When young children watch television they believe everything they see. They also believe that everything they see at Disney World is real. On that basis it would also seem reasonable to assume that if a child’s vision is blurred for distance objects that they will accept that this is how it’s supposed to be. They will also assume everyone else sees the world the way they see it. When they look at things which are up close everything is clear so they think that their eyes are working properly.
This is why children who are a bit myopic (short sighted) don’t know they have a problem. If a child has blurred distance vision they will avoid tasks that require clear vision. Rather than sitting on the sofa to watch the television they would sit close to the television on the floor. They would be more interested in tasks involving close work like reading and computers. Some children with myopia will also screw their eyes up to try and see more clearly. As a parent you should be aware of these signs and should make sure your children have regular eye tests.
An amblyopic eye (lazy eye) looks perfectly healthy from the outside but the vision is poor, even when spectacles are worn. The question I am often asked is why a child wasn’t aware of the problem. Firstly the child may assume that it is normal to have one good eye and one bad eye. The other reason is that the visual system does not separate the images from each eye so the child may not have noticed the difference between the eyes. The brain takes all the visual information from each eye creates a single picture of the world. It doesn’t matter if most of that information comes from one of the eyes or they both contribute equally. Amblyopia occurs when the image at the back of an eye is not clear or when the image in one eye is very different to that in the other. This is often because of a squint where the eyes are not looking in the same direction. The early detection of an amblyopic eye is critical for the development of your child’s eyes.
A squint often occurs when a child is long sighted. The method used by the eyes to change their power from distance to near is called accommodation. It is linked to the muscles the make the eye move closer to the noise when you read. This process is called convergence. Children who are very long sighted use their accommodation to correct for the long sightedness. Unfortunately because it is linked to convergence the eyes will also converge. Although convergence is normally equal in both eyes, the child will keep one eye straight and let the other one do all the converging. The result is an accommodative squint where one eye looks straight ahead and the other one turns into the nose. An eye that turns in will lose its ability to see small objects and become lazy (amblyopic). The accommodation in children’s eyes is so strong that it can mask large amounts of long sightedness. You optometrist may feel it necessary to put drops in your child’s eyes to relax the accommodation. Doing this will tell us if there is any hidden long sightedness that could result in a squint or amblyopic eye.
As your child’s eyes develop there is a plastic period where an amblyopic eye can with the correct spectacles and treatment regain good vision. The plastic period is generally thought to between the ages of 4 and 8. This is why is important to have all children’s eyes examined before they start school. Many parents tell us that their child is fine because the nursery tested their eyes. The important thing you need to understand about this is that NURSERIES DO NOT TEST YOUR CHILDS EYES. In the nursery they conduct vision screening. They set a side an hour or so and ask 20 or 30 children to identify the shapes on a chart. This screening will only pick up children with the most severe visual issues. An optometrist will spend 20 minutes (more if drops are required) examining your child’s eyes. The nursery screening has it’s place but it is not a substitute for a full eye test.
If your child has a squint or amblyopic eye they will be referred to the orthoptics unit in your local hospital eye department. Treatment may include wearing a patch or various exercises. The patch is worn over the good eye to force the poor eye to relearn how to see.
On occasions surgery is required to straighten an eye with a squint. The surgeon will often only corrected part of the squint by surgery because part of the squint is accommodative and part isn’t. If the squint was fully corrected by surgery the child would still have to accommodate to correct the long sightedness and the convergence would start to pull the eye in.
When a child has a squint the main push is to improve lazy eyes and help the eyes develop a visual system that uses both eyes (binocular vision). Some patients develop two visual systems. One for each eye which means the vision is good in each eye but when they use one eye the other is switched off and vice versa.
Some patients have one eye looking straight ahead and the other moved out towards the ear. Some have one eye higher than the other and occasionally the squint is only in one direction of gaze due to one of the muscles that controls the eye being damaged.
Parents often assume that a child who can see well with each eye doesn’t need spectacles. This assumption is untrue. Your child may be hypermetropic (long sightedness) and they maybe able to see well with each eye but they may also have difficulty finishing their school work. They may suffer from headaches or tiredness when the watch the television or use a computer. A child who has to constantly strain their eyes used to overcome hypermetropia can run into difficulties which on the surface do not appear to be connected to the eyes. Optometrists are happy to test children’s eyes even if the result show that no spectacles are required. Probably one out of every five children who appear to have good vision that come in for a routine eye test have a issue with their eyes.
Everyone knows a parent who’s child is a slow reader. It is possible that the child has a learning difficulty but what if that child is struggling to read for no reason other than the fact that he cannot see the print. We recently had a seven year old child in the practice for his first routine eye test. His mother was in tears at the end of the test when he said “Wow! Mummy I’ll now be able to see the small print in my book” he had completed almost 3 years of schooling before he was able to see the print in the books.
Your child may have astigmatism which would make close work difficult. There may be a large difference in image size between the eyes making it difficult for the brain to fuse them into one image. Your child may have difficulties moving his eyes inward towards nose when he wants to read (convergence problems). Take your child for an eye test – Nobody wants to be the parent with tears running down their cheek.