Anisocoria

Anisocoria is a condition in which the pupils of a person’s eyes are of an unequal size. Pupils are the black part in the center of the eye and are actually holes that have the ability to grow or shrink in order to allow an appropriate amount of light in. In other words, pupils will grow in darkness to take advantage of all available light, and they will shrink when conditions are bright, in order to protect the eyes from becoming damaged.

Around 20% of healthy individuals are believed to have anisocoria, but the condition can also occur as the result of a variety of medical issues. While it can oftentimes be of no serious concern, there are also instances in which the presence of anisocoria is an indication that you may be in need of immediate medical attention.

One famous instance of a person with anisocoria is musician David Bowie who, after getting into a teenage fistfight with a friend over a love triangle, permanently damaged his left eye. This caused his pupils to have two distinctly different sizes, but also heterochromia, a condition in which one’s eyes are two different colors.

Causes of Anisocoria

There are various reasons why your pupils may differ in size. In some instances, it is simply the result of genetics. There may be no underlying disorder that is responsible for the condition.

Pupils can also occasionally become temporarily uneven for a variety of reasons, including the use of eye drops and certain medications. Sometimes, there is no detectable cause. In these cases, there is generally no cause for concern.

Other more serious causes include:

Traumatic head injury
Direct injury to the eye
Brain abscess
Brain aneurysm
Glaucoma
Optic nerve inflammation
Encephalitis or meningitis
Tumors in the brain, upper chest, or lymph node
Diabetic oculomotor nerve palsy
Seizures
Brain swelling
Intracranial hemorrhage or tumor
Cataract surgery
Migraines

Should you experience anisocoria for an unknown reason, there may be no cause for concern, but it is still important that you do not ignore it. Consult your physician as soon as possible.

Symptoms of Anisocoria

Aside from differing pupil sizes, which can often be difficult to detect without close inspection, anisocoria can lead to a number of other symptoms including:

Eye pain
Difficulty with eye movement
Ptosis or drooping eyelid
Blurry vision
Double vision
Vision loss
Light sensitivity
Decreased sweating
Neck stiffness
Headache
Fever
Nausea

If you find that your pupils are of an uneven size and you are experiencing any of these symptoms, consult a physician right away.

Diagnosis of Anisocoria

Without other symptoms as indicators, anisocoria is not always easy to detect on your own, as the variance between your two pupils can be smaller than half a millimeter. However, your ophthalmologist should be able to easily diagnose you with the help of a few simple tests.

In order to make a diagnosis, your doctor will first ask you a series of questions about your pupil size, your vision, and any symptoms you may be experiencing. Next, they will expose your pupils to varying amounts of light in order to gauge the way in which your pupils react. Depending on their response, your doctor may be able to detect the affected eye.

Another way in which your ophthalmologist might attempt to form a diagnosis is through the use of a slit-lamp microscope. This device will give your doctor a much more detailed look at your eyes in order to detect abnormalities.

A full diagnosis may also require certain tests, including:

Head CT scan
Electroencephalogram or EEG
MRI scan of the head
Neck X-rays
Blood tests
Cerebrospinal fluid tests
Test for glaucoma

These tests will likely be contingent on the symptoms you may be experiencing and the results of the initial tests that your doctor conducts.

Potential Treatments for Anisocoria

Because anisocoria can be caused by such a wide variety of issues, treatments will vary widely depending on your exact diagnosis. In general, the anisocoria itself will not require treatment. In instances where there is no serious underlying condition, but the anisocoria causes vision issues or light sensitivity, bifocals, reading glasses, or photochromatic lenses may be prescribed.

Should the anisocoria be the result of an underlying medical issue, your doctor will work with you to determine a suitable treatment.

Frequently Asked Questions

The following are some common questions regarding causes, symptoms, diagnosis, and treatment of anisocoria.

Does Anisocoria Affect Vision?

Because the pupils are critical to vision, anisocoria can sometimes cause issues with your sight. These issues can include blurred vision, double vision, and vision loss. You may also experience a sensitivity to light if you have anisocoria.

Can Anisocoria Be Cured?

While there are certain instances in which it cannot be cured, anisocoria does not require treatment and can go away all on its own, depending on the cause of the condition. In instances where there is another condition causing the uneven pupil size, treatment for that condition can eventually cure the anisocoria. If the anisocoria is the result of an injury, however, surgery may be required to correct the issue.

Can Anisocoria Be Normal?

While there are a wide range of both minor and serious medical conditions that can cause anisocoria, it can also be a normal characteristic of a person’s eyes. Anisocoria can be passed down genetically, so if you have close relatives with differing pupil sizes, your own uneven pupils are likely no cause for concern. However, that doesn’t mean you shouldn’t consult a physician if you notice that you have anisocoria.

How Common is Anisocoria in Healthy People?

While it is difficult to gauge how frequently anisocoria occurs as a result of another medical condition, it is believed that normal, physiologic anisocoria is rather prevalent among healthy individuals. As many as 1 in 5 people are believed to have a significant enough variance in the size of their pupils to merit an anisocoria diagnosis.

Should I Be Worried if One Pupil is Larger than the Other?

Anisocoria is fairly common, so you shouldn’t panic if you find that your pupils are of uneven sizes. However, you should always consult a physician if you find that you have anisocoria, as it can be connected to a variety of medical issues.