Cataract and Glaucoma: Optimising Ocular Outcomes

Cataract and glaucoma are among the most common causes of visual impairment encountered in ophthalmic practice. Cataract remains the leading cause of reversible blindness worldwide, while glaucoma is the leading cause of irreversible blindness. As life expectancy increases, and patients remain visually active later in life, clinicians are increasingly faced with the challenge of managing both diseases simultaneously.

Historically, cataract and glaucoma were viewed as separate entities. Cataract surgery was undertaken to restore vision, while glaucoma treatment focused on preserving optic nerve function through reduction of intraocular pressure (IOP). Over the past two decades, however, our understanding of the relationship between these conditions has evolved dramatically. The crystalline lens is now recognised as an important contributor to glaucoma pathophysiology, particularly in angle closure disease. At the same time, cataract surgery itself has become an increasingly important glaucoma intervention.

The emergence of minimally invasive glaucoma surgery (MIGS) has further blurred the distinction between cataract and glaucoma surgery. For many patients, cataract surgery now represents an opportunity not only to improve visual function but also to reduce medication burden, improve pressure control, and potentially alter the course of glaucoma management.

Why Cataract and Glaucoma Commonly Coexist

The simplest explanation for the coexistence of cataract and glaucoma is age. The prevalence of both conditions increases significantly after the age of 60. Yet age alone does not explain the strength of their association.

Several glaucoma subtypes are closely associated with cataract. Pseudoexfoliation syndrome is a prime example. The deposition of pseudoexfoliative material throughout the anterior segment predisposes patients to secondary open-angle glaucoma and is associated with an increased prevalence and earlier development of cataract.^1,2 Similarly, primary angle closure disease is fundamentally related to age-related enlargement of the crystalline lens, with increasing lens thickness and anterior lens position contributing to progressive narrowing of the anterior chamber angle.^3,4

How Glaucoma and its Management Can Lead to Cataract

Epidemiological studies have demonstrated an association between elevated IOP and cataract. In the population-based Blue Mountains Eye Study, elevated IOP was independently associated with an increased prevalence of nuclear cataract, while the use of topical glaucoma medications was associated with an almost two-fold higher likelihood of nuclear cataract after adjustment for potential confounders.⁵ These findings suggest that both the glaucomatous disease process and its medical management may contribute to the coexistence of cataract and glaucoma, although the relative contributions of elevated IOP, medication exposure, and shared age-related mechanisms remain difficult to distinguish.⁵

The strongest association between cataract and glaucoma management exists for filtration surgery. The Advanced Glaucoma Intervention Study demonstrated a significantly increased risk of cataract progression following trabeculectomy.⁶ Although the exact mechanisms remain uncertain, postoperative inflammation, post-operative steroid use, hypotony, alterations in aqueous flow, and changes in lens metabolism are likely contributors.

Tube shunt surgery is also associated with cataract progression, although generally to a lesser degree than trabeculectomy.7 The practical implication is that many patients who undergo successful glaucoma surgery will eventually require cataract extraction.

How Cataract Can Cause Glaucoma

Throughout life, the crystalline lens continues to grow. This progressive enlargement can result in shallowing of the anterior chamber and narrowing of the iridocorneal angle.⁴

These anatomical changes play a central role in primary angle closure disease. As the lens enlarges, pupillary block increases and the peripheral iris is displaced anteriorly. Over time this can result in appositional angle closure, peripheral anterior synechiae formation, and elevated IOP.^3,4

The lens can also cause secondary glaucomas. Phacomorphic glaucoma results from an enlarged lens crowding the anterior segment and precipitating angle closure. Phacolytic glaucoma develops when proteins leak from a hypermature lens and obstruct trabecular outflow. Although these conditions are less common in developed countries, they illustrate the important role the lens can play in glaucoma pathogenesis.

Cataract Surgery as a Glaucoma Procedure

One of the most important developments in modern glaucoma care has been recognition that cataract surgery itself lowers IOP. Numerous studies have demonstrated sustained pressure reductions following uncomplicated phacoemulsification.^8-10

The magnitude of pressure reduction varies according to glaucoma subtype and baseline pressure. Patients with ocular hypertension and angle closure often experience the greatest benefit. In primary open-angle glaucoma, reductions of one to four millimetres of mercury are commonly reported.^8,9

Several mechanisms have been proposed. Removal of the crystalline lens deepens the anterior chamber, widens the angle, and improves access of aqueous humour to the trabecular meshwork (Figure 1). Changes in Schlemm canal geometry and trabecular function may also contribute.^9,10

Figure 1. Anterior segment optical coherence tomography (AS-OCT) comparing an eye with angle-closure A) before and B) after cataract surgery. Notable changes are the deepening of the anterior chamber, flattening of the iris profile and opening of the irido-corneal angle.

Importantly, cataract surgery frequently reduces medication burden. For patients requiring one or two medications, this can significantly improve adherence, reduce ocular surface toxicity, and enhance quality of life. Cataract surgery is, therefore, increasingly viewed as part of the glaucoma treatment spectrum rather than simply a vision-restoring procedure.8,10

The EAGLE Trial and Early Lens Extraction

The Effectiveness in Angle-closure Glaucoma of Lens Extraction (EAGLE) study challenged the traditional paradigm of treating angle closure disease with laser peripheral iridotomy followed by medical therapy.⁴

Patients with primary angle closure or primary angle-closure glaucoma were randomised to clear lens extraction or conventional treatment (Figure 2). The results demonstrated lower IOP, fewer medications, and better quality-of-life outcomes in the lens extraction group. Lens extraction was also shown to be cost-effective over time.⁴

Figure 2. The EAGLE trial compared A) clear lens extraction to B) standard of care laser peripheral iridotomy in patients with angle closure.

The significance of the EAGLE trial extends beyond the management of angle closure disease. Prior to its publication, most clinicians viewed laser peripheral iridotomy as the logical first-line intervention because it addressed pupillary block while avoiding the risks of intraocular surgery. Lens-based surgery was generally reserved for patients with visually significant lens opacity.

EAGLE challenged this paradigm. By demonstrating superior quality-of-life outcomes, lower IOP, and reduced medication dependence with clear lens extraction, the study suggested that the lens itself was the dominant anatomical driver of disease in many patients. Importantly, the benefit extended beyond pressure reduction alone. Patients reported improved health-related quality of life, supporting the concept that anatomical correction can provide broader functional benefits.⁴

The study also stimulated debate regarding the role of lens extraction in earlier stages of disease. While not every patient with narrow angles requires immediate surgery, EAGLE encouraged clinicians to think beyond the traditional framework of treating angle closure as a laser disease. Today, many glaucoma specialists discuss lens extraction far earlier in the disease course than would have been considered appropriate 15 years ago.

Managing the Patient with Both Cataract and Glaucoma

Management of coexisting cataract and glaucoma requires balancing visual rehabilitation against long-term glaucoma control. Patients with mild glaucoma and visually significant cataract may achieve excellent outcomes with cataract surgery alone. Others with moderate disease may benefit from a combined cataract-MIGS procedure. Patients with advanced glaucoma often require filtration surgery or tube implantation to achieve sufficiently low target pressures.

Several factors influence decision making. These include disease severity, target pressure, progression rate, medication burden, age, visual needs, and ocular anatomy. The surgeon must also consider future treatment options. Preserving conjunctival integrity may be particularly important in younger patients who may require filtration surgery later in life.

MIGS: Transforming Combined Cataract and Glaucoma Surgery

The emergence of MIGS has transformed the relationship between cataract and glaucoma surgery. Before MIGS, surgeons were often forced to choose between the modest pressure reduction associated with cataract surgery and the greater efficacy, but higher risk, associated with trabeculectomy.

MIGS created an intermediate option (Figure 3). Procedures such as iStent inject, Hydrus Microstent, canaloplasty, and goniotomy provide meaningful reductions in IOP and medication burden with a favourable safety profile.^10-16

Figure 3. Two of the most commonly performed MIGS in combination with cataract surgery in Australia are A) iStent infinite and B) Hydrus Microstent.

Robust evidence supports both the Hydrus Microstent and iStent inject when implanted in combination with cataract surgery for mild-to-moderate primary open-angle glaucoma. In the HORIZON trial, patients receiving the Hydrus Microstent achieved significantly greater reductions in IOP and medication use than those undergoing cataract surgery alone, with benefits sustained over five years, including a reduced need for subsequent incisional glaucoma surgery.¹¹ Similarly, a prospective randomised controlled trial demonstrated that implantation of two iStent inject devices at the time of cataract surgery resulted in significantly greater IOP reduction and a higher proportion of medication-free patients compared with cataract surgery alone.¹² Long-term follow-up and numerous real-world studies have confirmed sustained reductions in IOP and medication burden with a favourable safety profile.^13-16 Together, these devices have become well-established options for patients with mild-to-moderate glaucoma who wish to reduce medication dependence while avoiding the risks associated with traditional filtration surgery.

Australian Real-World Evidence for MIGS

Australian multicentre studies have made an important contribution to the evidence supporting both the Hydrus Microstent and iStent inject. Data from the Fight Glaucoma Blindness! registry have demonstrated sustained reductions in IOP and medication burden with both devices when combined with cataract surgery, together with favourable safety profiles in routine clinical practice. Comparative analyses have shown similar effectiveness for the Hydrus Microstent and iStent inject over two years, while longer-term registry data have confirmed durable outcomes for both implants across a broad spectrum of patients encountered in everyday clinical practice.^16,17 These real-world findings complement the pivotal randomised trials by demonstrating consistent effectiveness beyond the more selective populations typically enrolled in clinical trials.^15-18

Premium IOLs in Glaucoma Patients

One of the most debated topics in cataract surgery for glaucoma patients is the use of premium intraocular lenses (IOLs). Historically, multifocal lenses were considered unsuitable because glaucoma and multifocal optics both reduce contrast sensitivity.^19,20

Modern practice is more nuanced. The key question is not whether a patient has glaucoma, but whether glaucoma has significantly affected visual function.

Patients with ocular hypertension, glaucoma suspects, and those with mild stable glaucoma often remain suitable candidates for premium technologies. Toric lenses are particularly valuable and are frequently underutilised. Correction of astigmatism can dramatically improve uncorrected visual acuity without compromising contrast sensitivity.

Extended depth-of-focus lenses have emerged as an attractive compromise. They provide greater spectacle independence than monofocal lenses, while generally preserving contrast sensitivity better than traditional multifocal designs.¹⁹

Diffractive multifocal lenses remain more controversial. Careful patient selection and counselling are essential. Patients must understand that future glaucoma progression may affect visual satisfaction. For this reason, many surgeons reserve multifocal technology for patients with minimal disease and stable optic nerves.^19,20

Special Situations

Pseudoexfoliation syndrome presents some of the most challenging cataract cases encountered in clinical practice (Figure 4).

Poor dilation, zonular weakness, and increased postoperative inflammation all contribute to greater surgical complexity. These patients are also at higher risk of glaucoma progression and often require closer long-term follow-up.^1,2

Figure 4. Pseudoexfoliation syndrome is characterised by the presence of one or more of the following: flakey ‘dandruff-like’ material on the pupil margin and lens capsule, poor pupil dilation, unstable lens zonules, phacodonesis, iris transillumination defects, pigmentation of the trabecular meshwork, and angle closure.

The angle closure patient represents another unique scenario. Lens extraction often produces dramatic anatomical improvement, with deepening of the anterior chamber and widening of the drainage angle. In many cases, cataract surgery provides benefits that extend well beyond visual rehabilitation.^3,4

Previous trabeculectomy introduces additional considerations. Cataract surgery can jeopardise bleb function through postoperative inflammation and conjunctival scarring. Surgical planning should therefore aim to minimise trauma and preserve long-term filtration success.^6,7

Eyes with prior tube surgery present different challenges. Tube position, endothelial cell health, and anterior chamber anatomy must all be considered when planning surgery.⁷

The vitrectomised eye also warrants special attention. These eyes often exhibit altered fluidics, deeper anterior chambers, and greater zonular instability. Careful preoperative planning and intraoperative adaptation are important to achieve optimal outcomes.

Is Earlier Cataract Surgery Better?

Historically, cataract surgery was delayed until patients experienced significant visual disability. Advances in surgical safety and understanding of glaucoma pathophysiology have prompted reconsideration of this approach.

Earlier surgery offers several potential advantages. Cataracts are generally easier to remove, less phacoemulsification energy is required, and refractive outcomes are often more predictable. In glaucoma patients, earlier intervention may improve angle anatomy before permanent synechial closure develops.^3,8,9

The availability of MIGS further strengthens the case for timely intervention. Cataract surgery now provides an opportunity to address both visual impairment and glaucoma simultaneously.

Nevertheless, earlier surgery should not be interpreted as surgery at the earliest possible opportunity. The goal remains identification of the optimal point at which visual rehabilitation, glaucoma control, and surgical safety intersect.

When Should Optometrists Refer?

Optometrists play a central role in identifying patients who may benefit from cataract assessment. Referral should be considered not only when visual acuity declines, but also when cataract contributes to angle narrowing, medication burden, or difficulties in glaucoma management.

Patients with progressive angle closure, increasing dependence on topical medications, significant ocular surface disease, or interest in reducing treatment burden may benefit from earlier surgical consultation. Referral is also appropriate when visual field progression raises concerns regarding quality of life despite apparently adequate pressure control.^3,8-20

Increasingly, the cataract consultation represents an opportunity to optimise the entire glaucoma management strategy.

Looking Ahead

The next decade is likely to bring further integration of cataract and glaucoma care. Improvements in imaging technology may allow clinicians to better predict which patients will benefit most from lens-based intervention. Artificial intelligence and predictive analytics may assist in identifying individuals at greatest risk of progression.

MIGS technologies will continue to evolve, with newer devices seeking to balance safety, efficacy, and durability. Long-term registry data will become increasingly important in guiding treatment selection and informing patient expectations.^16-20

At the same time, growing recognition of the lens as a therapeutic target is likely to influence surgical timing. The traditional model of waiting for visually significant cataract may gradually give way to a more holistic assessment incorporating visual function, angle anatomy, medication burden, and long-term glaucoma risk.^3,8-20

For optometrists and ophthalmologists alike, the challenge will be to integrate these developments into patient-centred care. The ultimate goal remains unchanged: preserving vision and quality of life for patients living with glaucoma and cataract.

Dr Colin Clement MBBS BSc (Hon) PhD FRANZCO FGS is a Sydney-based ophthalmologist with expertise in the diagnosis and management of glaucoma, cataract, and general ophthalmology. He consults and operates in private practice in Sydney and is an Honorary Medical Officer in the glaucoma unit at Sydney Eye Hospital.

Alongside his clinical and research work, Dr Clement is committed to medical education. As a clinical senior lecturer at the University of Sydney, he delivers ophthalmology lectures and tutorials to medical and master’s students, nurses, optometrists, and other healthcare professionals.

References 

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10. Samuelson TW, Chang DF, Singh K, et al. A Schlemm canal microstent for intraocular pressure reduction in primary open-angle glaucoma and cataract: the HORIZON Study. Ophthalmology. 2019;126(1):29-37. doi: 10.1016/j.ophtha.2018.05.019
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20. Kumar BV, Phillips RP, Prasad S. Multifocal intraocular lenses in the setting of glaucoma. Curr Opin Ophthalmol. 2007;18(1):62-66. doi: 10.1097/ICU.0b013e328011d108.