If you’re just learning about strabismus, or an eye turn, you may be confused about exactly what it is. In fact, there are many variations of strabismus defined by a number of factors. Ultimately, the nature of the eye turn dictates the approach we take with vision therapy.
When assessing a strabismus patient, there are generally six factors we consider, including direction, frequency and severity of the eye turn. Fortunately, regardless of the type, vision therapy can help strabismus patients improve their vision.
Six Defining Factors of Strabismus
Direction of the eye turn - Although many people refer to strabismus as crossed eyes, the eyes can in fact turn in any direction including: up (hypertropia), down (hypotropia), inward (esotropia), outward (exotropia), or in rare cases, rotationally (cyclotropia).
Exotropia and esotropia are the most common types of strabismus, but a patient could also have a combination, such as one eye pointing inward and down (hypotropia and esotropia). Cyclotropia more commonly exists with other types of strabismus.
Frequency of the eye turn - Next, we want to know how often the eye turn occurs. Either the eyes are always misaligned (constant strabismus) or only some of the time (intermittent strabismus).
If a patient has intermittent strabismus, we try to determine when it happens and what’s triggering the turn. For some patients, the turn may occur at seemingly random times. For others, it may be a more specific catalyst, such as becoming tired.
Although we can tackle either case, it is more difficult to treat a patient with constant strabismus. It’s much more difficult to train someone’s eyes to work together when they’ve rarely or never done so before.
Which eye is affected - An eye turn can occur in one eye or both. We need to determine which eye is affected so we can train that eye to properly respond to neural signals, eventually helping it work together with its counterpart.
Additionally, if only one eye is turned constantly, it can cause amblyopia, or what many people refer to as a ‘lazy eye’ (not a clinical term). This is because an eye turn can cause a patient to see double, which is difficult for the brain to process. To compensate, the brain will begin to solely depend on the non-strabismic eye for viewing, suppressing information from the strabismic eye.
Extent of the eye turn - Some eye turns are severe, while others are barely noticeable. The extent of the turn may impact how soon it is detected. A person with a more dramatic eye turn may seek treatment at an earlier age while someone with a more subtle turn may not even know they have a vision problem.
It’s why we strongly encourage parents to schedule regular eye exams for their children. The longer strabismus remains untreated, the more embedded it can become. Additionally, undetected strabismus may have associated amblyopia.
Sensory issues - Our brain wants the images received from both of our eyes to fit together like a puzzle. This is difficult for strabismus patients, as their eyes don’t align to create a clear, single image. The result is double vision and/or suppression.
Cause of eye turn - The final thing we need to determine is the cause of the eye turn.
The root cause of a patient’s strabismus plays a big role in treatment options and the extent to which vision therapy can improve the condition.
Strabismus can stem from a variety of accidents or medical complications, such as muscle or nerve damage, trauma, a brain tumor, or an aneurysm. More commonly, it is a condition developed in the first few years of life.
When someone has strabismus, it is a sign that their vision is not working efficiently.
While the types of strabismus may differ, the goal of treatment is the same: Getting the entire visual system to work as efficiently as possible so that it doesn’t negatively impact a person’s performance in school, work or sports.