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Anisocoria is the pupil inequality and can occur at any age. Anisocoria may be physiological, but pupil asymmetry may also result from various diseases, such as brain cancer. For this reason, a patient who notices unequal pupils should definitely visit a doctor - the diagnosis of pupil inequality allows not only to find the cause of its occurrence, but also enables the implementation of appropriate treatment for a given patient.

Anizokoriais a term derived from the amalgamation of two Greek words, aniso (unequal) and cor (pupil), with the Latin suffix -ia (disease). Thus, anisokoria meanspupil inequality(this problem can also be referred to aspupil asymmetry ). A certain difference in the size of the pupils can be considered natural - but we are talking about a situation where the difference in size between two pupils does not exceed 0.4 mm.

Annisocoria can occur in a patient of any age: unequal pupils can be observed in infants as well as in the elderly. As is the age range at which pupil asymmetry may occur, there is an exceptionally large number of conditions that can cause anisocoria.

Anizokoria: symptoms

Basically, an anisocoria is not a disease entity, but a symptom of some existing disease in the patient. There are situations where the only deviation existing in the patient is anisocoria. However, there is a possibility that a patient with pupil inequality will develop other ailments - their finding is extremely important due to the fact that after analyzing them, there is a possibility of suspecting the cause of the anisocoria. Symptoms that should arouse special vigilance include :

  • eye movement disorders
  • drooping eyelid
  • photophobia
  • eye pain
  • headache (especially if it is severe)
  • visual disturbance (e.g. blurred vision)
  • fever
  • neck stiffness

Anizokoria: reasons

The pupils of human eyes function like apertures in cameras: changes in pupil size affect the amount of light that enters the deeper parts of the eyeball. In a situation when it is dark around, the pupil dilates (the sympathetic nervous system is responsible for this), andin the luminosity, the pupil behaves the other way around and it becomes constricted (the parasympathetic nervous system is responsible for this effect).

Many structures are responsible for the proper behavior of the pupil, such as muscles and nerve fibers.

Annisocoria can be essentially physiological as well as pathological.

The first of the mentioned types of pupil inequality -physiological anisokoria- contrary to appearances, it is encountered quite often. It turns out that even 1 in 5 people in the population have unequal pupils and this is not associated with any he alth deviations. In such a case, however, the difference in pupil size typically does not exceed 1 mm.

In people with physiological anisokoria, the different size of the pupils can be observed all the time, it is also possible that it appears and disappears periodically, and - after some time of the anisocory - a complete return to the symmetry of both pupils.

In a situation where the patient knows that he or she has a physiological anisocory, he should inform the examining doctors (especially ophthalmologists) about it - a persistent anisocoria is typically not a cause for concern.

Pupil asymmetry, however, is also associated with many different pathologies - it causes concern, especially when the patient has not previously been diagnosed with pupil inequality.Anisocoria in an infantmay be visible already at the moment of his birth. In the case ofcongenital anisocoriait is necessary to carry out a thorough diagnosis, as there is a possibility that the child may suffer, for example, from congenital Horner's syndrome.

Pupil inequality, however, can occur at any point in a patient's life. Here the list of possible causes of anisocoria is quite long, examples of which can be given:

  • various diseases of the eyeball (such as e.g. iritis, glaucoma),
  • neurological diseases (such as central nervous system ischemia, brain tumors, aneurysms and multiple sclerosis or migraine headaches),
  • injuries (affecting both the eyeball and the head; anisocoria may also occur after some operations within the eye),
  • unilateral palsy of the third (oculomotor) cranial nerve,
  • neoplasms located in other organs (an example of a tumor that may cause anisokoria may be a tumor at the apex of the lung, leading to Horner's syndrome).

You can also come across information that there is a certain relationship between anisokoria and neurosis. This dependence is notClearly, however, it is suspected that the pupil inequality in the course of various neurotic disorders would result from various dysfunctions of the autonomic nervous system (which is responsible for the degree of pupil dilation).

Sometimes the pupil inequality is downright… expected. This can happen in ophthalmic offices, where the patient will be administered medications leading to the dilatation of the pupil in only one eye. Examples of preparations that can cause anisokoria in the above-mentioned manner include atropine and tropicamide.

There is also a state that is referred to asapparent anisokoria . This phenomenon is also due to the pupil unevenness, but it can only be observed in patients who have had their eyeball removed for some reason (e.g. due to cancer) and who use an eye prosthesis for this reason.

Anizokoria: diagnostics

One thing should be emphasized: anisocoria that occurs suddenly in a child, in an adult or in an elderly person, always requires diagnostics. Initially, an ophthalmological examination is usually performed: the pupil's reaction to light is examined, and the examination in a slit lamp is also performed.

In a patient with anisokoria, it is necessary to determine which pupil behaves incorrectly: whether the one which is larger or the one which is smaller. If the pupil does not dilate in the dark, it means that the pathology occurs in this eyeball.

The opposite is true when one pupil does not narrow in the light - then the pathological process occurs on the side where the expected pupil size change does not occur.

Other tests performed on patients depend on the suspected cause of anisocoria. Often a neurological examination is performed, in the case of pupil inequality, patients are also often imaging tests (such as, for example, computed tomography of the head - these examinations are especially important in patients with anisocoria after a head injury).

Anizokoria: treatment

Anisokoria itself - due to the fact that it is a symptom and not a disease - is not treated. However, treatment may be required by the unit causing the anisokoria.

The type of therapy depends strictly on the patient's problem - for example, in iritis patients, pharmacological treatment is recommended, while in the case of anisocoria caused by a tumor of the central nervous system, patients may be offered, for example, surgery.

1. Payne W.N., Barrett M.J., Anisocoria; on-line access:
2. Eric R Eggenberger, Anisocoria, Medscape; on-line access:
3. American Academy of Ophtalmology materials, on-line access:

About the authorBow. Tomasz NęckiA graduate of the medical faculty at the Medical University of Poznań. An admirer of the Polish sea (most willingly strolling along its shores with headphones in his ears), cats and books. In working with patients, he focuses on always listening to them and spending as much time as they need.

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