Published in "Panorama"
When the eye becomes ‘lazy’
Sunita became suspicious when she observed her four year old son Rahul watching TV from a very close range. Further, he would protest if asked to sit some distance away from the screen and watch the programmes. Sunita's suspicions were eventually proved right - Rahul did have an eye problem resulting in Amblyopia! Also known as "lazy eye", Amblyopia is one of the most important conditions which lurks in the eye and goes undetected oftentimes, reveals Dr.Sathish, Specialist Ophthalmologist, Welcare Hospital Dubai.
Amblyopia, which affects roughly 5% of children, is actually reduced vision in one or both eyes that has resulted from inadequate use during early childhood. The only function of the eye is to help us to see. If the eye doesn't see in spite of being disease-free, then it is sheer laziness, explains Dr.Sathish. "A child with Amblyopia becomes used to blurred vision in either or both eyes. The problem develops when the pathways of vision in the brain, which carry messages from the eyes to the brain, are not visually stimulated to grow well enough. The eye might appear normal and alright, but it does not have the vision. Without timely treatment, the unused eye will settle for poor vision for the rest of its life!" He further clarifies about the common practice of referring to an abnormally moving eye as the lazy eye as being incorrect. The well coordinated movement of the eye is a facilitator of vision and not the vision itself. So laziness of the eye, that is, Amblyopia, should be perceived simply as a decrease in vision in one or both eyes which are otherwise healthy.
Amblyopia has many causes. A strong uncorrected spectacle error, as in shortsight or longsight can cause amblyopia as also a large difference in numbers between the two eyes. "Astigmatism is the other type of spectacle error which can cause laziness in the eye", reveals Dr.Sathish. "In this condition, objects near and far appear fuzzy and distorted. Under routine circumstances, if you put on correct spectacles, your vision should be fine. But in amblyopia, this does not happen. Lazy eye results more often from unattended misalignment of a child's eye that is also known as squint or strabismus or simply a crossed eye." Dr.Sathish continues, "Rarely, some children are born with abnormalities of the eye itself, like cataract & drooping eyelids, both of which affect vision development. For instance, if the child is having significant drooping lids which comes in the way of the vision development, then, the underlying healthy eye becomes lazy."
Thus, situations leading to a blurring of vision or crossed eyes during early childhood, result in one eye becoming stronger, suppressing the image of the other. If the condition is allowed to persist beyond 8 years of age, the weaker eye becomes useless forever! Though laziness originates in the eye, it is actually established in the brain. It is the brain which accepts the figures of each eye, recognizes the capacity of each eye individually, lets the images of the two eyes fuse and then lets you recognise the object of your observation. So seeing is a function of the brain. But if the brain doesn't get clear signals from the eyes, it discriminates between the two eyes and will recognise that eye's signal more, which is better. It begins to ignore the messages from the weaker eye which in turn may eventually lead to functional blindness in that eye. .The brain's vision system is complete by the time a child is 8 -9 years old. Beyond this age, it cannot develop. So amblyopia is best detected and treated at the earliest possible, much before 8 years of age; if not, it can lead to permanent vision loss in an otherwise healthy eye ! Once established, even Laser treatment will not restore the vision in such eyes." cautions Dr,Sathish
How does one even suspect amblyopia, particularly in a small child? Dr.Sathish explains, "It takes 3 months for a child to look at the mother and give the first smile of recognition even though it has been smiling from day one. This smile of recognition is an indication that the child's vision is growing. But if the child's lid is drooping or it has cataract, it impairs the development of vision. If the lid is droopy, most of the times, the parents themselves can make it out. Yes, cataract is difficult to make out. If there is a history of cataract in the family or if the pregnancy for the child had been stormy or if the delivery had been traumatic and prolonged, then the child needs to be examined in detail, very early." A fairly simple way of checking a growing child's vision is a home test, explains Dr.Sathish. "As the child is relaxed on the mothers lap & engrossed in the TV, gently close one eye with the palm of the hand and let the child watch the TV with the other eye. A few minutes later, do the same with the other eye. If the child protests the blocking of one eye more than the other, this is an indication that all is not right with the vision"
An authentic way of testing this would be in an ophthalmic clinic, adds Dr.Sathish. "Of course there's a challenge of testing a pre-verbal child in this manner. In a child of 1 or 2 years who has not yet begun talking, we assess vision by its ability to look into & follow light. When we shine the light on the eyes, the child should be looking straight at the light. When one eye is blocked, if it staggers or wavers, then we know that there is some problem leading to amblyopia. There are other technical ways of confirming the same."
Dr.Sathish emphasizes, "Children rarely complain of poor vision since they are very easily able to adapt to most visual impairments. Parents must be very observant of young children and especially see if the child squints or closes one eye while reading or watching television, or tilts its head in a certain direction while looking at objects. Also, it is important to take their children for a routine eye exam by the age of 2 -3 to detect potential problems, even if they do not observe any tell-tale defects. Eyes are too precious to be careless about."
With early diagnosis and treatment, the sight in the "lazy eye" can be restored, assures Dr. Sathish. The earlier the treatment, the better the opportunity to reverse the vision loss because the first few years of life are the most important for eyesight, re-emphasizes Dr.Sathish. Since amblyopia may result from various causes, treatment begins with treating the underlying cause, explains Dr.Sathish.
Drooping lids, crossed eyes and cataract may require surgery to start with. However, the commonest cause being spectacle defects, wearing the appropriate glasses on a constant basis is of foremost necessity. Once the cause is addressed, the child will have to exercise the weaker eye by constant use. To achieve this, a patch may be put over the stronger eye so that the child is forced to see with the weaker eye. Sometimes, eye drops or special glasses may be used to blur the vision in the stronger eye so that once again the child is forced to use the weaker eye. If the child has become amblyopic due to a strong uncorrected refractive error or a large difference between the spectacle errors of both eyes, amblyopia can be treated with even contact lenses plus the patching. In all instances, the patching may be stopped once vision in the weaker eye has strengthened to the desired extent, in keeping with vision in the other, stronger eye. Dr Sathish further emphasizes that the forcibly recovered vision in a hitherto lazy eye is likely to be lost if not periodically monitored until the child is 8 to10 years of age!