Strabismus is the misalignment of the eyes, known colloquially as “crossed eyes.” It occurs in 2-4% of the global population and most cases have no specific cause.
Types of Strabismus
- Convergent (Esotropia): when one of the eyes deviates inward.
- Divergent (Exotropia): when the eyes deviate outward.
- Vertical (Hypertropia or Hypotropia): when one eye is higher or lower than the other.
Strabismus can also appear in different forms: Intermittent, when it manifests in certain moments; or constant, when it is always present.
Types of Strabismus
Strabismus occurs due to changes in the neuromuscular system of eye muscles. It can be hereditary (when there are family cases) or not. Deviations can be present from birth or appear during childhood. It can also appear in adults, in cases of trauma, low sight in one of the eyes, and systemic diseases, such as diabetes.
What occurs to sight in strabismus:
When strabismus occurs in adulthood or in older children, it may cause double sight, as the misaligned eyes cause the brain to see two separate images. When the deviation occurs in children below 7, it may cause reduced sight in one of the eyes (amblyopia or “lazy eye”), as there is a trend of the brain using the deviated eye less.
Ophthalmologists who specialize in strabismus are the ideal professionals to diagnose and treat cases of strabismus. Treatment varies according to the type of deviation:
- Glasses: Indicated for when strabismus has a refraction component, which means the eyes align fully or partially with the use of glasses or contact lenses. This type of strabismus is also known as “accommodative.” Generally, this type of strabismus is more common in children with a high hyperopic error; they need to make too great an effort to focus on near objects and end up crossing their eyes “inward”. Ophthalmologists will thus prescribe glasses according to the patient’s error and reassess within a few weeks. In these cases, glasses serve to improve sight and align the eyes. If the eyes are aligned, treatment concludes with the constant use of glasses; if the eyes remain deviated, even with the child wearing glasses, the strabismus must be corrected with surgery. Hyperopic errors are expected to reduce in time and, in certain cases, patients may stop wearing glasses. But this can only be confirmed with regular ophthalmological monitoring.
- Eye patch or occlusion: Many people think eye patches are a treatment for strabismus, but the main goal of occlusion is treating amblyopia; by covering the eye with better sight, the impaired eye will be encouraged by the brain, causing sight to improve, thus helping control strabismus and providing better post-surgery results. In some cases, eye patches can help control strabismus and improve double sight, but it is not a definitive treatment.
- Strabismus Surgery: indicated to treat most cases of strabismus. It is not indicated in cases where strabismus improves completely with glasses (accommodative strabismus). It involves the weakening and/or strengthening of the eye muscles in one or both eyes. The eyes work together, so deviations in one eye may be corrected by operating on the other. In children, it is performed under general anesthesia; in adults, it may be performed under general or local anesthesia.
- Orthoptic Exercises: They are like a kind of physical therapy for the eye muscles. They are indicated in some specific cases of mild strabismus.
- Botulinum Toxin (Botox®): Indicated in specific cases of strabismus, such as muscle paralisies, Botulinum Toxin causes a temporary weakening of stronger muscles, thus allowing a paralyzed muscle to recover its strength.
- Prisms: Indicated to provide greater comfort to patients with double sight, in cases of mild strabismus acquired later in life.
In all cases, it is essential to go through an assessment by a pediatric ophthalmologist physician, or strabismus expert, for an accurate diagnosis and referral to the best treatment for each case.