What Is Cyclopia?

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Cyclopia is a rare form of holoprosencephaly—a condition where the front portion of the brain fails to divide into left and right hemispheres. It is otherwise known as alobar holoprosencephaly. It is characterized by the presence of a single eye, or a partially divided eye that occupies a single orbit. It is an extremely rare congenital anomaly affecting 1 in 100,000 newborns.

Unfortunately, this condition often results in a miscarriage or a stillbirth, with survival being limited to only a few hours after birth in most cases. There is no cure for cyclopia.

The types of holoprosencephaly include:

  • Alobar: A complete failure of the brain to divide into left and right hemispheres. This results cyclopia, the most severe facial expression of holoprosencephaly.
  • Semi-lobar: The left side of the brain fuses to the right side. It does this in the front and side regions of the brain. This can lead to closely spaced eyes, abnormally small eyeballs, or anophtalmia, where a baby is born without one or both eyes.
  • Lobar: A separation between the left and right hemispheres of the brain. The cerebral hemispheres are fused in the frontal cortex of the brain. This may result in bilateral cleft lip, closely spaced eyes, or a depressed nose.
  • Middle interhemispheric variant: Occurs when the brain is fused in the middle. This has led to closely spaced eyes, depressed and narrow noses, or an almost normal-looking face.

Cyclopia Symptoms

The singular eye or partially divided eye occupying one orbit is the most identifiable feature of cyclopia.

This eye is usually centered where the nose would typically be located. In this condition, the nose may be absent or replaced by a non-functioning nose in the form of a proboscis which is found above the eye. However, this condition may also affect other structures in the head and face.

Other signs of cyclopia include:

  • An absent nose
  • A proboscis or nose-like structure above the eye
  • Very closely spaced eyes
  • Absent eyes
  • Flattened nose
  • Cleft lip
  • Extra fingers or toes

Some cases of cyclopia may also feature omphalocele, a condition where the baby's internal organs stick out through the belly button. Likewise, renal dysplasia may be observed where fluid-filled sacs replace a baby's kidneys.


While the exact cause of cyclopia is unknown, there are certain risk factors that may increase the chances of its occurrence.

Gestational Diabetes

Uncontrolled gestational diabetes has been linked with neural tube defects in an embryo. This tube is a hollow structure where the brain and spinal cord are formed. This condition is one of the leading causes of disease in the central nervous system (e.g., holoprosencephaly).


In certain instances, abnormalities of the chromosomes which contain DNA may be to blame for holoprosencephaly.

These chromosome anomalies include:

  • Triploidy: In this condition, fetuses are born with an extra set of chromosomes in their cells. While humans typically have 23 sets of chromosomes, this condition may triple that number to 69—a triploid set.
  • Trisomy 13: An abnormality where a baby has an extra 13th chromosome when they should have just two (i.e., they have three sets of the 13th chromosome).
  • Trisomy 18: An extra 18th chromosome may cause severe growth defects as well as psychomotor difficulties.

Infections During Pregnancy

During pregnancy, certain infections may increase the risk of developing holoprosencephaly.

One of such infections is the TORCH syndrome which is an acronym referring to Toxoplasmosis, Other Agents, Rubella, Cytomegalovirus, and Herpes Simplex.

Any of these agents may cause a number of ailments in newborns such as fever, small areas of bleeding under the skin and notably—holoprosencephaly.

Gene Changes

In some instances, holoprosencephaly may be a product of genetic abnormalities. These abnormalities may cause the genes and their proteins to function improperly. When brain development is affected, it can lead to holoprosencephaly.

Alcohol Consumption During Pregnancy

Holoprosencephaly is a known defect caused by alcohol use during pregnancy.

Ethanol, which is the principal ingredient in alcohol is a known teratogen. A teratogen is a factor that can lead to deformities in an embryo following maternal exposure.

Maternal exposure occurs when the female parent carrying the fetus is subjected to potentially harmful agents in their internal or external environment (e.g., alcohol or hazardous chemicals).

Drug Use During Pregnancy

Certain types of drugs may increase the risk of developing cyclopia during pregnancy. They include salicylates like aspirin, anticonvulsants, retinoic acid, anticancer agents, fertility drugs, as well as hormones.

Consanguineous Unions

Consanguineous unions i.e., sexual relations between people who are related by blood are a major risk factor for the development of birth defects in children. 

This union encourages autosomal recessive diseases, which are traits or disorders passed down through families, and may be a cause of holoprosencephaly.

Cyclopia has been observed to occur in the offspring of a consanguineous marriage between first cousins.


A prenatal diagnosis of cyclopia may be made while the child is still in the womb by using an ultrasound. In certain cases, a diagnosis may be made by using an MRI.

If a prenatal diagnosis isn’t made, cyclopia may be identified by the physical examination of the newborn following delivery.

A Word From Verywell

As there is no cure or treatment options for cyclopia, if you've had a child with cyclopia, it is understandably a difficult and emotional situation.

If you are struggling with the aftermath of losing a child to cyclopia, a therapist or physician can help provide you and your family with healthy coping strategies.

8 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  6. Santos-Ledo A, Cavodeassi F, Carreño H, Aijón J, Arévalo R. Ethanol alters gene expression and cell organization during optic vesicle evaginationNeuroscience. 2013;250(100):493-506. doi:10.1016/j.neuroscience.2013.07.036

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By Elizabeth Plumptre
Elizabeth is a freelance health and wellness writer. She helps brands craft factual, yet relatable content that resonates with diverse audiences.