A baby’s eye color can change during early development, a common topic of curiosity for new parents.
How Eye Color Develops
The color of an infant’s eyes is determined by melanin, a pigment also responsible for skin and hair color. Specialized cells called melanocytes produce melanin within the iris, the colored part of the eye. At birth, many babies, particularly those with lighter skin tones, have low levels of melanin in their irises, often resulting in blue or gray eyes. This bluish appearance occurs because of how light scatters when there is minimal pigment, a phenomenon known as Rayleigh scattering.
After birth, as babies are exposed to light, their melanocytes become more active, increasing melanin production. This increased melanin can cause the eye color to gradually darken and shift. Darker eyes tend to remain dark due to higher initial melanin. If a baby’s eyes initially appear light, they may darken over the first year as more melanin accumulates.
When Eye Color Becomes Permanent
The most significant changes in a baby’s eye color typically occur within the first six to twelve months of life. During this period, melanin production stabilizes, leading to a more consistent hue. While many babies will have their lasting eye color by around nine months to one year of age, some can experience subtle shifts until they are two or three years old. Eye color usually stabilizes by six years of age, though subtle adjustments can continue into adolescence or adulthood for some, especially those with lighter eyes. Generally, eye color changes from lighter to darker, meaning blue eyes might transition to green, hazel, or brown, but dark eyes are unlikely to become blue.
What Determines a Baby’s Eye Color
A baby’s eye color is primarily determined by genetic factors inherited from both parents. Multiple genes influence the amount and type of melanin produced and distributed in the iris. For instance, the OCA2 and HERC2 genes, located on chromosome 15, play a substantial role in controlling melanin quantity and its distribution. The amount of melanin dictates the eye color: minimal melanin results in blue eyes, slightly more leads to green or hazel eyes, and a substantial amount produces brown eyes. While simplified inheritance patterns once suggested that brown eyes are dominant over blue, it is now understood that eye color inheritance is more complex due to the interplay of numerous genes. This complexity means that two blue-eyed parents could, in rare instances, have a brown-eyed child if certain genetic variations are present.
When to Seek Medical Advice
While most changes in a baby’s eye color are a normal part of development, certain unusual patterns warrant a consultation with a pediatrician. If a baby’s eyes are notably different colors (heterochromia), seek medical advice. While often harmless, heterochromia can occasionally indicate an underlying condition. Additionally, any sudden or significant eye color changes in an older child or adult should be evaluated by an eye care professional. Conditions such as ocular albinism, which involves reduced melanin in the iris, or certain syndromes like Waardenburg syndrome, might present with unusual eye coloration. Professional assessment ensures any potential health concerns are addressed.