Eye conditions

Strabismus and ptosis

Strabismus (‘turned’, ‘crossed’ or ‘lazy’ eyes) and ptosis (drooping of the upper eyelid) are the most common eye movement disorders affecting Australians.

What are strabismus and ptosis?

Strabismus is more commonly known as ‘turned’, ‘crossed’ or ‘lazy’ eyes. This is when the eyes are not pointing in the same direction. One eye or either eye may turn inward, outward, upward or downward. It may be present some or all of the time. The strabismus can be large or small.

Ptosis is where the upper eyelid droops or sags over the eye. The eyelid may droop a little, or it may cover the whole eye, appearing closed. It can occur in one or both eyes. Ptosis can restrict vision or even block it completely.

Strabismus and ptosis can sometimes occur together. This is because the nerve that controls eye lid movement also controls four of the muscles that control the eye.

Both strabismus and ptosis can cause poor vision (amblyopia).

Learn about our eye movement disorder research

Our researchers investigate eye movement disorders such as strabismus and ptosis, striving to understand the genetic causes, improve early detection and help find better treatments.

How common are they?

Strabismus affects up to five percent of people in Australia. It’s one of the most common eye problems in children.

There is little data on how often ptosis occurs in Australia. An American study found 7.9 out of 100 000 children up to age 19 had ptosis. Ninety per cent of these children had ptosis from birth.

Causes and risk factors

You can have strabismus or ptosis at birth, or you can develop these conditions any time in your life.

Strabismus or ptosis needs to be examined by a doctor to make sure it is not a sign of a more serious problem.


Problems with the eye muscles or the nerves that control these muscles can cause strabismus.

Most of the time it is caused by being long-sighted, having poor vision in one eye or a family history of strabismus. It is sometimes caused by an eye or head injury, or a more serious problem like an eye or brain tumour.


Ptosis occurs because of problems with the muscle that lifts the eyelid (the levator muscle).

This problem can be present at birth (congenital ptosis) or it may develop as you age (acquired).

Often ptosis is inherited and runs through families. Not all family members will be affected in the same way.

Acquired ptosis occurs when the levator muscle stretches or separates from the eyelid. It can be caused by:

  • The natural aging process
  • Overuse or adverse side effects of botox injections
  • Stroke, head injury or tumours.

Signs and symptoms

The most common signs of strabismus are:

  • Eyes that don’t look in the same direction at the same time ­– this may be hard to detect if the size of the eye turn is small
  • Eyes that don’t move together
  • Squinting or closing one eye in bright sunlight
  • Tilting or turning the head to look at an object
  • Bumping into things – strabismus can give you double vision and limits 3D vision.


The most obvious sign of ptosis is a drooping eyelid. Children may also tilt their chin up to look out from under their droopy lid.

Children with strabismus or ptosis may appear as if they have no problem with their vision. That is why it is important to have their eyes checked and make sure their vision is developing equally.


A GP, doctor, orthoptist or optometrist can perform specific tests to diagnose strabismus or ptosis and assess impact on vision. They will decide whether further testing is required to check for more serious problems.

Vision screening by the Maternal Child Health Nurse may detect strabismus or ptosis. But if you think your child has these conditions, you should take them to see your GP or optometrist.


Early diagnosis and treatment are essential for preventing vision loss, particularly in children. In most cases, vision problems caused by strabismus and ptosis can be successfully treated.

The type of treatment will depend on the specific condition and the cause. It may include glasses, eye patching, surgery or a combination of these.

Can it be prevented?

Strabismus and ptosis cannot be prevented. But early diagnosis and treatment can prevent or treat vision loss, especially in children.

Our eye movement disorder research

Researching eye movement disorders helps us understand what causes them and may lead to developing new or better treatments.

A few areas our researchers are investigating include:

  • Our Twins Eye Study, which confirmed the type of eye turns that are more likely to be inherited. Work continues in this area.
  • Working with researchers at the Children’s Hospital Boston to find the genes that cause childhood strabismus and congenital ptosis.
  • Contributing to a clinical trial for an iPod-based game to treat amblyopia. CERA was the only Australian site selected for this trial.

Learn more about our eye movement disorder research