Johnstone M. Kim, MD, is board-certified in ophthalmology. He's a practicing physician at Midwest Retina in Dublin, Ohio and previously served as a full-time faculty member at the Wayne State University School of Medicine and the Kresge Eye Institute in Detroit, Michigan.

Squint, known medically as strabismus, occurs when instead of moving in tandem, each of the eyes points in a different direction. While one is focused in the correct direction toward an object, the other may move up or down or turn in or out instead.

This is pretty common, occurring in about one out of every 20 children. While it normally affects children under the age of 5, squint can also occur in adults. Overall, about 4% of the U.S. population, or about 13 million people, are impacted.

There are four categories of squint that can occur depending upon the direction of the non-forward-looking eye. These include:

The type of squint, however, is related to the particular form you or your child may have. Here are the possibilities:

Apart from noticing that an eye appears to be turning, each form of squint may come with its own distinct symptoms, although not always.

With accommodative esotropia, symptoms can include:

For intermittent exotropia, the following symptoms can occur:

Other than a turning or a crossing of the eyes, usually there are no symptoms associated with this. There is generally no need for glasses or issues with double vision in these patients.

Having an eye out of alignment is one telling symptom. If you have adult strabismus, you may also notice symptoms such as:

Keep in mind that these symptoms do not have to be constant for you to have the condition.

While the cause of squint is not fully understood, this in many cases is known to involve a neuromuscular component with an abnormality. There are six muscles in the eye, and these must work together to successfully focus on a target. Problems that can interfere here and cause strabismus include:

To determine if you or your child (who is at least 4 months old) may have strabismus, it’s important to have a thorough eye examination. This should include the following:

There are a variety of approaches that can be used to tackle a squint issue. These include:

While it may be tempting to simply wait and see what happens with a squint, it’s important for a variety of reasons to seek treatment. Ignoring an emerging squint can lead to issues such as:

After undergoing treatment, it’s important to consult your doctor to see how successful this has been and determine if anything else needs to be done. The good news is that in young patients, if this is promptly treated, vision can develop entirely normally with perfect acuity.

Call a doctor immediately if you suddenly notice the appearance of squint, particularly in an older child or adult who may also have complaints of double vision. This may be an indicator of a more serious neurologic condition.

Squint (strabismus) is a condition in which one eye is focused in the correct direction while the other moves up or down or turns in or out instead. Several types of squint (strabismus) may occur at different ages with varying symptoms.

It has various causes, most of which involve the muscles and nerves that serve the eye. Squint can be diagnosed with an eye examination. Treatment will depend on the type of squint and may involve corrective lenses, eye exercises, eye patch, eye injections, or surgery.

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Moorfields Eye Hospital. Squint (strabismus).

Cleveland Clinic. Strabismus (crossed eyes)? Updated January 22, 2019.

Texas Children’s Hospital. Infantile esotropia.

American Academy of Ophthalmology. What is adult strabismus?

National Health Services. Overview squint. Updated January 6, 2020.

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