What is Amblyopia?
Amblyopia (lazy eye) is caused by various conditions which prevent the brain from using both eyes together. A lazy eye is an eye that experiences constant blurred vision that is not cleared with the appropriate spectacles or contact lenses.
The problem in this situation is not with the ability of the eyes to clear an image, but with the capacity of the brain to perceive this image as clear. The brain ‘suppresses or turns off’ the vision from the lazy eye because of some factor (blur from a refractive error, or double vision from a squint) leading to an inability to fuse the images from the two eyes.
Children with lazy eyes are unable to use their eyes together well and thus have difficulty with depth perception and the appreciation of 3D.
The Causes of Amblyopia
Refractive amblyopia: A lazy eye occurs because one eye has a much stronger prescription than the other eye. The differing blur from the difference in prescription makes it difficult for the brain to focus or fuse images together. The brain thus decides it is less confusing if it suppresses the image of the eye with the stronger prescription. As such messages from the weaker eye are blocked and the vision in this eye is left to deteriorate causing amblyopia.
Strabismus amblyopia: When the eyes are not directed at the same target when fixating, the brain is sent two different images, one from the straight eye, and one from the turned eye.
The brain can’t cope with double vision, so it suppresses the image seen by the eye with the turn. This means the child adapts to only using his/her straight eye to see. This can lead on to organic amblyopia.
Stimulus deprivation: Often a lazy eye occurs as a result of a stimulus depriving the eye of sight at an early age. This can be in the form of a cataract occurring at birth, or a ptosis (drooped lid) that stops light entering the eye. This stunts the development of normal vision, causing the brain to supress the underdeveloped image from the deprived eye, leading to amblyopia.
Don’t Forget To Book In For An Eye Test
A lazy eye is not always easily recognized. This is particularly concerning when you realise that 3% (1 in 30 kids) have a lazy eye! A child may not even be aware that one of his eyes is not working with the other. If the eye turn is so slight that the child does not have an obvious misalignment, parents will rarely be able to tell something is wrong just by looking.
Vision can be tested in infants and very young children, and it is recommended that a child be examined at least by the age of three.