Strabismus
Strabismus is a condition in which the two eyes are not aligned and do not look in the same direction at the same time. Normally, both eyes work together, pointing at the same object. In strabismus, one eye may look straight ahead while the other deviates inward (convergent strabismus or esotropia), outward (divergent strabismus or exotropia), upward (hypertropia), or downward (hypotropia).
Strabismus may be constant (always present) or intermittent (appearing from time to time). It may affect only one eye (unilateral strabismus) or alternate from one eye to the other (alternating strabismus). It is more common in children but can also occur in adults.
Symptoms of strabismus
The most obvious sign of strabismus is misalignment of the eyes. However, other symptoms may also be present, especially in young children who cannot always clearly express their discomfort:
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- Visibly misaligned eyes: one eye appears to deviate compared to the other
- Frequent blinking of one eye or squinting, especially in bright light
- Head tilt to see better
- Double vision (diplopia): seeing two images of the same object (especially in adults)
- Eye strain and headaches
- Difficulty judging distances and depth (impaired stereoscopic vision)
- Amblyopia (“lazy eye”): in some cases, strabismus may lead to amblyopia, a decrease in vision in one eye that is not sufficiently used
In babies, it can sometimes be difficult to distinguish true strabismus from pseudo-strabismus (the illusion of strabismus due to facial structure). If in doubt, an ophthalmologic consultation is recommended.
The causes of strabismus are varied and can be grouped into several categories:
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- Uncorrected refractive errors: hyperopia (difficulty seeing up close) is a common cause of convergent strabismus in children. Myopia (difficulty seeing at a distance) and astigmatism may also be involved.
- Convergence insufficiency: difficulty converging the eyes for near vision, which may lead to intermittent divergent strabismus.
- Oculomotor muscle disorders: weakness or imbalance of the muscles controlling eye movements; these may be congenital or acquired.
- Neurological disorders: involvement of the nerves or neural centers controlling eye movements (rarer).
- Congenital cataract, ptosis (drooping eyelid), tumors: may be associated with strabismus.
- Hereditary factors: strabismus is more common when family members are affected.
In many cases, especially in children, the exact cause of strabismus remains unknown (idiopathic strabismus). Identifying and treating the underlying cause is important whenever possible.
The diagnosis of strabismus is made during a comprehensive ophthalmologic examination. The tests are painless and allow the ophthalmologist to diagnose strabismus, determine its type and cause, and establish appropriate treatment. In children, early screening is crucial to prevent amblyopia.
Treatment of strabismus
The goal of strabismus treatment is twofold: to realign the eyes and to improve vision (especially in cases of amblyopia).
Treatment options vary depending on the type and severity of strabismus, the patient’s age, and whether amblyopia is present:
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- Corrective glasses
- Prisms: incorporated into eyeglass lenses, prisms can help realign the eyes in certain mild or persistent forms of strabismus.
- Orthoptic therapy sessions: visual exercises performed with an orthoptist to improve convergence, binocular vision, coordination of eye movements, and visual comfort.
Treatment of amblyopia (“rehabilitation” of the lazy eye)
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- Occlusion therapy: covering the dominant eye (the “good eye”) with a patch for part of the day to force the amblyopic eye (the “weaker eye”) to work and develop vision.
- Orthoptic rehabilitation: visual exercises with an orthoptist to stimulate the amblyopic eye and improve binocular vision.
Strabismus surgery
Surgical treatment consists of strengthening or weakening certain oculomotor muscles to realign the eyes. Surgery may involve one or several muscles, in one or both eyes. It is often considered in cases of significant or persistent strabismus despite other treatments. Surgery can be performed in both children and adults.
Strabismus treatment is personalized and tailored to each case. It is important to begin treatment as early as possible, especially in children, to maximize the chances of success and prevent amblyopia. Regular follow-up with the ophthalmologist and orthoptist is essential.
Proper eye alignment is essential for normal binocular vision, meaning the ability to use both eyes together to perceive depth and judge distances.
