What causes heterochromia?
Causes of heterochromia include:
- Genetic mutations that only affect eye color (and which are harmless).
- Congenital (present from birth) or acquired conditions.
- Eye injuries or complications from certain treatments.
Genetic mutations that only affect eye color
Harmless, isolated genetic mutations are a common cause of heterochromia. These mutations affect the genes that tell your body to make, transport and store melanin. Melanin is the pigment that gives color to your eyes.
Some people are born with mutations that affect eye color for no known reason, while others inherit the mutation as an autosomal dominant trait. Either way, such genetic variants cause no other symptoms. The mutation doesn’t harm your eye health and isn’t part of a medical condition.
Congenital or acquired conditions
Sometimes, congenital or acquired conditions can cause heterochromia. A congenital condition is something you’re born with. An acquired condition is one you develop later in life.
Many different conditions can affect melanocytes, which are specialized cells that produce melanin. One common example is Horner syndrome. Some babies are born with this condition, while some adults develop it later in life.
People with Horner syndrome have underlying nerve damage that affects one side of their face. This nerve damage affects eye color because the cells that produce melanin (melanocytes) rely on stimulation from your sympathetic nervous system to function.
Disruption of a nerve-signaling pathway in your face leads your melanocytes to produce less melanin. As a result, the iris on the affected side of your face has less melanin. Therefore, this iris appears lighter in color (the more melanin present, the darker your iris).
Besides Horner syndrome, there are many other conditions that can affect melanocytes or cause other changes that lead to heterochromia. Keep in mind, many of these conditions are rare.
Congenital causes of heterochromia
- Congenital Horner syndrome.
- Waardenburg syndrome.
- Parry-Romberg syndrome.
- Sturge-Weber syndrome.
- Neurofibromatosis Type 1.
- Ocular melanosis.
- Hypomelanosis of Ito.
- Bloch-Sulzberger syndrome.
Acquired causes of heterochromia
- Acquired Horner syndrome.
- Neuroblastoma.
- Fuchs heterochromic iridocycl*tis.
- Intraocular melanoma.
- Central retinal vein occlusion.
- Posner-Schlossman syndrome.
- Swelling from uveitis.
- Glaucoma.
Eye injuries or complications from treatments
Additional causes of heterochromia include:
- Injury or trauma to your eye.
- Latanoprost eye drops, which treat glaucoma.
- LATISSE®, a cosmetic treatment that helps eyelashes grow.
