The color of a baby’s eyes is one of the most common curiosities for new parents, as the shade seen at birth is often not the final one. Many infants are born with lighter eyes, frequently appearing blue or slate-gray, because the specialized cells that produce pigment have not yet fully activated. This initial appearance is largely due to the way light scatters off the iris with minimal pigmentation present. The eventual color is determined by a gradual, natural process that unfolds over the first months of life.
The Typical Timeline of Eye Color Change
The most noticeable shifts in a baby’s eye color typically begin around three to six months of age. During this period, the pigment-producing cells within the iris start to respond to light exposure, increasing the amount of color deposited. This process occurs as a subtle, progressive darkening of the initial lighter hue.
For many infants, particularly those born with light blue or gray eyes, the color will transition toward a new shade within the first year. The American Academy of Ophthalmology suggests that most babies will have the eye color that will last their lifetime by about nine months old. The exact timing and final shade are highly individual and depend entirely on the genetic instructions the baby inherited.
Not all babies experience a major color change; infants with darker skin tones are more likely to be born with brown eyes that may simply deepen in shade. In contrast, lighter eyes at birth have the greatest potential for change, possibly moving from blue or gray to green, hazel, or brown. The first birthday is often considered a significant milestone for parents to feel more confident about the direction their child’s eye color is taking.
The Role of Melanin and Genetics
The underlying mechanism for eye color change centers on the pigment called melanin, which is the same substance that colors skin and hair. Eye color is determined by the amount of melanin present in the front layer of the iris, known as the stroma. Because the baby developed in the low-light environment of the womb, the melanocytes (pigment cells) have not yet been stimulated to produce a significant amount of melanin.
Once the baby is born and regularly exposed to light, the melanocytes become active and begin to secrete the brown pigment. A low concentration of melanin in the stroma results in blue eyes because light is scattered. A slightly higher amount of melanin will produce green or hazel eyes, while a high concentration results in brown. Brown is the only pigment, and the final color is a result of its quantity and distribution.
The amount of melanin a child’s eyes can eventually produce is dictated by their genetic makeup, which involves multiple genes inherited from both parents. While two specific genes, OCA2 and HERC2, are the most common contributors, scientists believe as many as sixteen different genes can influence the final color. This complex genetic interplay explains why a child’s eye color can sometimes be unexpected, even if both parents share the same eye color.
When Eye Color Becomes Permanent
While the most significant color changes usually conclude by the child’s first birthday, the eye color is not always completely finalized. Subtle shifts and refinements in hue can continue in some children until they reach two or three years of age. The eyes may continue to darken as the melanocytes complete their pigment production and deposition.
Minor changes can continue even later, sometimes up to six years of age. Once the melanocytes have settled on a consistent level of melanin production, the eye color is considered permanent. Any sudden or noticeable color change in one or both eyes after the toddler years is uncommon and should be evaluated by an eye care professional.