Strabismus is the loss of the eyes’ parallelism. Deviation can be inward (convergent strabismus), outward (divergent strabismus) or vertical (upward and downward). The strabismus origin is multifunctional and many of the trigger factors are not yet known. What is certain is that around 97% of cases are due to a functional cause, that is to say, without any organic brain lesion. The rest of them arise from neurologic, metabolic, vascular or malformative diseases of the central nervous system.

Strabismus can appear at any age. Strabismus in childhood usually starts before the age of one in most cases. Late strabismus (over the age of three) is normally due to uncorrected refractive errors (above all hypermetropia). The point is that once it is established, it doesn’t disappear spontaneously.

The most apparent symptom is eye deviation which is the warning sign that makes parents consult a specialist. Nevertheless, deviation entails a series of “non-visible” consequences that are advisable to mention. First of all, amblyopia or lazy eye (the deviated eye is suppressed in order to avoid double vision). Secondly, the loss of binocular vision and, in consequence, of stereopsis. The earliest strabismus appears, the most serious these disorders are.

Strabismus can’t be prevented but early detection is extremely important to treat it as soon as possible in order to reverse the consequences above mentioned along the former paragraph. In this sense, we get a huge help from paediatricians who have a more continuous contact with children, who thoroughly know about this pathology and quickly refer them to the ophthalmologist’s. Anyway, and as a general rule, every child (even though parents don’t observe anything wrong) should be explored by an ophthalmologist at the age of three and, in those cases with prior family history of strabismus or lazy eye, even earlier.

A standard treatment of strabismus doesn’t exist although we can establish a therapeutic algorithm. First of all, a refractive defect must be ruled out and, should it exist, it is imperative that we prescribe glasses for vision correction. If there is amblyopy, it must be treated by means of the different available methods according to its seriousness (occlusion, penalisation, etc.). Finally, we will have to proceed to operate on in all those cases in which deviation causes an obvious aesthetic defect. Strabismus treatment is long and requires close surveillance for many years. Unfortunately, surgery must be repeated in 30% of cases. The reason of this high rate of failures is that a strabismic child’s brain not always accepts the position induced by surgery as the right one, and tends to drive the eye towards its initial position.