What is Amblyopia?

30 March 2019

Author: Jacci

What is Amblyopia?

Amblyopia, commonly known as lazy eye, is a condition where vision in one or both eyes does not develop correctly. This occurs when the eye and the brain are not working together correctly.

Usually only one eye is affected by amblyopia, as a result of the brain favouring the stronger eye. If ignored, over time, the brain will learn to completely disregard the images sent from the lazy eye- causing the problem to worsen as a result.

Amblyopia is a leading cause of vision loss in kids, affecting around three out of every 100 children.

Here we look into:

  • The symptoms of amblyopia
  • The causes of amblyopia
  • Treatment for amblyopia

Symptoms of amblyopia

Amblyopia typically develops in individuals from birth to around nine years of age. Because the stronger eye will make up for the shortfall of the lazy eye, some children do not notice the problem.

Amblyopia is therefore often not detected until a routine eye test is completed. 

Common symptoms of amblyopia include:

  • Blurred vision
  • Double vision
  • Squinting
  • Poor depth perception
  • Eyes that do not appear to work together
  • An eye that wonders inward, outward or to the side

The earlier diagnosis of amblyopia, the easier it is to treat. Children should attend eye examinations from the age of three or four. If your child is experiencing any of these symptoms an appointment with an optometrist should be made without delay.

Causes of amblyopia

Amblyopia is the inability for one eye to focus as well as the other, due to abnormal vision development after birth.

The vision process involves both the eyes and the brain to work harmoniously. Where amblyopia is present, the image processing part of the brain does not develop properly.

There are a few causes of amblyopia, which include:


Often referred to as crossed eyes, strabismus is the most common cause of amblyopia. This is defined as the constant turn of one eye in any direction; most commonly inward or outward.

This misalignment can result in double vision. To cope with this, the brain will often use the ‘healthy’ eye and suppress vision from the abnormal eye.


Anisometropia occurs when each eye possess a different prescription and therefore, an unequal refractive power.

Most people are born with a slight difference in their refractive power between each eye, but the brain learns to compensate so it does not destruct vision.

However, when an individual has anisometropia, the refractive power between both eyes is so dominant that it leaves your brain with no option but to ignore visual signals from the weaker eye; significantly interfering with vision. 

Physical blockage

Blockage of the eye can be caused by a number of factors, such as a cataract, trauma, lid droop (ptosis) or blocked tear duct.

In these cases the eye may blur and lead the brain to favour the stronger eye.

Treatments for amblyopia

In order to treat amblyopia, the brain must learn to pay attention to images being transmitted by the lazy eye- ultimately strengthening its vision.

This is done through the use of glasses, eye patches, eye drops or surgery.


Glasses are prescribed when amblyopia is caused by anisometropia (when both eyes have a significant imbalance in refractive error).

This works by sending clear images to the brain. This trains the brain to use the eyes together, to develop normal vision.

Eye patches

Eye patches are commonly used to treat amblyopia. Here, the healthy eye is covered for several hours of the day.

This encourages the lazy eye to work harder and thus become stronger, improving the signals sent to the brain via the optic nerve.

Eye patches may be required for several months, depending on the rate of improvement in the amblyopic eye.

Eye drops

Eye drops are offered as an alternative to eye patches. Similarly to the patches, they work by blurring the vision in the good eye, forcing the lazy eye to do all of the work. 

Atropine is the active ingredient, which numbs the muscles in the eye, stopping the lens from focusing for a few hours. The drops are usually administered twice per week and it can take several months for the atropine to correct the condition.


If amblyopia is caused by strabismus (the constant turn of one eye in any direction) and glasses, patches or eye drops do not help, surgery is an option.

Surgery involves the loosening or tightening of the eye muscles. This aims to correct the misalignment of the eyes by changing their position.


If your child is experiencing symptoms of amblyopia, we advise that you contact your local optometrist for an eye examination.


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