Getting a Diagnosis

The first step in getting an accurate diagnosis is learning more about your symptoms and health history. It is important to be completely honest, especially about any recent health changes. Your doctor will ask about your eyes and vision symptoms as well as about things like nausea, stiff neck, and fever.

Depending on what underlying cause your doctor suspects, there are several tests they might recommend.

  • Blood differential, complete blood count, and other blood studies
  • CT scan of your head
  • MRI scan of your head
  • Neck x-rays
  • Lumbar puncture to evaluate your cerebrospinal fluid
  • EEG testing to evaluate brain health
  • Tonometry if the doctor thinks you may have glaucoma


It is possible for your pupils to be two different sizes. Referred to as anisocoria, this can be a normal variation or due to an underlying cause. (Learn More)

Under normal circumstances, the pupils respond to the light level of the environment. When this condition is present, this does not occur with both pupils. One appears larger than the other. It may occur due to certain nervous system or eye disorders. (Learn More)

Most doctors can diagnose anisocoria with a basic eye examination. However, further testing is generally recommended to determine if there is an underlying cause. (Learn More)

If there is an underlying disorder, the treatment will be focused on addressing that condition. There is not an exact treatment to target pupil size differences. (Learn More)

anisocoria a condition of uneven tag

What Is Anisocoria?

The black spot in the center of your eye is known as the pupil. For most people, the pupils react to light, either enlarging or shrinking equally. But for some people, the pupils are not always the same size. This is referred to as anisocoria.

In many cases, people do not notice that their pupils are unequal because the size difference is not significant. The doctor usually picks up on the problem when they are giving an eye examination.

In some cases, this condition is only temporary. But people can experience it on a regular basis too.

What Are the Symptoms?

Uneven pupils are the primary symptom of this condition. Depending on the underlying cause, it is possible to have additional symptoms.

  • Double vision
  • Headache
  • Nausea
  • Blurry vision
  • Vision loss
  • Fever
  • Neck stiffness

If you notice any of these symptoms in addition to having uneven pupils, it is important to see a doctor right away. A stiff neck, fever, or vision loss warrant emergency medical treatment.

What Causes Anisocoria?

There is not always an underlying cause for this condition. If the difference in your pupils is under 1 millimeter and the doctor cannot find an underlying cause, it is referred to as benign, simple, or physiologic anisocoria. It is estimated that mild benign anisocoria may be present in about 20 percent of the population.

When there is an underlying cause, the following are possible:

  • Bleeding into the skull
  • Aneurysm
  • Direct eye trauma
  • Concussion
  • Brain tumor
  • Optic nerve inflammation
  • Meningitis
  • Seizure
All of these conditi...

All of these conditions are serious and need immediate medical treatment. If you are sick or experience an injury and notice a sudden unevenness in your pupils, you should go to the emergency room for evaluation.

There are certain chronic medical conditions that may also have uneven pupils as a symptom. Horner’s syndrome is an example of this. It is rare and characterized by upper eyelid drooping, no facial sweating, constricted pupils, and eyeballs sinking into their bony cavities.

Treatment Options

After testing to get a diagnosis of the underlying condition, your doctor will talk to you about a treatment plan. If the anisocoria is simple and benign, your doctor might not offer any treatment. In these cases, monitoring your pupil size and general health is often enough to maintain your eye health. Should the uneven pupils become more of an issue in the future, you and your doctor can reassess your treatment strategy.

If meningitis or another infection is responsible for your uneven pupils, medicines to fight the infection will be administered. Seizures and optic nerve inflammation may also be treated with medicines.

If trauma is the cause, a wealth of treatments can be given depending on the trauma and its severity. Your doctor will regularly assess your pupils as you recover.

If you have Horner’s syndrome or another chronic issue that is causing uneven pupils, your doctor will talk to you about the necessary long-term care. For Horner’s syndrome, radiation, chemotherapy, or surgery may be beneficial, depending on the cause and location of the tumor or lesion.

Anisocoria Prevention

Since some causes are the result of trauma, reducing your risk of accidents can help you to decrease the chances of experiencing uneven pupils. The following methods are ideal:

  • Always wear the appropriate protective gear for sports and work.
  • Wear your seatbelt when you are in a vehicle.
  • If you experience a fall, be mindful of the potential for a head injury.

If your pupils are uneven, seeing an eye doctor promptly is important. Any underlying condition needs to be treated to help you protect your vision from further issues. The exact treatment that is required will depend on the underlying issue that is causing your pupils to be uneven.


Anisocoria. Case Western Reserve University School of Medicine.

Anisocoria. (December 2018). Medscape.

What Is Anisocoria? (July 2019). Healthline.

Anisocoria. MedlinePlus.

Horner’s Syndrome. National Organization for Rare Disorders.

Meningitis. (March 2019). Centers for Disease Control and Prevention.