The term strabismus (misalignment of the eyes, squint eyes or cross eyes) refers to the straying of one eye from the intended line of vision, brought about by false eye placement. While one eye fixates on an object, the other (misaligned eye) looks past it. There are various forms of strabismus to distinguish, namely, external misalignment (exotropia), internal misalignment (esotropia) and vertical misalignment (hypertropia). Slight forms of misalignment which only the educated eye of the ophthalmologist notices during an examination, are called hidden misalignments and may also be referred to as exo, eso or hypertropia.

What are the possible causes of strabismus?

Strabismus can be congenital; however it can also be brought on by the paralysis of one or more muscles. Injuries, infections and other illnesses (corneal clouding, congenital clouding of the lens, tumours, retinal illnesses, haemangioma (strawberry mark) near the eyelids, etc.) in the region of the eyes can also present a cause of strabismus. Scientific examinations also document familial or hereditary components in the development of strabismus. Further, extremely prematurely born children are at a definite higher risk of suffering from squint/cross eyes, due to the impaired development of the still immature central nervous system. Internal misalignment can also be the consequence of an uncorrected or an inadequately corrected farsightedness in early childhood.

If the straying of an eye from the intended direction is not noticeable at first sight, it is possible to diagnose the misalignment with special ophthalmological tests. The back of the patient’s eye must first be precisely examined in order to diagnose or to rule out certain causes for the strabismus. Further, it is important to check the free movement of the eyeball and to determine whether the ability to see three dimensionally is present. Lighting both eyes with a small lamp immediately allows the displacement of the light reflex in the affected eye to be recognised.

What is an “apparent misalignment”?

Because the bridges of infants’ and small children’s noses are often comparatively wide, parents commonly have the impression that their child has internal misalignment. The reason for this is that the whites of the eyes on the nose side seem to be less than on the temple side. In such cases, the eye doctor can quickly clear away this suspicion, after having conducted various misalignment tests. Worried parents can be calmed, because pseudo-strabismus, the “apparent misalignment”, will literally grow out.

Because of the malposition of the misaligned eye’s axis, an object cannot be fixated upon by both eyes; this results in double images because the brain can’t process the two different pieces of visual information correctly. The affected person commonly takes a self-inflicted head position in order to prevent these double images. In many cases strabismus patients also have no spatial (3-dimensional) perception, and are therefore limited in their choice of profession.  Another important component which puts many persons with strabismus at a disadvantage is the unnatural facial expression. Many children are teased in school or laughed at because they look so strange.  Such social reactions lead the majority of affected persons to develop feelings of insecurity and inferiority.

What is amblyopia?

This term is understood to be a single or double-sided weakness of vision, although the eye is completely healthy. Amblyopia is often the consequence of an insufficiently treated strabismus in early childhood, namely during the time when a child learns to see. If one eye alone is used primarily as the so-called leading eye, then the other eye is in danger of not learning to see correctly, therefore staying behind in its development. In order to eliminate double images, the double image from the misaligned eye is suppressed, causing that eye to be used hardly at all for seeing. The affected eye will become amblyope if it is not recognised as a straggler and optimally treated in time (before reaching school age!).

What are the possible treatments for Strabismus?

If severe farsightedness exists in early childhood it is important to correct it with glasses in order to prevent internal misalignment as well as the following amblyopia. If the refraction of one eye differs more than 3 dioptres from the other eye, this so-called anisometropia has to be corrected with glasses or contact lenses for the same reasons mentioned above.

Even a small variance from the eye’s straight axis (external or internal) can be reduced with prism glasses. With prism glasses, the image appears in the exact place where the misaligned eye incorrectly looks. In this manner, double images and their side affects can be remedied. Prisms in the form of a prism foil placed on the inside of normal glasses or as a prism glass put into the glasses, can be used.

The early treatment of visual weakness (ambylopia) in manifest strabismus is paramount. The correction of malpositioned eyes can work properly only if the misaligned eye also learns to see as soon as possible. Such a treatment can often be tedious and requires much understanding and patience from the children, parents and doctors. To train the amblyope eye and to “force” it to see, the healthy eye, or the glasses lens on the healthy side, is covered with a matt foil, at intervals (occlusion treatment).

The malposition can ultimately be corrected by an operation so that both eyes “stand straight” again. The affected eye muscles are relocated on one side and shortened on the other in order to bring the misaligned eye into a correct physiological position.

The earliest possible treatment of and prophylaxis for amblyopia through the recognition of and therapy for strabismus in early childhood is fundamental for the prognosis of the affected person. Schools for eye training and early intervention sites offer ideal support and help in the intensive and tedious phases of strabismus treatment, for small patients and their parents.