Strabismus

Definition

Strabismus, which is a visual disorder and not a disease, is the deviation of one eye from the other. There are different types:

Esotropia corresponds to convergent strabismus: one eye deviates inwards.
Exotropia corresponds to divergent strabismus: one eye deviates outwards.
Hypertropia corresponds to a high position: one eye deviates upwards.
Hypotropia corresponds to a low position: one eye deviates downwards.

Symptoms

Deviation of one eye from its alignment.
Children rarely complain of an anomaly on their own.
Adults who develop strabismus have diplopia (double vision).

Frequency

Strabismus affects around 5% of children, both girls and boys, and is associated with amblyopia (poor vision in one eye) in half of cases.

In 80% of cases, strabismus begins before the age of 2.

Source: Ophthalmology

Causes

In all cases, the existence of a family history of strabismus is largely decisive, as the genetic factor has been widely demonstrated. A family history of strabismus is found in 50 to 80% of cases.

Source: Ophthalmology

Problems focusing vision (such as hypermetropia) can also lead to strabismus.

Mechanical causes can also be responsible for strabismus, when the eye muscles are limited in their movements.

Evolution

The most serious consequence of strabismus is that the fixed eye will spontaneously become dominant and work alone, while the other eye, the deviated eye, will not be called upon, will gradually lose its visual function and become amblyopic.

Source : Ophtalmology

Diagnosis

Your ophthalmologist will ask you questions about the onset of the disorder and your medical and family history. He/she will observe the way you or your child looks at objects to check head position and eye movements.
He/she will then carry out a number of routine tests, in particular visual acuity, refraction and fundus examination to check for the presence of any other sight problems.
To do this, he/she applies drops to the eyes to dilate (enlarge) the pupil. The dilation process lasts an average of four to six hours. During this period, you cannot drive because your vision is insufficient.

To clarify the causes of strabismus, your ophthalmologist may refer you to other specialists (paediatrician, neurologist, endocrinologist, etc.).
He/she may also order other tests such as a blood test, an MRI (magnetic resonance imaging) scan, a tomodensitometry (a type of CT scan) or imaging of the blood vessels.
imaging of blood vessels.

Source : HUG

Treatment

The first step is orthoptic treatment of the strabismus. The aim of this treatment, which may last several years, is to restore equivalent visual acuity in both eyes. We should also mention the importance of psychological care for the child, due to the aesthetic handicap.

The prescription of suitable glasses is an essential step in the treatment of strabismus, sometimes the only one sufficient, and in the treatment of amblyopia. Children are naturally hypermetropic, but this problem should only be corrected when there is strabismus or poor visual acuity.

Orthoptic treatment stimulates the visual zone of the deviated eye. Through re-education exercises with the help of an orthoptist, the child learns to make his two eyes work together.

This medical treatment eliminates strabismus in 15 to 20% of cases; in the other cases, it prepares the eyes for surgical treatment by combating amblyopia and neutralisation. Recovery of binocular vision is more difficult than that of amblyopia, and is actually achieved in around 30% of cases.

When everything has been done optically and orthoptically, if a deviation of one eye persists, surgery is necessary for aesthetic purposes.

Surgical treatment is rarely performed before the age of two and a half to three years, often before the child starts "big school". Of course, surgery can be performed at a later or earlier age, but each case is unique. Surgery should only be carried out after the amblyopia has been treated. Both eyes are usually operated on, but sometimes it is sufficient to operate on just one eye. A second operation may sometimes be necessary more or less long term after the first to improve the alignment of both eyes, especially in cases of severe strabismus.

In conclusion, the treatment of strabismus is a long-term undertaking and requires the collaboration of a whole team of doctors, surgeons and orthoptists, from early detection through to final surgery. After surgery, prolonged monitoring is necessary, as the strabismus or amblyopia may recur.

The results obtained are commensurate with the efforts made: lax treatment always leads to more or less severe failure; with consistent treatment, the aesthetic and visual future is excellent.