What is amblyopia and how do I detect it?
Amblyopia, also known as ‘lazy eye’, is a common cause of reduced vision in children. It begins during infancy and early childhood due to a disruption in the normal development of vision. Amblyopia affects around 3 per cent of children. Most cases can be treated successfully if detected and treated correctly at an early age. However if undetected or left untreated it can result in permanent vision loss.
What is Amblyopia?
Normally the retina of both eyes sends equal visual images to the brain. With amblyopia one eye’s image is obstructed and therefore two different images are sent to the brain. This causes the brain to ignore the images coming from the affected eye and only process the visual images from the normal eye. Over time the brain depends more heavily on the normal eye and the affected eye ‘switches off’ leaving it underdeveloped. This is why amblyopia is often referred to as ‘lazy eye’ as it does not do any work!
Signs and symptoms
Because amblyopia occurs during early childhood, children are often unable to describe their symptoms. A common cause is misaligned eyes, known as strabismus, where one eye does not look in the same direction as the other. This can be constant or intermittent. Other signs can include squinting of one eye or excessive head tilting. Older children may complain of vision problems in one eye, double vision or show signs of poor depth perception.
What causes Amblyopia?
There are several different types of amblyopia based on their underlying cause, all of which obstruct the vision in one eye.
Strabismus is the most common cause of amblyopia. When eyes point in different directions this usually results is double or blurred vision. To avoid this the brain suppresses the image from one eye, causing that eye to become amblyopic or ‘lazy’
If there is a significant difference in the refractive error between the eyes (i.e. one eye being a lot more long-sighted than the other) then the brain suppresses the image from the weaker eye causing it to become underused and amblyopic. This can be despite perfect eye alignment. This type of amblyopia is called refractive amblyopia.
Another less common cause is from a congenital cataract which is present at birth. This cataract obstructs light from entering the eye, once again affecting the visual image sent to the brain and causing that eye to ‘switch off’. Prompt diagnosis and treatment of congenital cataracts is vital to allow for normal vision development.
How can Amblyopia be treated?
The treatment for amblyopia depends on the cause. The most common treatment is the use of an eye patch over the good eye. This is to stop the child from using that eye and forcing them to use and develop their ‘lazy eye’. Patching in children should begin as early as possible to encourage the amblyopic eye to develop. If the child is non-compliant and frequently removes the patch then using eye drops which blur the vision can be an alternative.
If it is a refractive error, such as sort or long sightedness or astigmatism, contributing to the amblyopia, then prescription glasses may be enough to correct the problem.
Sometimes strabismus surgery is required to straighten the eyes and correct an imbalance in the eye muscles. Eye patching is usually prescribed after surgery. A congenital cataract may also require surgical removal.
Early detection and treatment is important
Most experts agree that early detection and treatment of amblyopia gets the best best outcomes as early intervention allows for better visual development. If diagnosed after 9-10 years or age it is much more difficult to treat with permanent vision loss more likely.
Optometry Australia recommends that the your child should have their first eye test done before the age of 6 months. This should be followed by an eye exam at the age of 3 years and another at the age of 6 years or more frequently if suggested by your optometrist.