Heterochromia refers to the same individual having color differences in the iris or irises. ‘Hetero’ means ‘different’ while ‘chromia’ means ‘color.’ For example, one eye may be blue while the other one may be green. The iris covers the pupil and contains the pigment melanin which gives color to the eye. It is a rare condition in human beings but very common in cats, horses and dogs.
The amount of melanin in the iris determines an individual's eye color. For example, individuals have different eye colors such as green, brown, hazel, black and blue. Brown eyes have the most amount of melanin while blue has the least. Heterochromia is not an eye disease and does not affect visual acuity.
Also Known As
- Differently colored eyes
- Eyes - different colors
- Asymmetry in the pigmentation of the irides
- Heterochromia iridis
- Heterochromia iridum
- Pigmentary abnormality of the anterior segment of the eye
- Complete heterochromia – It occurs when one iris’s color is different from the other
- Partial/Sectoral heterochromia – When there is a different color in one part of the iris while the rest has another color. The color difference can affect one or both eyes
- Central heterochromia – The color on the edges of the iris is different from the rest
Causes and Risk Factors
Heterochromia has many causes. It can be congenital or an infant may develop the condition right after birth. Children with congenital heterochromia usually do not display other symptoms. Also, they do not have other eye problems or issues with their health in general. Nevertheless, heterochromia could be an indication of another condition that needs investigating. The following conditions can cause heterochromia in infants:
- Horner’s syndrome – It results in a pupil decreasing in size, the eyelid drooping and in less sweating
- Sturge-Weber syndrome – A neurological congenital disorder characterised by a port-wine birthmark on the face. Neurological disorders include seizures. Eye problems such as glaucoma may also manifest
- Piebaldism – A rare inherited condition where an individual has a patch of white hair directly above the forehead
- Benign heterochromia – The disease occurs without any underlying abnormality
- Hirschsprung disease – A disease that involves the large intestines and causes problems with passing stool
- Bourneville disease – A genetic disorder where benign tumors grow in the body
- Parry-Romberg syndrome – An uncommon disorder where facial soft tissues and the skin progressively shrink. It affects one side of the face
- Von Recklinghausen disease – A genetic disease responsible for the growth of tumors on the nerves
- Bloch-Sulzberger syndrome – A hereditary disorder that involves skin pigmentation. It is associated with abnormalities in the teeth, central nervous system and skeletal system
- Neuroblastoma – A tumor that develops from immature nerve tissue in an infant or child below five years
In acquired heterochromia, individuals develop the disease later in life. The following may cause acquired heterochromia:
- Eye surgery
- Bleeding in the eye
- Foreign object in the eye
- Glaucoma and drugs used to treat it
- Acquired Horner’s syndrome
- Benign tumors of the iris
- Mild inflammation affecting only one eye
- Diabetes mellitus – Type 2 diabetes
- Trauma – Could be blunt or penetrating
- Posner-Schlossman syndrome – May cause a lighter iris
- Ocular melanosis – Increased pigmentation of the eye
- Latisse – Glaucoma medicine cosmetically used to thicken eyelashes
- Pigment dispersion syndrome – Loss of pigmentation from the posterior of the surface of the iris
- Chediak-Higashi syndrome – Infections and color changes in the skin and eye
- Iris ectropion syndrome – The back of the iris moves onto the front of the iris
- Swelling caused by uveitis (inflammation of the uvea) or iritis (inflammatory condition of the eye)
- Central retinal vein occlusion – The main vein that drains blood away from the retina closes off partially
- Fuchs’ heterochromic cyclitis – A rare form of chronic uveitis (swelling and irritation of the middle layer of the eye)
Signs & Symptoms
The only symptom for heterochromia is the variation of color in the iris or irises.
The eye care professional will confirm presence of heterochromia in infants. He/she will also check for any underlying causes. The professional needs to rule out the other conditions that may be causing the color variation. Also, he/she may want to know if the condition in the infant is congenital or acquired. A pediatrician should also examine the infant.
For adults, the eye professional will conduct a detailed eye examination to confirm there are no underlying causes. If another disorder is suspected, further studies may be done. Such tests include chromosome studies and blood tests. The professional can also diagnose heterochromia through a slit-lamp examination.
Treatment for heterochromia is directed towards treating any underlying causes.
If no underlying problems exist on the affected eye, then treatment may not be required.
Contact lenses with color can be issued for cosmetic purposes. These lenses can either darken or lighten the affected eye. Alternatively, two differing contact lenses may be used to arrive at an average color.
Many patients with heterochromia have no problems with vision. Most cases are mild and not associated with any other illness or rare disease. Those cases are also not progressive.
Patients with associated problems respond well to treatment. This prevents loss of vision.