Strabismus refers to the condition where, when a person is looking at an object, one eye looks directly at the object while the other eye is looking elsewhere.

Pediatric strabismus is a common condition seen in approximately 2 percent of children. This can be a cosmetic problem, and may cause a developmental delay in normal visual function, and poor vision.

Therefore, early diagnosis and treatment is important. Strabismus is divided into various forms depending on the expression type. 

Intermittent strabismus is not usually seen, but shows up during the examination for strabismus, or when the person is tired or under stress. On the other hand, constant strabismus is present all the time, shown as a misalignment of the eyes.

Esotropia is when the eyes move toward to the nose, depending on the position of the eyes, while exotropia is when they move toward the ears. Hypertropia and hypotropia refers to a condition where the visual axis of one eye is higher or lower than the fellow fixating eye, respectively. Excyclotropia is another type of strabismus.

Causes of strabismus

The causes of strabismus are not exactly known. Strabismus may be caused by anatomical, curvature, sensory, eye muscular, neurachy or genetic problems, or a combination of these.

Types and their treatment

1) Pseudoesotropia

A person with a low nose and further distance between the eyes, causing the skin of the nose to cover the whites of the eyes, can seem to have esotropia. However, this is normal and is a condition that is commonly seen in Asians. With growth and development, the nose will grow bigger and the skin of the nose will be pulled more tightly, to take a more normal appearance. Treatment is not needed.

2) Infantile esotropia

This is an ocular condition in which one eye turns inward in infants aged 6 months or younger. This must be diagnosed early so that surgery can be done. Surgery is ideally done before age 2. This is because three-dimensional vision is developed before age 2.

If the surgery is delayed until after this age, the child may not be able to recover normal three-dimensional vision.

3) Refractive accommodative esotropia

Refractive accommodative strabismus is caused by excessive internal movement of the eyes due to blurred vision caused by hyperopia, as an effort to see better. This can be corrected with the use of corrective spectacles.

4) Intermittent exotropia

This type of strabismus is not always present as the name implies. The eye may turn outward when looking far away, when sleepy or tired. Many of those with this type of strabismus tend to rub or squint one eye when in bright light. This is the most common type of strabismus seen in Korea.

The patients are usually aged between 18 months and 4 years, and tend to progress more as the children become older. The treatment is usually surgical. If not treated, this can lead to declining visual function of both eyes, and fixed strabismus.

5) Paralytic strabismus

This is usually due to palsy of the fourth cranial nerve. This is characterized by tilting of the head to one side. If your child tends to tilt the head to one side, an eye doctor should see him or her. If the child is diagnosed with paralytic strabismus, surgical treatment will be needed.

Treatment

The aim of strabismus treatment is to improve visual function of both eyes and to correct the position of the eyes to make the eyes look aligned. The treatment can be divided into medical or surgical.

1) Medical treatment

― Amblyopia treatment

If amblyopia is present, it should be treated first. This will improve visual function, and will allow maintenance of eye alignment after treatment for strabismus. The treatment will be wearing prescription glasses if there are curvature problems, covering the good eye, or using medication to use the eye with lower vision more frequently.

― Wearing glasses

Poor vision due to curvature problems will lead to the need for glasses due to poorer vision, while strabismus caused by curvature problems can be corrected by using glasses.

― Botox injection

Strabismus due to nerve palsy can be treated temporarily with botox injection while the paralyzed muscle regains strength.

― Prism treatment

If the angle of strabismus is small, a prism can be placed on or inside the glasses to correct for the angle of strabismus.

2) Surgical treatment

Because there are many types of strabismus, each individual may require different timing and type of surgery. Some types of strabismus require early surgical treatment. In particular, infantile esotropia should be treated surgically before age 2.

Constant strabismus should be surgically treated as soon as possible. Even if the surgery is delayed, it is best that the surgery is done before the child enters preschool or elementary school, when they can notice their different appearance.

Things that parents should watch out for:

1) Your child cannot make eye contact.

2) Your child tends to tilt the head to one side, or view objects by turning the head.

3) Your child complains of double vision when he or she is tired or physically exhausted.

4) Your child tends to squint one eye in bright light.

5) Your child often rubs or blinks his or her eyes.

By Oh Sei-yeul

The author is a doctor at Department of Ophthalmology at Samsung Medical Center and a professor of Sungkyunkwan University School of Medicine. ― Ed.