabecular bypass via excision of the trabecular meshwork. Goniotomy can be performed with a variety of devices allowing removal of 3 to 5 clock hours of the meshwork and can be done as a standalone or combined procedure. A 12-month study compared standalone goniotomy with combined phacoemulsification and showed that 71% of patients in the combined group achieved a 20% reduction in IOP versus 68% in the standalone group.⁷

Canaloplasty followed by trabeculotomy (OMNI, Sight Sciences) allows for combined viscodilation of Schlemm canal and removal of the trabecular meshwork. This procedure is currently approved for combination with cataract surgery or as a standalone procedure.

A supraciliary device (AlloFlo, Iantrek) was the most recently approved MIGS procedure. It differs from others in that it works to increase uveoscleral outflow. This is achieved through the manual creation of a cyclodialysis cleft, followed by the implantation of two biocompatible scleral tissue spacers, which serve to keep the cleft open. A 2-year study performed in combination with cataract surgery showed that 74% of primary open-angle glaucoma patients achieved > 20% IOP reduction.⁹

In the postoperative management of MIGS patients, the appropriate timing for reducing topical medications is crucial. Typically, ODs discontinue one medication 4 to 6 weeks after surgery if the patient is at their target IOP. At that time, the patient will have completed the postoperative steroid regimen, and the risk of an IOP spike is lower. Other common complications include anterior chamber inflammation, corneal edema, IOP spikes, and hyphema. If hyphema occurs, it often self-resolves in 1 to 2 weeks, but patients must be educated on the importance of maintaining proper head positioning, monitoring spikes in IOP, and continuing their postoperative regimen. Gonioscopy should be performed at every visit in the case of dense anterior chamber inflammation, elevated IOP, or concern of MIGS failure.

NOVEL DELIVERY METHODS

Drug delivery is the newest wave in the interventional glaucoma movement. Bimatoprost SR (Durysta, Abbvie), FDA approved in 2020, is a biodegradable implant that resides in the anterior chamber and offers sustained release of bimatoprost for 4 months. Early-phase trials and recent phase 4 trials show that some patients did not require retreatment for up to 24 months.¹⁰ Current approval is for one-time use; indications include standalone for ocular hypertension and any stage of glaucoma. Another treatment consideration for bimatoprost SR is a patient needing a “drop holiday” to treat the ocular surface or as dual therapy with SLT to minimize topical treatment.

The travoprost intraocular implant (iDose, Glaukos) is another intracameral implant that releases travoprost for up to 3 years (Figure 3). This implant is approved for ocular hypertension and any stage of glaucoma and can be used with phacoemulsification or standalone.

Studies show both implants achieved IOP reductions similar to topical prostaglandins (30% to 35%) while offering the benefits of around-the-clock IOP control.¹⁰ Common side effects associated with topical prostaglandins are reduced with these implants, as they are both placed inside the eye.

THE FUTURE IS HERE

Interventional glaucoma is here to stay and will only continue to grow. From laser therapy to MIGS to sustained drug delivery, these technologies offer better disease control with lower treatment burden. A revamped approach in managing this chronic condition will pay dividends in a patient’s overall quality of life.