Published in The International Malayalee
Early Detection of Amblyopia - a must for restoring vision
15 year old student Vishnu, accidentally discovered that he could not see properly with his left eye when he covered his right eye with his palm, in reaction to some foreign body falling in it. He was taken to see an eye specialist in the evening when he returned home from school. A complete eye examination revealed that he had a high minus power in the left eye, which had probably been there from birth and was not corrected since it had gone unnoticed. The right eye, however was perfectly normal. Now at 15, when the defect was spotted and he was given the full required number with spectacles, still vision in the left eye did not improve. That is, even with the specs on, he was not able to see properly with that eye!
This is exactly what Amblyopia is about, says Dr.Azim Siraj, FRCS(Edin, UK)., M.Med(Singapore)., DNB(Oph)., DO., MBBS, Specialist Eye Surgeon, Prime Medical Centre, Dubai. Amblyopia in lay terms means “lazy eye” and this condition affects 4% of kids in any general population, world over. Speaking of Vishnu’s case Dr.Azim reveals, “All the necessary tests were done including examination of the retina and optic nerve. Everything else was found to be normal. So the cause of Vishnu’s lazy eye was because of non-detection of a problem of the eye, a high minus power, which was not corrected on time, ideally, before the age of 7 years. Hence, even after full correction at the age of 15, he is not able to get improved vision in that eye. So Amblyopia, in essence, is a drop in or diminishing of vision in one or both eyes, in the absence of any detectable ocular abnormality which could contribute to that drop in vision. It is defective vision even after maximum correction!”
Therefore, It is important, emphasizes Dr.Azim that Amblyopia must be identified as early as possible and corrective measures, have to be taken to ensure that the child regains good vision in that eye. Else, vision in the affected eye may be permanently lost. And this can have far reaching consequences when the child grows up, in terms of not being able to take up certain types of jobs and pursue certain career which require good vision in both eyes. Further, at a later stage in life if the individual loses vision in the good eye due to an accident or for some other reason, there is no compensating eye to take over the function of seeing! He/She could become blind for good. “Amblyopia is essentially a condition which should be prevented. Treatment gives partial results unless detected early. The condition is preventable because if you catch the cause early, the underlying cause can be treated and Amblyopia prevented or even treated with very good results.”
HOW DOES AMBLYOPIA OCCUR?
Usually, Amblyopia occurs in one eye though it can affect both eyes. The stimulus for developing good vision is light. The visual pathway, which usually keeps developing till the age of 7, has got to get the stimulus to grow and this stimulus is light. So if light, or a focused image, is not presented to the eye, it does not actively take part in the formation of the functional visual pathway.
WHAT ARE THE CONDITIONS THAT CAUSE AMBLYOPIA ?
A child having a droopy eyelid (PTOSIS) since birth, which covers the pupilary margin cannot see since the incoming light is cut off. In these children amblyopia sets in due to deprivation of the visual stimulus. Similarly, amblyopia sets in a child born with a cataract,or any opacity in the line of vision due to deprivation of the visual stimulus. If the cataract is not detected and treated on time, the child only sees with normal eye and the affected eye falls into disuse, thus becoming lazy.
Amblyopia also sets in children having a squint (strabismus). In this condition, the eyes are not aligned properly to be in tune with each other. When each other looks at two different sets of objects at the same time, the brain is confused and will therefore not be able to fuse both images to produce a single projection of the objects in question. If the squint is not corrected adequately, then it will lead to a drop in vision in that eye.
Amblyopia can also occur in conditions where the image is not in focus. The image is very clear, say in one eye, but very blurry in the other. This may be because the weak eye has a very high plus or minus number (long-sight and short sight). That is, amblyopia can easily set in if the difference between the normal eye and the other eye is more than 3, plus or minus. When this happens, the brain cannot fuse the images. It tends to ignore the eye with the blurred image. This in turn creates a vicious cycle and worsens that eye’s vision. This is because of a diminished focus. This may also be brought about by the person having a high cylindrical error in one eye, so one plane alone is out of focus – a condition called astigmatism.
The commonest leading causes of are droopy eyelids, cataract, squint high myopia or short sight, high hypermetropia or long sight and astigmatism. Hence, correction of these conditions will prevent lazy eye from occurring in the first place, and if it has already occurred, it can be treated successfully, provided it is adequately detected and treated before a child reaches 7 years of age, emphasizes Dr.Azim.
HOW CAN AMBLYOPIA BE DETECTED?
Most often, Amblyopia is only accidentally discovered. It is a painless cause of diminished vision and it can be determined only by a proper eye evaluation. Eye screening for children should be done as early as between the ages of 3 and 4. In fact, it can even be suspected from the stage the child starts seeing its mother and recognizes her.
Remember…The child cannot help itself. Only parents and teachers should be vigilant to detect this problem .
Parents’ role in early detection of amblyopia:
1. Watch for the head posture of the child, especially while it is watching TV. For some children, it may be a natural habit to tilt their heads to one side while watching the TV. But this may also be an indication, an early manifestation of a hidden problem in the child. This is particularly so if the child squeezes its eye to see the TV or prefers to sit close to it; this is almost certain that the child has some eye problem.
2. In a tactful manner, try to cover any one eye of the child alternately with your palm, when it is watching TV, particularly a programme in which it is keenly interested. If both eyes are normal, the child will continue to see the TV without realizing the eye is covered. However, if even one of the eyes has a problem, the child will immediately try to push your hand away to watch the TV when the better eye is covered. This is a simple vision test, which parents can do at home.
3. If parents notice one eye of the child is watering while watching TV, it needs to be examined.
4. If parents notice a white spot in the eye, this child certainly needs an eye examination. This does not necessarily mean the child will have an eye problem, but it is something abnormal and it needs to be examined.
5. If the child complains of headache, particularly on one side, especially while watching TV, it may be an indication of a hidden problem and therefore needs to be examined.
6. Even If none of the above symptoms are noticed in a child, yet one of his/her parents is having a high number in one eye, or if there is a family history of Amblyopia in the immediate blood relations a thorough eye checkup is recommended so that Amblyopia can be detected on time. This is so even if the parents have had laser surgery to correct the high number.
7. If one sibling is having a high number, it is only appropriate to have the other siblings examined thoroughly for eye power.
Role of Teachers in Detecting Amblyopia:
1. The commonest thing teachers can observe in their students is when they write on the blackboard. A child with an eye problem is most likely to change his place from the back to the front seat in order to see the board. Or, the child may go close to the board to write down what the teacher has put up. The teacher should immediately notify the parents.
2. While the teacher is writing on the blackboard, a child prefers copying the same from her/his neighbour.
3. Normally when eye checks are done in schools, the children go close to the reading chart, memorize the letters there and repeat when the eyes are alternatively closed to test for vision. This would defeat the very purpose of the eye test and the condition can be completely missed. care should also be taken to ensure that the eyes are closed properly during such screening programs.
HOW IS AMBLYOPIA TREATED?
Once it is found out that a child has Amblyopia, FIRST it is important to find out the underlying cause and the extent of the amblyopia. The underlying cause should be first treated adequately so that the amblyopia doesn’t worsen, emphasizes Dr.Azim.
SECONDLY it is imperative to strengthen the weak eye by adequately correcting the defect it has. Seclude or cut off the image of the good eye to the brain, so that the brain is forced to use the images from the weak eye. This would provide the required stimulus to the weak eye so that it starts working again. This can be done in two ways, explains Dr.Azim Siraj. First, by closing the good eye mechanically with a patch. Alternatively, by putting drops in the good eye to cut off the quality of vision so that images become out of focus and blurred. Both these measures will force the weaker eye to start functioning. This should only be done under proper medical supervision and should be followed by regular checkups as per the doctor’s advice, emphasizes Dr.Azim.