Are your pupils unequal in size? This could be anisocoria. Typically, pupils are similar in size, but in the case of anisocoria, one pupil may be significantly larger or smaller than the other. In some cases, it's important to consult an eye doctor as soon as possible. Anisocoria may be a sign of an underlying medical problem. What is anisocoria? What causes uneven pupils? When should you seek medical advice? Find out all the answers in this article.
Anisocoria: Abnormal dilation of the pupils
Anisocoria is an eye disorder characterized by unequal pupil sizes in both eyes. The difference in pupil diameter is usually greater than 0.3 millimetres. Anisocoria can cause one or both pupils to become larger or smaller.
When the pupil enlarges, we speak of "unilateral mydriasis." Conversely, when it shrinks, we use "unilateral myosis."
Sudden appearance of uneven pupils
If you suddenly experience uneven pupils, go to the emergency room. Sudden anisocoria is quite rare, but it is considered a medical emergency. It may be a symptom of a more serious health problem.
Symptoms of anisocoria not to be overlooked
If other symptoms accompany the difference in the size of your pupils, go and see a doctor as soon as possible:
- Sagging eyelid, also known as ocular ptosis
- Intense headaches
- Vision changes
- Double vision
- Eye pain
- Neck pain
- Recent head trauma
- Recent eye injury
Change in pupil size without additional symptoms
Anisocoria may be a symptom of a medical condition or injury. However, it can occur in some people without any underlying problem. For example, some people naturally have one pupil slightly smaller than the other. But it's unlikely that a dilated pupil can be caused by fatigue.
The only way to determine the cause of anisocoria is to have an eye exam.
That's why, even if pupil size change isn't always a medical emergency, we recommend you make an appointment with our optometrists. You can also contact us by telephone at your nearest clinic.
What causes anisocoria?
Certain medications, such as ophthalmic eye drops, can cause pupil size differences. There are other possible causes of anisocoria.
Congenital anomalies
Some people may be born with a difference in pupil size due to structural anomalies.
Head injuries
Trauma to the head can damage eye muscles or nerves, resulting in anisocoria.
Ocular infection or inflammation
Eye infections such as uveitis or ocular inflammation sometimes cause temporary anisocoria.
Neurological disorders
Certain neurological disorders can affect the nerves or control centers of the pupils. For example, migraines, strokes or brain tumours can sometimes cause anisocoria, which is therefore neurological in origin.
What are the risk factors for anisocoria?
Anisocoria in babies can occur during difficult childbirth, particularly when forceps are used.
Some medications, such as scopolamine patches, can cause temporary anisocoria. These patches are used to treat problems such as motion sickness and nausea. They can cause the pupils to dilate, resulting in a difference in pupil size.
But this scopolamine-induced anisocoria is generally temporary, disappearing within a few days.
What is the treatment for anisocoria?
In many cases, no specific intervention is required if the anisocoria is physiological or results from a normal difference in pupil size.
Treatment will depend on the diagnosis, as the underlying disorder responsible for the difference in pupil size needs to be treated. According to the Merck Manual, treatment of the anisocoria itself is unnecessary.
