Eye color is not fixed throughout a lifetime. The answer to whether your eyes can change color is yes, but the reasons for this shift vary significantly depending on age and circumstance. The perceived color of the eye is determined by the pigmentation in the iris, the colored, muscular ring that controls the pupil’s size. While eye color is largely determined genetically, changes may be developmental, metabolic, or sometimes an indication of an underlying medical issue.
The Biological Basis of Eye Color
The coloration of the human iris is primarily governed by the pigment melanin, the same substance that dictates skin and hair color. Individuals with brown eyes possess a higher concentration of melanin, which absorbs a greater amount of light. Conversely, lighter eye colors like blue or green contain much lower levels of this pigment.
The appearance of lighter colors is a structural effect, not the result of blue or green pigment in the iris. This effect is known as Rayleigh scattering, where light entering the iris stroma—the middle layer—is scattered back, making the eye appear blue, similar to how the sky looks blue. Green and hazel eyes result from a moderate amount of melanin combined with this light-scattering phenomenon.
Eye color inheritance is a polygenic trait, meaning multiple genes, such as OCA2 and HERC2, work together to determine the final shade. These genes regulate the production and distribution of melanin within the melanocytes, the pigment-producing cells in the iris. While the potential color is set at conception, the final expression of that color can evolve over time.
Natural Changes from Infancy Through Adolescence
The most common shifts in eye color occur during the early stages of life as a normal part of development. Many Caucasian infants are born with blue or slate-gray eyes because their melanocytes have not been fully activated. Melanin production requires light exposure, which is minimal in the womb.
Once exposed to light after birth, the melanocytes begin to produce pigment, gradually darkening the eye color towards its genetically determined shade. This process explains why a baby’s initial light color may slowly transition to green, hazel, or brown. The amount of melanin produced stabilizes the final hue.
Significant color changes are typically observed between six months and one year of age, but the process is gradual and can continue for several years. For many children, eye color is not considered stable until they reach three years old, though minor shifts can occur throughout adolescence. These developmental changes are considered normal.
Acquired Color Shifts in Adulthood and Seniority
After developmental changes cease, a person’s eye color generally remains stable, but minor shifts can still occur due to metabolic or environmental factors. Long-term exposure to sunlight, for example, can cause a slight increase in melanin production, leading to a subtle darkening of the iris over many years. Likewise, a small percentage of adults may experience a slight lightening of their eye color later in life, though these changes are often very minor.
More significant, noticeable color changes in adulthood are linked to specific medical conditions or pharmaceutical interventions. Certain types of glaucoma drops, known as prostaglandin analogs, can cause a permanent darkening of the iris, particularly in individuals with lighter eye colors. This happens because the medication increases the production of melanin within the iris cells.
Several pathological conditions can also alter iris color, often by causing a loss of pigment or inflammation, a phenomenon called heterochromia. Conditions like uveitis, an inflammation of the eye’s middle layer, or Fuchs heterochromic iridocyclitis can cause the affected eye to lighten. Pigment dispersion syndrome causes pigment to flake off the back of the iris, which can lighten the color and potentially lead to glaucoma.
A common age-related change is the appearance of a gray or white ring around the edge of the cornea, known as arcus senilis. This ring is caused by lipid and cholesterol deposits and can make the iris appear as if its color has changed or faded. However, arcus senilis is a change to the cornea, the clear outer layer, and does not alter the actual pigment of the iris itself. Any sudden, noticeable, or asymmetric change in eye color in an adult warrants immediate consultation with an eye care professional.