deviation of the eye

What is strabismus?

It is a disorder in which the eyes are not aligned in the same direction and they do not look at an object at the same time. The loss of alignment can be permanent or temporary and can happen in any direction: inwards, outwards, upwards or downwards. In children, it needs to be treated early to avoid amblyopia or lazy eye, where the brain starts to ignore the image that the misaligned eye sends, ending up with irreversible vision reduction in that eye.


We can broadly categories the variations of strabismus into different types through the following criteria:

According to the time for which it persists

  • Intermittent strabismus – Appears only in certain circumstances (sickness, nervousness, tiredness, stress) or in a particular field or distance of the gaze (up close or far away). Indicates a certain degree of normal binocular vision.
  • Constant strabismus – Appears permanently.

According to whether or not there is a preference for one eye

  • Alternating strabismus – One eye or another is used indistinctly as the fixed eye while the other one deviates. The brain deletes the image of the misaligned eye, but because the strabismus alternates, this usually allows both eyes to develop to a similar degree, giving good visual acuity.
  • Monocular strabismus – There is a preference for one eye to remain fixed while the other constantly deviates. While children are developing (up until age 8), this condition is prone to amblyopia, to a greater or lesser extent, in the misaligned eye.

According to the direction of the deviation

  • Esotropia (convergent strabismus)

  • Exotropia (divergent strabismus)

  • Hypertropia

  • Hypotropia


At an early age, treatment seeks to preserve the vision of the misaligned eye and subsequent binocular vision whereas at later stages, the purpose of the treatment is aesthetic and seeks only to realign the gaze.

If there is a refractive error (myopia, hyperopia or astigmatism), this needs to be treated with vision correction measures (contact lenses) or refractive surgery. In children who have developed a lazy eye (amblyopia), the vision of that eye will need to be recovered, which usually happens with occlusion (patching) of the healthy eye.


Surgery for strabismus is only on the motor muscles of the eye, strengthening or weakening those responsible for the deviation of the eye. The number of muscles to be operated on depends on the type and degree of strabismus. The procedure takes place under topic anaesthesia in adults, always as an outpatient procedure and in just a few hours patients can go home on their own feet. Children, however, need to be operated on with a general anaesthetic. Other treatments available are:

Benefits of strabismus treatment

The different treatment options for strabismus have multiple benefits for patients, including the following:

  • Strabismus must be treated to ensure proper vision development throughout childhood, thereby preventing lazy eye.
  •  Correcting the strabismus will enable the child to have BINOCULAR VISION.
  •  The aesthetic goal is important, but it is not the main goal.
  • With strabismus that has been progressing for a very long time, the aim is to improve the AESTHETIC appearance.
  • With strabismus that has recently appeared, the aim is to improve the diplopia or double vision (as well as the aesthetics).


At Clínica Oftalmológica Rahhal, our units specialise is each area of vision so as to offer our patients a comprehensive treatment service. As such, this teamwork enables us to tackle more complex treatments or combinations of different disorders.

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I am 32 years old and I had double vision as a result of strabismus. The only doctor who assured me that it was going to be fine and that he was going to cure me was Dr Alonso, a specialist in strabismus at Clínica Rahhal, and that’s exactly what happened. Aside from the fact that they took great care of me during the surgery, once I left the operating room I no longer saw double”.

Javier Alonso. 

“I am an adult and as a result of the strabismus that worsened as I grew older, I developed diplopia, double vision. They cured me and I no longer see double. Thank you. I owe them my life”.

Ricardo Climent. 

“I have been a patient for some time and I am delighted with them. The staff are attentive and very professional, and the facilities are excellent. Highly recommended!”

Esther Herranz. 



At CLÍNICA RAHHAL, we don’t want to make it expensive to see and we want to ensure our strabismus treatments are accessible to our patients.

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From what age is it appropriate to correct strabismus in children?

In children, it is crucial to closely monitor the strabismus from the moment it appears as it can be indicative of an underlying disorder. Many eye diseases (such as retinal disorders) manifest through the deviation of one eye, so when this symptom is detected, it is vitally important to contact an ophthalmologist. Also, certain types of strabismus that progress over time can give rise to amblyopia or lazy eye, which means that the child’s vision will not develop properly, leading to low vision in adult life.

Are all cases of strabismus corrected with surgery?

No. There are different type of strabismus and depending on the individual case, some can be corrected with vision correction measures (glasses), botulinum toxin or some may need surgery.

At what age is it appropriate to operate?

This will depend greatly on each patient. Surgery can be delayed so long as the strabismus, and therefore the risk of amblyopia or lazy eye is being managed by other measures (with vision correction, botulinum toxin, etc.). We usually wait and do not perform surgery until the child is able to cooperate well so as to take the measurements needed for the surgical correction. However, as we said before, each patient needs to be looked at on a case-by-case basis.

Is surgery permanent?

Most of the time, yes. However, bear in mind that a lack of cooperation in some cases to carry out the necessary measurements, and the fact that the surgery needs to be performed under general anaesthesia, does not allow us to adjust the muscles during the surgical procedure (in adults, when performing the surgery with just topical anaesthesia – drops – we can adjust the results during the surgery itself), so in a small minority of cases a second future surgery will be needed to obtain the desired result.

Does patching solve strabismus?

The goal of using patches is to slow the development of amblyopia or lazy eye by forcing the brain to work with both eyes, preventing a lack of development in one of them. However, it will not permanently solve a deviation of the eye.


If lazy eye or amblyopia develops because of strabismus in childhood, can I recover vision with surgery?

Unfortunately, no. A lazy eye or amblyopia is only treatable at the early stages of life as it is due to a lack of development of the vision system due to a lack of stimulation. Corrective surgery for strabismus in adult patients suffering from strabismus from childhood is essentially for aesthetic purposes.

Is surgery permanent?

The extraocular muscle system is relatively complex and it is often difficult to know exactly which muscles are affected when strabismus has been developing for a long time because even though the problem begins in one, they all end up being affected as a result. So, even though the problem is often resolved with the first surgery, in some, more complex cases, a second surgery is needed to get the desired result. The need for a second surgery is much less likely when the surgery is performed under topical anaesthesia, i.e., with just drops, as this way we can adjust the muscles during the procedure and see the results live. This technique requires a great deal of experience and offers the most satisfactory results from the first time patients are able to see the changes that we are doing “live”, meaning that we can get more accurate results.

Can I have refractive surgery despite having strabismus?

Of course. In fact, defects are highly linked to strabismus and correcting them is an add-on to treatment.

If the strabismus has appeared recently (for example, after trauma, as a result of diabetes or cardiovascular abnormalities) can I develop a lazy eye?

No. In these cases, the patient develops double vision (diplopia) as the vision system already finished developing at the early stages of life and the brain cannot “cancel out” the image of one eye selectively as is the case in childhood. Being unable to ignore one of the two images and unable to fuse them leads to double vision.

Is there a surgical solution for strabismus is these cases?

Acquired cases need to be assessed particularly carefully as not all are going to need surgery. Some will resolve spontaneously, others with a session of botulinum toxin and in other cases with the use of prism glasses. The intensity of the strabismus and its cause will be decisive when it comes to choosing the best treatment option in these patients.

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