Heterochromia
Heterochromia iridis is an eye disease in which a person has different colors of eyes. It occurs congenitally at birth or later in life due to genetic conditions or injury. Heterochromia is more common in animals such as dogs, cats, and horses and rarely occur in human.
Highlights
- Heterochromia iridis is an eye disease in which a person has different colors of eyes.
- Heterochromia iridis is mainly caused by an uneven distribution of melanin pigment in the iris of the eyes.
- Heterochromia can be congenital and develops at birth or is acquired later in life due to injury, illness, or medications.
- Because heterochromia does not cause complications, illness, or medical emergency, it does not require special diagnosis or treatment.
What is heterochromia?
The word heterochromia is derived from two Greek words, “hetero” means different, and “chroma” means color. Heterochromia can occur in various organs like skin, eyes, etc. Eyes heterochromia appears explicitly in the colored part of the eye called the iris. That’s why it is called heterochromia iridium or heterochromia iridis (Figure 1). In this condition, our eyes look different from each other. For example, one eye looks green and the other brown.
Types of heterochromia
Heterochromia can develop in anyone, irrespective of familial origin. It has three main types depending on whether a complete iris or its portion is affected by the color change.
- Complete heterochromia means when the iris of one eye is completely different in color from the iris of another.
- Sectoral heterochromia means when a small portion of the iris of one eye is different from the rest of the iris of the same eye.
- Central heterochromia means when only the inner ring of the iris has a different color from the rest of the iris.
Why does heterochromia iridis occur?
Melanin is a color-producing pigment present in the skin. It is responsible for our skin, eyes and hair color. In the eyes, melanin deposits in the iris, giving it color; for instance, people with brown eyes have an excess of melanin in the iris, whereas people with blue eyes have less melanin in the iris. Variations in the distribution of melanin produce different colored irises. However, iris color may change in life; even the blue eyes of a newborn baby may get darker within three years of age.
Causes of heterochromia
What causes heterochromia iridis depends on its origin. If heterochromia iridis develops at birth due to genetic variations, it is called congenital heterochromia. In contrast, acquired heterochromia develops later in life due to injury, illness, or medication.
Congenital heterochromia occurs due to unknown benign mutations in the melanocytes of the eyes. Consequently, melanocytes produce varying amounts of melanin pigment in the iris. Common congenital diseases and syndromes that affect iris color include:
- Horner’s syndrome
- Waardenburg syndrome
- Piebaldism
- Sturge Weber syndrome
- Parry-Romberg syndrome
- Hirschsprung disease
- Bourneville disease
- von Recklinghausen disease
- Tuberous sclerosis, also known as Bourneville syndrome
- Duane syndrome
- Bloch-Sulzberger syndrome
Not all heterochromia iridis cases develop at birth; many have been found later in life, resulting from illness, injury, or medication. Common causes of acquired heterochromia iridis are:
- Neuroblastoma or cancer of nerve cells of the sympathetic nervous system.
- Glaucoma is a progressive eye disease that damages the optic nerve.
- Fuchs’ syndrome or Fuchs’ heterochromic cyclitis of the eye.
- Eye melanoma or ocular cancer of the melanocytes of an eye.
- Central retinal vein occlusion or leakage of blood and fluid into the retina.
- Eye surgery, trauma, or injury.
- Diabetes.
- Tumor of the iris.
- Iris ectropion syndrome.
- Swelling of the eye.
- Pigment dispersion syndrome.
- Posner-Schlossman syndrome.
- Certain medications, such as Latisse and latanoprost, also cause heterochromia. Latisse was a glaucoma medicine, now prescribed explicitly for the thickening of eyelashes. Similarly, latanoprost is another glaucoma medicine associated with eye color change in patients who have been taking it for more than five years.
Diagnosis and Treatment
Because none of the people with heterochromia iridis has been affected by vision loss or other serious illnesses or complications, this condition does not require special diagnostics or treatment. However, a person may use colored contact lenses for cosmetic reasons so that their eyes look similar.
