by Hollenstein J
(Tropia; Crossed Eyes)


Strabismus is a misalignment of one or both eyes. It prevents both eyes from focusing on the same point at the same time. Prompt treatment is needed to avoid vision problems, including blindness.

The names associated with strabismus are based on the type, and direction and appearance of the eye.

Strabismus can be:

  • Constant—the eye turns all the time
  • Intermittent—the eye turns only some of the time, like in times of stress, illness, concentration, or when tired

Direction of the eye:

  • Hyper—eye turns upward
  • Hypo—eye turns downward
  • Exo—eye turns outward (away from the nose)
  • Eso—eye turns inward (toward the nose)

Appearance of the eye:

  • Tropia—can be seen when both eyes are open
  • Phoria—can be seen only when one eye is covered
Exotropia of the Left Eye
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Eye movement is a coordination of muscles and nerves that support the eye. Strabismus is normal in infants (up to about 4 months of age) until the eyes straighten out. It can be present at birth or develop during the course of childhood. Some causes of strabismus include:

  • Visual problems with the eyes, like cataracts or farsightedness
  • Problems with the muscles and/or nerves that support the eyes
  • Trauma (more likely in adults)
  • Tumors (rarely)

In most cases, the cause of strabismus is unknown.

Risk Factors

Strabismus is most common in children, but it may occur in adults. Other factors that may increase the chances of strabismus:

  • Family members with strabismus
  • Diabetes
  • Thyroid disorders
  • Retinopathy of prematurity
  • Vision impairment in one eye—the affected eye will often turn in or out


Strabismus may cause:

  • Crossed eyes
  • Eyes that do not align properly
  • Uncoordinated eye movements
  • Double vision
  • Problems with depth perception
  • Eye strain, which may cause headaches or blurred vision
  • Squinting
  • Favoring a certain head position

Many aspects of strabismus are noticed by other people.


The doctor will ask about any symptoms, and medical and family history. A physical exam will be done. In general, misalignments of the eye can be seen. An eye specialist will test the eyesight and look for other abnormalities. A neurological exam can help rule out other causes.


Treatment may include:


Glasses or contact lenses may be prescribed for the eye with weaker vision. The prescription lens improves the ability to focus and helps with poor vision. Better eyesight may help with improving strabismus. For some conditions, special prism lenses can be placed in the glasses. The prism will help to reduce double vision that may occur.


In children, an eye that is not properly aligned may not mature properly. If this is not corrected, permanent vision loss can occur. In some cases, a patch is applied over the unaffected eye. This forces the child to fixate and use the affected eye. This will help the visual development in that eye. The length of time the patch is worn depends on the severity of the condition and the age of the child.


Eye drops or ointment may be put in the good eye to temporarily blur the vision. This also forces the affected eye to fixate properly. These drops may be used as a substitute for patching.

Injections of botulinum toxin may also be used to treat strabismus caused by muscle imbalances. The injections are used to partially paralyze the muscle pulling the eye in the wrong direction.


Surgery may be used to straighten the eyes if nonsurgical means are not successful. The surgery may shorten certain eye muscles of move some of them into a new location. This may improve the ability of the eye muscles to keep the eyeball in its proper place.


There are no current guidelines to prevent strabismus. If you notice that you or your child’s eyes are not properly aligned, visit their eye doctor right away.


American Academy of Ophthalmology 

National Eye Institute (NEI) 


Canadian Association of Optometrists 

Health Canada 


Strabismus. American Association for Pediatric Ophthalmology and Strabismus website. Available at: Accessed January 29, 2021.

Strabismus. Kids Health—Nemours Foundation website. Available at: Accessed January 29, 2021.

Strabismus. Merck Manual Professional Version website. Available at: Accessed January 29, 2021.

What is strabismus? American Academy of Ophthalmology website. Available at: Accessed January 29, 2021.

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