This disease is known as the 'silent thief of sight'

In glaucoma, damage to the optic nerve is caused by too much pressure within the eye. — Photos: 123rf.com

Glaucoma affects about 80 million people worldwide and is the second leading cause of blindness globally, after cataracts.

However, it creates a greater public health challenge than cataracts, as the blindness caused by glaucoma is irreversible.

It is a disease that progressively affects the optic nerve of the eye.

The nerve damage is usually the result of an abnormally high pressure within the eye.

The majority of patients have no symptoms, especially during the early stages of the disease, which is why glaucoma is also known as the “silent thief of sight”.

Glaucoma cannot be cured, but the progression of the disease can be halted.

The goal of treatment is to preserve the visual field (the total area you can see when your eye is fixed on one point) and prevent the progressive loss of visual function that is associated with the disease.

Lowering the abnormal pressure within the eye is the most important treatment strategy to halt the progression of glaucoma.

In recent years, advancements in diagnostic and therapeutic methods for glaucoma have allowed for earlier diagnosis, better monitoring and safer therapeutic intervention to change the course of the disease in order to preserve vision and minimise loss of visual function.

Catching it early

Perimetry is the fundamental tool used for the detection and monitoring of glaucoma through the measurement of your visual field.

However, now, we are able to diagnose glaucoma even before any changes to your visual field can be detected on standard perimetry testing.

The new swept-source optical coherent tomography (OCT) technology with a scanning rate of up to 100,000 A-scans per second allows for a wide-angle, high-quality image of the optic nerve and macula in a single scan.

This allows doctors to discriminate between healthy and glaucomatous eyes with less error.

The damage that glaucoma causes to the eye’s retinal cells leads to characteristic structural changes of the optic disc and retinal nerve fibre layer (RNFL) with subsequent loss of vision.

The high reproducibility of modern OCT systems permits the detection of progressive RNFL loss, even though its thickness is still within normal range.

This means that glaucoma can be diagnosed at a very early stage, even before it affects your vision, and with the right treatment, your vision can be effectively preserved.

Another new and non-invasive technique allows doctors to measure and monitor the amount of blood flow in the optic nerve head.

Known as OCT angiography, it can scan the eye and generate images of blood circulation in a matter of seconds, helping doctors to diagnose glaucoma, especially in early stage suspected cases.

As previously mentioned, eye pressure is a critical factor in the development of glaucoma.

Just like our blood pressure, eye pressure is not a fixed value and can fluctuate throughout the day.

If it goes up too high, it can lead to disease progression and visual field damage.

That is why it would be ideal if doctors could monitor the patient’s eye pressure continuously throughout the day.

However, this was not practical previously, and glaucoma management usually relied on single eye pressure measurements when the patient comes to the clinic.

Now, there are two methods that enable 24-hour monitoring of eye pressure at home.

One is a hand-held tonometer (a device that measures inner eye pressure), which allows patients to measure their own eye pressure at home.

And the other is a soft disposable silicone contact lens that has a micro-sensor embedded within it.

This micro-sensor can record changes in corneal shape, which are correlated to changes in eye pressure throughout the day.

The data is transferred via Bluetooth to a software programme that can then be accessed by the patient’s doctor.

If you have any of these risk factors for glaucoma, you should get your eyes checked regularly so that you can catch the disease early and preserve your sight.

Advances in treatment

Current glaucoma treatment is more personalised, with due consideration and empathy for the patient, who might experience treatment-related side effects.

Doctors will strive to provide convenience and minimise side effects, while still ensuring the effectiveness of the treatment.

There are three types of treatment available for glaucoma:

> Medical treatment

Topical eye drops are the most widely-used treatment to lower eye pressure.

However, they frequently cause side effects like dry eyes, discomfort, allergy, redness of the eye and pigmentation of the eyelids, among others.

Topical treatment can also be quite confusing and troublesome for patients, as it might require them to be on multiple types of eye drops that each need to be applied a different number of times a day, at different times.

Unsurprisingly, many patients tend to forget the proper times to apply the eye drops or can’t be bothered to follow the regime strictly.

This jeopardises the effectiveness of their treatment, leaving them vulnerable to the worsening of their glaucoma.

Side effects like allergies or dry eyes can be caused by long-term exposure to benzalkonium chloride, which is a preservative used in a majority of glaucoma eye drops.

In order to minimise such adverse effects, pharmaceutical companies are now able to produce not only preservative-free eye drops, but also fixed-dose combinations of two to three types of necessary eye drops.

In addition to reducing side effects, these fixed-dose combinations help to improve patient compliance as they only have to use one to two bottles of eye drops, compared to three to four bottles previously.

In 2020, the US Food and Drug Administration (FDA) also approved the first-ever injectable, biodegradable, sustained-release eye implant, which provides continuous drug delivery.

This implant lowered eye pressure in glaucoma patients by approximately 30% and was shown to maintain its effectiveness for 12 weeks.

Thus, all the patient needs to undergo is a single injection, which can provide continuous treatment for at least three months.

> Laser treatment

Laser trabeculoplasty is an advanced laser-based ophthalmological procedure for the treatment of glaucoma.

It improves the eye’s drainage system and reduces the intra-ocular pressure that causes the condition.

It is prescribed when the eye pressure is uncontrolled.

Suitable candidates include patients with difficulties in administrating eye drops; patients who have developed side effects or allergies to the eye drops; patients who have difficulty complying with topical treatment; elderly patients with multiple other illnesses; and pregnant women in whom eye drop therapy should not be used (i.e. contraindicated).

Traditional Argon Laser Trabeculoplasty (ALT) is more destructive to the microstructure of the eye.

However, the newer Selective Laser Trabeculoplasty (SLT) and Micropulse Laser Trabeculoplasty (mLT) are relatively safe and effective.

A successful laser trabeculoplasty treatment can provide eye pressure control in about 70% of cases in the first year.

This control decreases at a rate of about 6-10% per year, dropping to 50% at five years and 2-30% in 10 years.

However, the treatment can be repeated as long as no microstructure damage has occurred.

> Surgical treatment

The conventional approach to glaucoma treatment is to start with medications, then only proceed to surgery if visual field defects and disease progression occur.

By that point, however, a significant number of retinal cells would have already been lost.

Interventional glaucoma represents a paradigm shift in glaucoma care.

It involves a proactive, rather than reactive, approach to treatment.

In other words, we act before visual field defects and disease progression occur, rather than reacting only when such defects and progression are seen.

The use of OCT technology for early detection in RNFL changes allows for this proactive approach as it can detect glaucoma even before the patient’s visual field is affected.

The advent of minimally-invasive glaucoma surgery (MIGS) and implantable drug delivery systems have also facilitated this approach.

MIGS works by either helping to increase fluid outflow from various parts of the eye or decreasing fluid production within the eye.

Traditional glaucoma surgeries such as trabeculectomy and tube shunt implantation carry the risk of sight-threatening complications.

MIGS however, is associated with lower complication rates.

It typically requires a shorter operation time and allows for more rapid recovery.

It can also be combined with cataract surgery.

In addition to preventing or slowing early glaucomatous damage, interventional glaucoma aims to improve patients’ quality of life by minimising the treatment burden associated with pressure-lowering eye drops.

But there are still patients with advanced cases who need traditional glaucoma surgery.

For such patients, surgical techniques has been improved to enhance the outcome of the surgery.

For example, the Moorfield’s Safe Surgery System is designed to preserve visual acuity (clarity or sharpness of vision) by minimising the complications of trabeculectomy, while achieving a desirable post-operative eye pressure.

Trabeculectomy is a surgery that creates a new pathway for fluid inside the eye to be drained, thus reducing the pressure within the eye.

Another common surgical treatment in glaucoma is tube shunt implantation.

The tube shunt is a small silicone device implanted on top of the eye in order to drain the fluids within the eye so that the eye pressure is reduced.

This procedure has been shown to be successful in patients in whom trabeculectomy did not work, patients not suitable for other surgical interventions, and patients with complicated glaucomas, such as uveitic glaucoma (glaucoma caused by inflammation of the uveal tissues – the middle layer of the eye), neovascular glaucoma (glaucoma caused by abnormal blood vessels) and paediatric glaucomas (glaucoma in children), among others.

Since the introduction of the first glaucoma drainage device, various modifications of the original design and improvements in surgical techniques over the past 40 years have led to greater success and lower complication rates.

In addition, other glaucoma drainage devices have been introduced that offer unique features designed to facilitate implantation, improve eye pressure control, and reduce immediate and long-term complications.

The majority of people with glaucoma are treated with eye drops, which can be challenging in terms of side effects and complicated dosage regimes.

Get your eyes checked

As we enter 2022, the advances in glaucoma care include improved mechanisms of diagnosis, monitoring and treatment.

These will ultimately help us to determine which patients require more aggressive treatment and which treatments will maximise efficacy while minimising risk.

Medical treatment is still the mainstay of glaucoma management.

However, eye drops won’t work if patients do not use it properly.

Thus, the development of effective eye drops with better tolerability, less side effects and reduced frequency of application, help a lot in ensuring patient compliance and persistence in usage.

In early to moderate glaucoma cases, interventions such as SLT, mLT and MIGS are longer-lasting and more preferable from a patient lifestyle standpoint, compared to topical eye drops, although these may still be used to supplement treatment.

Traditional glaucoma surgeries, such as trabeculectomy and tube shunt implantation, are also still irreplaceable as they are more effective in advanced and complicated glaucoma cases.

However, the methods and devices used in such surgeries have also evolved to provide better outcomes for patients.

But the concept of interventional glaucoma is more than just techniques and devices.

As consultant eye surgeon and surgical innovator Professor Dr Iqbal “Ike” K. Ahmed said: “The term interventional glaucoma refers to more than simply technology.

“It is a mindset that the available technologies bring to us as surgeons and clinicians.

“Instead of being passive and watchful, waiting for our patients to progress, interventional glaucoma allows us to be actively involved in their care by providing interventional therapies that change the course of the disease.”

With the rapid advancement of technology and instillation of the concept of interventional glaucoma, doctors can deliver more patient- centric care, which incorporates vision-preserving diagnostics and therapeutics to enhance patient outcomes.

However, the first step still lies with the patient themself as no amount of technology can diagnose someone who does not go for an eye check-up.

Make sure you get your eyes checked regularly – at least once a year – especially those with risk factors for glaucoma like being 50 and above, having relatives with glaucoma (i.e. family history), being extremely short-sighted or long-sighted, previous eye injuries, and conditions like diabetes, high blood pressure and heart disease.

Dr Gan Eng Hui is a consultant ophthalmologist, cataract and glaucoma surgeon, and committee member for World Glaucoma Week 2022 in Malaysia, which is being organised by the Malaysian Glaucoma Society; the Health Ministry; the Malaysian Society of Ophthalmology; the College of Ophthalmologists, Academy of Medicine, Malaysia; Universiti Malaya; Universiti Kebangsaan Malaysia; and Universiti Sains Malaysia. For more information, email [e-mail] or click here. The information provided is for educational and communication purposes only, and should not be considered as medical advice. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this article. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.