Sectoral heterochromia is a condition where one iris contains two distinct colors, typically a wedge or patch of a different color set against the main eye color. A common example is a brown section in an otherwise blue eye. It affects fewer than 200,000 people in the United States and is usually harmless, requiring no treatment.
How Sectoral Heterochromia Differs From Other Types
Heterochromia comes in three forms, and the differences are straightforward. Complete heterochromia means each eye is an entirely different color, like one blue eye and one brown eye. Central heterochromia produces a ring of a different color around the pupil, creating a starburst effect. Sectoral heterochromia falls in between: a distinct patch or segment of one iris is a different color from the rest of the same eye.
The patch can be small or take up a large portion of the iris. It can appear in one eye or both, though one eye is more common. The color contrast ranges from subtle (green against hazel) to striking (brown against blue).
What Causes the Color Difference
Eye color is determined by the amount and distribution of pigment in the iris. People with more pigment have brown eyes; people with less have blue or green. In sectoral heterochromia, the pigment-producing cells in one section of the iris either produce more or less pigment than the surrounding area. A brown patch in a blue eye, for instance, contains a denser concentration of pigment than the rest of the iris.
When the condition is present from birth, it results from uneven pigment distribution during fetal development. As the eye forms, the cells responsible for producing pigment migrate into the iris. If that migration is slightly uneven, one section ends up with a different pigment density than the rest. This process involves multiple genes that influence pigment production and transport, and small variations in any of them can produce the effect. Most congenital cases are isolated and benign, meaning they aren’t linked to any broader genetic condition.
Congenital Conditions Linked to Sectoral Heterochromia
In a small number of cases, sectoral heterochromia appears alongside a genetic syndrome. The most well-known is Waardenburg syndrome type 1, a condition that affects pigmentation and hearing. Partial or segmental heterochromia (two different colors in the same iris, typically brown and blue) is one of the major diagnostic criteria for this syndrome. Other features include widely spaced eyes, a white forelock of hair, and hearing loss in one or both ears. People with Waardenburg syndrome often have unusually vivid blue eyes or iris hypopigmentation in a sector pattern.
Having sectoral heterochromia alone does not mean you have Waardenburg syndrome or any other condition. The vast majority of people with a color patch in one iris have no associated health problems. But when a newborn presents with heterochromia, an eye exam is recommended to confirm there’s no underlying cause.
Acquired Causes in Adults
Sectoral heterochromia that develops later in life has a different set of causes, and these deserve more attention than the congenital form because they can signal an underlying problem.
- Eye injury or trauma can damage pigment cells in one area of the iris, causing that section to lighten or darken over time.
- Iron deposits from a metallic foreign body in the eye (a condition called siderosis) can darken a portion of the iris.
- Glaucoma eye drops containing prostaglandin analogs can gradually darken the iris, particularly when used in only one eye. The cosmetic eyelash-growth product LATISSE works through the same mechanism and can produce the same effect.
- Fuchs heterochromic uveitis, a type of chronic low-grade inflammation inside the eye, can cause one iris to lose pigment over months or years.
- Horner syndrome, which results from disruption of certain nerve pathways, can lighten the iris on the affected side.
- Iris tumors or abnormal pigmented growths, including melanoma, can create a visible color change in one sector of the iris.
The key distinction is timing. If you’ve had a color patch in your iris since childhood and it hasn’t changed, it’s almost certainly benign. If the color appeared or shifted in adulthood, that warrants investigation.
Does It Affect Vision?
Sectoral heterochromia on its own does not affect visual acuity, light sensitivity, or pupil function. There are no symptoms beyond the visible color difference. It does not worsen over time, and it does not increase your risk of eye disease. When vision problems do occur alongside heterochromia, the cause is the underlying condition (such as glaucoma, uveitis, or trauma) rather than the color variation itself.
Diagnosis and What to Expect
In infants, an ophthalmologist will examine the eyes to confirm that the color difference is simply uneven pigmentation and not a sign of a tumor, inflammation, or a syndrome like Waardenburg. This is typically a straightforward exam and doesn’t involve invasive testing.
For adults who notice a new color change, the evaluation is more involved. An ophthalmologist will look for signs of inflammation, abnormal growths, iron deposits, or nerve damage. They’ll ask about eye drops you’re using, any history of eye injury, and whether the change happened gradually or suddenly. The goal is to rule out treatable conditions that happen to show up as a color shift in the iris.
Treatment and Cosmetic Options
Congenital sectoral heterochromia requires no treatment. It’s a cosmetic variation, not a medical problem. Many people consider it a distinctive feature and prefer to leave it as is.
If the color difference bothers you cosmetically, colored contact lenses can create a uniform appearance. These are available by prescription and come in both corrective and non-corrective versions. When heterochromia results from an acquired condition, treatment targets the underlying cause rather than the color change itself. In some cases, treating the cause (such as removing a foreign body or managing inflammation) may partially reverse the iris discoloration, though pigment changes are often permanent.