Fernández Vega Ophthalmological Institute - Strabismus - Instituto Oftalmológico Fernández Vega


Strabismus is the lack of co-ordination between the eye muscles, impeding the vision of both eyes from fixing upon the same point in space. This causes incorrect binocular vision that affects the perception of depth and loss of parallelism between the two.


 There are multiple causes and they may be grouped by their effects:

  • Paralysis or muscle alterations cause paralytic strabismus.
  • Differences of vision between both eyes cause refractive or accommodative strabismus.
  • Injuries or sensory interference cause convergent strabismus.
  • Other mechanical disturbances of the muscles are less frequent.
  • Idiopathic patients do not have a clear cause.


Depending on the deviation it may be:

  • Horizontal outwards (divergent), or inwards (convergent).
  • Vertical upwards (superior) or downwards (inferior). 

The ophthalmologist evaluates the angle of strabismus with the use of the so-called occlusion test or cover-test and the aid of prisms. The eyes of the patient with strabismus should be examined as soon as possible to avoid the amblyopic eye, commonly known as a lazy eye.



Congenital strabismus has to be treated from the first months to the age of visual maturity, which is 10 years old, with patches on the healthy eye to stimulate the lazy eye.


In accommodative strabismus, the patient can find the solution to his or her problem of refractive differences between both eyes with the appropriate glasses or contact lenses. A strabismus whose origin is motor-related can be solved with surgery on one or both eyes.


Surgery´s purpose is to change the length or position of one or some of the muscles of the eye system, to strengthen muscles and / or to weaken muscles in order to change the effective forces on the eyeball and achieve alignment.

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