Strabismus (“crossed eyes” or “crossed look”) is a visual condition in which the eye position is not parallel and eyes are unable to focus the same image at the same time. It occurs most often in childhood (4% -5% of new-borns have strabismus).

Strabismus may be constant or intermittent, monocular or alternating.

Normally, the muscles around each eye cause synchronous movement in the same direction and at the same time of both eyes. Strabismus occurs when the eye muscles do not function properly for coordinating eye movements. In this case, the eyes are not properly centered and the brain has difficulty in merging the two images coming from each eye.

Depending on the direction of the deviation:

• Esotropia (convergent) - eye is deviated nasally (inwards)

• Exotropia (divergent) - eye is deviated outwards, temporally

• Vertical (hypertrophy – deviated upwards; hypotrophy – deviated downwards)

Depending on the age (e.g.: congenital, which occurs in the first 6 months of life). Other types of strabismus can occur later (e.g.: around the age of 2 years).

Acquired strabismus (e.g.: paralytic or posttraumatic).

• In 60% -80% of the cases, it is hereditary - when parents “transmit” the refractive errors to their children (hyperopia, myopia, astigmatism). In particular, the anisometropia (refractive error difference between the two eyes) is incriminated as a cause of strabismus and the hyperopia is commonly associated with the convergent squint.

• Neurological disorders, prematurity, infectious diseases;

• Brain or orbital trauma;

• Organic diseases (e.g. unilateral congenital cataract or unilateral ptosis - fallen eyelid);

Children with strabismus can sometimes be diagnosed easily by simply observing the position of the eyeballs.

The most common visible signs are:

• the eyeballs are not aligned in the same direction, at the same time;

• the eyeballs do not move in a coordinated manner (depends on the type of strabismus the person suffers from);

• crossed eyes or closing one eye when looking towards bright light;

• tilting or turning the head to look at an object;

• the person’s stumbling over the objects standing in his/her way (strabismus limits the correct assessment of the distance from/to objects);

Children with strabismus may complain of these symptoms:

• Double vision (this usually occurs at the onset of strabismus);

• Eyestrain;

• Sensitivity to bright light.

In most cases, symptoms are transient, may be present or absent, but they can get worse if the child is tired or ill. When the child’s eyes are not aligned at the same time to view an object, by the age of 4 months, it is necessary to have the baby undergo an eye examination by a specialist. This examination should be conducted as soon as possible.

The strabismus treatment should be started as soon as possible from the time of diagnostic, in order to be effective. The goal is realigning eye axes and improving visual acuity (the ideal is a normal visual acuity in both eyes).

The treatment for strabismus is complex, personalized and it may consist of:

• Correct diagnosis and treatment of refractive errors (suitable glasses). This involves instilling cycloplegics drops that temporarily suppress the accommodative ability of the eye lens;

• The amblyopia should be treated and the results should be maintained (e.g. by occlusion: covering the good eye to force the weak eye to see);

• Surgery is used only at the ophthalmologist’s recommendation and it is established depending on the onset of the deviation (e.g. congenital strabismus should be operated as soon as possible, while a squint appeared later should be operated before the child turns 4.5 years old);

Orthoptic exercises (with the synoptophore) - usually indicated after strabismus surgery, for the cases that have no operative indication (e.g. small deviation angle, insufficient convergence, in the treatment of amblyopia or in accommodative disorders). The purpose of the orthoptic exercises is to obtain binocular vision (the patient sees with both eyes simultaneously).