The Top 5 Causes of Blindness

As the hair on your head starts to grey, your eyes begin to dim too. The passing of the years not only leads to the wear and tear of the windows to the soul, but also raises one's chances of getting diseases that can close the shutters of those windows - for good.

With the average lifespan of a person rising from 63_years in 1960 to 80 years now and the population greying rapidly, more people here will face the risk of losing their sight.

Four of the top five causes of blindness here, including reversible blindness, are linked to ageing. They are:

  • cataract,
  • glaucoma,
  • age-related macular degeneration (AMD)and
  • diabetic retinopathy

For diseases which are age-related, the longer you live, the higher the likelihood of getting them.

The only other major cause of blindness here that does not plague just the elderly is severely undercorrected refractive error, which comprises mainly short-sightedness.

The growth in the number of people suffering from refractive errors and diabetic retinopathy is a result of changes in lifestyle here.

In the past, vision loss would probably have been caused more by malnutrition, such as vitamin A deficiency, and by infectious diseases, such as trachoma, which are still major problems in developing countries.

In developed countries now, we have mostly age-related and lifestyle associated ones. For example, more people are short-sighted now compared to 30 years ago, as children spend more time reading and less time outdoors.

The incidence of such diseases will continue to rise as the population is ageing rapidly, but it takes time for people to modify their lifestyles to promote good eye health. It may be decades before any change can be seen.

It is not known exactly what proportion of the population here is blind or has low vision, which is defined as the inability to see well enough to drive.

A study on 3,280 Malays aged 40 to 79, completed in 2006, gives an idea of the extent of vision loss and sight-threatening eye diseases here.

The Singapore Malay Eye Study found that 0.3 per cent of the Malay population here are blind in both eyes, and 4.4 per cent have low vision in both eyes.

Of the Malays who were blind in both eyes, 65 per cent suffered from cataracts, while almost 20 percent had undercorrected refractive errors.

Those with AMD made up less than 5 per cent of those who were blind in both eyes. The glaucoma and diabetic retinopathy groups each made up a similar proportion.

The good news is that the top two causes of blindness here - cataract and undercorrected refractive errors - can be treated effectively and hardly anyone with them has to be blind permanently.

Treatment methods for glaucoma, diabetic retinopathy and AMD have also improved over the years and can help slow or even halt vision loss, especially for those who are diagnosed and treated early.

However, many patients do not seek help early enough because they do not know about the disease and the fact that it can be treated. Some may fear consulting doctors or are afraid that the treatment will be costly. This results in unnecessary loss of quality of life.

Nevertheless, the fact remains that - You won't have optimal quality of life if you don't have at least driving vision. You'll also be at a greater risk of falls.

As many eye diseases do not have obvious symptoms, the key to detection and prevention is regular screening. Diabetic patients should go for screening every year, while those aged above 40 should have an eye check every two years. Such eye checks can be done by optometrists or doctors.

If the disease is caught early, there is a chance it can be prevented from getting worse. If it is found late, we may not be able to reverse the damage done.

1. Cataract

Cataracts are the No. 1 cause of blindness here but, fortunately, the condition can be easily treated and the blindness reversed.

A cataract is formed when the usually clear lens of the eye becomes cloudy. This hinders light from entering the eye and causes vision to become blurred over time. Patients may also see halos around lights or feel that colours look dull.

About 65 per cent of those blind in both eyes here suffer from cataracts. The condition is often caused by ageing. More than a third of people aged 40 and above have cataracts, a 1998 study on 1,152 adults found. This rises to over 90 per cent for those aged 70 and above.

Prolonged exposure to ultraviolet (UV) rays present in sunlight, long-term use of drugs like steroids and some diseases like diabetes raise the risk of developing cataracts.

Young people can also be born with cataracts or can develop them because of eye injuries. To avoid developing cataracts, wear sunglasses with UV protection and lead a healthy lifestyle to prevent diabetes.

The standard treatment is to remove the cloudy lens and replace it with a clear artificial one. The lens can be designed to correct refractive errors like short-sightedness, which is a bonus for patients as they will not need spectacles after surgery.

However, in rare cases where the patient's cataracts are too severe and have damaged the cornea, the condition cannot be treated and the person is left permanently blind.

2. Undercorrected refractive errors

Undercorrected short-sightedness, long-sightedness, astigmatism and other refractive errors are problems which can be easily fixed.

People with severe short-sightedness can develop complications that can blind them permanently, although this happens very rarely.

To prevent it from developing or worsening, take regular vision breaks - five-minute breaks from reading or writing - and spend more time outdoors.

3. Glaucoma

Glaucoma causes fluid in the eye to build up, which ratchets up the pressure inside. The high pressure damages the optic nerve which sends signals from the eye to the brain to -enable the person to see. The damage is irreversible and can lead to blindness in severe cases.

The disease comes in several forms. The majority of patients develop a form called primary open angle glaucoma. It progresses slowly and painlessly and destroys peripheral vision before centralvision, so patients often do not notice that their vision is deteriorating.

Another form called acute angle closure glaucoma, which tends to hit older Chinese, occurs suddenly. Pressure in the eye rises rapidly, causing pain and redness in the eye, blurred vision, headache and nausea.

Less than 5 per cent of the population suffer from glaucoma, which is linked to ageing. The risk of getting it is about 3 per cent for those aged 40 and above, but about - 9 per cent for those aged 70 and above.

The risk also rises when there is a family history of glaucoma, extreme short-sightedness or chronic diseases like diabetes and high blood pressure. Eye inflammation, advanced cataracts, tumours, injuries and surgery can cause glaucoma.

Most of the risk factors cannot be prevented. Screening to detect the disease early is important, as treatment can arrest its progression in most cases.

The disease is usually treated with eye drops to lower the pressure. Laser treatment or surgery are used usually at a later stage. However, some patients still end up losing their sight for good. In a 2003 study on 186 patients in the United States, 9 per cent were found to be blind in both eyes after 15 years, despite treatment.

4. Macular degeneration

Age-related macular degeneration (AMD) causes the macula - the centre of the retina - to deteriorate.

It can be the dry type - when yellow waste material is deposited on the macula - or the wet type - when abnormal blood vessels grow under the macula, leak and damage it.

Nine in 10 patients have the dry type, which has a 10 per cent risk of becoming wet. The wet type leads to 90 per cent of AMD blindness. About 5 per cent of the population have this condition.

Of those who are blind in both eyes, 5 per cent have AMD. The risk of getting it rises from 2 per cent at age 40 to 10 per cent at age 70.

Exposure to high-energy visible light from the sun may raise the risk of AMD, so wearing sunglasses will help. Consuming vitamins A, C and E, and zinc and copper, may slow down its progression. Regular laser therapy can seal leaky blood vessels and drugs can be injected regularly into the eye to stop their growth.

5. Diabetic retinopathy

Diabetic retinopathy causes abnormal blood vessels, to grow over the retina and optic nerve of a diabetic patient, which then leak and damage the retina and nerve.

It causes blurring of vision and "floaters" - black spots so called as they seem to float. It can cause the retina to detach, damage the retina's centre or develop into glaucoma.

A study in 2006 showed that the condition caused blindness in less than 5 per cent of people who lost their vision in both eyes. This is the most common diabetes-related eye disease, affecting 35 per cent of diabetic patients in the study.

The longer a person has diabetes, the greater the risk of having diabetic retinopathy. Diabetic patients should control their blood sugar and blood pressure levels to avoid it.

Laser therapy is used to bum off the abnormal blood vessels and dead parts of the retina and to prevent further damage to the eye.

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