Double vision or diplopia

Medical content revised by - Last revision 29/09/2020
Double vision or diplopia

What is diplopia?

Diplopia is a vision alteration consisting in the perception of double vision. Therefore, the patient usually goes to the consultation reporting the fact of seeing double. Double vision may be:

  • horizontal, when overlapping images stand side by side;
  • vertical, when images stand one on top of the other; or
  • oblique, when images overlap diagonally.

Patients suffering from diplopia report having experienced at some point a double vision episode, whether occasionally or continuously through time.

There are several types of double vision, a condition that may be due to several causes, some of them more serious than others. Therefore, when experiencing this symptom, it is important to undergo an emergency eye exam. Strabismus, uncorrected refraction errors, cataracts, retinal diseases and some muscular and neurological alterations are among the causes that may lead to double vision.

Causes of monocular (in one eye) double vision

Causes of binocular (in both eyes) double vision

Refraction errors

Crystalline lens conditions, such as cataracts

Corneal diseases

Retinal alterations, such as epiretinal membranes


Nerve palsies or malfunctions

Alterations in central nervous system

Thyroid problems or muscular diseases

It requires an urgent examination in order to rule out more serious conditions.

Diplopia may be classified into:

  • Monocular diplopia. Double vision persists even when closing an eye alternately.
  • Binocular diplopia. Double vision disappears when closing an eye, and the cause is always an eye misalignment.

Double vision or diplopia may occur at any point in life. Children may suffer from diseases leading to double vision, and, in case of strabismus, when the disease is being consolidated, during acute moments when there is a rapid decompensation, episodes of double vision may occur. Nevertheless, eye deviations caused by strabismus, especially in young ages, are usually compensated by our brain over time, and double vision is not consolidated. In case there has been a deviation from childhood, when the child reaches the adult age, he usually won’t experience.


Causes are classified depending on the type of double vision (monocular or binocular).


Monocular double vision is usually caused by eye structural causes, and in very few cases it is related to neurological alterations. Some of its causes may be:

  • eye alterations, such as refractive errors, which means that the patient requires glasses but does not wear any type of correction means, in which case it could be corrected by wearing glasses;
  • problems in the crystalline lens, such as cataracts, which may lead to experiencing double vision in that eye;
  • corneal diseases such as scars or opacities in the cornea;
  • or retinal alterations, such as epiretinal membranes, which are membranes growing on the retina.

In all these eye structure alteration cases, once the alteration is corrected, double vision disappears.


In case of binocular double vision, a neurological alteration or eye muscle problems may be at the root of the problem. Some of its causes may be:

  • an strabismus, which could be decompensated, i.e. an eye deviation present from childhood that may be decompensated in adult age;
  • neurological alterations, such as paresis or intra-cranial nerve palsy (nerves that bring information to muscles and may suffer infarctions, which paralyses the muscles and causes an eye misalignment leading to double vision);
  • alterations in central nervous system, that cause an eye misalignment and, thus, double vision; and
  • problems in neuromuscular junction (the union between the nerve and the muscle), such as myasthenia gravis, may also be present.
  • Other factors such as thyroid problems or even mechanical problems in the extraocular muscles may also lead to eye misalignment.


Diplopia is a symptom. It may become evident during consultation, but it is usually a symptom that the patient reports in consultation stating they are “seeing double”, as it is usually pretty striking and causes great visual discomfort.

In consultation, in order to carry out a diagnosis and determine why does the patient see double, we perform a comprehensive eye exam, including:

  • an assessment of eye motility(ability of the eyes to move in coordination) in order to exactly determine whether there is a muscle that is not working properly due to a palsy or due to an hyperfunction of such muscle, which means the muscle is working more than it should;
  • we perform orthoptics testing, which are measurements mad in every sight position;
  • we request additional tests going from general testing, hormone tests (in order to examine the thyroid) or even tests to rule out infectious or autoimmune diseases; image tests brain and eye MRI or computerized tomography when a neurological or compressive cause is suspected; as well as electromyography when a muscle disease is suspected, among other tests.

Is it serious? Do I need to go to an emergency room?

A patient should go immediately to an emergency room  whenever he or she experiences double vision in order to determine the cause of this symptom.

If it is due to a decompensated strabismus, there will be enough time to perform an examination. However, it is important to rule out any neurological cause requiring urgent performing of studies and even hospital admissions in order to determine the cause of such double vision. Therefore, it is always recommended in case of acute double vision to go immediately an eye emergency room.



Surgical interventions are performed to correct double vision and diplopia only when the disease or the double vision cannot be treated by means of prismatic correction.

Prisms are lenses that are applied in glasses and help displace and, thus, correct the images causing double vision.

Whenever this method cannot be used because the deviation is too large or because the patient does not get used to prisms, whether for the deviation degree or for aesthetic reasons, it is possible to administer botulin toxin or to perform surgery contingent upon every patient’s case and disease.

Surgery is carried out in case of eye misalignment. Therefore, it is the same surgery performed as in case of strabismus and it consists in adjusting the muscles in order to correctly align the eyes.  It is an outpatient surgery which usually does not require the patient’s admission. In most cases, the patient goes back home the same day of surgery. Procedure is performed under topical anesthesia effects with some kind of sedation. In some very specific cases, it may be performed under the effects of general anesthesia.

Postoperative period

After a strabismus surgery, the recovery time is relatively short. Usually, patients may resume their daily tasks (job, studies…) within the first week after the surgery.

Nevertheless, patients may experience some discomfort, such as foreign body sensation or the feeling that something scrapes their eyes, but this evolves favorably and, some weeks after, discomfort completely disappears.

It is, however, recommended for patients to avoid going to the beach or swimming pool, as well as to not perform any sports contact during approximately the first 10 to 20 days.

The patient will need to follow a treatment with eye drops during the first month and to attend the required control visits.

Usually, a control visit is scheduled 24 hours after surgery. Then, contingent upon the evolution, we carry out another control visit after a week. Finally, one month after surgery we are already able to determine the more or less definite surgery outcome and the impact it’s had on double vision.

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