To evaluate anisocoria, the examiner first determines which pupil is abnormal by noting pupil size in darkness and in light. When the larger pupil is abnormal (does not constrict well), the degree of anisocoria is greatest in bright light (as the normal pupil becomes small).
Full Answer
Why is thorough clinical evaluation important for the diagnosis of anisocoria?
Thus, thorough clinical evaluation is important for the appropriate diagnosis and management of the underlying cause. Generally, anisocoria is caused by impaired dilation (a sympathetic response) or impaired constriction (a parasympathetic response) of pupils.
What is anisocoria?
Anisocoria is a condition characterized by unequal pupil sizes. It is relatively common, and causes vary from benign physiologic anisocoria to potentially life-threatening emergencies.
How is an aneurysm diagnosed in anisocoria?
An aneurysm can be most effectively imaged with a computed tomography angiogram (CTA) or a magnetic resonance angiogram (MRA) of the head.[12] If Horner syndrome is causing the anisocoria and a carotid artery dissection or aneurysm could be the cause, imaging is recommended. A CTA or MRA of the head and neck should be performed.
What is the normal range of anisocoria?
Physiological Anisocoria Physiologic anisocoria is usually defined as a pupillary inequality of 0.4 mm, seldom greater than 0.8 mm, not due to a secondary cause. If the anisocoria is physiologic, the difference in pupil sizes should remain equal in dim and bright lights.
How do you evaluate anisocoria?
Anisocoria greater in the dark indicates the small pupil to be abnormal due to poor pupillary dilation. A small amount of anisocoria that is equal in both light and dark conditions most likely represents physiologic anisocoria.
What is anisocoria and what does it indicate for the patient?
Anisocoria is when your eye's pupils are not the same size. The pupil allows light to enter the eye so that you can see. Anyone can have pupils that differ in size with no problems. In fact, one out of five people have pupils that are normally different sizes.
What is the most common cause of anisocoria?
Anisocoria can be caused by a lot of conditions in your body, injuries, traumas and even some medicines. Some of the most common causes include: Migraine headaches. Glaucoma.
Who can diagnose anisocoria?
Interpretation of findings. and physiologic anisocoria. An ophthalmologist can differentiate them because the small pupil in Horner syndrome does not dilate after instillation of an ocular dilating drop (eg, 10% cocaine). In physiologic anisocoria, the difference in pupil size may also be equal in light and dark.
What type of doctor treats anisocoria?
The precise cause of this type of anisocoria has yet to be discovered. If you have different size pupils, contact an eye doctor near you, who can diagnose and treat the condition.
What cranial nerve causes anisocoria?
The 3rd cranial nerve also controls the muscles that move your eyes up, down, and in, as well as open your eyelid. Damage to the 3rd cranial nerve can result in a dilated pupil, droopy eyelid and double vision (when the 2 lid is lifted) because the eye does not move normally.
Can anisocoria be benign?
Pupil asymmetry or anisocoria can have benign or malignant causes, and be categorized as acute or chronic. It can also be a normal finding in about 20% of cases. Benign episodic unilateral mydriasis is an isolated benign cause of intermittent pupil asymmetry.
Can anisocoria be normal?
The term anisocoria refers to pupils that are different sizes at the same time. The presence of anisocoria can be normal (physiologic), or it can be a sign of an underlying medical condition.
What does it mean when one pupil is dilated?
Benign Episodic Unilateral Mydriasis This condition means only one pupil is dilated. It's called "benign" because it's not related to any serious conditions, but it can sometimes affect young women who get migraines. The pupil usually goes back to normal size within a few hours, but it can last for several days.
What is a normal pupil size?
The normal pupil size in adults varies from 2 to 4 mm in diameter in bright light to 4 to 8 mm in the dark. The pupils are generally equal in size. They constrict to direct illumination (direct response) and to illumination of the opposite eye (consensual response). The pupil dilates in the dark.
What is the most common cause of anisocoria?
Etiology of Anisocoria. The most common cause of anisocoria is. Physiologic (present in about 20% of people): The difference between pupil sizes in physiologic anisocoria is typically ≤ about 1 mm. See table Some Common Causes of Anisocoria for other causes of anisocoria.
Why is my pupil smaller in the dark?
If the difference in size is greater in the dark , the smaller pupil is abnormal (because the pupil should dilate in the dark to let in more light). Common causes include Horner syndrome and physiologic anisocoria.
What is Horner syndrome?
Horner syndrome (eg, congenital, traumatic, postsurgical, due to migraine or lung tumors) Ptosis, miosis, anhidrosis, delayed dilation after constriction, features of causative disorder. Iris or other ocular dysfunction after surgery. History. Physiologic anisocoria.
Is anisocoria a difference in pupil size?
In physiologic anisocoria, the difference in pupil size may also be equal in light and dark. If the difference in pupillary sizes is greater in light, the larger pupil is abnormal (because the pupil should constrict in the light to let in less light). If extraocular movements are impaired, particularly with ptosis, 3rd cranial nerve palsy is likely.
What is the most concerning condition in the differential diagnosis of a child with anisocoria?
However, the most concerning condition in the differential diagnosis of a child with anisocoria is Horner syndrome, a loss of the sympathetic tone to the eye (oculo-sympathetic paresis). The typical presentation of Horner syndrome includes unilateral ptosis and miosis.
What is Horner syndrome?
The differential diagnosis of Horner syndrome in children is different than adults and includes neuroblastoma and other upper chest/lower neck masses, carotid and brainstem lesions, and brachial plexus birth trauma, all of which can damage the sympathetic chain .
Why is urine catecholamine screening done?
Additionally, urine catecholamine metabolite screening (Vanillylmandelic acid and homovanillic acid, VMA/HVA) is sometimes completed because excess production of these catecholamines and their metabolites is common in neuroblastoma.
Does AC dilate the iris?
AC will have the opposite effect; the Horner iris will dilate, whereas the unaffected iris will not. When a Horner syndrome is confirmed with cocaine or AC and/or is very obvious on exam, an imaging evaluation should include MRI of the head, neck, and upper chest with and without contrast, as well as MRI-angiogram of the neck.
Is anisocoria an isolated finding?
Anisocoria associated with other disorders, particularly Horner syndrome and third nerve palsy, is not an isolated finding. If a patient has ptosis along with anisocoria, referral to a pediatric ophthalmologist is indicated for evaluation of possible Horner syndrome or third nerve palsy.
Does anisocoria cause vision problems?
Physiological anisocoria does not cause any problems with development of vision. 2. Horner syndrome. Horner syndrome occurs due to interruption of the oculosympathetic chain that begins in the hypothalamus, travels through the spinal cord to the thorax, and ascends along the internal carotid artery to the orbit.