Isocoria: Definition, Related Conditions, Causes, Symptoms, Diagnosis, Treatment and Prevention

It refers to the equality in the size of both pupils.

There is a colored disk known as the iris when the eye is observed. This structure is a circular muscle, and at its center, it has an empty hole that allows access to light to the eye. This open hole is known as the pupil.

The pupils should have the same size in both eyes in everyday situations, called anisocoria. In this case, they must constrict and expand simultaneously.

But there is a condition where the size of the pupils is different and is called anisocoria.

It is essential to know that anisocoria as a condition may be expected. However, there are cases in which the presence of anisocoria indicates an underlying medical condition.

When anisocoria occurs at birth, it may not be associated with other disorders. If other family members have a similar condition, then the difference in the pupils could be genetic.

There are slight variations in the size of the pupils, approximately in twenty percent of healthy people. The variations in diameter are less than 0.5 mm, and the difference can be 0.05 inches (1 mm).


When this condition is not related to others, it is called physiological anisocoria. In these cases, the variations that occur in the size of the pupils would be more minor than one millimeter.

When these variations that occur in the size of the pupils are more significant than 1 mm, and when they do not return to their state of anisocoria, it can be a sign of more severe disorders that require medical attention.


Anisocoria can be caused by certain physiological conditions resulting from a deterioration of the efferent neuron fibers that control the pupil and by physical injuries or medications. As it is the case of:

  • Aneurysm in the brain.
  • Bleeding caused by a head injury.
  • A tumor in the brain.
  • The pressure inside the high eye.
  • The swelling of the brain causes an increase in intracranial pressure caused by an intracranial hemorrhage, an acute stroke, or an intracranial tumor.
  • The appearance of an infection of the membranes surrounding the brain, such as meningitis or encephalitis.
  • Migraines .
  • Seizures produce a difference in the size of the pupils that may persist after the end of the episode.
  • The presence of a tumor, a mass, or a lymph node that causes pressure on a nerve can cause decreased sweating, a small pupil, or a drooping eyelid, all on the affected side, as Horner’s syndrome.
  • A cataract surgery

There are causes, for example, the use of eye drops and other drugs such as chemicals that can alter the size of the pupil.

Symptoms of anisocoria

The only visible symptom of Anisocoria is the unequal size of the pupils.

Associated with the different sizes of the pupils may be symptoms related to underlying diseases such as:

  • Loss of visual acuity and inability to see small details (blurred vision).
  • Diplopia or double vision.
  • Present some sensitivity in the eyes to light.
  • Febrile pictures.
  • Headaches
  • Sight loss.
  • Presence of vomiting.
  • Eye pain.
  • Presence of stiffness in the neck.


The objective of the diagnosis is to determine whether anisocoria is the result of pathological reasons or is simply a physiological condition.

When the medical history is made, they will be checked when this condition was first noticed.

If it was presented before, if you suffered a recent trauma or surgery, the physical examination was performed.

The critical aspects of this physical examination are:

  • The size in mm of the pupil in the light.
  • The size of the pupil in the dark.
  • The reactivity of the pupil to light and darkness.

Additional features such as eyelid position, ptosisataxia, pain, diplopia, numbness, dysarthria, or weakness help generate a differential diagnosis.

It is essential to diagnose this condition adequately since the differential diagnosis involves ruling out the presence of the following diseases:

  • The Adie syndrome.
  • Botulism.
  • The alcoholic intoxication.
  • cerebral aneurysm .
  • Un tumor is cerebral.
  • Diabetes
  • Encephalitis
  • An infection like herpes.
  • Injuries in the iris.
  • La iridocyclitis.
  • The ischemia .
  • Poisoning by lead.
  • An intracranial hemorrhage.
  • Multiple sclerosis
  • Diseases present in the retina.
  • Tuberculosis.
  • A trauma.
  • The neoplasia .
  • Ocular prostheses
  • Syphilis
  • Keratitis
  • Neurological degenerative disorder.
  • Syringomyelia.
  • The aniridia.

Laboratory tests, electrodiagnosis, diagnostic imaging, and pharmacological tests should be performed to locate the underlying cause of the disease, such as:

  • Blood tests such as complete blood count to diagnose or rule out diseases associated with the characteristics of the blood and the leukocyte formula (white blood cells).
  • Lumbar puncture to perform the cerebrospinal fluid examination.
  • Computed tomography of the head.
  • Electroencefalograma.
  • Magnetic resonance imaging (MRI) in the head.
  • Ocular tonometry is used to rule out glaucoma.
  • X-ray in the neck.

Once anisocoria is confirmed, all types of exposure to specific extrinsic pharmacological agents should be ruled out.


Anisocoria is a benign condition, so it does not present a posterior complication.

But this condition can cause some vision problems and cause an infection in the eye, and other ophthalmic issues.

Consequently, appropriate treatment should be prescribed when a patient is diagnosed with this condition.

It is usually recommended ceratin procedures that the patient can adopt for the treatment of this condition:

Specific therapies for anisocoria:

Specific ophthalmic therapies are recommended, which the patient must follow to help reduce the effects of this condition, controlling this problem from the nucleus.

Suspension of medication:

If the cause of the contraction or dilatation of the pupil is a reaction to specific pharmacological medications, such as inhalers to combat asthma or ophthalmic drops.

Then the treatment is to stop applying these medications because it is possible that eliminating the drug will remedy the condition.

Absence of treatment:

No prescription of treatment is required for the appearance of idiopathic efferent mydriasis since there is no available treatment to correct atrophy of the iris sphincter or any congenital malformation.

Adopt a healthy lifestyle:

To control the adverse effects of the condition, it is essential to adopt a healthy lifestyle.

To maintain the immune system and avoid infections and any other ophthalmic problems due to the condition.

When some underlying disease causes the anisocoria, then it must be:

Determine what the cause of the condition is. Anisocoria has a wide range of circumstances that can cause it. It can present due to oculomotor nerve paralysis, problems such as glaucoma, encephalitis, and tumors, among others.

It is impossible to cure this condition until the cause is established and the appropriate treatments and therapies are applied. Prescribing inappropriate treatment can only make the situation worse.

If anisocoria is detected, treatment is suggested according to what caused the condition. When there is a suspicion that anisocoria is a consequence of Horner’s syndrome, the cure for this disorder is based on a 10 percent cocaine solution.

If this condition arises due to a recent stroke, treatment should be assigned for its cause, and the appearance of significant neurological damage should be avoided.

If there may be a tumor somewhere in the cervical spine or a lung, it is essential to refer the patient to a specialist in oncology to rule out or treat a malignancy.

The diagnosis of mechanical damage to the iris may result from an inflamed, traumatized, or torn iris, especially if the patient has recently undergone surgery.

The existence of a trauma or a tear should be monitored while this condition comes to heal, and in case of inflammation should be administered medication.

When treating paralysis of the common ocular motor nerve, treatments to reduce inflammation of the optic nerve and relieve pain are recommended.

Treatment for brain tissue swelling with cortisone injections in the brain can be recommended on the face or in other areas. By reducing inflammation, the pupils’ regular opening is recovered.


There is no way to prevent changes in the size of the pupils, but the risks of developing the condition can be reduced by reporting any vision change immediately to the doctor.