It is reckoned that up to 80 per cent of blindness cases can be avoided, says eye surgeon Dr Low Cze Hong.

The common causes of avoidable blindness include cataracts, glaucoma, diabetic retinopathy and age-related macular degeneration.

While each eye condition has unique symptoms, there are some easily-observed signs that one should not ignore. As the eye is a visual organ, the most obvious sign that something is wrong is if vision is blurred or not like what it usually is, said Dr Low, who runs a practice at Mt Elizabeth Medical Centre. A second symptom is pain, or an aching sensation around the eye.

This could indicate glaucoma, which is due to a build-up of pressure within the eye. The pressure can damage the optic nerve, which transfers visual information from the eye to the brain.

"Pain is an important symptom. By the time people have pain, the pressure will be quite high already. If they wait a day or two, the condition may become irreversible," explains Dr Low.

A third sign is redness of the eye. "You should have an examination if you keep having redness of the eye - especially if there is a headache with it.

"It could be a glaucoma attack," said Dr Low. "Some people have eyes that look red all the time, so they may ignore it. So the thing to do is to get your eye pressure checked."

Dr Low recommends getting a checkup at the age when most people start to get eye strain and start needing reading glasses - the age of 40. If everything is fine then, subsequent checkups should be done once every five years.

After the age of 50, the frequency increases to once every two years; after 60, a check every year is recommended, said Dr Low.

The full barrage of tests could set one back by $100 to $200 each visit. Fairly pricey, but Dr Low does not advise giving it a miss.

"If a person goes blind, what is the cost? You can't calculate it.

"The person may become dependent on society. He may lose his job, the family has to look after him, and the government has to spend money providing services for him.

"It's beyond dollars and cents," said Dr Low.

Cataracts
A cataract is a clouding of the lens of the eye. As the lens focuses light onto the retina at the back of the eye, clouding reduces the amount of light reaching the retina and causes vision to become blurred. The lens is located behind the pupil and iris in the centre of the eye.

Ageing is the most common cause of cataracts, so it is common to find them in the elderly as cataracts are part of the natural ageing process.

An eye lens, which is normally clean, becomes yellowish due to cataract.

Symptoms:
Blurry vision that cannot be improved well with glasses
Colours appearing dull
Poor vision in bright light, seeing glare or a halo around lights
Poor night vision
Frequent changes in your eyeglasses or contact lenses

Surgery is necessary when vision cannot be improved well with glasses. The cloudy lens is removed through surgery and replaced with a clear artificial lens. Dr Low estimates that 20,000 people go for cataract surgery each year.

Glaucoma
According to the Singapore National Eye Centre (SNEC), glaucoma accounts for 40 per cent of blindness in Singapore. It is a condition where the pressure within the eye increases because fluid within the eye is produced faster than it can be drained off. If the pressure, gets too high, the optic nerve can get damaged and lead to vision loss or blindness.

Glaucoma can also be caused by a cataract that grows too large.

Glaucoma can develop slowly like in the primary open-angle and chronic angle-closure types, or rapidly within a matter of days like in the acute angle-closure glaucoma. When glaucoma develops slowly, it often goes unnoticed for a long time as there are usually no symptoms early on. Acute angle-closure glaucoma, however, is quite painful.

Symptoms:
Eye or facial pain
Headaches
Red eyes
Tearing
Sensitivity to light
Dilated pupils
Cloudy vision with coloured halos appearing around lights
Frequent changes of eyeglasses, none of which is satisfactory
Gradual loss of peripheral vision and night vision

Though glaucoma cannot be cured, it can be controlled. Treatment to increase fluid drainage can be in the form of eyedrops, laser therapy or surgery.

Diabetic retinopathy
Diabetic retinopathy is a disorder of the retinal blood vessels resulting from diabetes mellitus.

Diabetes can cause diabetic retinopathy, which wreaks extensive damage.

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