Strabismus, also called an eye turn, can be intermittent or constant— depending on how often it occurs.
Intermittent strabismus occurs occasionally, most often during stressful situations or when the person is ill. Constant strabismus is present at all times.
The distinction between intermittent and constant strabismus is an important determining factor in the diagnosis of strabismus, as it helps to determine the type and timing of treatment.
Up to the first six months of age, intermittent strabismus is a normal developmental milestone. If the eye turn is present after six months, it should be evaluated by an eye doctor experienced in strabismus and vision therapy.
Types of intermittent strabismus
Intermittent esotropia is a type of strabismus that causes the eye to turn inward. This type of strabismus can often be controlled for most of the day. However, it most frequently occurs during stressful situations or prolonged near vision activities.
Intermittent exotropia is a common type of strabismus that causes the eye to turn outward. This type of eye turn may only be visible during stressful situations or when the person is tired, ill or anxious.
Advantages of an intermittent eye turn
When the eye turn is only occasional, and the eyes are straight at least some of the time, a child’s visual system will continue to develop— specifically their binocular vision and depth perception.
Additionally, the possibility for the development of improved vision and visual skills in the future is still present, as there is at least some communication between the brain and the turned eye.
Further development of the eye-brain connections can be achieved through vision therapy.
Disadvantages of an intermittent eye turn
When the eye turn only occurs some of the time, it can go undetected and undiagnosed for years. Furthermore, an occasional eye turn may cause a person to be mislabeled as having poor eye contact, distracted, disinterested, daydreaming, or lazy.
How is intermittent strabismus diagnosed?
Intermittent strabismus can be difficult for an eye doctor to diagnose due to the nature of the eye turn. Parents might notice their child’s occasional eye turn and bring them for an eye exam, but the eye doctor may not be able to find it or induce it. This can occur when the child is trying hard to pay attention or make a good impression. However, children with this type of strabismus will often close their eye in bright sunlight, or when a bright light is shined in their eye— this sign may help diagnose the eye turn.
A developmental optometrist with experience in strabismus and vision therapy has the required training to detect intermittent exotropia.
How is intermittent strabismus treated?
Eye muscle surgery is rarely recommended by optometrists as the first option of treatment, due to the fact that the eye turn is only occasional, and any permanent change from surgery may disturb the eye-brain connections. Surgery increases the risk of permanent vision loss, and/or lazy eye.
The most common treatment options for intermittent strabismus include vision therapy, patching and eyeglasses with corrective lenses.
The most successful form of treatment is in-office, supervised vision therapy with home reinforcement.
Vision therapy retrains the eye-brain connections and helps to cure the underlying problem.
In a comparative study using both optometric and ophthalmological journals, vision therapy had an overall success rate of 78 percent, as compared to surgery which held a success rate of 48 percent.
Surgery should be used as a last resort, only when the eye turn is significant, as in cases of large angle intermittent exotropia, and only after in-office vision therapy not been as successful as expected. In those cases, surgery will probably only yield cosmetic benefits.
Can intermittent strabismus be a symptom of another vision condition?
When the outward turn of one eye only occurs during near vision tasks, then the eye turn may be the symptom or result of another common binocular vision problem, called convergence insufficiency.
Convergence insufficiency (CI) is the most common type of eye muscle or visual-motor problem, affecting up to 13 percent of children and adults.
The most common symptoms of CI can include diplopia (double vision), headaches, motion-sickness, loss of concentration while reading, avoidance of reading, blurred vision, and/or eyestrain. Symptoms worsen with extended periods of reading, desk work, and computer use.
When to see an optometrist
If you are concerned about an eye turn that occurs on occasion, schedule an appointment with an optometrist who has experience with strabismus and vision therapy.
An optometrist who has training in vision therapy can diagnose an eye turn and provide an effective treatment plan— helping you to see clearly comfortably all of the time.