June 4, 2009
Eyes right - Cover story
Losing sight of your eyes
Most eye diseases show up after the age of 40. Experts stress the importance of regular eye checks to monitor your eye health
By Poon Chian Hui
For many of us, eye diseases probably trail below worries about heart problems or getting cancer.
However, we should be equally concerned, said Professor Donald Tan, the medical director of Singapore National Eye Centre (SNEC).
'Most eye diseases show up after the age of 40,' he said. 'In Singapore, eye health is a growing concern because of ageing population.'
Besides the climbing numbers of older people, there is also the factor of greater longevity.
Said Prof Tan: 'People are living longer - the older you are, the greater the risk of eye diseases.'
A study on the local Malay population last year found that people aged 80 and above are 15 times more prone to visual impairment than those aged 40 years and below.
The truth is that eye diseases tend to be inevitable. As we grow older, our eyes become less efficient, said Dr Clement Tan, a consultant ophthalmologist at National University Hospital (NUH).
'Our lenses harden and the ciliary muscle, which is responsible for focusing, weakens,' said Dr Tan. 'Additionally, the lens starts to lose its transparency.'
Colour perception and contrast is also reduced, said Dr Hoh Sek-Tien, a consultant eye surgeon at Gleneagles Hospital. A reason is that the ageing lens increases the scattering of light.
The ageing process causes a range of problems from presbyopia (long-sightedness) to cataracts. Up to 90 per cent of people aged between 70 and 80 years have cataracts, said Prof Tan.
Other serious afflictions include glaucoma - the leading cause of blindness in Singapore, accounting for 34per cent of the total number of blindness cases - and age-related macular degeneration, said Dr Leonard Yip, a consultant ophthalmologist at Tan Tock Seng Hospital.
The trouble is that unlike many ailments where pain is an obvious indicator, severe eye diseases tend to be painless and symptom-free.
Hence, many people are unaware that they have an eye problem until much later, said ophthalmic surgeon Cheryl Lee of Pacific Healthcare Specialist Centre.
'The danger is that blinding eye diseases are usually painless,' said Dr Lee, who is also a medical and surgical retinal specialist. 'For example, in age-related macular degeneration - a condition where central vision is affected - you can be all right one day and wake up blind the next day.'
The slow progression of diseases like glaucoma also spells danger.
Local researchers who did a study in 2003 on Tanjong Pagar residents found that over 90 per cent of those who were found to have glaucoma were unaware they had the condition.
One reason could be that glaucoma - often termed as a 'silent thief' of sight - damages peripheral vision before central vision; hence, people can still see well in the earlier stages as we rely on our central vision more, said Prof Tan.
Dr Lee added: 'If one eye is affected, the other eye will compensate. Overall, you may still be able to see pretty well.'
Also, the elderly often dismiss vision problems as part and parcel of the ageing process.
'It's common for the elderly to neglect poor vision and put it down to growing old,' said Dr Mandeep Singh, an associate consultant opthalmologist at NUH.
He added: 'It's important to be alert to signs like difficulty in reading and bumping into objects - they could signal an eye disease.'
Some people also have grave misconceptions about eye diseases. An example would be the belief that cataracts have to be hard or 'ripe' enough before they can be treated. Dr Singh said this is not true.
Other than ageing, eye problems can also be heightened if one has a chronic disease like diabetes. This is because diabetes tends to affect small blood vessels in the eyes.
Diabetic retinopathy is the most common form of diabetic eye disease and a major cause of blindness in adults worldwide. Here, the retina becomes damaged from bleeding, leading to vision loss.
While this is most often seen in older diabetic patients, Prof Tan noticed that sufferers are getting younger in recent years.
For these people, proper management of blood sugar levels is imperative, said Dr Singh.
Other conditions that may trigger eye problems are hyperthyroidism and immune disorders like rheumatoid arthritis, said Dr Hoh.
Hence, the safest bet for all is to go for regular eye checks to enable early detection, said Dr Yip.
'Loss of vision can be prevented with early detection,' he said.
'If you are between 40 and 64 years old, you should consider an eye examination by an ophthalmologist every two to four years.' If you are above 65 years old you should have one every one to two years.
Meanwhile, diabetics should have their eyes checked every year; those with a family history of eye diseases like glaucoma should go for eye checks once every three to five years and more frequently from the age of 40 onwards, he said.
Prof Tan said that at the very least, one should go to an optical shop for a free eye test to rule out myopia and other simple refractive errors. If your vision does not seem to improve despite being fitted with glasses, see an ophthalmologist for a thorough check-up.
Also, people who experience abnormal signs like sudden blurring of vision, eye pain and seeing flashing lights or floaters should see a doctor, said Dr Yip.
This is because they may be due to more serious causes, like retinal tears and detachment which can result in loss of vision, said Dr Hoh.
'The eye is very special - it's the only part of the body where we can see the blood vessels inside easily,' said Prof Tan. 'Hence, many eye problems can be detected with a simple, non-invasive check-up.'
Eye examinations by an ophthalmologist for eye diseases are done at SNEC and major hospitals. Prices start from about $70 for a consultation as a private patient and vary according to the seniority of the doctor and the eye centre that you go to.
Eye screenings, which are also available at polyclinics, are a good option as well. This refers to tests to detect certain eye diseases.
Screening packages are generally less comprehensive than eye examinations, said Dr Yip, as the ophthalmologist can order further tests if necessary.
Diseases that blind
The eye resembles a camera that detects, captures and transmits images to our brain.
The cornea, a transparent layer covering the front of the eyeball, allows light through.
When it reaches the lens, which has the camera-like ability to 'autofocus', the light is bent to create sharp images on the retina, a light-sensitive layer at the back of the eye.
These images are then transmitted through the optic nerve to the brain, enabling us to see.
Hence, when one or more of these components malfunction, our vision becomes poorer. In some cases, we may even go blind.
Mind Your Body looks at four serious eye diseases that have the potential to cause blindness.
Simply put, cataract is clouding of the lens, said Dr Cheryl Lee, a consultant ophthalmic surgeon at Pacific Healthcare Specialist Centre.
Vision becomes blurred, akin to 'looking through a fog', said Dr Lee.
'Cataracts are commonly due to chemical changes in the lens that are related to ageing,' said Dr Leonard Yip, a consultant ophthalmologist at Tan Tock Seng Hospital.
Other than blurred vision, sufferers may experience glare and loss of colour intensity, he added.
Although cataracts are the second most common cause of blindness, this loss of sight can be restored by removing the clouded lens and implanting artificial ones.
At the Singapore National Eye Centre (SNEC), cataract surgery is the most common operation, with over 10,000 done per year, said Professor Donald Tan, the centre's medical director. Success rate is very high - close to a 100 per cent.
Here, the optic nerve is damaged due to high eye pressure, which may also injure blood vessels.
Glaucoma is the top cause of blindness in Singapore, making up 34 per cent of all blindness cases, said Dr Yip. There are two kinds - the slow, progressive type and the acute form.
The former, known as open-angle glaucoma, is where peripheral vision gradually gets 'eaten away'. However, the person may notice changes in vision only at the very late stages. By then, 80 per cent of the optic nerve might have been damaged, said Prof Tan.
'It's like having high blood pressure - you don't know you have it until you get a stroke,' he said.
If detected early, further vision loss can be prevented by the use of eye drops, laser treatment and surgery if necessary, said Dr Yip.
Most glaucoma sufferers here are believed to have the open-angle variant. In Singapore, about 3 per cent of those over the age of 50 have glaucoma.
The acute form, or closed-angle glaucoma, is more dramatic. However, only about 300 to 400 Singaporeans are affected by this acute form annually, said Dr Yip.
In this case, the drainage system in the eye suddenly closes or becomes blocked, causing eye pressure to shoot up, said Prof Tan. Sufferers tend to experience sudden blindness and acute eye pain.
Prof Tan said the acute form is especially prevalent in East Asians, particularly among the Chinese. It also tends to affect the elderly more.
The reason may be due to East Asians' narrower eye angle, which increases the likelihood of blockage in the eye's drainage system.
3: AGE-RELATED MACULAR DEGENERATION (AMD)
There are two types of AMD - dry and wet. Dry AMD progresses slowly, over months or even years, and is more common, accounting for about 90 per cent of all cases. In wet AMD, the deterioration is swift and one can go blind overnight, said Dr Lee.
Because the macula is responsible for clear central vision, sufferers may see distortion or dark splotches in the middle but details in the periphery appear sharp, she said.
The third most common cause of blindness here, it results from the breakdown of light receptors in the macular, or from the formation of abnormal blood vessels that damage these receptors, said Dr Yip.
Treatment options include laser treatment and injections into the eye.
4: DIABETIC RETINOPATHY
In diabetic retinopathy, the retina is damaged, usually through bleeding, which may then cause blindness, said Prof Tan.
Because the disease progresses slowly, regular screening is crucial.
If detected early, laser treatment can be administered to induce abnormal blood vessels to regress and prevent the condition from worsening.
Late detection, however, may require complex surgery to remove blood and affected membranes.
However, good control of blood sugar levels is perhaps the most important preventive measure as the risk of getting this disease hinges on how well one's diabetes is controlled, said Prof Tan.