BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuAnisocoriaEnlargement of one pupil; Pupils of different size; Eyes/pupils different sizeAnisocoria is unequal pupil size. The pupil is the black part in the center of the eye. It gets larger in dim light and smaller in bright light. Considerations Slight differences in pupil sizes are found in up to 1 in 5 healthy people. Most often, the diameter difference is less than 0.5 mm, but it can be up to 1 mm.Babies born with different sized pupils may not have any underlying disorder. If other family members also have similar pupils, then the pupil size difference could be genetic and is nothing to worry about.Also, for unknown reasons, pupils may temporarily differ in size. If there are no other symptoms and if the pupils return to normal, then it is nothing to worry about.Unequal pupil sizes of more than 1 mm that develop later in life and do not return to equal size may be a sign of an eye, brain, blood vessel, or nerve disease. Causes The use of eye drops is a common cause of a harmless change in pupil size. Other medicines that get in the eyes, including medicine from asthma inhalers, can change pupil size.Other causes of unequal pupil sizes may include:Aneurysm in the brain Bleeding inside the skull caused by head injury Brain tumor or abscess (such as, pontine lesions) Brain tumorA brain tumor is a group (mass) of abnormal cells that grow in the brain. This article focuses on primary brain tumors in children.ImageRead Article Now Book Mark Article AbscessAn abscess is a collection of pus in any part of the body. In most cases, the area around an abscess is swollen and inflamed.ImageRead Article Now Book Mark Article Excess pressure in one eye caused by glaucoma GlaucomaGlaucoma is a group of eye conditions that can damage the optic nerve. This nerve sends the images you see to your brain. Most often, optic nerve da...ImageRead Article Now Book Mark Article Increased intracranial pressure, because of brain swelling, intracranial hemorrhage, acute stroke, or intracranial tumor Infection of membranes around the brain (meningitis or encephalitis) MeningitisMeningitis is an infection of the membranes covering the brain and spinal cord. This covering is called the meninges.ImageRead Article Now Book Mark Article EncephalitisEncephalitis is irritation and swelling (inflammation) of the brain, most often due to infections.Read Article Now Book Mark Article Migraine headache Seizure (pupil size difference may remain long after seizure is over) Tumor, mass, or lymph node in the upper chest or lymph node causing pressure on a nerve may cause decreased sweating, a small pupil, or drooping eyelid all on the affected side (Horner syndrome) Decreased sweatingAn abnormal lack of sweat in response to heat may be harmful because sweating allows heat to be released from the body. The medical term for absent ...Read Article Now Book Mark Article Drooping eyelidPtosis (eyelid drooping) in infants and children is when the upper eyelid is lower than it should be. This may occur in one or both eyes. Eyelid dr...ImageRead Article Now Book Mark Article Stroke Injury to the carotid or vertebral artery Diabetic oculomotor nerve palsy Prior eye surgery for cataracts Home Care Treatment depends on the cause of the unequal pupil size. You should see a health care provider if you have sudden changes that result in unequal pupil size. When to Contact a Medical Professional Contact a provider if you have persistent, unexplained, or sudden changes in pupil size. If there is any recent change in pupil size, it may be a sign of a very serious condition.If you have differing pupil size after an eye or head injury, get medical help immediately.Always seek immediate medical attention if differing pupil size occurs along with:Blurred vision Double vision Double visionThere are many types of eye problems and vision disturbances, such as: Halos Blurred vision (the loss of sharpness of vision and the inability to see...ImageRead Article Now Book Mark Article Eye sensitivity to light Fever Headache Loss of vision Loss of visionBlindness is a lack of vision. It may also refer to a loss of vision that cannot be corrected with glasses or contact lenses. Partial blindness mean...ImageRead Article Now Book Mark Article Nausea or vomiting Eye pain Eye painPain in the eye may be described as a burning, throbbing, aching, or stabbing sensation in or around the eye. It may also feel like you have a forei...Read Article Now Book Mark Article Stiff neck What to Expect at Your Office Visit Your provider will perform a physical exam and ask questions about your symptoms and medical history, including:Is this new for you or have your pupils ever been different sizes before? When did it start? Do you have other vision problems such as blurred vision, double vision, or light sensitivity? Do you have any loss of vision? Do you have eye pain? Do you have other symptoms such as headache, nausea, vomiting, fever, or stiff neck?Tests that may be done include:Blood studies such as CBC and blood differential CBCA complete blood count (CBC) test measures the following:The number of red blood cells (RBC count)The number of white blood cells (WBC count)The tota...ImageRead Article Now Book Mark Article Blood differentialThe blood differential test measures the percentage of each type of white blood cell (WBC) that you have in your blood. It also reveals if there are...ImageRead Article Now Book Mark Article Cerebrospinal fluid studies (lumbar puncture) Lumbar punctureCerebrospinal fluid (CSF) collection is a test to look at the fluid that surrounds the brain and spinal cord. CSF acts as a cushion, protecting the b...ImageRead Article Now Book Mark Article CT scan of the head CT scan of the headA head computed tomography (CT) scan uses many x-rays to create pictures of the head, including the skull, brain, eye sockets, and sinuses.ImageRead Article Now Book Mark Article Electroencephalogram (EEG) ElectroencephalogramAn electroencephalogram (EEG) is a test to measure the electrical activity of the brain.ImageRead Article Now Book Mark Article Head MRI scan Head MRI scanA head MRI (magnetic resonance imaging) is an imaging test that uses powerful magnets and radio waves to create pictures of the brain and surrounding...ImageRead Article Now Book Mark Article Tonometry (if glaucoma is suspected) TonometryTonometry is a test to measure the pressure inside your eyes. The test is used to screen for glaucoma. It is also used to measure how well glaucoma...ImageRead Article Now Book Mark Article X-rays of the neckX-rays of the neckA neck x-ray is an imaging test to look at cervical vertebrae. These are the 7 bones of the spine in the neck.ImageRead Article Now Book Mark Article Treatment depends on the cause of the problem.Open ReferencesReferencesBalcer JL. Pupillary disorders. In: Liu GT, Volpe NJ, Galetta SL, eds. Liu, Volpe, and Galetta's Neuro-Ophthalmology. 3rd ed. Philadelphia, PA: Elsevier; 2019:chap 13.Cheng KP. Ophthalmology. In: Zitelli BJ, McIntire SC, Nowalk AJ, eds. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 20.Thurtell MJ, Rucker JC. Pupillary and eyelid abnormalities. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 17.AllVideoImagesTogNormal pupil - illustration The pupils of an individual are usually very symmetrical in appearance. In certain instances the pupils may vary in size. Occasionally, differing pupil size is inherited and there is no underlying disorder. Varying pupil size may also be due to infection, tumors, disease or trauma.Normal pupilillustrationNormal pupil - illustration The pupils of an individual are usually very symmetrical in appearance. In certain instances the pupils may vary in size. Occasionally, differing pupil size is inherited and there is no underlying disorder. Varying pupil size may also be due to infection, tumors, disease or trauma.Normal pupilillustrationRelated Information Head injury - first aid(Injury) Review Date: 5/4/2021 Reviewed By: Joseph V. Campellone, MD, Department of Neurology, Cooper Medical School at Rowan University, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- © 1997- All rights reserved. A.D.A.M. content is best viewed in IE9 or above, Firefox and Google Chrome browser.Content is best viewed in IE9 or above, Firefox and Google Chrome browser.