Strabismus is a condition where the eyes are misaligned. In other words, one eye is turned in a different direction from the other. Sometimes, this is referred to as crossed eyes. Although strabismus can affect a person of any age, it is most common in children. Strabismus affects about two to five percent of the population.
It is important to identify strabismus as soon as possible, as it can lead to further visual difficulties. However, it’s not always easy to tell whether there is a problem.
In the first few months of life, an infant’s eye muscles are just developing. Therefore, it is perfectly normal to see their eyes occasionally wandering. This is usually no cause for alarm, unless the eyes are constantly misaligned.
By about three months though, infants should have greater control over their eye muscles. If there is suspected ocular misalignment, the child should be evaluated by an eye doctor.
Signs of childhood strabismus are often identified by a parent, teacher, school nurse, or pediatrician. They include:
- The child’s eye turns in, out, up, or down.
- The child closes one eye when looking at an object.
- The child tilts their head when looking at an object.
- The child squints, especially in bright sunlight.
If the child is older, they may report:
- Double vision.
- Trouble with depth perception.
The eye turn may occur all the time, or only sometimes. Eye fatigue or illness could be a trigger, for example. In some cases, the same eye turns each time. In others, the eyes alternate.
There are six muscles that work together to coordinate eye movements. These are controlled by the brain via multiple nerves. Therefore, strabismus can be caused by problems with the eye muscles, nerves, or the control center for eye movements in the brain. It can also develop in children with certain health conditions, eye conditions, and injuries.
Risk factors include:
- Family history – Strabismus is more common in those children with a parent or sibling who has it.
- Refractive error – Farsighted children are more likely to develop strabismus due to the effort they have to make to focus their eyes.
- Eye conditions – Certain eye conditions that inhibit good vision, such as cataract, make strabismus more likely.
- Medical conditions – Strabismus is more common in children with cerebral palsy, down syndrome, hydrocephalus, premature birth, or head injury.
An optometrist or pediatric ophthalmologist can diagnose childhood strabismus. They will use tests like:
- History (personal and family).
- Visual acuity measurement.
- Refractive error measurement.
- Eye alignment and focusing evaluation.
- Eye health assessment.
The strabismus will be classified by direction of the eye turn:
- Esotropia: inward turning.
- Exotropia: outward turning.
- Hypertropia: upward turning.
- Hypotropia: downward turning.
Other features of the strabismus will be assessed, such as:
- Frequency of eye turn (constant or intermittent).
- Whether it is always the same eye turning or whether they take turns (unilateral or alternating).
Characterizing the strabismus will help to determine the best treatment plan.
There are several treatment options when it comes to strabismus, including glasses, contact lenses, prism, vision therapy, and surgery.
Eyeglasses or contact lenses – Sometimes, all that’s needed to realign the eyes are glasses or contact lenses. By correcting refractive error, the visual stimulus for eye alignment is restored. This is especially common in children with hyperopia (farsightedness).
Prism – Prisms alter the orientation of light entering the eye, and are sometimes a helpful addition to eyeglass lenses.
Patching or blurring – Patching or blurring the eye that doesn’t turn can encourage the turning eye to straighten out. This can help to strengthen the misaligned eye over time.
There are various colorful and creative options available for children’s eye patches. Blurring, an alternative to patching, is achieved through the use of eye drops, which also dilate the pupil.
Vision therapy – Vision therapy involves a prescribed regimen of eye exercises designed to train the eyes and brain to work together more optimally. Activities are aimed at improving eye focusing and coordination. Treatment is guided by visits to the eye doctor, and supplemented by homework, much like physical therapy.
Surgery – In some cases, surgery can be used for eye muscle repositioning. This may be necessary in one or both eyes, depending on the situation. Surgery is generally supplemented by eyeglasses, patching, and/or vision therapy to optimize the outcome.
Childhood strabismus, or crossed eyes, is most effectively treated when caught early. Even if there are no apparent problems, children should be routinely examined by an eye doctor by six months of age, and then again between the ages of three to five. This will help to identify any visual issues and initiate treatment.
There are several options when it comes to the treatment of strabismus, including eyeglasses, contact lenses, prism, vision therapy, and surgery. Your eye doctor will recommend what’s best for your child based on the strabismus characteristics, optimizing the chances for cure.
Boyd, K. (2021). Strabismus in Children. American Academy of Ophthalmology.
Kanukollu, V.M., Sood, G. Strabismus. (2022). Treasure Island (FL), StatPearls Publishing.
American Optometric Association. Strabismus (Crossed Eyes).