MIGS & EAGLE(S): Redefining the Role of the Lens in Glaucoma Management

In the UK, the management of patients presenting with co-existing cataracts and glaucoma requires a sophisticated, multi-factorial approach. Clinical decision-making is no longer a matter of addressing the lens in isolation; according to NICE and The Royal College of Ophthalmologists, practitioners must weigh the severity of the glaucoma, the specific subtype (e.g., POAG vs. Angle Closure), and the patient’s longitudinal eye health. A “one-size-fits-all” approach is insufficient; rather, a bespoke strategy is required to balance surgical risk against the potential for life-long intraocular pressure (IOP) control.

Effect of Cataract surgery alone

While phacoemulsification is known to reduce IOP, significant uncertainties remain regarding the magnitude and durability of this effect, particularly in glaucoma patients where a true “washout” of medications is rarely performed in clinical practice.

The systematic review by Brizido et al. (2023), which analysed six RCTs using a full washout of hypotensive therapy, provides the most rigorous data on unmedicated IOP changes. The results demonstrated:

• A consistent IOP reduction of 4.1–8.5 mmHg.
• A mean reduction of 0.2–1.0 hypotensive agents postoperatively.

However, the “washout” effect in these trials highlights that the IOP-lowering benefit of cataract surgery alone often attenuates after 24 months, frequently leading to a higher risk of resuming topical therapy.

Cataract surgery

Consultants must remain vigilant regarding the early postoperative period. While long-term IOP may decrease, glaucoma patients have a significantly higher incidence of IOP spikes immediately following surgery. These spikes were not fully evaluated in the Brizido analysis but are clinically critical.

Clinical Warning: Early postoperative IOP spikes can be visually damaging and lead to permanent glaucomatous progression.

EGS guidelines – Minimally Invasive Glaucoma Surgery

The European Glaucoma Society (EGS) defines MIGS as ab-interno, non-bleb-forming procedures. They are categorized by their specific mechanism of action:

Evidence for Combined Surgery

There is now overwhelming evidence, supported by Cochrane reviews, that canal-based MIGS with implants provides superior outcomes compared to phacoemulsification alone.

The HORIZON Trial (Hydrus Microstent), led by Ike Ahmed, and the COMPARE Study provide the benchmark for this evidence. Combined surgery not only addresses the lens but utilizes the existing surgical access to optimize the outflow pathway.

Hengerer study – iStent inject Outcomes

Long-term 5-year data for the iStent inject® demonstrates sustained glaucoma control. Key findings include:

• IOP Reduction: Approximately 39–42% reduction sustained at 60 months.
• Medication Burden: Reduced by 69–75%, significantly improving the ocular surface.

Horizon study

The 5-year data from the HORIZON trial for the Hydrus Microstent reinforces these gains:

• Medication Reduction: 66% of patients remained entirely medication-free.
• Visual Field Stability: Combined surgery showed a slower rate of VF progression; phacoemulsification alone had a higher proportion of “fast progressors.”
• Surgical Prevention: A >50% relative reduction in the need for secondary incisional surgical interventions (SSI) such as trabeculectomy or tube shunts (2.4% for Hydrus vs. 5.3% for phaco alone).

 Quality of life

The impact of MIGS extends beyond numerical IOP. As seen in Jones et al. (2023), MIGS + phaco significantly improves patient-reported outcomes. By reducing or eliminating the need for preserved anti-glaucoma drops, there is a marked improvement in Ocular Surface Disease (OSD). This leads to higher quality of life and better long-term compliance in those who still require minimal therapy.

 Cost effective

From a health economics perspective, cost-utility analyses confirm that both iStent inject® and the Hydrus Microstent are cost-effective options for mild-to-moderate POAG. Evaluated from the Italian NHS perspective and applicable to the UK, the initial cost of the device is offset by the long-term reduction in medication costs and the decreased need for expensive secondary surgeries.

Cataract Surgery and Glaucoma Surgery

Patient Selection

Successful outcomes depend on six key pillars:

1. Glaucoma Severity: Optimized for mild-to-moderate cases.
2. Angle Anatomy: Primarily indicated for Open-Angle Glaucoma.
3. Patient Preferences: Tolerance for drops vs. desire for surgical intervention.
4. Target IOP: Typically aimed at the mid-teens.
5. Ongoing Care: Where will follow-up occur? Consider the decoupling of services, if this occurs it could lead to patients benig lost in the crucial post operative period and timely, appropriate care, must be ensured.
6. Manage Expectations: Define “success”—is it drop reduction, OSD improvement, avoiding invasive surgery or a bridging treatment before filtration surgery?

Decision to perform MIGS – Clinician Overseeing patient’s long term care

According to the Ansari et al. (2025) UKEGS survey, the decision to perform MIGS should rest with the specialist managing the patient’s chronic care.

• Glaucoma patients undergoing cataract surgery must be offered MIGS and educated on its benefits.
• Decision to perform MIGS – Clinician Overseeing patient’s long term care
• Procedure carried out by specialists experienced in long term care
• MIGS in Independent Sector Treatment Centres (ISTCs) should be limited to surgeons with glaucoma fellowship training to ensure safety and continuity.

Which surgery should you proceed with first ?

Glaucoma Surgery First

This is unusual and occurs in high-risk emergency scenarios—such as uncontrolled IOP in advanced glaucoma or an immediate risk of permanent vision loss—cataract surgery is secondary. In these cases, emergency trabeculectomy + MMC or tube surgery remains the standard of care.

Combined Filtration Surgery + Cataract

Phaco trabeculectomy is now rarely performed in the UK. It is associated with a higher risk of failure and higher morbidity, generally reserved for severe glaucoma cases where both interventions are unavoidable.

Cataract and MIGS – the new Gold standard

The consensus is clear: if you are already inside the eye for cataract extraction, failing to address the IOP is a missed opportunity.

• Surgical Benefit: Preserves the conjunctiva for future interventions.
• Patient Benefit: Enhances QoL and reduces medication burden.
• System Benefit: Proves cost-effective and reduces the burden of secondary incisional surgery.

Clinical Scenario – Where to refer

Patients should be referred to a Glaucoma Specialist-led service. This ensures the patient is counselled on the full range of surgical options, receives the Phaco-MIGS procedure from an experienced specialist, and benefits from timely, expert long-term follow-up.