Amblyopia (lazy eye)

Amblyopia is reduced vision that is caused by disruption of the normal development of vision during childhood.

Sometimes also known as 'lazy eye', amblyopia is a common cause of reduced vision in children. Usually one eye is affected, but both may be affected in some cases.

Amblyopia is thought to affect about 3 per cent of children. Most cases can be treated successfully if detected at an early age. However, if it isn’t treated early enough, in some cases amblyopia can result in permanent vision impairment or blindness in the affected eye.

What is amblyopia?

Amblyopia is reduced vision that is caused by disruption of the normal development of vision during childhood.

At birth, a baby’s visual system is not yet fully developed. Development of the visual system in infancy and early childhood requires focussed, aligned images being sent from both eyes to the brain.

When an eye condition causes blurry or distorted vision in one eye, the brain can learn to suppress or ignore the image from the affected eye. This lack of proper visual stimulation means that the the nerve connections between that eye and the brain don’t develop properly, resulting in amblyopia.

What eye conditions can cause lazy eye?

Eye conditions that commonly cause amblyopia include strabismus (misalignment of the eyes) and refractive errors (problems with focus).

Strabismic amblyopia

Strabismus (sometimes called a squint) is when the eyes point in different directions. In adults, this usually results in double vision or blurred vision. However, to avoid this, a child's brain is able to suppress the image from the eye that’s not straight, causing that eye to become amblyopic or 'lazy'. This is known as strabismic amblyopia.

Refractive amblyopia

When amblyopia is caused by refractive errors (such as long-sightedness, short-sightedness or astigmatism) it is called refractive amblyopia.
 
When there is a significant difference in the refractive error between the eyes — such as one eye being much more long-sighted than the other — the brain suppresses the image from the weaker eye, causing it to become amblyopic. A high refractive error in both eyes (such as both eyes being very long-sighted) may cause amblyopia in both eyes.

Deprivation amblyopia

Less commonly, amblyopia may be the result of eye diseases such as a congenital cataract (cataract present at birth), corneal scar, drooping eyelid (ptosis) or a tumour of the eye. These conditions deprive the affected eyes of normal visual experience, which can significantly affect the development of the visual system.

This type of amblyopia is called deprivation amblyopia, and is often the most severe type.

Symptoms

Children with amblyopia are often too young to describe their symptoms. Parents may notice symptoms of an underlying eye problem or signs of reduced vision in one eye.

You may notice:

  • your child covering one eye;
  • your child squinting or shutting one eye;
  • your child holding objects closely to try to see them clearly; or that
  • one eye does not look in the same direction as the other (crossing in or turning outwards).

Older children may notice they have problems with vision in one eye or with depth perception.

How is amblyopia diagnosed?

Amblyopia can usually be diagnosed by a full examination of the eyes. If you suspect that there is any problem with your child’s eyes, you should consult your doctor. A child is never too young to have their eyes examined.

Because of the importance of early detection, eye checks are recommended for infants and children as part of their routine health checks. All children should routinely have their eyes tested before school age. This is especially important for conditions where the eyes look normal but in fact have refractive errors or other problems that are preventing the normal development of vision.

If your doctor thinks your child has amblyopia they will most likely refer you to a paediatric ophthalmologist - a specialist in children's eye problems.

Treatments for lazy eye

The treatment for amblyopia usually involves:

  • treatment of the underlying cause; and
  • using eye patches or eye drops to strengthen the lazy eye.

The earlier amblyopia is treated, the better the chance that your child will regain normal vision. However, studies have shown that amblyopia treatment can also help improve vision in older children.

Eye patches and eye drops for amblyopia

A widely used treatment for amblyopia involves stopping your child from using their good eye, and forcing them to use their lazy, or weak, eye. This commonly involves covering the good eye with a patch. An alternative to patching is putting eye drops in the good eye, which temporarily blur the vision in that eye.

Your doctor will recommend treatment for a certain amount of time each day.

Eye patches or drops can lead to the improvement of vision in just a couple of weeks. Sometimes it may take several months to notice a difference. Ongoing, or maintenance, treatment may be recommended for months or years.

Treatment of the underlying eye condition

If a refractive error, such as short sightedness, long-sightedness or astigmatism, is contributing to lazy eye, then glasses or contact lenses may be prescribed. Additional treatment with eye patches or drops is often needed to help strengthen the amblyopic (weak) eye. Children with amblyopia affecting both eyes may be treated with glasses or contact lenses alone.

Treatment for strabismus (squint) may involve eye exercises (orthoptics therapy), which can help the eyes work together. Surgery to correct an imbalance in the eye muscles is often recommended to treat strabismus.

Surgical treatment may also be recommended to treat cataracts and drooping eyelids (ptosis). Children treated with surgery usually also need treatment with glasses, patching or eye drops.

Follow-up

It’s recommended that children with amblyopia have regular check-ups and eye tests to monitor their vision.

Last Reviewed: 25 June 2017
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References

1. Mayo Clinic. Lazy eye (amblyopia) (updated 3 May 2016). http://www.mayoclinic.org/diseases-conditions/lazy-eye/home/ovc-20201878 (accessed May 2017).
2. Merck Manual Professional Version. Amblyopia (updated May 2016). http://www.merckmanuals.com/professional/pediatrics/eye-defects-and-conditions-in-children/amblyopia (accessed May 2017).
3. National Eye Institute. Facts about amblyopia (updated Sep 2013). https://nei.nih.gov/health/amblyopia/amblyopia_guide (accessed May 2017).
4. American Association for Pediatric Ophthalmology and Strabismus (AAPOS). Amblyopia (updated Mar 2017). https://www.aapos.org/terms/conditions/21 (accessed May 2017).
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