Heterochromia: Causes And Types
Heterochromia: Causes And Types
Heterochromia is a unique condition that affects the color of the eyes. Derived from the Greek words heteros and chroma, the word means “different colors”. Though more frequently seen in other members of the animal kingdom, such as cats, heterochromia can and does affect humans as well. In most cases, this is a benign condition that typically does not affect one’s ability to see clearly. However, there are several different types of heterochromia and a diverse array of potential causes.
What causes heterochromia?
The most common cause of heterochromia is a genetic mutation that results in an individual born with two differently colored eyes. This mutation is not usually harmful and, as mentioned, usually does not influence the quality of vision. Some versions of congenital heterochromia can be linked to rare diseases such as Waardenburg syndrome, though these are less common. This genetic tweak changes the way the body expresses pigmentation in the iris, leading to the differing colors. There are other ways to acquire heterochromia after birth, however, that are not related to the usual benign mutation.
Severe eye trauma is perhaps the most common cause, as was the case with the famous musician David Bowie. Trauma that causes damage to the iris may result in color changes both temporary and permanent as well as affect visual acuity. Some eye diseases, such as glaucoma — and even one of the primary medications used for glaucoma treatment — can lead to heterochromia-like aberrations in eye color. Medical conditions such as diabetes, as well as eye surgery, can sometimes trigger these changes as well, but acquired heterochromia of this type is substantially rarer than the congenital types.
The key types of Heterochromia
Heterochromia does not manifest in the same way for every individual. Variations across a broad spectrum can exist. There are three main categories used to classify heterochromia based on the specifics of the irregularities.
Complete heterochromia is what most people tend to think of when they hear of this condition, and is when each eye is a completely separate color. For example, one eye may be completely blue while the other is fully brown.
Partial, or sectoral heterochromia, affects only the portion of the iris within one eye. This often
manifests as a portion or patch or a different color within the iris. The third type, central heterochromia,
is another internal color variation. Both irises are the same dominant color, but the inner iris near the
pupil differs from the rest of the eye. While there can be some variation between these three types,
most individuals will fall into one of these categories.
Are there treatment options available?
There is no need to treat heterochromia except when there is an underlying condition. Individuals with congenital heterochromia experience no detrimental effects to their vision as a result. In all other cases, treating existing health issues is sufficient to safeguard the eyes from further damage. However, once an iris undergoes a color change, it is permanent. Prosthetic contact lenses may be used to disguise this change.