What causes amblyopia?
Amblyopia can develop from other eye and vision problems, such as:
- Strabismus – when the eyes point in different directions. The brain receives two different images and is confused. To avoid seeing double, the brain may ignore the image from the eye that is not looking straight ahead. This constant ignoring of the image from one eye during a child’s visual development can result in poor vision. Untreated, your child’s vision will remain poor.
- Refractive errors – having a refractive error means being nearsighted, farsighted, or having astigmatism. A child may have a refractive error that’s worse in one eye. That eye can “turn off” and vision won’t develop properly. Sometimes this is difficult to detect since the child’s vision seems good when both eyes are being used.
- Blockage of vision – anything that blocks images from being focused on the retina will stop the eye from sending signals for vision and results in amblyopia. This is called deprivational amblyopia and is a very strong stimulus for amblyopia to develop. Causes of this include cloudiness in the normally clear parts of the eye – some children are born with a cataract, where the eye’s normally clear lens is cloudy, or a droopy eyelid (ptosis) blocking images entering the eye.
Factors that can be associated with an increased risk of lazy eye include:
- Premature birth
- Small birth size
- Family history
- Developmental disabilities.
What are the symptoms of amblyopia?
Symptoms include:
- Poor vision in one eye
- An eye that wanders inward or outward
- Poor depth perception
- Squinting or shutting an eye
- Head tilting
How is amblyopia diagnosed?
Eye specialists diagnose amblyopia by:
- Checking to see if vision differs between the two eyes
- Covering one of the child’s eyes to see how well they can follow a moving object, and watching to see how the child reacts when one eye is covered.
- Performing a complete medical eye exam to check for other eye problems that could be affecting vision
- Undertaking tests designed specifically for pre-verbal children.
Poor vision in one eye doesn’t always mean a child has amblyopia. In some cases, wearing glasses to correct a refractive error in one eye can improve vision.
All children should have their vision checked at or before their fourth birthday. Many schools offer vision screening as part of the child health screening service in kindergarten. Alternatively, your optometrist or health practitioner can check your child’s vision.
If there is a family history of misaligned eyes, childhood cataracts or serious eye disease, an ophthalmologist should check your child’s eyes when they are an infant.
How is amblyopia treated?
It is important to start treatment for amblyopia as soon as possible in childhood, when the connections between the eye and the brain are forming.
Treatment options depend on the cause of lazy eye and on how much the condition is affecting your child’s vision. It is usually corrected by making the child use their weaker eye, and it generally takes months or even years to strengthen vision in the weaker eye.
Treatments include:
- Corrective eyewear – glasses or contact lenses can correct problems such as nearsightedness, farsightedness or astigmatism that result in lazy eye
- Eye patches – your child wears an eye patch over the eye with better vision for two to six or more hours daily
- Bangerter filter – this special filter is placed on the eyeglass lens of the stronger eye and blurs the stronger eye and stimulates the weaker eye
- Eye drops – these can temporarily blur vision in the stronger eye and encourage your child to use the weaker eye
- Surgery – might be required if your child has droopy eyelids (ptosis) or cataracts that cause deprivation amblyopia or if the appropriate glasses don’t stop the crossing or wandering eye.
Continued monitoring of your child’s eye is required as amblyopia can recur.
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