Eyesight is an integral tool in the development of a child, but how do we assess eyesight, especially in a young child who can’t communicate his or her thoughts in a manner that can be understood by adults?COLIN KHOO takes a close look at the issue.
THERE is more to “seeing” than meets the eye. Often, a toddler is taught by his parents to talk and walk. In the realm of “seeing”, however, he is left completely to himself.
While he mimics his parents in the way they talk and walk ? his vision is entirely his own. Thus, learning to see is a process that goes on, generally, without assistance or informed awareness. At times, a visual defect goes on unnoticed in the private visual world of an infant.
This is so as a child in his early years is only interested in his immediate surroundings. As a result, these visual problems (or rather latent problems) will hardly manifest.
For example, myopia (or shortsightedness) would hardly affect a toddler, unless it is very serious, as an infant would not bother to look far enough to be affected by the condition.
At times, uncorrected visual problems can lead to complications such as amblyopia, or in lay-terms, lazy eyes.
“This is a condition where the eye is structurally fine. It is poor vision in an otherwise normal appearing eye, which occurs when the brain does not recognise the sight that was registered by the eye.
“Two common causes are strabismus (squint eyes), and a difference in the refractive error (shortsighted, longsighted or astigmatism) between the two eyes,” says Dr Chin Pik Kee, a consultant ophthalmologist.
When a child, for instance, is shortsighted in one eye while the other is normal ? the condition on the weak eye would often be neglected as the child would be able to see. His vision would naturally depend on the normal eye and the weak eye would go undeveloped.
“When an infant is born, the visual pathways and nerves are not matured. In order for the pathways and nerves to fully develop, both the eyes have to see equally well,” says Chin.
Thus the weak eye, though it might be structurally functional, might be further impaired as the visual pathways, and nerves in the brain corresponding to the eye are underdeveloped.
“If untreated, amblyopia can cause irreversible visual loss. The best time for treatment is usually the preschool years. To treat amblyopia, we have to look at the underlying causes –whether it is caused by myopia or cataracts or squint eyes.
“We would first treat this problem. Then, we would give the patient a patching treatment, whereby the good eye is covered for a few hours a day. This would help the weak eye develop.
“Improvement of vision after the child is eight or nine years old is rarely achieved as the visual systems would, by then, be matured,” says Dr Chin.
Screening the eyes of toddler is thus important. Most parents, however, are unaware that even toddlers can be screened to check their eyesight.
If left unattended, bad vision can affect a child’s proper physical development and educational progress.
“Vision is the main sensory organ for knowing our surroundings. Most of what we learn as children is not through careful study, but just by watching and observing. However, if a child’s vision is seriously impaired, he would have to be told what’s happening around him,” says Dr Chin.
In other words, the child would only know what’s going on indirectly. This slows the learning process.
“There may be some visually disabled children who cannot be treated, and thus parents should try to teach them through other means – through the sense of touch, smell and sound to build a visual image in the boy’s mind.
“If the parents disregard this visual disability and send them to a normal school, they would often be left behind,” says Dr Chin.
But though vision does affect a child’s development, it does not necessarily follow that poor eyesight leads to learning problems. If a child is merely short or long-sighted, and has his vision corrected, there is no reason why his studies should be affected.
It is, however, quite a widely held belief that some learning disabilities such as attention deficit syndrome and dyslexia are caused by visual problems. The controversies surrounding this topic has however been resolved largely by the American Academy of Paediatric, American Association for Paediatric Ophthalmology and Strabismus and American Academy of Ophthalmology.
“Learning disabilities are common conditions in paediatric patients. The causes of these difficulties are multi-factorial ? reflecting genetic influences and abnormalities of brain structure and function.
“Visual problems are rarely responsible for learning difficulties. Eye defects, subtle or severe, do not cause the patient to experience reversal of letters, words, or numbers,” emphasises Dr Chin.
Sometimes parents, not knowing better, might seek alternative treatment for children suffering from conditions such as attention deficit ? mistaking it for bad eye sight.
“No scientific evidence exists for the efficacy of eye exercises or the use of special tinted lenses in the remediation of these complex paediatric neurological conditions. There’s also no evidence to support claims that learning disabilities can be improved with treatments that are based on visual training, including muscle exercises, ocular pursuit and tracking exercises.
“These more controversial methods of treatment, which relates the problem to the eye, may give parents and teachers a false sense of security that a child’s reading difficulties are being addressed, which may delay proper instruction or remediation.
“The expense of these methods is unwarranted, and they cannot be substituted for appropriate educational measures. Claims of improved reading and learning after visual training, neurological organisation training, or use of coloured lenses are almost always based on poorly controlled studies that typically rely on anecdotal information,” explains Dr Chin.
Experienced optician, Thomas Kok, who has been dealing with children for many years, thinks it seldom that a kid who has a serious visual problem would go unnoticed for long, especially after he starts schooling.
“Firstly, parents and teachers would be able to tell if a kid has visual difficulties after a certain age. It would manifest itself ? as he wouldn’t be able to see the blackboard and would be straining to see things.
“If this problem is not addressed, the kid might get dizzy or probably become more sluggish,” says Kok.
Myopia and children
It has been maintained for a long time that “genetics” was the sole determining factor of myopia in a child.
But then many population base studies have recently shown that communities that emphasise a lot on reading have much higher rates of myopia.
“The evidence from these studies is quite conclusive. Myopic rates are increasing all over. If it’s due to ‘genetics’ alone, we wouldn’t expect the rates to increase by so much.
“The countries that have a high percentage of people with myopia are basically those whose culture emphasises a lot on reading ? countries such as Taiwan, Hong Kong and Singapore, where about 70% of the population are myopic.
“Even the Jewish community has a high percentage of people with myopia,” observes Dr Chin.
The current hypothesis posed by eye-specialists is that the more children are subjected to sustained close work, the more their eyes will be elongated.
“The eye is like an auto-focus camera. For children, the focus range is generally very wide – they can see far and near easily. This degree of ‘accommodation’ gets less and less as we grow older.
“Thus when children are subjected to long hours of close work continuously, the eye adapts itself. As a result, it elongates. And so the natural focus of the eye is brought nearer. Thus, if the eyes has its natural focus at a near distance, it would not focus well at a long distance,” says Chin.
In some places, children with perfect eyesight have even been prescribed with preventive reading glasses to reduce the strain of living in a closed up society.
“The reading glasses focuses for the eyes. The eyes would, then, not have to use its own accommodative powers, and this would prevent the eyes from naturally adapting its focus to a near distance.
“At times, atropine (a strong eye drop) is also used as it completely relaxes the focusing mechanism of the eye.
“Again, all these have not yet been scientifically proven to be effective. It has yet to show any real benefits, i.e. that it actually stops the progression of myopia,” says Dr Chin.
And despite all the studies on myopia, scientists and doctors have not been able to isolate the risk factors of this condition.
“Most of the remedies prescribed are very general. Doctors can only advice children to adopt the right reading postures, to rest their eyes by looking at distances.
“At the moment, nothing is quantified. Doctors can’t tell patients how too much reading is bad and they can’t predict the right age at which children should begin reading,” says Dr Chin.
Even dim lighting and bad posture while reading has not been scientifically proven to be bad for one’s eyes.
As to the subject of under-correction of myopia, there has been some controversy of late. Recent research by an optometrist at the Anglia Polytechnic University in Cambridge, England, as reported by Reuters late last year, showed that under-correction of myopia could make vision worse.
At the moment, there are many various opposing schools of thought on this subject, some of which believe that under correction might lead to blindness, while others don’t. As for Dr Chin, she does not think that it might lead to something as drastic as that. “The debate on this is still going on?and there are many differing opinions,” says Dr Chin.
Kok, on the other hand, thinks that there are certain situations when under-correction might be the better option. “Sometimes under-correction is beneficial ? especially for children who have been diagnosed with high levels of myopia or astigmatism.
“This is so as a person wearing glasses for the first time may feel uncomfortable and giddy. Imagine a kid who’d never wore glasses before and asked to put on a high-powered one – he would definitely not be used to it. He would need time to adapt visually.
“Often, if such a case arises, we would prescribe a lesser-powered pair of glasses for the child to wear. This would give the child time to get use to his new ‘vision’ before introducing him to an optimally powered pair of glasses. Sometimes, we give him a year to get used to it,” says Kok.
Case studyBEFORE he was diagnosed with amblyopia, Adrian was thought to have learning disabilities. When he was young, his mother, Janet Lee, would teach Adrian with picture cards. He would stare at the picture without realising what it was.
“He would also take a long time to read. Initially, we just thought that he had problems learning,” says Lee.
It was discovered, eventually, that the problems were due to his vision.
“When we found out that something was wrong with his eyes at the age of four, we took him to an optometrist. We were told that he had a severe case of amblyopia, myopia and long sightedness.
“The optometrist told us that it was too late to do anything,” says Lee.
Not giving up, they went to an opthalmologist. After therapy and correctional glasses, Adrian was able to see and function just like any other child.
“The eye-specialist told us that if we had delayed sending Adrian, he would probably have lost his sight,” says Lee.
These days, Adrian, who is now in Form 2, is often shy and lacks confidence. This, to a certain extent, has affected his schoolwork as well as his social life.
“He lacks the confidence now as he probably thought he was not good enough during the first four and a half years. We all thought that he had learning disabilities and this probably made him think so as well,” says Lee.
Going cross-eyedSTRABISMUS, or squints, is basically misalignment of the eyes in any direction. When this occurs, i.e. when one eye is focused at an angle and is at odds with the focus of the other eye, double vision occurs.
“In order for our eyes to be coordinated, both the eye muscles have to act in the same way. For people with squints, their two eyes are not pointing together at the object they are looking at. This may be due to eye muscle imbalances or a minor glitch in the brain.
“Thus, when double vision occurs, the image will be distorted. Children, however, seldom have double vision. If the child has it for a long time, the brain will just disregard the vision of the eye that strays away. So, if the brain continually favours one eye and switches up the other eye, the eye will not get enough visual stimulus and, as a result, the function of that eye remain undeveloped.
“This will lead to amblyopia. And if it goes untreated, this would result in much reduced vision. If early detection of amblyopia secondary to strabismus is followed by effective treatment, then excellent vision may be restored. The eyes can be aligned in some cases with glasses and in others with surgery. However, restoration of good alignment does not ensure elimination of amblyopia,” says Dr Chin.
Then there’s also such a thing as latent strabismus.
“Most people do not have perfectly coordinated eyes. However, the brain is able to control the eyes so that squint doesn’t occur. For people with latent squints, their eyes may stray slightly when they are very tired,” Dr Chin explains. – By COLIN KHOO