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.

The Importance of Treating Amblyopia

Amblyopia is not a condition that can be corrected with glasses alone. The issue is with the brain as well as the eye. As such the brain must be re-taught to stop suppressing the weaker eye and begin accepting visual input from it. This is achieved by patching the good eye, and forcing the weaker eye to work.

If patching is done as per guidelines, vision in the ‘bad eye’ is likely to improve to a level equal to the good eye. This has huge implications not just with acuity, but also with the ability to attain depth perception.

An eye that is left untreated will continue to deteriorate. The longer the condition is left untreated, the harder it is to rectify the deficiency and achieve a good result with therapy. As well as the implications on vision and depth perception, studies have revealed that untreated amblyopes generally perform poorly academically. When Children with untreated amblyopia grow to be adults, their choice of career may be limited and, if they are unlucky enough to lose vision in their one good eye, they could be visually impaired or legally blind for life.

What are the treatment options?

Most children do not outgrow amblyopia so early detection and treatment are important. Early diagnosis and treatment can increase the chance for a complete recovery.

To correct amblyopia, glasses must be prescribed first. If the underlying cause of the lazy eye is strabismus, then the eye turn must also be addressed. Some children require patching of the good eye for specific periods of time, forcing the blurry eye to ‘turn on’.

Note: Recent research indicates that not nearly as much daily patching time is necessary as was previously thought.  A study by the National Eye Institute showed that for many kids,  2 hours a day was as beneficial as patching six hours or more.

Unfortunately, the gains from patching are sometimes not stable.  Your child may get better when using the patch, then worse when it’s removed.

While patching usually improves vision, it is not always possible to restore the child to normal 20/20 vision with the patch alone, especially if the child had really poor eyesight in the eye to begin with.  This is because the underlying cause of the lazy eye, was never addressed.

For a permanent solution, the brain must be taught to stop suppressing (turning off) the blurry eye and trained how to align and use the two eyes together. If this is not done, the brain will still suppress the lazy eye once the patch is removed.  As a result, some of the improvement from patching will be lost over time.

Vision Therapy as an option

Vision therapy is highly successful in remediating a lazy eye. At least 95% of patients treated fully in office based vision therapy will have full resolution of their amblyopia! Click here to find out more about vision therapy.

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