Having two differently colored eyes, or multiple colors within the same iris, is known as heterochromia. The word comes from Greek roots meaning “different colors,” and the condition can occur in both humans and animals. Heterochromia isn't a disease itself. It simply describes a difference in pigmentation. In many people, that difference has been present since birth and has no effect on vision or ocular health.
What matters medically is why the color difference exists and whether it has always been there. A lifelong difference in otherwise healthy eyes is very different from an iris that suddenly begins changing color in adulthood.
This article explains the different types of heterochromia, congenital and acquired causes, when an eye-color change should be examined, and how custom contact lenses can be used when someone wants the eyes to appear more symmetrical.
What Is Heterochromia?
Heterochromia is a difference in iris coloration either between the two eyes or within a single iris. Eye color is largely determined by the amount and distribution of melanin within the iris. Differences in pigmentation can therefore produce variations ranging from a small section of another color to two noticeably different-colored eyes.
Heterochromia describes an appearance rather than a specific disease.Some people are born with it as an isolated and harmless characteristic. In other cases, differences in iris color can be associated with a genetic condition, eye disease, trauma, medication, or previous surgery.
That distinction is why the history of the color difference is important.
The Three Types of Heterochromia
Heterochromia generally falls into three patterns:
Image has been altered
Complete Heterochromia
Complete heterochromia, or heterochromia iridum, occurs when one iris is a distinctly different color from the other. For example, one eye may be brown while the other is blue or green.
This is the form most people picture when they hear the word heterochromia.
Sectoral or Partial Heterochromia
Sectoral heterochromia, also called partial heterochromia, occurs when one portion of an iris differs in color from the remainder of that iris.It may look like a wedge, patch, or segment of a different color extending through part of the iris.
Central Heterochromia
Central heterochromia describes a ring of color surrounding the pupil that differs from the predominant color of the remainder of the iris. The transition between colors may appear particularly noticeable in lighter-colored eyes. Natural variations in iris pigmentation are common, so not every multicolored iris necessarily represents a medically significant abnormality.
What Causes Heterochromia?
Heterochromia has many possible causes, but one of the most useful distinctions is whether the color difference was present from birth or childhood or developed later.
Congenital Heterochromia
Congenital heterochromia is present at birth or becomes apparent during early childhood as eye color develops. In many cases, it occurs as an isolated variation in pigmentation and is not associated with an eye problem or visual impairment. However, heterochromia can occasionally occur in association with congenital or genetic conditions.
These include conditions such as:
- Waardenburg syndrome
- Congenital Horner syndrome
- Piebaldism
- Sturge-Weber syndrome
- Other less common genetic or developmental conditions
Having heterochromia does not mean someone has one of these conditions. Most people with an isolated color difference do not. However, when heterochromia is noticed in a baby or child, an eye examination can help confirm that the eyes are otherwise healthy and determine whether additional evaluation is warranted.
What Causes Heterochromia Later in Life?
A change in iris color that develops after childhood is called acquired heterochromia. Unlike a lifelong, stable color difference, a new change in iris pigmentation deserves evaluation because it may reflect a change occurring inside the eye.
Potential causes include:
Eye Trauma
An injury to the eye can damage the iris or alter its pigmentation.
Depending on the injury, changes may be accompanied by an irregular pupil, light sensitivity, glare, reduced vision, or other symptoms.
Inflammation
Inflammation inside the eye can affect iris appearance and pigmentation. Conditions associated with iris color changes include certain forms of uveitis, including Fuchs heterochromic iridocyclitis. Inflammation may also cause pain, redness, light sensitivity, floaters, or blurry vision, although some forms can be relatively quiet.
Horner Syndrome
Horner syndrome affects the sympathetic nerves supplying the eye and face. When it develops early in childhood, reduced sympathetic stimulation can affect iris pigmentation and leave the affected iris lighter.
Other findings may include a smaller pupil on one side and a drooping upper eyelid.
New anisocoria or eyelid drooping requires medical evaluation because Horner syndrome can have several underlying causes.
Glaucoma Medications
Certain prostaglandin-analog medications used to lower eye pressure can gradually increase brown pigmentation of the iris. The effect may be particularly noticeable when medication is used in only one eye.
Latisse
Latisse (bimatoprost) is related to medications originally developed for glaucoma and is used cosmetically to increase eyelash growth. Bimatoprost can increase iris pigmentation, particularly in eyes with mixed-color irises. Patients using Latisse should follow the application instructions carefully and discuss potential ocular side effects with their prescribing professional.
Eye Surgery
Previous eye surgery can sometimes alter the appearance of the iris directly or contribute to other changes that affect iris color.
Iris Lesions and Other Eye Conditions
Pigmented lesions of the iris and other ocular conditions can sometimes create an apparent new area of color. A new or changing pigmented spot on the iris should be examined rather than assumed to be harmless heterochromia.
When Should a Change in Eye Color Be Checked?
A stable color difference that has existed since childhood is very different from a new change in eye color.
Schedule an eye examination if:
- One eye has recently become lighter or darker
- A new patch or area of pigmentation has appeared
- An existing area of pigmentation is changing
- The pupil looks different in size or shape
- One eyelid has newly started drooping
- Eye-color changes occur after an injury or surgery
- The change is accompanied by pain, redness, light sensitivity, or blurry vision
Some of these findings may require more urgent evaluation depending on how suddenly they developed and which symptoms accompany them. If you're unsure whether your eyes have actually changed, older photographs can sometimes be useful for comparison during an examination.
Does Heterochromia Affect Vision?
Heterochromia itself usually does not affect vision.
Someone born with two differently colored but otherwise healthy irises can have completely normal visual function. If vision is affected, it is generally because of the underlying condition causing the iris change, rather than the difference in color itself.
For example, eye trauma might produce both an iris-color change and an irregular pupil. Uveitis may change the appearance of the iris while also causing inflammation and blurred vision.
This is why acquired heterochromia requires more attention than an isolated color difference that has been stable throughout someone's life.
Can Heterochromia Be Treated?
Heterochromia itself generally doesn't require medical treatment. If an eye disease or other medical condition is causing the change, treatment is directed at the underlying condition, not simply at changing the color of the iris. Whether an acquired color change persists depends on its cause. For patients whose eyes are healthy but who are bothered by the cosmetic difference, a professionally fitted contact lens can alter the appearance of one or both eyes.
Custom Contact Lenses for Heterochromia
Custom cosmetic and prosthetic contact lenses can be designed to make two differently colored eyes appear more similar. At Miami Contact Lens Institute, we work with both computer-generated and hand-painted custom prosthetic lenses. Depending on the patient's needs, a lens can be designed to reproduce details such as:
- Iris color
- Iris pattern
- Limbal appearance
- Pupil size and appearance
- Opacity
- Other characteristics of the fellow eye
For patients with iris damage, a prosthetic lens may serve more than a cosmetic purpose. Depending on the underlying condition, an opaque or specially designed pupil can sometimes reduce symptoms such as glare, photophobia, or visual disturbances associated with an irregular or damaged iris.
The goal is to create a lens that not only looks natural but is also appropriately designed and fitted for the patient's eye.
Can You Use Regular Colored Contacts for Heterochromia?
For a simple cosmetic color change, some patients may be candidates for commercially manufactured colored contact lenses. However, contact lenses, including cosmetic lenses, are medical devices and should be professionally prescribed and fitted.
A contact lens that does not fit properly can cause discomfort, inflammation, corneal injury, and other complications. Improper lens hygiene or purchasing lenses from unregulated sources can also increase the risk of serious eye infection. Patients with significant differences in eye color, iris abnormalities, trauma, or a need for a highly realistic color match may require a custom prosthetic or hand-painted lens rather than a standard colored contact lens.
What About Eye Color-Changing Surgery?
Procedures marketed specifically to permanently change eye color deserve significant caution. Cosmetic iris implants have been associated with serious complications, including inflammation, elevated eye pressure, corneal damage, cataracts, glaucoma, and vision loss. Other procedures designed to alter iris appearance should also be carefully evaluated for their risks, evidence, and regulatory status before being considered. For someone who simply wants a different eye color, professionally fitted cosmetic contact lenses provide a reversible, nonsurgical option.
How Miami Contact Lens Institute Can Help With Heterochromia
If you've always had differently colored eyes and your eyes are healthy, heterochromia may simply be one of your natural characteristics. If your eye color has recently changed, however, the priority is determining why.
At Miami Contact Lens Institute, we can evaluate changes in iris appearance and ocular health and determine whether additional medical evaluation or treatment is necessary. For patients interested in changing or matching the appearance of their eyes, we also specialize in custom cosmetic and prosthetic contact lenses, including highly customized computer-generated and hand-painted designs. Contact Miami Contact Lens Institute to schedule an evaluation. Patients closer to Broward County can also be seen at our Weston office.
