Glaucoma

Glaucoma is widespread and insidious: at least half of glaucoma sufferers won’t know that they have it.  Sadly, if left untreated, it can lead to blindness. According to the World Health Organization, glaucoma is the second leading cause of irreversible blindness. It is estimated that at least 300,000 Australians have it, and it is most common in people over 70, but can develop earlier. By the age of 40, about one in 200 Australians have glaucoma and this rises to one in eight by age 80.

What is glaucoma?

Glaucoma is caused by pressure inside the eye causing damage to the optic nerve, which is the ‘cable’ that connects your eye to your brain. Just like water dripping on a rock will slowly thin down that rock, so will pressure pushing on the optic nerve cause the nerve tissue to thin. This thinning is called glaucoma. If untreated, it can result in blindness.

The front part of the eye is filled with a watery, nutrient-rich fluid called the aqueous humour. The eye produces this fluid constantly, and it drains away through a series of mesh-like channels, known as the trabecular meshwork.

In glaucoma, this fluid isn’t drained away fast enough, and pressure inside the eyes increases, causing progressive thinning of the optic nerve tissue. Usually, glaucoma will affect both eyes, although one eye may be more affected than the other.

red eye glaucoma nick andrew sight specialists gold coast cataract surgery glaucoma macular degeneration

There are different types of glaucoma. Most forms of glaucoma have no warning signs, as the change in vision is so gradual that it often goes unnoticed.  This provides yet another reason to get your eyes checked regularly if you are over 40.

Is eye pressure related to blood pressure, or to having a watery eye?

I’m often asked this question and I’m sure you were wondering the same thing. The simple answer is no, your eye pressure has nothing to do with your blood pressure and the two are unrelated. If you have a watery eye, this means that your eye is producing too many tears for your tear duct. This is unrelated to the production of aqueous humour, which is the fluid inside your eye.

Can glaucoma be prevented?

Glaucoma can’t reliably be prevented and it cannot be cured. But it can be managed and slowed down.

There are three main reasons why people lose vision from glaucoma:

  1. They are undiagnosed, or diagnosed very late.
  2. They are not properly treated.
  3. They don’t comply with their treatment, such as administering their medications as scheduled.

Glaucoma can change suddenly, requiring an adjustment in your eye medications or perhaps even surgery, depending on the type of glaucoma that you have.

Types of glaucoma

There are many different types of glaucoma and the classification system can be confusing. Always remember that ‘glaucoma’ simply refers to optic nerve damage due to eye pressure. The glaucomas are classified according to what is causing the abnormal eye pressure. Glaucoma is broadly divided into primary and secondary glaucoma, and open-angle and closed-angle glaucoma.

In primary glaucoma, the eye is otherwise healthy. The rise in intraocular pressure is caused by genetic factors, or by an unusual shape of the eye. In secondary glaucoma, the increased eye pressure is a by-product of another eye disease. Ie the glaucoma is not the primary or original eye problem, but is a side effect of another disorder. Below are some examples of secondary glaucoma:

  • Pseudoexfoliation syndrome glaucoma. The eye sheds proteins into the aqueous humour, which block up the drainage channels. This is like leaves falling in a pool and blocking up the skimmer box.
  • Pigment dispersion syndrome glaucoma. The eye sheds iris pigment into the aqueous humour, which blocks the drainage channels. This tends to affect near-sighted men.
  • Angle recession trauma. This is damage to the drainage channels as a result of a strong impact (trauma) to the eye.

Open-angle glaucoma and closed-angle glaucoma is exactly as the names suggest. The ‘angle’ is the part of the eye that contains the trabecular meshwork drainage channels. In open angle glaucoma, the drainage channels are accessible to aqueous humour, but are less permeable than they should be. In closed angle glaucoma, the drainage channels are physically obstructed by iris, and therefore aqueous humour can’t even reach them.

There are three common types of glaucoma:

  1. Primary open angle glaucoma, (POAG) where, for some reason, the intraocular pressure increases, even though the drain of the eye is open. It is thought that genetic factors cause the drainage channels to have abnormal resistance in POAG. It is by far the most common form of glaucoma, accounting for 90% of all cases in Australia.
  2. Acute angle closure glaucoma, occurs when the aqueous humour stops circulating, because the drain is physically obstructed by iris. This can cause the intraocular pressure to increase suddenly. It often causes pain, vomiting, and rapid loss of vision. It is a medical emergency and the symptoms are so severe that it is one of the few eye problems that people will routinely call an ambulance for. You are more likely to suffer angle closure glaucoma if you are Asian, or are very far-sighted. Always seek medical attention immediately if you suffer strong eye pain associated with any of the following:
    • Nausea and vomiting
    • Eye redness
    • Severely blurred vision and seeing halos around lights
  3. Normal pressure glaucoma (sometimes called normal tension glaucoma), where eye pressure remains within the normal range, but the optic nerve is nevertheless damaged. It can occur if your optic nerve tissue is abnormally fragile and sensitive to pressure. It is most common in Japanese people.
Glaucoma surgery Angle closure nick andrew sight specialists southport gold coast eye surgeon ophthalmologist

Above: a cross-section of an eye affected by angle closure glaucoma.

What causes glaucoma?

It is unknown why many people develop glaucoma.  We do know that it typically appears in older people.

Some common risk factors for glaucoma include:

  • A family history of glaucoma
  • People of African, Japanese, Inuit, or Scandinavian descent
  • Extreme nearsightedness or farsightedness
  • Use of corticosteroid medications (e.g. cortisone, hydrocortisone, and prednisolone).
  • Extremely thin corneas
  • Some drugs used for bladder control or seizures (if you have an eye at risk of angle closure glaucoma).

There are also inherited forms of glaucoma that affects infants and children, but these will not be discussed here. Fortunately, only about 1 in 10,000 babies are born with glaucoma.

How do I know if I have glaucoma?

The problem is that it is almost impossible for you to tell if you have glaucoma. Most forms of glaucoma develop slowly and painlessly, so people don’t realize they have it until severe, irreversible damage has occurred. This is why glaucoma is sometimes referred to as “the silent thief of sight”.

In advanced glaucoma, patients may notice that something is wrong with their peripheral vision. They may have difficulty driving, or notice blind spots. Other symptoms include gradual blurriness of vision, and difficulty in dim lighting.

Because glaucoma doesn’t have symptoms until very late, it is very important that you have your eyes checked by an optometrist or ophthalmologist. This is especially important for people over 40 years old.

How is glaucoma diagnosed?

I always undertake a comprehensive examination, including a review of your medical history. In addition, several tests are necessary.

  1. Tonometry – measuring eye pressure. There are many ways to measure eye pressure, and some are more reliable than others. The Goldman Applanation Tonometer is generally considered to be the “gold standard”.
  2. Pachymetry – measuring the thickness of your corneas (the front window of the eye).
  3. Gonioscopy – inspecting the drainage angles of each eye. I do this with both a laser scanner and a microscope.
  4. Optic nerve examination– checking for damage to your optic nerve with a microscope called a “slit lamp”.
  5. Optical Coherence Tomography (OCT) – measuring the thickness of your optic nerve tissue.
  6. Visual field test (perimetry)– checking for patches of missing vision, both central and peripheral.

Glaucoma treatment

If you are diagnosed with glaucoma, then you will usually need to start treatment right away. However, sometimes it is appropriate to simply monitor mild glaucoma that isn’t progressing quickly. The goal of glaucoma treatment is to reduce intraocular pressure to stop any additional eyesight loss.

There are two categories of treatment: medications, including eye drops, and surgery, which includes laser surgery and incisional surgery.

Medications

Eyedrops

Prescription eyedrops are often the initial treatment for glaucoma. The eyedrops lower pressure by either reducing the creation of fluid inside your eye (turning down the tap), or increasing fluid outflow (opening up the drain). Their use needs to be monitored in case the dosage needs to be changed or you develop side effects.

Examples of glaucoma eye drops include:

  • Prostaglandin analogues (e.g. Xalatan, Lumigan, Travatan)
  • Carbonic anhydrase inhibitors (e.g. Azopt, Trusopt)
  • Beta blockers (e.g. timolol)
  • Alpha agonists (e.g. Alphagan)
  • Combination drops that contain two medications in the one bottle.

Glaucoma tablets

In emergency situations I may prescribe an oral tablet, known as Diamox (acetazolamide), which rapidly lowers fluid production inside the eye.

Laser treatment of glaucoma

An alternative to eyedrops is laser. This can also be used in combination with eyedrops. A laser is amplified light energy of a specific wavelength (colour). It can   be precisely targeted to different parts of the eye with minimal or no damage to surrounding structures. There are many different eye laser procedures, and some of these have a role in glaucoma.

Laser trabeculoplasty

Also known as Selective Laser Trabeculoplast (SLT), this is a non-invasive, non-destructive treatment performed in clinic to unblock your clogged drainage channels. SLT uses laser light to activate the cells that naturally clean out your trabecular meshwork. It often takes several weeks before you notice the results, and it may need to be repeated after a couple of years.

Cyclodiode Laser Treatment

This kind of laser therapy uses heat to permanently reduce the production of aqueous humour from the ciliary body (tissue behind the iris). Although effective, it can have unpredictable side effects and is generally reserved for end-stage glaucoma when all other treatments have failed.

Laser Peripheral Iridotomy (LPI)

Laser iridotomy cuts a tiny hole in the peripheral iris, to reduce a person’s risk of angle closure glaucoma.

Endocyclo-photocoagulation (ECP)

This can be a stand-alone procedure, or used with other surgical treatments. It lowers fluid production inside the eye in a much more controlled fashion than cyclodiode laser.

Surgery

Glaucoma surgery is used to lower eye pressure when laser or medications are not effective. Surgery can either rejuvenate your eye’s natural drainage system, or create an entirely new plumbing system for the eye.

Let’s start with the traditional glaucoma surgeries, trabeculectomy, and glaucoma tube shunts. These drain aqueous humour into a fluid-filled bubble behind your upper eyelid known as a ‘bleb’.

Trabulectomy

During trabeculectomy surgery, an opening is created in the eye, and the white sclera is fashioned into a pressure-sensitive valve. This allows fluid to slowly drain from the eye. Although newer techniques have now emerged, trabeculectomy is still a common glaucoma surgery.

Glaucoma drainage tube shunts

These are silicone implants approximately the size of a 20 cent coin. These implants shunt fluid from the eye to behind the upper eyelid, through a hollow tube

Minimally invasive glaucoma surgery (MIGS)

Conventional glaucoma surgery is effective but it is also associated with significant surgical risks and recovery time. In contrast, MIGS offers an improved safety profile, less post-operative care, and faster recovery, at the expense of slightly reduced effectiveness. This is a newer set of treatments requiring only tiny incisions and microscopic devices. The key to success with MIGS is selecting the correct procedure for the correct patient, combined with meticulous surgical technique.

Types of MIGS

Many procedures fall under the umbrella of ‘MIGS’ and they all work in different ways.  I commonly perform the following MIGS procedures:

  • Hydrus glaucoma microstent
  • iStent
  • Xen Gel Stent
  • iTrack ab internao canaloplasty (ABiC)
  • Goniotomy with the Kahook Dual Blade
  • Ab interno canaloplasty

iStent

The iStent was the first micro-invasive glaucoma surgery (MIGS) device and is the smallest medical appliance in the world at just 360µm in size. It increases fluid outflow into Schlemm’s Canal, the drainage channel of the eye.

Hydrus microstent

The Hydrus microstent is a curved flexible stent that opens Schlemm’s Canal. It is 8mm long (approximately the size of an eyelash). It widens and dilates the natural drainage channel in the eye.It’s more difficult to implant than the iStent but I have been very impressed with the results.

iTrack canaloplasty

The iTrack is a flexible illuminated micro catheter that is just 220µm in width. It is used to cannulate Schlemm’s Canal and flush the drainage pathways of the eye. It is a versatile device that can also perform other micro-invasive glaucoma procedures such as Gonioscopy-Assisted Transluminal Trabeculotomy (GATT). Ellex is an Australian company and a world leader in advanced technology and innovation. See my post on the iTrack here.

Less conventional treatments for glaucoma: cannabis and vitamin B3

This is likely the section that everyone has been waiting for! Let’s talk about cannabis first.

Cannabis does lower eye pressure; however, it’s not a viable glaucoma treatment for several reasons. The pressure reduction is short-lived, it requires high doses, and the benefit tends to wear off with repeated use. I’ve written an entire blog post on the topic, which you can read here.

Vitamin B3 doesn’t lower eye pressure, but it may help to make your optic nerve more resilient. Unfortunately, the data we have for this principally comes from mice studies (as of September 2021). It is expected that the results of human trials will be available soon. Given the uncertain benefit, I currently only recommend vitamin B3 to patients who are not responding to conventional treatments.

Seeing better for longer

If your eye pressure can be lowered then vision loss can be slowed or even stopped. However, because there’s no cure for glaucoma, you’ll likely need treatment for the rest of your life to regulate your pressure. Unfortunately, vision that is lost to glaucoma cannot be restored.

How I can help you

  • Do you wish to reduce or eliminate your glaucoma eyedrops?
  • Are your eyes sore or red?
  • Is your eye pressure uncontrolled?
  • Is your glaucoma progressing?
  • Are you interested in micro-invasive glaucoma surgery (MIGS)?

I have been trained in conventional glaucoma surgery as well state-of-the-art glaucoma management, including minimally-invasive glaucoma surgery (MIGS) and glaucoma laser. I have undertaken two specialist glaucoma fellowships, including the prestigious GAASS fellowship in Toronto with Dr Ike Ahmed, who is considered by many to be the pre-eminent world leader in this field.

I deliver individualised care tailored to the specific needs of each of my patients. This means that I will perform both traditional glaucoma surgeries as well as newer alternatives that can offer improved outcomes for some patients, as indicated by your condition.

If you’d like to learn more about my background and expertise, please see my ‘About Dr Nick Andrew’ page.

Opening hours

Monday to Friday: 8am – 4.30pm

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Dr Nick Andrew

Ophthalmologist and Eye Surgeon Gold Coast

Sight Specialists, Level 2, 95 Nerang St, Southport QLD 4215

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