Optometry in Focus: Eye Turns (Strabismus)

For those of you with children, have you ever seen your child’s eye turn in or out and wonder how concerned you should be?

In working with pediatrics, this is one of the more common questions that I am asked, and so, for tonight’s post, I’ll try to shed some light on eye turns.  Check it out!

Strabismus

The Basics

Eye turns, or strabismus, can be described in several ways.  The first is by consistency, with the deviation being either constant or intermittent.  The second is by time of onset – whether congenital/early onset or acquired.  Eye turns can also be described by the direction of the eye turn. In this, the eye can turn in (esotropia), out (esotropia), up (hypertropia), or down (hypotropia).  Finally, a single eye can turn, or the eyes can alternate.

Who?

At the end of the day, essentially anyone can have an eye turn. However, early onset eye turns may have a genetic component. Additionally, eye turns may be associated with ocular pathology or problems with the development of the brain (ie hydrocephalus).  Inward eye turns that are worse when focusing at near may be associated with a moderate to high far-sighted prescription.
Acquired eye turns are more likely to present after an acquired brain injury, as a result of damage to the nerve pathway.

Signs/Symptoms

The biggest sign or symptom of strabismus is simply an eye turn. However, additional signs include closing or covering an eye and blinking excessively.  These both may be indications that your child is seeing double.  The first is used to remove the second image formed by the deviating eye, while the second is used to help focus.
In new onset or acquired strabismus, double vision, or diplopia, is common, as the brain has not adapted to automatically suppress the additional image.  This may be perceived as blur. 

Why?

The complete explanation behind early onset eye turns is not fully known, but the basis is this:
All eye movements are controlled by six muscles on each eye.  These 6 muscles in turn are controlled by three cranial nerves (in each eye).  Damage to the nerve or the muscle can cause  deviation from normal eye position and movements.

When to be Concerned

In the first few months of life, it is very common for your child’s eyes (as well as the rest of their body) to not be perfectly synced.  They’re just trying to get the hang of coordinating and focusing, so this should come as no real surprise.
However, if an eye turn continues after the first 3-4 months, or is constant or always the same eye, it’s worth getting checked out to rule out pathology.  Additionally, a constant, or near constant, eye turn is a risk factor for ambloypia – decreased vision that is not attributable to glasses prescription alone!
Additionally, if you ever notice a new onset eye turn, or your child begins to complain of double or closes an eye for specific tasks, an exam is warranted.

Treatment Options

The treatment options for eye turns vary significantly depending on the size, direction, and frequency of deviation.  Large angle deviations often end up requiring surgery to decrease the demand on the muscles.  Smaller angle outward eye turns, or exotropias,  may be managed by vision therapy, additional minus lens power, or prisms.  Inward eye turns, or esotropias, especially those associated with focusing the eyes (accommodation) may be managed by plus lenses, prisms, or in more rare cases vision therapy.
Eye turns up or down (though the eye that is higher, or hyper, is more typically referenced), are less frequent than eye turns in or out.  When they’re small, prisms, or a combination of prisms and vision therapy, may be used for treatment.  Larger deviations, as before, are more likely to be surgically managed.
And there you have it!
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