Glaucoma

What is Glaucoma?

Glaucoma is a group of eye conditions that can damage the optic nerve, the vital part of the eye responsible for sending visual information to the brain. This damage is often caused by high pressure within the eye, known as intraocular pressure (IOP). Glaucoma is one of the leading causes of blindness worldwide, but with early detection and treatment, its progression can often be slowed or even prevented.

When the IOP rises above 21, this is above the “normal range”.  Eight percent of the normal population have pressures above 21 when we take single measurements.

 

How is Glaucoma Diagnosed?

Your eye doctor (optometrist or ophthalmologist) will perform a series of tests to diagnose glaucoma and assess the health of your eyes.

These tests include:

Tonometry:  Measures intraocular pressure (IOP) to check for elevated pressure inside the eye, a key factor in glaucoma.

Ophthalmoscopy:  Involves examining the optic nerve for signs of damage. A dilated eye exam is usually performed to get a better view of the back of the eye.

Perimetry (Visual Field Test):This test maps out your peripheral vision and can detect blind spots, a common symptom of glaucoma.

Optical Coherence Tomography (OCT):  This test takes cross-sectional images of the retina and optic nerve, helping to detect early changes in the nerve fibers and retina.  This is the most useful test to measure your eye.   Glaucoma is diagnosed mostly with OCT scans which show when there is damage to the optic nerve and the retinal thickness at the back of the eye.  The retina thins as glaucoma progresses, leading to a characteristic appearance of the nerve in severe cases.  As glaucoma attacks, this layer is gradually thinned, leading to a large central “cup” forming in the centre of the nerve.

 

We monitor IOP is because raised pressure is one risk factor for glaucoma.  The higher the IOP, the more likely a patient will develop glaucoma.  

Other risk factors are family history, age, high blood pressure, steroid use, sufferers of migraines or cold hands, diabetes, and eye injury.

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What are the Symptoms of Glaucoma?  

In the early stages, glaucoma often does not cause noticeable symptoms, which is why it is referred to as the "silent thief of sight."

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As the condition progresses, symptoms can include:

• Peripheral (side) vision loss: One of the earliest signs of glaucoma.

• Blurred vision or difficulty focusing.

• Halos around lights.

• Eye pain, headache, or nausea (in the case of angle-closure glaucoma).

• Sudden loss of vision (in acute angle-closure glaucoma).

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Because symptoms may not appear until significant damage has been done, regular eye exams are essential for early detection.

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What are the Causes of Glaucoma?

There are several types of glaucoma, each with different causes:

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Primary Open-Angle Glaucoma (POAG):The most common type of glaucoma.  The drainage system of the eye becomes less efficient over time, leading to a gradual increase in intraocular pressure.  The exact cause is unclear, but it is often linked to genetics and family history.

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Angle-Closure Glaucoma:  This Occurs when the angle between the iris and cornea is too narrow, obstructing the drainage of fluid in the eye.  It can cause a sudden increase in intraocular pressure, leading to severe symptoms and possible vision loss if not treated quickly.

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Normal-Tension Glaucoma:  In this form, optic nerve damage occurs even when intraocular pressure is within normal ranges.The cause may involve poor blood flow to the optic nerve.

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Secondary Glaucoma:  Can be caused by another condition such as eye injuries, inflammation, tumors, or the use of certain medications (like steroids).

Congenital Glaucoma:  A rare condition where infants are born with an abnormality in the eye's drainage system, leading to glaucoma.

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WHAT IS OCULAR HYPERTENSION?

When the IOP is elevated, and there is no nerve damage, we call this “Ocular hypertension”.  Patients are usually observed without treatment, because the risk of developing glaucoma in 5 years is low.

 

When there is obvious damage to the nerve, we diagnose glaucoma, and commence treatment.  Once treatment is started, it will need to continue for the rest of your life.  Once present, glaucoma never goes away. 

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How is Glaucoma Treated?

Treatment for glaucoma aims to lower intraocular pressure and prevent further damage to the optic nerve. 

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Options include:

Laser Treatment:  Laser Trabeculoplasty: For open-angle glaucoma, this treatment improves drainage by using a laser to help the eye’s drainage system work more effectively.  The LIGHT study demonstrated that this is very effective and is the preferred first treatment for most cases of glaucoma.  Laser Iridotomy: In cases of angle-closure glaucoma, a laser creates a small hole in the iris to allow better fluid drainage. 

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Medications (Eye Drops):  Medications that either reduce the amount of fluid produced in the eye or increase the drainage of fluid, helping to lower eye pressure.  Common types include beta-blockers like TIMOLOL, prostaglandins XALATAN, alpha agonists ALPHAGAN, and carbonic anhydrase inhibitors TRUSOPT.

Oral Medications:  In some cases, oral medications may be prescribed to complement eye drops, especially if pressure remains high. DIAMOX

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Surgery:  If medications and laser treatments do not lower intraocular pressure adequately, surgical options may be considered:

Trabeculectomy: Removal of part of the trabecular meshwork to create a new drainage channel for the eye fluid.

Glaucoma Drainage Devices: Implantation of a tiny tube to help drain fluid and lower pressure.  The iSTENT is commonly used at the time of cataract surgery.

Cyclophotocoagulation: A procedure that uses a laser to reduce the production of eye fluid.

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Lifestyle Modifications:

Regular eye exams are crucial for monitoring the condition.

Protect your eyes from injury.

Maintain a healthy lifestyle by eating a balanced diet, exercising regularly, and managing stress.

Avoid excessive alcohol and smoking, which can worsen glaucoma.

 

The only way to treat glaucoma is to lower the IOP.  For some patients, an IOP of 20 will be fine.  For others, 15 may be too high.  To determine your “safe” level, we take multiple readings of the IOP, optic nerve, and visual fields.  Only by comparing with past tests can we detect any progression of the disease.  If there is progression, then we need to change treatment.

 

IOP varies constantly throughout the day.  When we measure it in the clinic, it represents just one split second of the day.  We cannot measure the IOP constantly.  The more frequently we measure IOP, visual fields and disc nerve thickness, the better our information will be.  Field tests are usually repeated every 6-12 months, and disc analysis every 1-2 years.

 

Once treatment is started or changed, you need more frequent review to determine whether the IOP is responding to treatment.

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Living with Glaucoma

While glaucoma can’t be cured, with proper management, many people can live full lives without significant vision loss. Regular follow-up visits to your eye doctor are critical to monitor the condition.