The word " heterochromia " comes from the Greek words "heteros" (miscellaneous) and " chromaticity " (color). As the name suggests, people with heterochromia, also called iris heterochromia, have a different color for the iris (the area around the pupil ) of each eye . There are also different types of heterochromia: complete, partial, and central heterochromia. Some people are born with this condition, while others may develop heterochromia later in life due to injury, medication, or disease.
Although the color of the iris is determined by genetics, it is not permanent. The color of the eyes is directly dependent on the quantity and quality of melanin in the iris. People with brown eyes have a lot of melanin in the iris, while people with blue eyes have a lot less melanin. Several diseases can influence the distribution of melanin throughout the iris.
Types of heterochromia
There are several types of heterochromia, and they are determined by where the color is different.
Central heterochromia is when there is an inner ring that is different in color from the outer area of the iris. This often occurs in both eyes when two different colors appear in each eye. People with this type of heterochromia will have a golden or brown tint near the edge of their pupils. A common form of central heterochromia appears as predominantly blue eyes with a smaller brown ring in the center that extends outward.
Complete heterochromia is when one iris differs in color from another. For example, one of them is green and the other is brown.
Partial heterochromia occurs when part of an iris is a different color from the rest. The color spectrum of this form of heterochromia is usually unique and varied. In humans, it can develop in one or both eyes.
Symptoms of heterochromia.
In most cases, babies born with heterochromia do not experience other symptoms because they do not have other eye or general health problems. However, in some cases, heterochromia can be a symptom of another condition.
The baby may be born with heterochromia or develop shortly after birth. In these cases, it is called congenital heterochromia. When people develop heterochromia later in life, it is called acquired heterochromia. The causes of congenital and acquired heterochromia are different.
Causes of heterochromia in babies include:
- Horner syndrome : When this condition occurs in children younger than 2 years old, it can cause complete heterochromia. Horner syndrome affects the cervical sympathetic nerves, which can affect the pigmentation (coloration) of melanin in the iris.
- Sturge-Weber syndrome : This is a rare condition characterized by a port birthmark and can cause various eye abnormalities. Some children with Sturge-Weber syndrome develop complete heterochromia due to hyperpigmentation in the affected area.
- Waardenburg syndrome : This is a group of genetic conditions that can cause hearing loss and discoloration of the hair, skin, and eyes. In this case, patients can develop any type of heterochromia.
- Hirschsprung's disease : It is an intestinal disease that is often associated with partial heterochromia.
- Bloch-Sulzberger syndrome : This condition affects the central nervous system, hair, teeth, skin, nails, and eyes. When it reaches the visual system, the affected eye darkens.
- Piebaldism : This condition is characterized by a lack of pigmentation in the skin, eyes, and hair. As a result, some parts of these areas are lighter in color.
- Borneville syndrome : Also known as tuberous sclerosis, it is a rare syndrome that causes benign tumors in various parts of the body. When these tumors press on nerves in certain areas, they can affect melanin pigmentation and iris color.
Causes of acquired heterochromia include:
- Neuroblastoma : This is a cancer that develops from immature nerve cells found in various parts of the body and mainly affects children. It is the most common extracranial solid tumor in children. This may be due to Horner syndrome, which causes heterochromia.
- Fuchs syndrome : It is also known as heterochromic cyclitis syndrome and is a form of uveitis (inflammation of the middle layer of the eye). In this case, heterochromia is predominantly seen in patients with a clear iris.
- Pigment dispersion syndrome: Pigment dispersion syndrome occurs when pigment granules (small particles), which normally adhere to the back of the iris, exfoliate into a clear liquid that forms in the eye. Increased pigmentation can lead to discoloration of the eyes.
- Central retinal vein occlusion : It is a common vascular disease of the retina, especially among the elderly. It can affect the ocular system in a number of ways, including discoloration of the eyes.
- Melanoma of the eye : This is a type of cancer that develops in pigment-producing cells. It often develops between the three layers of the eye and goes unnoticed. People with this type of cancer can develop dark spots on the iris of the eye.
- Eye injury or injury : Damage and trauma to the eyes can lead to depigmentation of the eyes.
- Glaucoma Medicines : Some medicines can change the color of your eyes. Patients using latanoprost, which is used to treat glaucoma , often develop heterochromia after several years of using the drug.
An ophthalmologist can diagnose heterochromia. They will confirm the appearance of heterochromia and find the root causes. In most cases, there will not be any serious disease or condition causing the discoloration of the eye. However, it is important to exclude these conditions.
If you develop heterochromia in adulthood, your ophthalmologist can perform a detailed eye exam to rule out any underlying causes and, if necessary, develop a treatment plan.
Heterochromia is usually benign and does not require any treatment as it does not cause any harm. If there is an underlying medical condition or injury, treatment will depend on each case and the patient should discuss the options with the doctor.
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People should consult a doctor if eye color changes suddenly, especially after an eye injury or other symptoms. Only a doctor can tell if a change in heterochromia is associated with a disease. In most cases, however, there is no reason to be concerned about heterochromia, and it is usually benign. This condition is generally not harmful and does not affect a person's quality of life.