Strabismus (crossed eyes) is a condition in which the eyes don’t line up or are misaligned, causing one eye to turn or look in one direction, while the other turns or looks in another.
There are four classifications of strabismus, depending on the direction the eyes are turned:
- Esotropia (turned inwards)
- Exotropia (turned outwards)
- Hypertropia (turned upwards)
- Hypotropia (turned downwards)
Strabismus may also be classified according to how often it occurs (frequency), and which eye(s) is/are affected (unilateral or alternating).
Strabismus is more common in children than adults. Many newborns will also exhibit signs of strabismus occasionally when they are tired or sick, but these would eventually subside by 4 to 6 months of age. For adults, strabismus can be caused by injuries or more serious conditions such as a stroke or cerebral palsy.
What Causes Strabismus?
Each eye is equipped with 6 muscles that control how the eye moves. With strabismus, there is a problem with eye movement control, which can signal a problem with the eye muscles, with the nerves that transmit movement to the eye muscles, or with the brain that trigger activity in the eye muscles. Injury and illnesses can also lead to strabismus.
Additionally, there are factors that increase one’s risk of developing strabismus, which include a family history of having crossed eyes, hyperopia (farsightedness), or conditions such as head or brain injury, Down syndrome, cerebral palsy or a stroke.
How is Strabismus Treated?
Strabismus should be treated immediately. Left untreated, the brain will continue to receive two images, which lead to double vision, and eventually will ignore the image received from the weaker eye. This results in permanently reduced vision in the weaker eye (amblyopia).
Treatments for strabismus include the following:
- Eyeglasses and/or contact lenses – For patients whose strabismus is caused by refractive errors, prescription glasses and contact lenses help to reduce focusing efforts and keep the eyes straight.
- Prism lenses – These are special glasses that are designed specifically to alter or bend the light that enters into the eye, thereby reducing the amount of turning the eye does to look at an object.
- Medications – Eyedrops (atropine drops) and botulinum toxin type A (Botox) can be applied to address overactive eye muscles to reduce eye turning.
- Eye exercises – Visual exercises can help improve the eyes’ coordination and focus, as well as strengthen the eye-brain connection.
- Eye muscle surgery – This is done to alter the length or position of the eye muscles so that they are correctly aligned.
The treatment will depend on the type of strabismus and its severity.