What Is Glaucoma?

Glaucoma is an eye condition characterized by loss of vision secondary to damage to the optic nerve. We have one optic nerve in each eye, and each optic nerve serves to transmit information (things we see) from our eyes to our brain. Usually, but not always, damage to the optic nerve in glaucoma is caused by raised pressure within the eyeball.

In Singapore, glaucoma affects about 3 percent of those aged over 40. This risk increases with age.

How Does Glaucoma Occur?

The eye is like a ball filled with fluid which provides oxygen and nourishment to the rest of the eye. It has an inflow tap (ciliary body) and an outflow drain (trabecular meshwork).

To maintain normal pressures, the inflow must balance the outflow. In certain types of glaucoma, e.g., angle-closure glaucoma, if the drainage is blocked, fluid accumulates, and pressure in the eye builds up. This raised pressure may damage the optic nerve.

Can Glaucoma Be Prevented?

Glaucoma cannot be prevented, but the visual loss can be prevented if treatment is started before optic nerve damage has occurred. Glaucoma can run in families, and glaucoma genes have been identified.

Acute Glaucoma

Seek urgent review by your doctor if you develop painful red eyes with blurred vision.

Chronic Glaucoma

It is important to have your eyes checked regularly once you are over 40, especially if you have a relative who has glaucoma.

What Is Normal Eye Pressure?

Our normal pressure can range from 10 to 25 mmHg, and this can vary throughout the day. In general, we are more concerned with whether your current eye pressure is sufficiently low enough to slow or prevent glaucoma damage to your eyes.

If the pressure is more than 21 mmHg, as checked by your doctor or optician, you should consult an eye specialist. The eye specialist or ophthalmologist can accurately determine if your eye pressure is normal or is high and associated with glaucoma.

Your eye pressure will be checked at each visit, and its trend and, in particular, its progression will be monitored by your eye doctor.

What Are the Types of Glaucoma?

Glaucoma can be classified into primary (not associated with other eye diseases) and secondary (as a result of other eye diseases). These can be further subdivided into open- angles and closed-angles glaucoma.

Primary open-angle glaucoma is the most common type of glaucoma. Its symptoms are usually gradual, and you may not notice any vision loss unless in the advanced stages.

Primary angle-closure glaucoma may be acute or chronic.

Acute Primary Angle-closure Glaucoma

• Occurs more commonly in the middle-aged or elderly Chinese females especially those who are long-sighted.
• Characterized by a sudden increase in the eyeball pressure, causing a sudden onset of pain, redness and blurred vision in one or both eyes. There may be headaches, nausea and vomiting as well.
• Urgent treatment to lower the pressure is essential to save vision.

Chronic Angle-closure Glaucoma

• Vision loss is progressive, with side vision usually being affected first.
  
• The disease is often very advanced before a visual loss is noted.
• That is why this disease is often called the "thief of vision".

In both forms of glaucoma, laser treatment (peripheral iridotomy), along with anti-glaucoma eye drops, might be needed.

Secondary glaucoma occurs when other eye diseases cause an increase in eye pressure, leading to optic nerve damage. This can be related to other medical conditions such as diabetes mellitus or can happen following injury to the eye.

One can also be born with glaucoma, in the case of congenital glaucoma.

What Is Normal Tension Glaucoma?

In normal-tension glaucoma, susceptible individuals develop optic nerve damage even when their eye pressures are within normal limits.

Risk factors for the development of normal-tension glaucoma include:

• Family history of glaucoma
• History of major blood loss or blood transfusion
• History of migraine
• History of Raynaud's phenomenon- spasm of blood vessels leading to discolouration of fingers and toes.

Treatment with anti-glaucoma eye drops is the first line for this condition. 

What Are the Risk Factors for Glaucoma?

 The risk factors for glaucoma include:

• Positive family history of glaucoma

• Older age 
  • ​Risk increases once you are above 50 years old.

• ​​​​​Ethnicity
  • Asians are at a higher risk of angle-closure glaucoma as compared to Caucasians.

• Co-existing medical conditions
  • E.g., Diabetes Mellitus and Hypertension 

• Co-existing eye conditions
  • High short-sightedness
  • Previous eye injury 

• Use of steroids

There are no specific diets or lifestyle activities that are associated with glaucoma.

What Are the Symptoms of Glaucoma?

In open-angle glaucoma and chronic angle-closure glaucoma, you may not notice any vision loss until it is in its advanced stage. Vision loss is gradual, with side vision typically being affected first.  As the condition progresses, the vision (visual fields) gets increasingly narrower. Eventually, only a small central island of vision is left, and you will only be able to see what is directly ahead of you.

In acute angle-closure glaucoma, symptoms are typically more sudden and severe. You may notice/experience the following:

• Blurring of vision
• Eye redness
• Eye pain, often associated with headache
• Nausea and vomiting

If you do experience the following, please visit your ophthalmologist immediately. Early treatment is essential to prevent further vision loss.

How Do You Diagnose Glaucoma?

The diagnosis of glaucoma will be made by your eye doctor following a comprehensive eye examination and review of investigations.

You may undergo the following tests/investigations:

• Tonometry

1. 1. This measures your eye pressure.
   2. Your eye pressure can be measured using a machine (commonly known as "air puff") or manually by your eye doctor.

• Gonioscopy​

1. 1. This is done by your eye doctor to determine if your glaucoma is of the "open-angle" type or the "angle-closure" type.
   2. Anaesthetic eye drops will be given prior to the placement of a special lens/ mirror on your cornea. This examination is quick and painless.

• Visual Fields Assessment

1. 1. This takes about 15 minutes and is usually carried out in a dark room.
   2. You will be asked to look at a central light source on a white screen. Flashes of light of different intensities and sizes will appear on the screen, and you will be required to press a button when you see them.
   3. This assesses the degree of optic nerve damage and measures the extent to which each eye can see on either side of an object.

• Assessment of the Optic Nerve

1. 1. This is done by your eye doctor who will look at the back of the eye through a special lens to assess the health of the optic nerve.
   2. Photographs and specialised scans of the optic nerve may also be taken to help your eye doctor assess the degree of nerve damage.

Can I Be Cured of My Glaucoma?

Glaucoma can be treated but not cured. Once the optic nerve is damaged, the loss of vision is permanent.

The treatment aims to lower the intraocular pressures to an acceptable level, thus preventing further damage to the optic nerve.

Because treatment can only control but not cure the condition, it must be continued throughout life.

What Is the Treatment for Glaucoma?

Management of glaucoma depends on the type of glaucoma, degree of optic nerve damage, your eye pressure, the presence of other eye problems and your age.

It can be classified into

• Medical treatment
• Surgical treatment
• Laser treatment

Medical Treatment For Glaucoma

This is the most common form of treatment, and compliance with your eye drop regime is of utmost importance in ensuring the success of medical therapy.

Some of the eyedrops do have side effects, and these arise because the drops are absorbed into the bloodstream. This absorption can be minimized by pressing a finger against the lower lid where it meets your nose or by closing your eye for one minute after instilling the eyedrop. Any side effects should be reported to your doctor. It is important if there is more than one glaucoma eyedrop to instill them at least five minutes apart.

Up to 3 or 4 eye drops maybe prescribed before medical therapy is considered futile.

Sometimes when the eye pressure is very high, intravenous or oral anti-glaucoma medications may be given to help reduce the eye pressure.

Surgical Treatment For Glaucoma

This is usually done if medical therapy with anti-glaucoma eye drops fails. 

The most common surgery is trabeculectomy, where an opening is created for the fluid in the eye to escape into the surrounding tissues and be absorbed. This allows the pressure inside the eyeball to be relieved.

Other kinds of surgery are available and include inserting a tube to drain the fluid from the eye. This is often indicated in complicated glaucoma.

Laser Treatment For Glaucoma

This is usually carried out in patients with angle-closure glaucoma (laser peripheral iridotomy) or patients with acutely high eye pressure not responding to medical treatment (laser peripheral iridoplasty).

It is important to tell your eye doctor if you have the following conditions/ drug allergies as it may affect the type of treatment given:

Any form of drug allergies- especially sulphur allergy

• Kidney disease
• Heart disease- especially heart block and heart failure
• Asthma

Can I Use My Medisave To Pay For My Anti-glaucoma Medications?

No, unfortunately, you cannot use Medisave to pay for your anti-glaucoma medications.

How Do I Prevent the Progression of Glaucoma?

Compliance with anti-glaucoma eye drops, together with regular follow-ups with your eye doctor, is key to preventing your glaucoma from getting worse.

Are There Any Things That I Should Avoid if I Have Glaucoma?

No, you may continue with your usual activities and diet.

If you are on steroids, please inform your eye doctor as this may sometimes contribute and lead to the progression of your glaucoma.

What Is the Prognosis of Glaucoma?

Glaucoma is a potentially blinding condition. However, its progression is usually gradual, and hence if detected early, with good compliance to treatment and follow-ups, the risk of blindness can be reduced.

If diagnosed early, we can treat glaucoma and prevent blindness in most cases.

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