About Strabismus

What is Strabismus?

We speak of strabismus (or crossed eyes) when the two eyes do not look in the same direction at the same time. Normally, both eyes have coordinated movement in the same direction. Control of eye movements is performed by the brain through 6 muscles.

Strabismus appears when nervous control over one of the extraocular muscles is no longer exercised (paralysis), when a muscle is too weak, or when a muscle is too strong (hyperfunction).

There is convergent strabismus (esotropia) or divergent strabismus (exotropia). There is also hypertropia (upward deviation) and hypotropia (downward deviation).

Eye deviation can be unilateral or bilateral, permanent, may appear only when tired, or may be alternating.

Is Strabismus Just an Aesthetic Problem? How Does It Affect Vision?

Beyond the fact that aesthetically, strabismus is an unpleasant problem (many people are self-conscious about it), people with strabismus do not have normal vision. In adults, the presence of strabismus can affect them emotionally, socially, and even economically.

When the 2 eyes are not aligned, the brain receives 2 different images and, to avoid diplopia, tends to ignore the image received from the deviated eye. Thus, vision in that eye will not develop normally.

Alignment of both eyes' movements is mandatory to avoid double vision (diplopia), to perceive depth of space (three-dimensional vision), or to avoid decreased vision in one of the eyes.

When Does Strabismus Appear?

Usually, strabismus appears in childhood, but it can also develop in adulthood.

The risk is higher in children from families with strabismus. When there are untreated refractive errors (hyperopia, myopia) in one or both eyes, strabismus may appear.

In childhood, strabismus can appear from birth (infantile esotropia – which should also be operated as early as possible, up to 6 months) or later (accommodative esotropia) – this usually is associated with the presence of some diopters. In this second situation, optical correction (wearing glasses) is initially done, possibly surgery later.

In adulthood, the most common cause of strabismus onset is stroke, accompanied by paralysis of one of the 3 nerves involved in coordinating the extraocular muscles. Other causes may be eye trauma involving muscles, Graves' orbitopathy, neurological problems, etc.

Can It Be Treated?

There are several treatment options – glasses, eye exercises, prisms, occlusion, surgery.

In children, strabismus present at birth has surgical indication from the start. For strabismus appearing after 6 months, depending on the degree of eye deviation, glasses, prisms, amblyopia therapy, and possibly later – surgical intervention can be used.

Important to note, in children, vision and strabismus correction should be done as early as possible, knowing that vision develops up to age 6-7.

Can Adults Also Benefit from Strabismus Correction?

In adults, recently appeared strabismus does not have immediate surgical indication.

In those with stroke who have developed oculomotor nerve paralysis, a minimum of 6 months is waited from the event, since improvement may occur during this interval. During this period, for diplopia – patients can be helped with prism glasses to ease their situation. If after this interval there is no improvement, surgical intervention can be performed.

In those with Graves' myopathy or other muscular diseases, the underlying disease is treated.

In situations where we speak of strabismus in an adult that extends from childhood, there is a theory that surgical intervention should not be performed because post-intervention diplopia may appear. This may happen, but usually it is transitory and can be improved by wearing prism glasses.