The origin may be the presence of a strabismus, refractive defect or other diseases such as palpebral ptosis (drooping of the eyelid, which covers the eye), childhood cataract or retinal pathologies. Strabismus: it is produced by an alteration in the control of the movement of the eyes, so that the extraocular muscles in charge of it - guided by the brain - do not act in a coordinated way. Strabismus can be congenital (hereditary factor) or acquired and, although there are many possible causes, one of the most frequent in childhood is the association of a refractive defect. Other eye problems, as well as neurological problems, may also be behind. Refractive defects: appear when the light rays that enter the eye to form images are not focused just on the retina, but rather in front of it (myopia), behind (hyperopia) or are scattered (astigmatism) . These blurring problems can be explained by the dioptric power or “power” of the eye's lenses - the cornea and the crystalline lens - and by the shape of the eyeball, which is larger, smaller or curved than normal (myopia, hyperopia or astigmatism, respectively).