What is Strabismus?

Strabismus is the scientific term used to explain an eye turn. In patients with strabismus the eyes will appear to be out of alignment. The condition can be caused by the brain’s inability to coordinate both eyes simultaneously.  Children with strabismus may develop additional complications with amblyopia, or “lazy” eye.

Eye turns can be linked to either poor eye coordination and binocular balance, or muscular imbalances. Muscular imbalances denote a mechanical problem with the eye muscles themselves, where there is limited movement, due to restriction e.g. Brown’s Syndrome, or paralysis e.g. nerve palsies.

Types of Strabismus

  • The eye can go “in” toward the nose.  Esotropia
  • It can go “out” from the nose.  Exotropia
  • It can go “up” or “down”.  Hypertropia or Hypotropia
  • It can happen part time or all the time.  Intermittent
  • It can be either eye.  Eye turns do not always occur in isolation so often patients may have more than one of the above.

An eye turn is not always constant and may only occur when the child is tired, or when they looking at an object at a certain distance (accommodative problem) or in a certain direction (muscle imbalance). The degree of the turn is not always noticeable, often smaller eye turns cause more symptoms and visual discomfort.

Why Does The Eye Turn

Somewhere early in the child’s development, the brain fails to develop ‘binocularity’ or the ability to use both eyes at the same time. The condition can be congenital or acquired.

Congenital eye turns mean a baby is born with an eye turn or develops an eye turn within the first 3 to 6 months of life. In most cases the eye turns inwards and surgery is usually required.

Acquired eye turns’, particularly esotropia’s are the most common, and develop around the ages of 2 to 6.

Surgical Options to treat Strabismus

Ophthalmologists, or eye surgeons, may recommend surgery to correct strabismus if spectacles alone does not correct the crossed eye.  This is an important treatment where the appearance of the eye turn is distressing for the parent and/or the child and the child has not responded well to or cannot do non-surgical corrections.

A common misconception is that strabismus is caused by “weak” eye muscles, but this is not true. The problem is not muscular, but in the brain.  Strabismus is the result of faulty coordination between the brain and eye muscles – in other words, strabismus is a brain-based problem.

A simple procedure can show this.  Place your finger in front of the child and have him look at it. Now cover the straight eye with your other hand and watch the crossed eye. It immediately straightens. The muscles in the crossed eye automatically aim the eye without difficulty. The real problem is not weak muscles, but the inability of the brain to control the muscles in both eyes at the same time–in other words, faulty signals from the brain to the two eyes.

The need for surgery is often explained as “the weak eye muscles must be operated upon to realign the eye and correct the problem.”  However, two considerations must be made:

  • Since weak muscles aren’t the cause of strabismus, then surgical intervention is addressing only the appearance and not the cause.
  • In the vast majority of cases, surgery does not “correct” the child’s inability to use both two eyes together; it cosmetically aligns the eyes so they look straight.

Surgery can make the eyes look straight, but rarely improves visual function such as the ability to achieve 3D vision.  As it deals only with muscles, it does nothing to train the brain how to use both eyes together.

Less than 20% of children who undergo one eye surgery alone for a crossed eye eventually achieve binocular fusion (two-eyed vision) with normal depth perception and visual function. 

The Vision Therapy Option

Vision therapy can help address the cause of strabismus. It corrects the problem by teaching the eyes how to aim together and training the brain to receive and fuse the visual images from both eyes at the same time. Click here to find out more about vision therapy.

Book an appointment with a behavioural optometrist to assess whether vision therapy is an option. 

Have You Had Your Eyes Checked? Book A Behavioural Assessment With Us At Your Most Convenient Location