Strabism

Strabism of the child

Types

Classically, one divides strabism into 2 types: concomitant strabism and inconcomitant strabism. This classification is not used any more and gently fall all in the lapse of memory.

Concomitant strabism

The angle of deviation is appreciably the same one in all the deviations of the glance (a tolerance of 10 dioptres is admitted) for the same distance from fixing. The deficit can be in the sensory part or the driving part of the visual system.

Inconcomittant strabism

The angle of deviation changes according to the direction of the glance. The cause of this strabism is, either a paresis, or one diminishes of a muscle extra-eyepiece following a traumatism, or a degenerative ignition or modifications. Incomitant strabism can also be of central or innervationnelle origin.

Physiopathology

Driving phenomenon

The strabism of the child (the child “has a cast”) is very mainly a convergent strabism. It is partly related to the Hypermétropie. This anomaly of the Refraction, frequent in the child, involves an accommodation of the Cristallin to compensate for the hypermétropie (however, all the hypermétropes do not have strabism). However, there exists a physiological reflex associating accommodation and convergence. The majority of strabisms can be avoided or reduced by the port of an optical correction (glasses) as of the appearance of strabism or at the time of discovered of an excessive hypermétropie.

Sensory phenomenon

This permanent convergent strabism involves a Diplopie: the child sees double. To cure this sensory handicap, the Cerveau neutralizes (he “is unaware of”) the image provided by one of both eyes. The consequence is a loss of the direction of the relief which is final if strabism begins in the first months from life. The mechanism can become permanent on an eye even if the other eye is closed: it is the Amblyopie. With time, that will involve a amblyopie which can be final if it is not treated. The eye concerned becomes partially-sighted person and the child definitively loses the binocular vision essential to the three-dimensional sight.

Diagnosis

The strabism of the child and his consequences is a problem to which must be attentive the Médecin general practitioner and the Pédiatre in order to detect it as soon as possible. Generally, the child is unable to complain about double vision. It is the strabism which must alert the parents. It is now possible to appreciate the Vision during the first year by masking each eye successively to observe the behavioral reaction of the child. When one masks the healthy eye (not amblyope), it has a defense reaction (one indeed has just neutralized his only functional eye).

The remainder of the assessment seeks a differential diagnosis (they are rare) by the Fond of eye:

Rétinoblastome
congenital cataract

Treatment

The treatment rests on four axes:

the total optical correction (it is determined by cycloplégie). The Myopie ets corrected with concave glasses, the Astigmatisme by cylindrical glasses and the Hypermétropie by convex glasses what makes it possible to remove the accommodative share of strabism,
the Rééducation of the eye amblyope: it is practiced only in the child. For that it is necessary to mask the healthy eye in order to stimulate the vision by the eye amblyope.
the Prisme S make it possible to remove the Diplopie (vision doubles) at an individual having a normal binocular vision. the purpose of
the Surgical operation is to give the right eyes. Even carried out early in childhood, it is impossible to find a normal binocular vision if it did not exist before the operation. But on the other hand it can make it possible to preserve a stereoscopic vision in the child reached by an intermittent strabism which becomes constant.

The effect of convergence sought by the operation can also disappear with the profit from a divergence from the yeux.

External bonds

French Site devoted to strabism
Of the useful informations on Swiss strabism
Site on strabism

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