Glaucoma is a group of diseases with characteristic optic nerve damage, resulting in irreversible loss of vision. Most, but not all of these diseases are characterised by raised pressure in the eye (intraocular pressure). The level of pressure that causes damage can vary in different individuals and the resistance level of the optic nerve.

Glaucoma is known as the ‘silent thief of sight’ as the initial vision loss is mainly peripheral and not readily noticeable. Central vision and reading vision are usually spared until later.

The patient may not experience any symptoms until late in the disease when most of the vision has already been irreversibly lost.

Normal Vision

Vision with glaucoma

What are the different types of glaucoma and their symptoms?

• Open-angle glaucoma
  Open-angle glaucoma accounts for the majority of glaucoma in most countries. It often has no symptoms and progresses slowly. The rise in intraocular pressure is slow and painless.
• Closed-angle glaucoma
  Angle-closure glaucoma can either be acute or chronic. Acute angle-closure glaucoma is characterised by a sudden, dramatic increase in intraocular pressure. This can cause severe eye pain, redness, blurred vision and the appearance of haloes around lights. Headaches, nausea and vomiting may follow. This emergency requires prompt treatment. The chronic form may show no symptoms, as in open-angle glaucoma.
• Congenital glaucoma
  Congenital glaucoma is rare and occurs at birth. Enlargement of the infant’s eyes, corneal haze, tearing and unusual light sensitivity are symptoms that warrant an eye examination.
• Secondary glaucoma
  Secondary glaucoma may be caused by conditions such as poorly controlled diabetes, inflammation of the eye, tumours, previous eye surgery, injuries or cataracts in their advanced stages, or the use of steroid medications on the eye.

Most risk factors of glaucoma such as age, hereditary risk and race cannot be prevented. If you have a family history of glaucoma or are taking medications that put you at risk, regular eye examinations are essential. Early diagnosis is the key to prevent blindness as glaucoma nerve damage is irreversible.

What causes glaucoma?

Glaucoma is usually caused by fluid pressure in the eyeball that is too high for the optic nerve to tolerate. The optic nerve carries visual impulses from your eye to the brain. This pressure build-up occurs because of an imbalance between the production and drainage of fluid within the eyeball.

Who is at risk of glaucoma?

Risk factors for glaucoma include:

• Age – your risk increases when you are over 80 years old
• Chronic diseases – you are at increased risk if you have diabetes or high blood pressure
• Ethnicity – Asians are more susceptible to angle-closure glaucoma than Caucasians
• Eye injuries
• Family history
• Use of corticosteroid
• Inherently high pressure inside the eye
• Refractive error (short-sightedness or myopia is a risk factor for open-angle glaucoma; long-sightedness or hyperopia is a risk factor for closed-angle glaucoma)

Glaucoma is diagnosed by measuring intraocular pressure of the eye and assessing the optic nerve at the back of the eye for any damage. A visual field test is usually performed and other tests can be added to further assess the optic nerve and the state of the drainage system for fluid in the eye.

The visual field test assesses the function of the optic nerve by checking if you can see spots of light of different intensities at different locations inside a visual field machine. It helps the ophthalmologist determine if your disease is worsening or stable.

Visual field test:

• To perform well, stare at the central marker and do not look elsewhere.
• Press the button only if you see a spot of light.
• Hold the button in a depressed position if you need to rest or pause the test.
• If you are tired or unwell, do let the technician know.

Glaucoma cannot be cured, but in most cases, it can be successfully controlled.

Treatment depends on the type of glaucoma you are diagnosed with. Treatment modalities include:

• Eye drops
• Oral medications
• Laser surgery
• Filtering surgery
• Drainage implants

All these treatments lower the intraocular pressure to a level that is safe for the eye. Your ophthalmologist will be able to advise on individualised treatment options. Even after successful control of the pressure, regular monitoring is still required.

Glaucoma is a chronic condition requiring lifelong review. The aim of treatment is to preserve the remaining vision. Damage from glaucoma cannot be reversed, hence the importance of early diagnosis.