Eye color, a distinctive personal characteristic, can subtly shift over a person’s lifetime. While dramatic changes are uncommon, minor alterations are normal. These shifts often stem from natural biological processes, reflecting human development and aging.
How Eye Color is Determined
Eye color is primarily determined by melanin, a pigment also responsible for skin and hair color. This pigment is located within specialized cells called melanocytes in the iris. The amount and distribution of melanin within the iris’s front layers dictate the final eye color. High concentrations result in brown eyes, while lower amounts lead to lighter shades like blue or green. The appearance of blue, green, and hazel eyes also involves light scattering by the stroma, a layer within the iris, similar to how the sky appears blue.
Why Infant Eye Color Changes
Many infants, particularly those of European descent, are born with lighter eye colors, often blue or gray. This initial hue is due to the relatively low amount of melanin in their irises at birth. As a baby is exposed to light, melanocytes begin to produce more melanin. This increase in pigment can cause the eye color to deepen or change, typically stabilizing between 6 to 12 months of age, though subtle shifts can continue up to three years. The change usually progresses from lighter to darker shades.
Adult Eye Color and Aging
While less common and more subtle than in infancy, adult eye color can also undergo gradual changes with age. Over many years, the amount of melanin in the iris can naturally decrease or redistribute, potentially leading to a slight lightening or dulling of eye color. This is a slow process, often imperceptible.
Other age-related physiological changes can create the appearance of altered eye color. Arcus senilis, common in older adults, manifests as a white, gray, or bluish ring around the cornea’s edge. This ring, caused by lipid deposits, can make the eye appear to have two different colors. Similarly, cataracts, which involve the clouding of the eye’s natural lens behind the iris, can make colors appear faded or yellowish, indirectly influencing eye color perception.
When to Seek Medical Advice
Any sudden or dramatic change in eye color in adulthood, especially if it affects only one eye, warrants prompt medical evaluation. Such changes can indicate an underlying health issue. Seek medical attention if the change is accompanied by symptoms like pain, vision changes, redness, or light sensitivity.
The development of different colored irises (heterochromia) later in life, if not present from birth, should also be investigated. Specific conditions that can cause eye color changes include Fuch’s heterochromic iridocyclitis, an inflammatory condition that can lighten the affected iris, or Horner’s syndrome, a neurological condition that may cause eye lightening. Pigmentary glaucoma, where pigment from the iris can clog the eye’s drainage system, leading to increased eye pressure and potential color changes, is another condition.