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 focused and 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 ignore the image from the affected eye. This lack of proper visual stimulation means that the nerve connections between that eye and the brain don’t develop properly and results in amblyopia.
What eye conditions can cause amblyopia?
Strabismus (sometimes called a squint) is when the eyes point in different directions. In adults, this generally results in double vision or blurred vision.
Though, 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.
When the cause of amblyopia is 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.
Less commonly, amblyopia can be the result of eye disorders such as a congenital cataract (cataract present at birth), corneal scar, drooping eyelid (ptosis) or a tumor of the eye. These kind of 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.
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.
Symptoms of amblyopia
Children with amblyopia are often too young to describe their symptoms. Parents might 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
- 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.
Treatment for amblyopia
The treatment for amblyopia usually involves:
- The treatment of the underlying cause and
- By using eye patches or eye drops to strengthen the lazy eye.
The sooner amblyopia is treated, the better the chance that your child will regain normal vision. Though, studies have depicted that amblyopia treatment can also help improve vision in older children.