Medically reviewed by Seunggu Han, M.D. — Written by Adrienne Stinson on June 11, 2019
- Is it serious?
- Types
- Causes
- Diagnosis
- Treatment
- Outlook
Pupils, or the black parts at the center of the eyes, change size to regulate the amount of light entering the eye. Pupils are large in the dark to let more light in and small in bright light.
Usually, the pupils in each eye dilate or constrict at the same time. When they do not, the pupils may appear to be different sizes.
The medical term for pupils of different sizes is anisocoria. Anisocoria is a symptom of many conditions but is not a condition on its own.
In this article, learn about the possible causes for pupils of different sizes, as well as when to see a doctor.
If a person’s pupils are suddenly different sizes, it is best to seek medical attention. While not always harmful, a sudden change can indicate serious and dangerous medical conditions.
It is especially important to seek medical attention if the change occurs after an injury or with other symptoms.
Share on PinterestPhysiological anisocoria is the most common type of anisocoria.
Image credit: ThomasBonini, 2019
There are three types of anisocoria:
- physiological
- mechanical
- pathological
Physiological anisocoria: This is when the pupils are naturally different sizes. It is the most common type of anisocoria, and the difference between the pupil sizes is no more than 1 millimeter. Physiological anisocoria may be temporary or permanent, depending on individual cases.
About 15–30% of the population experiences physiological anisocoria. The difference between the pupil sizes is more or less constant, even when the light changes, and is not usually of concern.
Mechanical anisocoria: This type of anisocoria is the result of physical damage to the eye, such as an injury or a condition that causes inflammation to the eye.
Pathological anisocoria: This type is when the difference in pupil size comes from one of the following:
- a disease affecting the iris, or colored area
- a disease affecting the pupil
- a disease affecting the information pathways to the pupil
Anisocoria may not have an underlying cause. Physiological anisocoria is when there is a natural, small difference in the size of a person’s pupils. This is not harmful and does not require treatment.
However, a sudden and pronounced change in one pupil size can indicate a medical condition.
Medical conditions that may lead to anisocoria include:
Third nerve palsy
Third nerve palsy (TNP) can cause the pupils to be different sizes.
Causes of TNP include a brain hemorrhage, trauma, or aneurysm. Anyone experiencing symptoms after a head injury must see a doctor.
Aside from the pupils being different sizes, other symptoms of TNP include:
- slight drooping of the eyelid, known as ptosis
- abnormalities in the muscles around the eye
- potential loss of ability to focus on objects
Other causes of TNP in children include migraine and severe infections, such as meningitis. However, some cases of TNP in children are congenital, meaning they occur from birth.
TNP can be due to pressure on the third nerve from an artery aneurysm. An aneurysm causes pain and is a life-threatening condition that needs immediate attention.
Horner’s syndrome
People with Horner’s syndrome have one abnormally small pupil. They will also have all or some of the following symptoms:
- a drooping upper eyelid on that side
- slightly higher lower eyelid
- an eye with a sunken appearance
- little or no sweating on that side of the face
Tonic pupil or Adie syndrome
Tonic pupil is where one pupil will appear abnormally large in light, taking a long time to constrict. It is not a life-threatening condition.
About 90% of cases occur in women between 20 and 40 years of age.
Although usually not harmful, having a tonic pupil may lead to someone becoming miotic, or chronically having a small pupil.
Medications
Certain medications can also cause pupils to be different sizes.
These include:
Mechanical causes
Physical problems with the eyes that can cause the pupils to be different sizes include:
- eye trauma, such as being hit or poked in the eye
- iritis and uveitis
- acute angle glaucoma
- intraocular tumors
In cases of pathological anisocoria, medical professionals need to determine which pupil is abnormal by looking at how they react in different lights.
In the light, the pupil that is bigger is usually the abnormal pupil. In this case, doctors may suspect third nerve palsy and would do a CT or MRI scan for diagnosis.
In the dark, the smaller pupil is usually the abnormal pupil. In this case, doctors may diagnose Horner’s Syndrome.
Share on PinterestWith pathological anisocoria, a doctor may recommend a CT scan to rule out dangerous underlying causes.
People with physiological anisocoria do not usually need treatment, as it is typically harmless.
Mechanical anisocoria may require surgery to correct the damage a trauma has caused.
If the damage is due to an underlying condition, such as uveitis or glaucoma, a doctor will develop an individualized treatment plan.
If a person’s medication is causing anisocoria, a doctor may recommend a different drug. The symptoms of tonic pupil often subside with glasses and a prescription for pilocarpine.
With pathological anisocoria, such as TNP or Horner’s Syndrome, a doctor must first rule out dangerous underlying causes, such as stroke, tumor, hemorrhage, and aneurysm. They will usually use physical tests and scans, such as CT scans or MRIs, as soon as possible.
The medical term for pupils of different sizes is anisocoria, and doctors categorize this into three further types, depending on the underlying cause.
Many people have very slight differences in the size of their pupils, which is usually not harmful. However, significant size differences or symptoms that come on suddenly can be a sign of dangerous health problems, including a brain aneurysm.
If the pupils change suddenly or with other symptoms, such as drooping or other abnormalities, contact a doctor immediately.
Last medically reviewed on June 11, 2019
- Emergency Medicine
- Eye Health / Blindness
- Neurology / Neuroscience
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- Anisocoria. (n.d.).
//www.ncbi.nlm.nih.gov/mesh?Db=mesh&Cmd=DetailsSearch&Term=%22Anisocoria%22%5BMeSH+Terms%5D - Boisvert, C. J., & Tran, N.-A. (2019). Anisocoria.
//eyewiki.aao.org/Anisocoria - Horner's syndrome. (2017).
//rarediseases.info.nih.gov/diseases/6670/horners-syndrome - Kennedy, S., et al. (2013). Examining the pupils.
//www.ncbi.nlm.nih.gov/pmc/articles/PMC3680589/ - Label: Salagen — pilocarpine hyrochloride tablet, film coated. (2019).
//dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=fb4810ec-d26f-429d-b87c-5898a7870169 - Modi, P., & Arsiwalla, T. (2019). Cranial nerve III palsy.
//www.ncbi.nlm.nih.gov/books/NBK526112/ - Payne, W., & Barrett, M. J. (2019). Anisocoria.
//www.ncbi.nlm.nih.gov/books/NBK470384/ - Pilocarpine ophthalmic. (2017).
//medlineplus.gov/druginfo/meds/a682874.html - Steck, R. P., et al. (2018). Physiologic anisocoria under various lighting conditions.
//www.ncbi.nlm.nih.gov/pmc/articles/PMC5757963/
Upper and lower limb reduction defects occur when a part of or the entire arm (upper limb) or leg (lower limb) of a fetus fails to form completely during pregnancy. The defect is referred to as a “limb reduction” because a limb is reduced from its normal size or is missing.
How Many Babies are Born with Limb Reduction Defects?
Researchers estimate that about 1 in every 1,900 babies is born with a limb reduction defect in the United States. Some of these babies will have both upper and lower limb reduction defects.1
What problems do children with limb reduction defects have?
Babies and children with limb reduction defects will face various issues and difficulties, but the extent of these will depend on the location and size of the reduction. Some potential difficulties and problems include:
- Difficulties with normal development such as motor skills
- Needing assistance with daily activities such as self-care
- Limitations with certain movements, sports, or activities
- Potential emotional and social issues because of physical appearance
Specific treatment for limb reduction defects will be determined by the child’s doctor, based on things like the child’s age, the extent and type of defect, and the child’s tolerance for certain medications, procedures, and therapies.
The overall goal for treatment of limb reduction defects is to provide the child with a limb that has proper function and appearance. Treatment can vary for each child. Potential treatments include:
- Prosthetics (artificial limbs)
- Orthotics (splints or braces)
- Surgery
- Rehabilitation (physical or occupational therapy)
It is important to remember that some babies and children with limb reductions will have some difficulties and limitations throughout life, but with proper treatment and care they can live long, healthy, and productive lives.
What causes limb reduction defects?
The cause of limb reduction defects is unknown. However, research has shown that certain behaviors or exposures during pregnancy can increase the risk of having a baby with a limb reduction defect. These include:
- Exposure of the mother to certain chemicals or viruses while she is pregnant
- Exposure of the mother to certain medications
- Possible exposure of the mother to tobacco smoking (although more research is needed)
CDC works with many researchers to study risk factors that can increase the chance of having a baby with limb reduction defects, as well as outcomes of babies with the defect. Following are examples of what this research has found:
- A woman taking multivitamins before she gets pregnant might decrease her risk for having a baby with limb reduction defects, although more research is needed.2
- Certain sets of limb reduction defects might be associated with other birth defects, such as heart defects, omphalocele, and gastroschisis.3
Can limb reduction defects be prevented?
There is no known way to prevent this type of defect, but some of the problems experienced later in life by a person born with a limb reduction defect can be prevented if the defect is treated early.
Even so, mothers can take steps before and during pregnancy to have a healthy pregnancy. Steps include taking a daily multivitamin with folic acid (400 micrograms), not smoking, and not drinking alcohol during pregnancy.
References
- Mai CT, Isenburg JL, Canfield MA, Meyer RE, Correa A, Alverson CJ, Lupo PJ, Riehle‐Colarusso T, Cho SJ, Aggarwal D, Kirby RS. National population‐based estimates for major birth defects, 2010–2014. Birth Defects Research. 2019; 111(18): 1420-1435.
- Yang QH, Khoury MJ, Olney RS, & Mulinare J. Does periconceptional multivitamin use reduce the risk for limb deficiency in offspring? Epidemiology. 1997;8: 157-61.
- Rosano A, Botto LD, Olney RS, Khoury MJ, Ritvanen A, Goujard J, et al. Limb defects associated with major congenital anomalies: clinical and epidemiological study from the International Clearinghouse for birth defects monitoring systems. Am J Med Genet. 2000;93: 110-16.