Glaucoma is a condition that damages the eye's optic nerve -- vital for optimal vision -- often due to an abnormally high pressure in the eyes.

It is one of the leading causes of blindness in people aged over 60. It can occur at any age but is more common in adults.

Many forms of glaucoma have no warning signs. The effect is so gradual that one may not notice a change in vision until the condition is at an advanced stage.

As vision loss due to glaucoma cannot be restored, it is important to have regular examination of eye pressure so a diagnosis can be made in its early stages and treated appropriately. If glaucoma is recognised early, vision loss can be slowed or prevented. If the condition persists, the patient may generally need treatment for the rest of his or her life.

There are several types of glaucoma, like open-angle glaucoma, angle-closure glaucoma, normal-tension glaucoma, glaucoma in children, pigmentary glaucoma and angle recession glaucoma (after trauma), etc.

The signs and symptoms of glaucoma vary depending on the type and stage of condition.

For example, in case of open-angle glaucoma, symptoms include patchy blind spots in side periphery of one's vision, or central or tunnel vision in the advanced stages.

In case of acute angle-closure glaucoma, symptoms include severe headaches, eye pain, nausea and vomiting, blurred vision, halos around lights or eye redness.

As chronic forms of glaucoma can damage vision before any signs or symptoms are apparent, be aware of these risk factors: being over 60, having a family history of glaucoma, having certain medical conditions such as diabetes, heart disease, high blood pressure and sickle-cell anaemia, previous eye injury and taking corticosteroid medications, especially eyedrops, for an extended period.

Steps that can help detect glaucoma in its early stages include: regular comprehensive check-ups by an eye specialist, knowing family's eye health history and taking prescribed eye drops regularly if you have glaucoma.

Untreated glaucoma will eventually cause blindness. So, regular eye check-ups by a specialist -- at least once every six months -- is necessary.