Beyond Cataract Surgery: Standalone Glaucoma Intervention

The introduction of minimally invasive glaucoma surgery (MIGS) has revolutionised our approach to treating this sight-threatening disease, offering new options to patients and expanding the toolkit available to ophthalmologists.

The benefits of MIGS in combination with cataract surgery are well-established and widely recognised. These procedures have demonstrated remarkable efficacy in reducing the need for glaucoma medications, slowing visual field progression, and minimising the necessity for more invasive secondary surgical interventions such as trabeculectomy.1 Performed concurrently with cataract surgery, MIGS procedures provide added efficacy without adding significant risk to the patient.

However, as we continue to advance glaucoma care, an important question arises: Why limit the benefits of MIGS only to those undergoing cataract surgery? There exists a substantial population of glaucoma patients who either do not yet require cataract surgery or have already undergone the procedure. These individuals represent an opportunity for improved glaucoma management through standalone MIGS procedures.

The potential benefits of early standalone MIGS intervention are significant:

1. Improved intraocular pressure (IOP) control: Achieving and maintaining target IOP with less reliance on medication.
2. Enhanced quality of life: Reducing or eliminating the daily burden of eye drops and their associated side effects.
3. Preservation of ocular health: Minimising long-term exposure to preservatives in eye drops, potentially reducing ocular surface disease.
4. Disease management optimisation: Intervening earlier in the disease process, potentially slowing progression and preserving vision.

This article explores the limitations of traditional medical therapy, the shift towards early surgical management of glaucoma, and the range of technologies available for early surgical intervention. It also discusses the crucial role that optometrists play in identifying suitable candidates for these procedures and the importance of patient education.

By considering early standalone MIGS intervention, we have the opportunity to significantly improve the quality of life for our glaucoma patients and potentially alter the course of their disease progression. As eye care professionals, it’s our duty to stay informed about these advancements and consider how they might benefit our patients.

LIMITATIONS OF RELIANCE ON MEDICAL THERAPY

Historically, the mainstay of glaucoma treatment has been medical therapy – primarily eye drops – to reduce IOP and minimise the risk of glaucoma progression. However, medical therapy has significant limitations that can impact its long-term effectiveness and patient outcomes.

Adherence Challenges

One of the most significant issues with medical therapy is poor patient adherence. Studies have consistently shown that a substantial proportion of patients fail to use their glaucoma medications as prescribed. More than half of patients are nonadherent with therapy after three to four years of treatment.^2,3 This low adherence rate is concerning, as it directly impacts the effectiveness of treatment.

The implications of non-adherence are significant. Nonadherent patients are more likely than adherent patients to experience disease progression.^4,5 This underscores the importance of consistent medication use in maintaining visual function.

Tolerability and Side Effects

Glaucoma medications can cause a range of side effects that affect patient quality of life and willingness to continue treatment.

These include:

1. Ocular surface disease: Preservatives in eye drops, particularly benzalkonium chloride (BAK), can cause or exacerbate ocular surface disease. BAK is found in 70% of all ophthalmic formulations and is linked to multiple cytotoxic effects on ocular surface cells.^6,7,8
2. Prostaglandin-associated periorbitopathy (PAP): Long-term use of prostaglandin analogues can lead to changes in the periocular tissues. PAP is characterised by eyelash changes, hyperpigmentation of the iris and periorbital skin, potentially irreversible deepening of the upper eyelid sulcus, periorbital fat loss, ptosis, and enophthalmos.^9,10,11
3. Systemic side effects: While less common, some glaucoma medications can have systemic effects. For instance, beta-blockers have been associated with respiratory and cardiovascular side effects in susceptible individuals.

Challenges with Multiple Medications

As glaucoma progresses, patients often require multiple medications to control their IOP. This polypharmacy approach introduces several problems:

1. Increased risk of side effects and nonadherence: Each additional medication increases the likelihood of side effects and reduces adherence rates.
2. Washout effect: When multiple drops are used in close succession, there’s a risk of one drop washing out the previous one, reducing overall efficacy.
3. Conjunctival inflammation: Chronic use of multiple medications can lead to conjunctival inflammation, which may reduce the success rate of future filtration surgery if needed.¹²

Difficulty with Instillation

Many glaucoma patients, particularly older individuals, struggle with the physical act of instilling eye drops or remembering to take them. This can lead to underdosing and reduced treatment efficacy.

Diurnal IOP

Control Eye drops typically provide pulsatile IOP control, with peak effectiveness shortly after instillation followed by a gradual decline. This can lead to IOP fluctuations, which some studies suggest may be a risk factor for glaucoma progression.

Given these limitations, there’s a clear need for treatment options that can provide consistent IOP control while minimising the burden on patients. Early surgical intervention with MIGS procedures offers a potential solution, providing continuous IOP control without the adherence and tolerability issues associated with medical therapy.

EARLY SURGICAL MANAGEMENT: A PARADIGM SHIFT

The limitations of medical therapy have prompted a re-evaluation of glaucoma management strategies. There is growing evidence to support earlier surgical intervention in the glaucoma treatment paradigm, particularly with the advent of MIGS procedures.

Supporting Evidence

Several landmark studies have demonstrated the potential benefits of early surgical intervention in glaucoma management:

1. Moorfields Primary Treatment Trial: This study evaluated primary surgical treatment for glaucoma and showed better visual field outcomes in laser and surgery groups compared to medical therapy alone.¹³
2. Collaborative Initial Glaucoma Treatment Study (CIGTS): This large, multicentre randomised trial compared initial treatment with medications to initial treatment with trabeculectomy. The study found that patients in the initial surgery group had a lower risk of substantial visual field loss over time, particularly in patients with more advanced disease at baseline.¹⁴
3. Early Manifest Glaucoma Trial (EMGT): While not specifically comparing surgical to medical therapy, this study demonstrated the importance of IOP reduction in slowing glaucoma progression.¹⁵

The MIGS Revolution

The introduction of MIGS procedures has fundamentally altered the risk-benefit profile of early surgical intervention. Traditional glaucoma surgeries, while effective, carry significant risks that often relegated them to later stages of the disease. However, MIGS procedures offer several advantages that are challenging this paradigm:

1. Enhanced safety profile: MIGS procedures have demonstrated a favourable safety profile compared to traditional glaucoma surgeries. A meta-analysis by Lavia et al. found that MIGS procedures had a lower rate of severe complications compared to trabeculectomy.¹⁶
2. Faster recovery: Most MIGS procedures are associated with rapid visual recovery and minimal postoperative care, allowing patients to return to normal activities quickly.¹⁷
3. Preserves future options: Many MIGS procedures spare conjunctival tissue, preserving the option for traditional filtering surgery if needed in the future.¹⁷
4. Reduced medication burden: MIGS procedures have been shown to significantly reduce the need for glaucoma medications.¹⁸

Benefits of Early Intervention

Early surgical intervention with MIGS offers several potential benefits:

1. Improved quality of life: By reducing or eliminating the need for daily medications, early MIGS intervention can significantly improve patient quality of life.¹⁹
2. Better IOP control: MIGS procedures can provide more consistent 24-hour IOP control compared to medical therapy, potentially slowing disease progression.
3. Preservation of ocular surface: By reducing the need for topical medications, early MIGS intervention may help preserve ocular surface health.²⁰
4. Cost-effectiveness: While the initial cost of MIGS procedures is higher than medical therapy, early surgical intervention may be cost-effective, particularly when considering the costs of long-term medical therapy and potential disease progression.

This paradigm shift towards earlier surgical intervention offers the potential to improve long-term outcomes for glaucoma patients. By addressing the limitations of medical therapy and intervening before significant disease progression occurs, we may be able to preserve vision more effectively and improve patient quality of life.

AVAILABLE TECHNOLOGY FOR EARLY SURGICAL INTERVENTION

The landscape of MIGS has expanded rapidly in recent years, offering a range of options for early surgical intervention. This section focusses on some of the key MIGS technologies available, with a particular emphasis on those that are funded or emerging in the Australian market.

iStent Infinite

The iStent infinite (Glaukos) trabecular micro-bypass system is the latest iteration of the proven iStent platform designed to reduce IOP in patients with primary openangle glaucoma (POAG), pseudo-exfoliative glaucoma, or pigmentary glaucoma. It consists of three heparin-coated titanium stents that are implanted into Schlemm’s canal, providing access to more clock hours of the eye’s natural outflow system.

The stents are inserted ab interno through a small corneal incision, bypassing the trabecular meshwork to improve aqueous outflow.

A prospective, single-arm, multicentre clinical trial of iStent infinite as a standalone procedure in patients with refractory glaucoma showed promising results.²¹ At 12 months post-operative:

• 76% of eyes achieved ≥20% IOP reduction from baseline,
• Mean IOP reduction was approximately 25%, and
• 74% of subjects achieved IOP ≤18 mmHg on the same or fewer medications compared to baseline without secondary surgical intervention.

The study demonstrated that iStent infinite can provide clinically significant IOP and medication reductions in a challenging patient population with refractory glaucoma, with a favourable safety profile through 24 months.²¹ While effective in refractory glaucoma, in Australia the use of iStent infinite is not restricted to this patient population.

Hydrus Microstent

The Hydrus Microstent (Alcon Surgical) is an 8 mm long trabecular bypass device that is implanted into Schlemm’s canal to improve aqueous outflow.

The device is inserted through a small corneal incision and placed within Schlemm’s canal, where it bypasses the trabecular meshwork but also dilates the canal and provides direct aqueous access to multiple collector channels.

The efficacy of standalone Hydrus MicroStent insertion has been proven and examined relative to two first generation iStents in the COMPARE study – a prospective, multicentre, randomised clinical trial. The study found that the Hydrus Microstent was more effective in reducing the number of ocular hypotensive medications and achieving surgical success compared to two first generation iStent devices. At 12 months postoperatively, 46.6% of patients in the Hydrus group were medication-free compared to 24% in the 2-iStent group. Additionally, eyes treated with the Hydrus device were more likely to achieve an IOP of ≤18 mmHg without medications (30.1% vs 9.3%). Both devices demonstrated similar safety profiles with no significant differences in adverse events.²² The findings suggest that the Hydrus Microstent may be a more effective standalone MIGS option. However, it is important to note that these findings relate to the first generation iStent and that the performance of the iStent infinite may vary; although this has yet to be examined.

Miniject

Miniject (iSTAR Medical) is a minimally invasive glaucoma drainage implant made of a porous material designed to be implanted into the supraciliary space.

The device is implanted ab interno through a clear corneal incision into the supraciliary space, enhancing uveoscleral outflow.

The Miniject supraciliary drainage device has demonstrated significant promise in treating open angle glaucoma (OAG), particularly when used as a standalone procedure. Multiple studies have highlighted its efficacy and safety, making it a valuable option for eye care professionals to consider.

The STAR-I trial, a first-in-human study, reported that the Miniject device significantly lowered IOP by 40.7% and reduced the need for glaucoma medications by 50% at 24 months post-surgery.²³ This trial included 25 patients with uncontrolled glaucoma and showed no serious ocular adverse events, underscoring the device’s favourable safety profile. Commonly observed issues, such as anterior chamber inflammation and IOP elevation, were generally mild and resolved without the need for additional surgical intervention.

Further supporting the device’s efficacy, a meta-analysis conducted by Dick et al. assessed the Miniject’s performance up to two years after implantation in 82 individuals across multiple countries. The study confirmed the device’s consistent IOP-lowering effects and minimal adverse events, reinforcing its long-term safety and effectiveness.²⁴

The STAR-II trial also provided encouraging results, with a 40% reduction in IOP and a 63% decrease in medication burden.²⁵ This European multicentre trial included 29 patients and demonstrated that the Miniject device maintains its efficacy over time while having minimal impact on corneal health.

In conclusion, the Miniject device offers a promising surgical option for managing OAG, combining significant IOP reduction with a strong safety profile.

iTrack

iTrack Advance (Nova Eye Medical) is an ab interno canaloplasty procedure that uses a microcatheter to viscodilate the entire 360° of Schlemm’s canal.

The microcatheter is inserted into Schlemm’s canal via a small corneal incision. As it is withdrawn, viscoelastic is injected to dilate the canal and associated collector channels. iTrack provides a very comprehensive approach, targeting all three sites of resistance to aqueous outflow.

Studies on the standalone use of iTrack for glaucoma have demonstrated its effectiveness and safety in reducing IOP and decreasing the need for glaucoma medications. A retrospective single-centre study followed 27 eyes of 21 patients with OAG for up to four years, showing significant reductions in both IOP and the number of medications required.²⁶ Another study extended this observation to six years, confirming sustained IOP reduction and decreased medication use in patients with POAG and pseudoexfoliative glaucoma.²⁷

Additionally, a case series involving 45 eyes of 35 patients with controlled mild to moderate POAG reported effective long-term medication reduction and maintenance of target IOP levels over a three-year period.²⁸ These findings consistently support the use of standalone iTrack canaloplasty as a viable, long-term treatment option for glaucoma, providing significant benefits in terms of IOP control and medication reduction, with a favourable safety profile.

It’s important to note that while these technologies show promising results, they are not suitable for all patients. The choice of MIGS procedure should be tailored to the individual patient based on factors such as the stage of glaucoma, target IOP, prior surgeries, and anatomical considerations.

At the time of publication many, but not all, of these procedures were eligible for Medicare funding or reimbursement by health insurers. This article focusses on early surgical intervention for patients with mildto- moderate glaucoma. For patients with more advanced disease or those refractory to maximum medical therapy, subconjunctival MIGS devices, such as Xen or PreserFlo, may be more appropriate options.

The rapid evolution of MIGS technologies offers exciting possibilities for early surgical intervention in glaucoma management. As we continue to gather long-term data on these procedures, through tools like the International Glaucoma Surgery Registry and the Fight Glaucoma Blindness! Registry, we will be better equipped to optimise their use in our treatment algorithms.

THE IMPORTANCE OF EDUCATION

As MIGS procedures become more prevalent in the management of glaucoma, it is crucial that all eye care professionals, particularly optometrists, are well-informed about these treatment options. Education plays a vital role in ensuring that patients receive timely and appropriate interventions.

Identifying potential candidates for early surgical intervention

Optometrists are at the frontline of glaucoma detection and management; playing a crucial role in identifying patients who might benefit from early MIGS intervention. Potential candidates for early surgical intervention typically include:

1. Patients with early to moderate glaucoma,
2. Patients without significant cataract or those who are already pseudophakic,
3. Cases where the effect of selective laser trabeculoplasty (SLT) has been short-lived or ineffective,
4. Patients experiencing side effects from medical therapy,
5. Cases where medical therapy is not achieving the target IOP, and
6. Patients showing signs of progression but not to a degree warranting more invasive surgery.

In these patients, standalone MIGS can be used for IOP reduction, medication reduction, or both, depending on the individual’s unique circumstances.

Understanding MIGS Safety Profile

When discussing MIGS with patients, it’s crucial to highlight its safety profile. A meta-analysis by Lavia et al. found that MIGS procedures had a lower rate of severe complications compared to trabeculectomy.¹⁶ Key points to emphasise include:

1. Minimally invasive nature of the procedures,
2. Lower complication rates compared to traditional glaucoma surgeries,
3. Shorter recovery times, and
4. Preservation of conjunctival tissue for potential future surgeries if needed.

Surgeon Selection

For standalone MIGS procedures, the choice of surgeon is particularly important. When not performed with cataract surgery, it is critical that standalone procedures achieve the desired surgical goal. Points to consider include:

1. The surgeon’s experience with MIGS procedures,
2. The learning curve associated with MIGS techniques, and
3. The surgeon’s outcomes and complication rates.

Patient Decision Making

Educating patients about MIGS options is crucial for informed decision making. Key points to cover include:

1. The potential benefits of early intervention,
2. The limitations of continued medical therapy,
3. The range of available MIGS options,
4. Realistic expectations of outcomes, and
5. Potential risks and complications.

Collaborative Care

Effective glaucoma management requires a collaborative approach between optometrists and ophthalmologists. Regular communication and shared care protocols can ensure that patients receive timely referrals for MIGS when appropriate.

By staying informed about MIGS technologies and their appropriate use, optometrists can play a pivotal role in improving outcomes for glaucoma patients. Early identification of suitable candidates for MIGS, coupled with timely referral, can help preserve vision and improve quality of life for many individuals living with glaucoma.

CONCLUSION

The introduction of MIGS has ushered in a new era in glaucoma management, offering the potential for earlier surgical intervention with a favourable risk-benefit profile. The limitations of medical therapy, coupled with the growing evidence supporting early surgical intervention, make a compelling case for considering MIGS procedures earlier in the treatment paradigm.

The range of available MIGS technologies provides options for tailored treatment approaches, addressing the diverse needs of patients with mild to moderate glaucoma. However, the success of these interventions relies heavily on proper patient selection, surgeon expertise, and a collaborative approach between optometrists and ophthalmologists.

By embracing early surgical intervention when appropriate, we have the opportunity to potentially alter the course of glaucoma progression, reduce medication burden, and improve quality of life for our patients. The field of MIGS is rapidly evolving, and ongoing research will continue to refine our understanding of the long-term outcomes and optimal use of these procedures.

However, it’s crucial to remember that the decision to pursue early surgical intervention should always be tailored to the individual patient. Factors such as the stage of glaucoma, target IOP, overall health, and patient preferences must all be carefully considered. The collaborative efforts of optometrists and ophthalmologists will be essential in identifying suitable candidates for early MIGS intervention and ensuring optimal outcomes.

To earn your CPD hours from this article visit mieducation.com/beyond-cataractsurgery- benefits-of-early-standalone-glaucomaintervention.

Dr Nathan Kerr BHB MBChB MD FRANZCO is a leading ophthalmologist specialising in glaucoma and cataract surgery. As principal investigator for numerous clinical trials, he is at the forefront of innovative treatments for glaucoma.

With a passion for minimally invasive glaucoma surgery (MIGS), Dr Kerr has performed thousands of laser and MIGS procedures and is renowned for his expertise in this field. He regularly trains fellow surgeons in these advanced techniques, both in Australia and internationally.

Dr Kerr has published extensively in peer-reviewed journals and is a frequent speaker at international conferences. His work bridges the gap between cutting-edge surgical techniques and practical, patient-centred care.

As a strong advocate for collaborative eye care, Dr Kerr works closely with optometrists to ensure comprehensive management of glaucoma patients. He believes in empowering both practitioners and patients with the latest knowledge and treatment options.

Dr Kerr practises at Eye Surgery Associates in East Melbourne, Doncaster, and Vermont South. doctorkerr.com.au.

 

 

 

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