Glaucoma management has always been a balancing act: lowering intraocular pressure (IOP) enough to prevent optic nerve damage, while minimizing the risks of treatment. In recent years, glaucoma stents, part of the growing field of minimally invasive glaucoma surgery (MIGS), have offered ophthalmologists more tools to achieve this balance. However, it can sometimes be a case of “lower risk, but lower benefit” with glaucoma stents. So, how do we decide when to use them, and when a more traditional surgery is warranted? 

Glaucoma stent surgery is typically considered when glaucoma is worsening or not adequately controlled with medications or laser treatment. It is not usually a first-line intervention, but rather a step taken when pressure remains too high or optic nerve progression is detected despite other therapies. 

Classes of Glaucoma Stents 

Glaucoma stents are designed to facilitate aqueous humor outflow and reduce IOP, but they differ in mechanism, surgical approach, and risk profile. Broadly, they fall into two categories: 

• Trabecular Micro-Bypass  Stents 

Example: iStent, Hydrus 

Mechanism: Bypass the trabecular meshwork into Schlemm’s canal.

Risk/Benefit: Very safe with minimal complications but typically result in modest IOP reduction. 

• Subconjunctival  or  Filtering  Stents 

Example: XEN, PreserFlo 

Mechanism: Creates a controlled drainage pathway to the subconjunctival space.

Risk/Benefit: Greater IOP reduction, closer to traditional trabeculectomy, but with higher risk of hypotony, bleb-related complications, or need for postoperative interventions. 

Indications for Glaucoma Stents 

Choosing the right glaucoma stent begins with understanding the patient’s disease severity, target IOP, ocular surface health, and the practical realities of long-term treatment. While no single device fits every scenario, the following principles can help guide decision-making: 

Mild to Moderate Glaucoma – Ideal for Trabecular Stents 

Trabecular micro-bypass implants, such as the iStent, are particularly well-suited for patients with mild to moderate primary open-angle glaucoma. These stents offer excellent safety, preserve the conjunctiva, and can meaningfully reduce IOP with a very low complication rate.  

Moderate to Severe Glaucoma – When Subconjunctival Stents Become Appropriate 

In patients with more advanced disease or those requiring a significantly lower target pressure, subconjunctival stents such as the XEN or PreserFlo may be considered. These devices provide greater IOP reduction because they create a bleb-based outflow pathway – similar in concept to a trabeculectomy but with more predictable outflow and fewer early complications. 

For Rapidly Progressing or Advanced Disease

For some patients with moderate to severe glaucoma – especially when very low target pressures are essential or when stent-based approaches are unlikely to achieve adequate control – a traditional trabeculectomy is the most effective option. While it carries higher risk, it remains the gold standard for achieving the lowest postoperative pressures and is an important consideration when disease progression is rapid or aggressive. 

Weighing Risk vs Benefit

The central dilemma with stents is trade-off: a low-risk procedure often means a smaller reduction in IOP, and a potential need for later surgery. Conversely, traditional surgeries like trabeculectomy or tube shunts offer greater IOP reduction but come with higher risks – hypotony, infection, bleb failure, or vision-threatening complications.

Key considerations include: 

• Assess disease severity and target IOP: If a patient has early glaucoma with moderate pressure, a trabecular stent may suffice. If advanced damage or low target pressures are needed, subconjunctival or filtering procedures may be justified. 
• Consider patient factors: Age, comorbidities, prior ocular surgery, and lifestyle can influence the risk-benefit balance.  
• Stepwise approach: Starting with a minimally invasive stent doesn’t close the door on future interventions. A patient may later require a filtering surgery, but you’ve preserved conjunctival tissue and minimized early complications. 

Is a Stepwise Approach a Bad Thing?

Glaucoma stents offer ophthalmologists a spectrum of choices along the risk-benefit continuum. The key is individualised decision-making: match the procedure to disease severity, patient-specific factors, and realistic IOP goals. Low-risk stents may not lower pressure as dramatically, but they can be an elegant first step in a stepwise surgical strategy – one that keeps eyes safe today while leaving options open for tomorrow. In glaucoma management, sometimes slow and safe wins the race, even if it means a second or third step down the line.